UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA PICKLING GREEN OLIVES W. V. CRUESS BULLETIN 498 October, 1930 UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY, CALIFORNIA 1930 PICKLING GREEN OLIVES 1 W. V. CRUESS2 INTRODUCTION Owing to increasing production of ripe olives in California and the difficulty of extending the market for this product, it is becoming increasingly difficult to dispose of the olive crop at a profit. In the region east of the Rocky Mountains green olives are con- sumed in much larger quantities than California ripe olives; most of the pack of ripe olives is consumed in the Pacific Coast states. Since the Spanish green olives are so well known, possibly a con- siderable portion of the California crop could be converted into green TABLE 1 Imports of Green Olives tor 1920 to 1930* Years Gallons Declared value in dollars at port of entry Approximate equivalent in cases on basis of 6 gallons per case Production of California canned olives, cases (approximate) 1920 3,642,653 No data No data 3,851,995 6,440,920 3,419,148 4,778,176 4,473,308 7,040,718 3,105,665 4,074,970 1,448,684 2,885,175 3,681,052 4,104,111 2,916,300 3,756,434 4,219,760 4,090,402 1,862,916 607,108 No data No data 641,999 1,073,420 569,858 796,363 745,551 1,006,786 545,184 150,000 1921 250,000 1922 410,000 1923 675,000 1924 425,000 1925 400,000 1926 474,000 1927 428,000 1928 r. 865,000 1929 600,000 4,594,072 3,303,940 748,284 458 , 700 Data through courtesy of U. S. Department of Commerce and California Olive Association. pickled olives and sold in competition with the imported olives as a means of disposing of the surplus. The present tariff on green olives would in part compensate for the difference in cost of production between that of Spain and California. The relative amounts of ripe and of green olives consumed in the United States may be judged from table 1. i This bulletin is supplementary to Circular 278 " Olive Pickling in Mediter- ranean Countries, " published in 1924. 2 Associate Professor of Fruit Products and Chemist in the Experiment Station. 4 University of California — Experiment Station For the past two years the average importation of green olives approximately equals the production of California canned olives. There should be, therefore, a considerable potential market for Cali- fornia green olives. Utilization of an appreciable proportion of the crop for this purpose should benefit the ripe olive industry. The investigations reported in this bulletin were undertaken in 1924 by the Fruit Products Laboratory, University of California, and have been continued until the present in order to ascertain what modifications in the Spanish process are necessary for California conditions. The results are presented according to the problems stud- ied and in sequence of the operations involved. The procedure recom- mended for pickling of green olives in California is given in a later section. COMPARISON OF VARIETIES FOR GREEN PICKLING In laboratory experiments the Sevillano, Barouni, Manzanillo, Ascolano and Mission olives varied in respect to their suitability for green pickling in the order named. The Sevillano was best and the Mission the least desirable for this purpose. The Sevillano fermented more rapidly and satisfactorily than the Manzanillo, Ascolano and Mission. The Barouni, however, fermented about as rapidly as the Sevillano and made an excellent green olive. While somewhat tough, the Barouni olive was found to possess excellent flavor. The flavor and texture of the Ascolano was good but the color after pickling was often nearly white. Sorting before pick- ling could be used to remove most of the light colored fruit. The Manzanillo fermented much more slowly than* the Sevillano and usually required the addition of sugar. The Mission gave good results when pickled sufficiently green. The foregoing observations made in small scale tests were con- firmed for Sevillano, Manzanillo, Mission and Ascolano olives by fac- tory tests. EFFECT OF LOCALITY In comparing the suitability for green pickling of Sevillano olives from the Corning, Lindsay and Oroville districts; of Mission and Manzanillo olives from the Oroville, Fairoaks, Lindsay and Los Angeles districts; and of Ascolano olives from Oroville, Lindsay and Westhaven, there appeared to be little effect due to locality. Bul. 498] Pickling Green Olives 5 Mission olives from Imperial Valley were very small but fermented satisfactorily. Ascolanos from Imperial Valley were very light in color and on this account less desirable for green pickling than those from other districts. EFFECT OF MATURITY In the Seville district of Spain olives are accepted for green pick- ling until they have become faint pink in color. In laboratory experiments and in factory tests conducted at Visalia during three seasons, Manzanillo olives showing a faint pink color over about one-fourth or less of the surface gave a pickled product of satisfactory yellow color; those that had attained much more color than this were gray or mottled in color after pickling. Sevillano, Ascola.no and Mission olives showing pink color on one-fourth to one- half of the surface were too tender in texture after pickling. All varieties gave better products when free of pink or red color. In an experiment at Corning, on a factory scale, Sevillano olives were picked very early in the season and toward the end of the season. The olives in the first picking were "grass green" and very hard in texture. Their oil content was 9.41 per cent. Those of the second picking were for the most part straw yellow in color but free of red or pink color, and contained 11.48 per cent oil. The olives from both pickings gave excellent pickles, although those picked near the end of the season were more tender and devel- oped more gas pockets during fermentation than those picked early in the season. In addition to giving a better product, picking early in the season permits a longer period of natural incubation in the sun before the onset of cold weather. SUITABILITY FOR GREEN PICKLING OF OLIVES PREVIOUSLY STORED IN BRINE Fresh olives are often stored in brine for several weeks before use for ripe pickling. The question of utilizing for green pickling olives from storage brines has frequently arisen. In order to determine the suitability of such olives a large scale experiment was conducted in 1924 in coopera- tion with Geo. C. Roeding. 3 s Formerly a prominent olive grower and nurseryman; died 1928. 6 University of California — Experiment Station Sevillano, Ascolano, Mission and Manzanillo olives previously stored in 50-gallon barrels for four to six weeks in brine were placed in a 2 per cent lye solution which was allowed to penetrate about two- thirds of the way to the pit. They were then washed free of lye and stored in brine of 44° salometer in 50-gallon barrels in a warm room for two months. Thereafter they were stored at ordinary room tem- perature. After three months fermentation the acidity of the brine in the twelve barrels ranged from .06 to .54 grams per 100 cc. The Sevillano olives were highest and the Mission lowest in acidity. All of the olives were dark gray in color and on this account unsal- able as green olives. However, the flavor was fairly satisfactory. CONTAINERS FOR FERMENTATION In a number of factory tests oak barrels were found superior to paraffin-lined spruce barrels. The wood of the spruce barrels imparted a rather undesirable taste to the olives, whereas, the flavor absorbed from the oak barrels improved the quality of the olives. Oak barrels are sturdier, are not so apt to leak, and they withstand shipment better than the spruce barrels. When the common ripe olive shipping barrel with 6-inch head bung was used leakage usually occurred. When the barrels were placed on end to prevent leakage, the bung soon became loosened and per- mitted evaporation with formation of a head space and consequent growth of film yeast and mold. Second hand olive shipping barrels were used by several packers for preparation of green olives. This proved to be a. very serious mis- take — most attempts to use such barrels resulted in eventual spoilage and loss of the olives. Such barrels can not be kept tight and well filled, and are often infected with spoilage organisms. Second hand, clean, sound oak barrels were thoroughly "soaked out" with dilute sal soda solution and water, and used successfully for three successive seasons in the laboratory tests. In filling barrels equipped with side bung only, the hoops on one end of the barrel were loosened with a hammer and hoop driving iron, and the head removed. The olives were filled into the barrel, the barrel shaken back and forth to settle the fruit to the inside level of the head ; the head was then put in place, the hoops driven tightly, and the barrel filled at once with brine through the side bung. Bttl. 498] Pickling Green Olives EXPERIMENTS ON LYE TREATMENT AND WASHING Experiments were made to determine the effect on quality of the following" factors : lye concentration ; depth of lye penetration ; tem- perature ; changes in composition during lye treatment and washing ; exposure to air during washing and size and character of container used for lye treatment and washing. Changes in Composition During Lye Treatment. 4 ' — It was observed that fermentation of the green olives used in experiments during the TABLE 2 Changes in Total Sugar and Mannite Content of Green Olives During Lye Treatment, Washing and Fermentation Sample Total sugar, per cent in flesh Mannite, per cent in flesh Sugar and mannite Acid in flesh per cent as lactic Sevillano, fresh Sevillano, after washing to remove lye Sevillano, after 3 months fermentation Manzanillo, fresh Manzanillo, after washing to remove lye 1 6 1 2 3 1 1 1 3 1 84 37 00 16 86 14 90 95 00 40 16 20 85 56 67 23 00 1 2 1 2 4 3 3 2 2 1 85 90 15 28 12 20 02 51 15 08 68 32 8 2 2 80 08 3 1 8 2 4 1 7 1 5 4 2 6 69 27 15 44 98 34 92 46 15 48 84 52 65 76 87 03 .83 .05 .45 .68 .15 .34 Manzanillo, fresh. From commercial test, Oro\ille.... Manzanillo, after washing to remove lye Manzanillo, after 3 months fermentation Barouni, fresh Barouni, after washing to remove lye Barouni, after 3 months fermentation 1 05 .07 .56 .04 .04 .20 No data No data Manzanillo, after washing to remove lye No data Average after lye treatment and washing 2 08 1924 and 1925 seasons was slow and that usually less than the desired amount of lactic acid was formed. It was suspected that the low yield of lactic acid might be due to lack of fermentable material. Analyses of several varieties of olives were made at various stages of the process. Table 2 gives the results obtained. In another experiment it was found that the total sugar content of Sevillano olives before lye treatment was 3.17 per cent, after lye treatment 2.19 per cent, and after washing .96 per cent. In an experi- ment with Manzanillo olives the corresponding values were : before lye treatment, 2.60 per cent, after lye treatment 1.80 per cent, and after washing .71 per cent. 4 From analyses made by B. E. Lesley, W. V. Cruess and S. A. Kaloyereas. 8 University of California — Experiment Station The loss in total sugar plus mannite during lye treatment and wash- ing of the olives reported in table 2, was approximately 65.6 per cent of that originally present. The average total sugar plus mannite remaining in the flesh after washing to remove lye was 2.08 per cent. In the fermentation container there are approximately equal quanti- ties of brine and olives (somewhat less of brine than of olives) . Allow- ing for the pits which it is assumed furnish no fermentable material, there would be about 1 per cent of fermentable material in the mixed contents of the fermentation container. Theoretically, from 1 per cent of fermentable material, 1 per cent of lactic acid should be formed; the yield actually would be less, even under optimum con- ditions, owing to unavoidable loss as by other kinds of fermentation. The acidity of the olive flesh is almost completely destroyed by the lye treatment ; hence practically all of the acidity in the pickles must come from lactic fermentation of the sugars and mannite. Comparison of Containers for Lye Treatment. — In many of the experiments the olives were treated with lye and washed in the barrels in which they were later to be fermented. The barrels were fitted with 6-inch head bungs which permitted filling with olives, or liquid, and draining. To drain, the barrels were merely turned on end on a 2x3 inch scantling on a concrete floor, or a short piece of "2x3" was nailed to the head (see fig. 1). A serious objection to this barrel with 6-inch head bung is that the bung is very apt to leak so badly, when the barrels are later placed on their sides, that spoilage occurs. When barrels with side bungs only were used, one head was removed and most of the opening was covered with coarse burlap. This permitted easy filling and draining. Some packers have "headed up" the filled barrels and drained and filled through the side bung. This method has the advantage of reducing oxidation to a minimum during washing. In several factory tests ripe olive vats were used for lye treatment of green olives. Where the quantity treated was sufficient to nearly fill the vats these containers proved very satisfactory. However, when the vats were filled to a shallow depth only, darkening of the color was excessive. During the 1926 season green olives were treated in a large circular redwood vat successfully at the California Cooperative Cannery in Visalia. 5 In a typical test 2% tons of large size Manzanillo olives were placed in the vat; 700 gallons of lye of 11° salometer was added at 3 :15 p.m. A false head made of heavy slats with intervening spaces s This experiment was conducted by J. P. Scherb. Bul. 498] Pickling Green Olives 9 was placed in the vat to keep the olives submerged during" lye treat- ment and washing. The temperature after the olives and lye had reached equilibrium was 75° P. At 8 :00 p.m. the lye had penetrated two-thirds of the way to the pit. The solution was drained from the olives, ten minutes being required for draining. The temperature was still 75° F. The olives were rinsed by quickly filling the vat with water Fig. 1. — At left, 50 -gallon barrel with screen for draining. At right, filling barrel with water during washing. and draining three times. The water was changed the following day at 7 a.m., 10 :15 a.m., 1 p.m., 3 p.m., 5 p.m., 8 p.m., and at 7 a.m. on the second day, at which time the olives were ready for barreling. The olives were ' ' sluiced ' ' into the barrels in a metal chute in a. stream of water. All things considered the usual ripe olive vat is a satisfactory con- tainer for the lye treatment and washing of olives for green pickling, provided care is taken to avoid undue exposure of the olives to the air and unnecessary aeration of the wash water. Decrease in Lye Concentration. — Many determinations were made of the sodium hydroxide content of lye solutions before and after application to the olives. The data given in table 3 are typical of the observations made in the commercial scale experiments at Visalia. 10 University of California — Experiment Station The average decrease in lye concentration shown by titration was 1.10 per cent or about 55 per cent of the initial concentration, and the average decrease in salometer degree was 4.7° or approximately 37 per cent of the initial salometer degree. In other words the decrease in density was less than the decrease in actual lye concentration shown by titration. This means that part of the density of the spent TABLE 3 Typical Changes in Lye Concentration of Manzanillo Olives in Factory Tests, Visalia, October, 1926* Barrel No. Initial concentration, per cent sodium hydroxide Final concentration, per cent sodium hydroxide Initial degrees salometer Final degrees salometer Decrease in sodium hydroxide, per cent Decrease in concentration, degrees salometer 1 2.0 .90 12 7.0 1.10 5 2 2.0 .88 12 7.0 1.12 5 3 2.0 .88 12 7.5 1 12 4 5 4 2.0 .85 12 7.5 1.15 4.5 5 2.0 .92 12 7.5 1 08 4 5 Temperature of solution and olives, 68°-72° F. Length of application, 4 to 41 hours. TABLE 4 Changes in Lye Concentration During Lye Treatment of Olives in the Laboratory: Temperature 65°-68° F Variety Initial lye concentration, per cent Final lye concentration, per cent Length of application, hours 2.09 1.75 1.75 1.75 .52 .50 .70 .90 7 Sevillanp 9 8 8 lye solution was due to other materials in solution, such as coloring matter and salts of sodium. In laboratory experiments the length of application was somewhat longer than shown in table 3. The data given in table 4 are typical of laboratory experiments made with 5-gallon lots. In most laboratory tests the decrease in lye concentration amounted to about 60-65 per cent. In a number of cases the spent lye, after reinforcing by the addi- tion of fresh lye, was used for a second lot of olives successfully. Depth of Lye Penetration. — The depth of lye penetration was found to greatly affect the character of the finished product. In lab- oratory experiments green Manzanillo and Sevillano olives were Bul. 498] Pickling Green Olives 11 treated with 2 per cent sodium hydroxide, portions of the fruit being removed from the solution when the lye had penetrated about one- fourth, one-half and two-thirds way to the pit, respectively. In a few cases the lye was permitted to penetrate completely to the pit. The Manzanillos treated one-fourth to the pit remained very bitter after one year 's storage ; those treated one-half to the pit remained too bitter to be palatable ; while those treated two-thirds to the pit lost most of their bitterness in less than six months. Those treated com- pletely to the pit did not ferment properly except when 2 to 3 per cent dextrose sugar was added and they were too soft and too light in color. The flesh of most of the olives treated one-fourth and that of a number treated one-half to the pit turned brown, near the pit. The Fig. 2. — Various depths of lye penetration. 1, less than one-half to the pit; 2, about one-half to the pit; 3, nearly to the pit; and 4, about two-thirds to the pit. Photograph by G. A. Pitman. flesh of those treated two-thirds to the pit, or more deeply, remained light in color. Lye treatment of Sevillano olives one-half to a scant two-thirds to the pit gave the best results. This variety has less bitterness than the Manzanillo and is not so apt to turn brown near the pit. The Asco- lano behaved much like the Sevillano in respect to lye penetration. Mission and Barouni olives contain a great deal of bitterness and required a depth of lye penetration of fully two-thirds to the pit. In factory experiments at Visalia the laboratory results were con- firmed. At the Curtis Corporation factory in Long Beach, Sevillano olives treated approximately one-half to a scant two-thirds to the pit gave a good product of normal color, flavor and texture. Others treated nearly to the pit failed to ferment properly and shriveled very badly. It is apparent that the Sevillano and Ascolano require less depth of penetration than the Manzanillo, Mission and Barouni. Figure 2 illustrates different depths of lye penetration. 12 University of California — Experiment Station For rapid curing of green olives it was found that lye penetration should be somewhat deeper than usual in order to remove most of the bitterness and to hasten the change of color from green to yellow. In all experiments where penetration of lye was deeper than usual the addition of sugar was found necessary. Lye Indicator. — Phenolphthalein indicator applied to the cut sur- face of samples from the vat or barrel is very useful in observing lye penetration and progress of washing. A dilute solution of this indi- cator, about 1 per cent in denatured alcohol, may be obtained from any druggist. A drop placed on the cut surface turns pink or red, if lye is present. Time Required- for Lye Penetration. — The time required for pene- tration of 2 per cent lye two-thirds to the pit was recorded for 187 individual 50-gallon barrels at Visalia during October and in early November, 1925. The maximum time required was 6% hours and the minimum 4 hours. The time required for lye treatment from October 10 to Octo- ber 28 was about 1 hour less than on October 31 and November 3, owing, no doubt, to a difference in temperature. The average time for Manzanillo olives was 4% hours and for Sevillano, 4% hours. The temperature of the lye solution was generally 70 to 75° F. In a fac- tory test at Corning, 4% hours was required for treatment of Sevillano olives with 2.47 per cent lye solution and 9 hours for 1.58 per cent solution. In the laboratory the average time required for lye treatment of Manzanillo olives with 2 per cent lye solution was approximately 6 hours and for Sevillano and Barouni olives approximately 7 hours. The temperature of the lye solution was 60-65° F, i.e., somewhat lower than in most factory tests and the concentration was in most tests less than 2 per cent. Time Necessary for Washing. — In the laboratory 24-36 hours washing was generally sufficient for Manzanillo and Mission olives when the water was changed at 3-hour intervals during the day and applied for a 10-hour period during the night. Sevillano and Asco- lano olives required 36 to 48 hours washing in most laboratory experiments. In the commercial experiments at Visalia and Oroville 30 to 36 hours washing was required. The lye is more easily and quickly removed from the green olives than from those treated by the California ripe olive process, where 4 to 6 days washing is generally required. Bul. 498] Pickling Green Olives 13 It was found that it is not necessary to remove the last trace of lye from all of the olives ; when 75-80 per cent of the olives gave no pink or red color with phenolphthaleon and the remainder gave a faint red color, the olives fermented satisfactorily. In the Seville factories in Spain many of the olives give an intense red color to phenolphthalein at the end of the washing period. However, this fact may account for much of their loss by bacterial spoilage. Effect on Quality of Exposure to Air During Washing. — A number of experiments were made in which some of the olives were exposed to the air during washing until they were brown or gray. During sub- sequent fermentation much, but by no means all, of the brown or gray color disappeared. After fermentation was complete these olives were in all cases inferior in color and thus of lessened commercial value. In filling the vat or barrel with fresh water, violent aeration must be avoided, as otherwise dissolved and occluded air will darken the olives rather severely. Exposure between changes of water and during filling of the barrels must also be as brief as possible. Weight of Olives and Volume of Liquid Per Barrel. — The weight of fresh Manzanillo olives required to fill a 50-gallon barrel was found to range from 253 to 265 pounds. The average was about 260 pounds. Several measurements of the volume of solution required for each barrel gave an average of approximately 20 gallons to a 50-gallon barrel of olives. Lye Concentration and Blistering. — Sevillano olives frequently blistered during washing. This was found to be more severe in olives that had been treated with strong (2 to 2.25 per cent) than in those treated with lye of moderate concentration (1.6 to 1.75 per cent). Evidently the strong lye causes separation of the cells by dissolving the pectinous cementing material. Very green olives blistered less than mature ones. BRINING EXPERIMENTS IN THE LABORATORY Manzanillo and Sevillano olives were treated with 2 per cent lye solution two-thirds of the way to the pit, then washed free of lye and placed in brines of various concentrations in one quart glass top jars at room temperature. Several acidity determinations were made during fermentation and salometer readings were made at the begin- ning and end of the experiment with the results given in table 5. At the end of six months all of the olives were completely fer- mented. At that time numbers 14 and 15 of the Manzanillo series and 21 and 22 of the Sevillano series were best. 14 University of California — Experiment Station TABLE 5 Effect of Initial Salt Concentration of Brine on Fermentation and Quality of Green Olives Variety Initial degrees, salometer Final degrees, salometer Acidity of brine as lactic, grams per 100 cc 19 days 43 days 85 days 28 20 .11 .20 .50 32 23 23 20 .30 36 25 .10 20 20 40 27 .10 15 .15 44 30 15 15 .15 48 35 .10 10 10 60 39 .10 10 .10 28 21 .13 .65 .80 32 24 .05 54 .75 36 26 05 48 .65 40 28 23 54 .75 44 31 20 49 .70 48 35 .20 41 .70 60 38 .12 45 .40 Observations at 85 days Manzaniilo: Lot 11 Lot 12 Lot 13 Lot 14 Lot 15 Lot 16 Lot 17 Sevillano: Lot 18 Lot 19 Lot 20 Lot 21 Lot 22 Lot 23 Lot 24 Excellent color and liavor. Still "raw" but no shrheling. Still "raw" but no shriveling. Still "raw" but no sl.meling. Still "raw " but no shriveling. Still "raw" but no shriveling. Still "raw" but no shriveling. Some gas pockets. Not so good as 21. Some gas pockets. Not so good as 21. Not so good as 21. Well fermented. Hest of Sevillano series. Second best. Shriveling has disappeared. Shriveled slightly. Not completely fermented. TABLE 6 Changes in Brine Concentration in 50-Gallon Barrels of Green Olives Variety Time in days Initial degrees, salometer Final degrees, salometer Manzaniilo - Ascolano 21 21 21 21 21 21 21 21 21 21 3 3 3 3 3 3 44 44 44 44 44 44 44 44 44 44 40 40 40 40 40 40 27 28 26 30 28 28 27 29 26 26 Manzaniilo 24 Manzaniilo 27 Sevillano 24 Sevillano 26 Ascolano 24 Ascolano 24 Bul. 498] Pickling Green Olives 15 The Manzanillo olives did not shrivel in any of the brines, but the Sevillanos shriveled temporarily in all brines of 36° and above. At the end of 85 days the shriveling had completely disappeared except in brine that had been originally 60° salometer. The experiment illus- trates the fact that Sevillano olives ferment more rapidly than the Manzanillo ; a fact that was observed repeatedly in other tests. Fig. 3. — Above: one method of adding salt to increase density of brine. Below: barrels of green olives in the sun. Note the skids to elevate the barrels off the ground. BRINING EXPERIMENTS IN THE FACTORY Observations were made during several seasons on the decrease in brine concentration in barrels of green olives. Typical results are given in table 6. The Manzanillo olives responded very satisfactorily and either were not shriveled or were shriveled slightly for a few days only. The Sevillanos and Ascolanos, however, shriveled considerably and some of the olives remained permanently shriveled. During the 1926 season a weaker brine, 10°-15° salometer, was added to the olives and the salometer degree was progressively increased by small additions of salt every other day over a two-weeks period to 28-30° salometer (see fig. 3). Little shriveling occurred and 16 University op California — Experiment Station fermentation was satisfactory. The brine may be tested readily in the barrels by inserting a perforated metal cylinder through the bung and placing a hydrometer therein (see fig. 4). In experiments at Corning in 1929 brines of 36° to 44° salometer were added to Sevillano olives. Temporary but not permanent shriveling occurred. The experiments indicate that it is desirable to place on Manzanillo olives a brine of 44° salometer rather than one of 40° and that it will be A L»J Fig. 4. — Perforated hydrometer cylinder for testing brine in barrels. (Designed by J. P. Scherb, 1926. A A, level of liquid in the barrel and cylinder; B, stave of barrel; C, perforated bottom of hydrometer. necessary also to add more salt to many of the barrels after olives and brine have reached the same salt content. It was found that olives and brine reach the same salt content quickly, usually in less than three days. In both laboratory and factory tests the optimum final brine strength for green olives proved to be 27° to 32° salometer. Above 32° the olives were too salty in taste; below 27° there was danger of gas formation in the olives, and softening and other forms of spoilage increased. The brines were tested by inserting a perforated metal cylinder through the bung and floating a salometer hydrometer therein (see fig. 4). Bul. 498] Pickling Green Olives 17 EFFECT OF TEMPERATURE ON FERMENTATION In the warm climate of the Seville district of Spain fermentation of green olives proceeds rapidly to completion in large casks stored in open yards. In most localities in California cold weather prevails during the late fall and the winter months and on this account in experiments made in 1924, 1925 and 1926, it was found that olives stored in the open fermented very little during this period of the year. 6 o O <*T 9CfF AT 85T (0 fr>OOM 7 ^£MP. § TIM e isv Day, 5 o" 10 15 ZO ZS 30 35 40 4 J Fig. 5. — Effect of temperature on rate of fermentation of green olives. For this reason a number of experiments were made in order to determine to what extent fermentation could be promoted by incubation. Laboratory Experiments. — In a laboratory experiment conducted during the 1925 season green Manzanillo olives were prepared in the usual manner and were placed in 44° salometer brine in three 5-gallon kegs. One keg was stored at room temperature 65-70° F, one in an incubator at 85° F, and one at 90-92° F. The rates of acid forma- tion were determined by frequent titrations. The results are given graphically in figure 5. 18 University of California — Experiment Station Fermentation proceeded very rapidly at both 85° and 90° F but at 90° F the olives at the end of the incubation period had developed numerous white wax-like spots beneath the skin and were less desir- able in flavor than those held at 85° F. After the 26th day the acidity decreased at 90° F, probably because of growth of organisms destruct- ive to lactic acid. At the end of the incubation period, 46 days, the brine in the keg at room temperature was still considerably below that at 85° F in acidity. All three kegs were then stored at room tem- perature. Acid loss in keg 3 ceased and kegs 1 and 2 eventually attained approximately the same total acidity of .63 to .65 grams per 100 cc. Many other fermentation tests were made in the laboratory with results similar to those reported above. Factory Experiments. — During the 1924-25 season it was found that the fermentation of olives in barrels stored in the sun had prac- tically ceased by mid-November. Approximately 50 barrels were then stored for two months in a room held at 70°-75° F by means of several small kerosene stoves and small electrical heaters. Acid for- mation during this period was fairly rapid, the increase being approx- imately .2 grams per 100 cc in most of the barrels. During subse- quent storage at factory temperature acid formation practically ceased until the natural rise in temperature during the spring. During the 1925-26 season 187 barrels, and during the 1926-27 season 145 barrels, were incubated in the factory at Visalia with beneficial results. Unfortunately, no non-incubated barrels were held under observation. However, it was observed that fermentation had ceased in the barrels stored in the open by November 15 and that it resumed rapidly under incubation at about 70°-75° F. The incuba- tion period was approximately two months for each of the two years. The room used for incubation was large enough to hold about 300 barrels placed on their sides and stacked two high. A low ceiling of beaver board at about seven feet from the floor reduced heat loss. During the 1925-26 season the barrels were stored on end and during the 1926-27 season on the side. The room was heated by an apartment house size Hall gas furnace installed near the center of the room. The air was warmed by passing upward over heated pipes. Air circulation was obtained by natural draft. The products of combustion escaped through a stove pipe. It was found that when the products of combustion were permitted to remain in the room " sweating" of the barrels was excessive from condensation of moisture generated by the burning gas, "Sweating" caused rusting of the hoops, growth of mold on the staves, and dis- Bul. 498] Pickling Green Olives 19 coloration of the wood. In spite of removal of products of combus- tion by the stove pipe the unavoidable decrease in temperature during the night caused condensation of moisture vapor from the air and some sweating of the barrels. A larger furnace, or two of the size used, would have permitted more uniform temperature regulation. It would have been advisable also to have coated the barrels and hoops with shellac or other moisture-proof coating. The cost of the furnace used was $70 and of gas to maintain an average temperature of 75° F, about $1.00 a day at the industrial rate prevailing at that time. If the room had been filled to capacity, 300 barrels, the cost of gas would have been about 20 cents a barrel or % cent a gallon for the two months incubation period. It was found that temperatures taken early in the morning about 20 feet from the heater and about 3% feet above the floor varied from 50° F to 73° F, and in mid-afternoon from 68° F to 85° F. Temperatures of the brine and olives taken at a depth of about 10 inches below the barrel bung varied from 68° F to 75° F depending on proximity of the barrels to the heater. During the 1929 season, four 25-gallon barrels of Sevillano olives were allowed to ferment in the sun at the Corning Olive Growers factory, and four at the Glick Brothers factory. Owing to the warm sunshiny weather prevailing in November and December that year the fermentation in all of these barrels proceeded satisfactorily. Most of the olives were ready for marketing before March 1, 1930. At Long Beach it was found by the Curtis Corporation in 1926 that green olives fermented satisfactorily in the sun during the fall, winter and spring months. The Adams Olive Company at Sunland stores the barreled green olives at Porterville for several months and transfers them to Sunland during the winter or early in the spring where they are stored in the sun for completion of fermentation. Very little fermentation occurs during storage at Porterville. Numerous titrations have showed that fermentation in most of the barrels is completed during the ensuing summer. The following acid determinations made on July 1, 1929, on samples of the 1928 season are typical: brines from barrels of Sevillano olives, acidity as lactic, .58, .91 and .86 per cent ; brines from barrels of Manzanillo olives, .57 and .90 per cent. Dextrose sugar (Cerelose) had been added to the two barrels of Manzanillos. Olives that had been ' ' cut ' ' rather deeply with lye and treated with dextrose were ready for sale before August 1 of the following summer; those that were "cut" less deeply were still some- what bitter and improved in quality with further storage in the sun. 20 University of California — Experiment Station Conclusions Regarding Incubation. — In view of the extra cost and care required for artificial incubation of the barrels and since expe- rience and experiment have proved that satisfactory fermentation can always be secured in the sun during' the spring and summer, it is recommended that most of the pack for any given factory be allowed to ferment in the sun. Only such portion of the pack as is required for early delivery need be artificially incubated. Thus a relatively small incubation room, heated at little cost would suffice. Also any olives for early delivery, in order to avoid excessive bitter taste, should be "cut" more deeply with lye than when they are to be allowed to ferment ten to twelve months before sale. EFFECT OF ADDITION OF STARTER ON FERMENTATION It is desirable that the fermentation of green olives begin promptly after barreling and brining. However, experiments reported in Bulletin 368 6 show that lye treatment destroys most of the microor- ganisms present, including lactic acid forming bacteria. The barrels used for green olives are generally new and the well water used in most factories is relatively free .of microorganisms. Consequently there probably will be very few lactic acid bacteria in the brine to initiate fermentation. In a number of small scale laboratory experiments in which no starters were used green olives failed to undergo lactic acid fermenta- tion but instead, merely molded and putrefied. In several barrels of olives in factory tests the brine became slimy from growth of slime forming bacteria. Many other fermentations were very ineffi- cient, that is, the fermentable sugars were destroyed with formation of much less than the theoretical amount of lactic acid. Starters of yeast and bacterial cultures are used very generally in the fermenta- tion and dairy products industries. It was believed that a starter would be beneficial also in the fermentation of green olives. Accordingly in factory tests, from one pint to one-half gallon of brine from imported Spanish olives or that from a barrel of good quality California green olives was added as a starter to each of a number of 50-gallon barrels of olives. Similar experiments were conducted in the laboratory. The results from several experiments are given in table 7. « Cruess, W. V., and E. H. Guthier. Bacterial decomposition of olives. Cali- fornia Agr. Exp. Sta. Bui. 368:1-16. 1923. Bul. 498] Pickling Green Olives 21 TABLE 7 Effect of Addition of Starter on Acid Formation Experiment Length of fermentation period, days Acidity of brine as grams lactic per 100 cc 150 150 60 60 60 60 30 30 30 30 44 44 .20 Manzanillo, barrel. Spanish brine starter .36 .10 30 .34 Manzanillo, quart jar. Spanish brine starter .25 Sevillano, quart jar. No starter .22 Sevillano, quart jar. Spanish brine starter .32 Manzanillo, quart jar. No starter .22 .25 .45 £0 In most cases acid formation was more rapid in the inoculated than in the non-inoculated brines. The brine used for inoculation should come from olives of normal odor and flavor and as nearly free as possible from mold and film yeast. The addition of brine heavily contaminated with film yeast would naturally do more harm than good. ACIDIFICATION OF THE BRINE Addition of acid to the brine of green olives was made experi- mentally at two stages of the process; first before fermentation in order to neutralize traces of remaining lye and to promote the growth of lactic acid bacteria; and, secondly, after fermentation in order to prevent spoilage of olives of low acidity. Acidification Before Fermentation. — The results of several experi- ments made to ascertain the effect of acidification of the brine before fermentation are given in table 8. TABLE 8 Effect of Acidification of the Brine Before Fermentation Treatment Period of fermentation in days Acidity as grams lactic per 100 cc Manzanillo, quart jar. Not acidified . 44 44 38 38 38 38 12 12 200 200 20 Manzanillo, quart jar. Acidified with .25 gram acetic acid per 100 cc Ascolano, quart jar. Not acidified .30 15 Ascolano, quart jar. Acidified with .2 gram lactic acid per 100 cc Sevillano, quart jar. Not acidified .10 38 Sevillano, quart jar. Acidified with .2 gram lactic acid per 100 cc... .58 Manzanillo, 50-gallon barrel. No acid 07 Manzanillo, 50-gallon barrel. Acidified with 1 gallon cider vinegar of 4.5 per cent acid 18 Manzanlillo, 50-gallon barrel. No acid 18 Manzanillo, 50-gallon barrel. Acidified with \ gallon cider vinegar of 4.5 per cent acid .49 22 University of California — Experiment Station In most experiments the acidity of the acidified brines increased more rapidly than of the non-acidified brines and the quality of the pickled olives was usually better. Both vinegar and lactic acid were found suitable for acidification ; the vinegar taste noticeable soon after addition disappeared quickly. Acidification After Fermentation. — In several factories barrels of green olives were not filled frequently enough with brine during storage to prevent growth of film yeast, with consequent loss of acid. Several such barrels of olives lost practically all of their acid and spoiled. Others were saved by adding vinegar or lactic acid and others by adding dextrose sugar which was fermented to increase the acidity. Several experiments in which sugar was added are described TABLE 9 Effect of Addition of Acid to Green Olives After Fermentation Acidity as grams lactic per 100 cc. Treatment 1 month after treatment 2 months after treatment 3 months after treatment Observations at end of experiment Untreated One quart 100-?rain distilled vinegar to 10-gallon keg.... 3/£ pint lactic acid at start; and y 2 pint at end of first .25 f .68 \ .33 .28 .57 .47 .35 .60 \ .63 Color rather gray. Flavor lacks acidity. No perceptible vinegar taste. Better than untreated. Satisfactory. elsewhere. Three 10-gallon kegs were filled with olives in which fer- mentation was complete and in which, the acidity had decreased to near the spoiling point, were treated as shown in table 9. The addition of vinegar and of lactic acid both gave satisfactory results in this test. In the factory at Visalia it was found necessary to add vinegar to most of the barrels that remained unsold during the summer months because leakage through the large head bungs had permitted growth of film yeast with loss of acid. On June 1, the acid had decreased to very nearly the spoiling point; in six typical barrels the acidity was .25, .13, .31, .24, .10, and .06 per cent respectively as lactic acid. One gallon of 100 grain distilled vinegar was then added to each of the barrels then on hand. Two months later the treated olives were in fair to good condition, and the few barrels of untreated olives had spoiled. The acidity of the six barrels previously mentioned were early in September .36, .40, .40, .36, .33, and .27 per cent respectively. Bul. 498] Pickling Green Olives 23 A second addition of one gallon of vinegar per 50-gallon barrel was made at that time with good results. The acidity of the treated olives was maintained above .3 gram of lactic per 100 cc in most barrels; that of the untreated olives dropped to the spoiling point and the olives were lost. For the first two to three weeks after addition of the vinegar the olives tasted rather strongly of distilled vinegar. Two months after its addition the vinegar taste had disappeared. Lactic acid did not change the flavor of the olives but its cost is higher than for the equivalent quantity of vinegar. EFFECT OF ADDED SUGAR ON FERMENTATION OF GREEN OLIVES In experiments made during the 1924 season and from analyses of green olive brines from the Adams Olive Company, it was found that the concentration of acid developed in brines of green olives pre- pared in California was much below that formed in Spanish green olive brines. TABLE 10 Effect on Acid Formation of Addition of Sugar to Manzanillo Olives Before Fermentation Acidity of brine as grams lactic per 100 cc Sample April 27, 1928 October 15, 1928 December 21,* 1929 I. 25-gallon barrel. Two per cent Cerelose sugar added .42 .25 .15 .20 .95 .60 35 .18 .60 II. 5-gallon barrel. One per cent Cerelcse sugar added .40 III. 5-gallon barrel. One per cent lactose (milk sugar) .20 .10 * On October 15, 1928, the olives were placed in jars, fresh brine added and the jars sealed and stored at room temperature. This treatment accounts fcr the decrease in acidity between October 15, 1928, and December 21, 1929. The analyses given in table 2 show that much of the fermentable sugars and mannite is lost during lye treatment and subsequent washing. These analyses together with the observations made in the following experiments indicate that lack of fermentable material is the most important limiting factor in acid formation. Sugar Added Before Primary Fermentation. — In an experiment made in cooperation with Libby, McNeill and Libby Company during the 1927 season, Manzanillo olives of Extra Large size were treated 24 University of California — Experiment Station with lye, washed free of lye, and. then shipped in brine of 44° salo- meter in a 50-gallon barrel to Berkeley. The fermentable material in the olives after washing" to remove lye was 2.87 per cent. At Berkeley the olives and brine in which they were shipped were divided among four barrels and treated as shown in table 10. The barrels were stored in a warm room and acid determinations were made at intervals. On October 15, 1928, the olives were packed in glass containers in freshly prepared brine of 30° salometer. The effect of addition of dextrose sugar (Cerelose) was very striking. Thus, the olives from barrel I on October 15, 1928, were firm, of bright golden yellow color and of excellent flavor. Two per cent of dextrose sugar was added to the brine in this barrel. Those in barrel II, which had received one per cent of dextrose sugar, were satisfactory but not quite equal to those of I in flavor and color. The olives in barrel III were not sufficiently acid in taste and were rather gray in color indicating that lactose sugar was not well utilized. Those in barrel IV were decidedly gray in color; many were soft and the flavor was very poor. After packing in fresh brine in vacuum sealed jars and storing for 14 months the differences in quality were still more pronounced. Most of the olives from IV had become soft and had developed a decidedly rancid odor. A number of other experiments made to determine the effect of addition of sugar confirmed the results reported above. EFFECT OF ADDITION OF SUGAR IN FACTORY EXPERIMENTS During the 1929 season green Sevillano olives were prepared for fermentation in the usual manner at the Maywood Olive Company, at Corning, with the assistance of G. A. Pitman and E. Hazen. The olives were then filled into 10-gallon paraffin-lined spruce kegs ; brine of 36° to 44° salometer was added and the kegs were shipped to Berkeley. Additions of Cerelose sugar and of green olive brine starter were made to some of the kegs. After arrival at Berkeley the kegs were stored at 75° to 80° F. In this experiment as in those made on a large scale with Manza- nillo olives the addition of Cerelose sugar increased the concentra- tion of acid formed in the brine. However, some of the Sevillano olives in the kegs to which sugar had been added developed ''gas pockets" ; this defect was less common in the untreated olives. Appar- ently, however, gas pocket formation was due principally to use of too strong a lye solution. While some of the olives were somewhat Bul. 498] Pickling Green Olives 25 too sour for table use direct from the keg they were satisfactory a few days after packing in fresh 30° salometer brine in glass contain- ers. All of the olives were satisfactory in color, texture and flavor. The Adams Olive Company of Sunland, California, has for many years prepared olives by the Spanish process and marketed them successfully in southern California, Acid determinations were made on brines from a number of barrels in storage at the factory in 1925, 1926 and 1927. It was then suggested that sugar be added to several barrels of low acidity in which fermentation had apparently ceased. Increase in acidity followed and the olives were much improved in flavor and general quality by the secondary lactic fermentation. During the following season, 1928, Cerelose, that is, commercial corn sugar, was added to most of the barrels prepared by the Adams Company at the time of barreling, before fermentation. Unfortunately very few untreated barrels were retained as checks. Acid formation in the treated barrels was rapid and reached a much higher average than in previous years. In previous years also loss from bacterial spoilage had been appreciable but it is reported that no barrels of olives to which sugar has been added have been lost by spoilage. The company has found that Sevillano olives often do not require the addition of sugar. At various times acid determinations have been made at the Adams factory on brines from untreated and treated barrels. The average acidity, as lactic, of brines from barrels of olives to which no sugar had been added was .38 per cent; that of brines to which dextrose sugar (Cerelose) had been added was .73 per cent. The minimum acidity of untreated brines was .18 per cent and of treated brines .50 per cent. The maximum acidities were .58 and .91 per cent respectively. From 3 to 5 pounds of sugar were added to each 50-gallon barrel; in most cases 3 pounds was found sufficient. The sugar was added before fermentation. In an experiment made in 1926 in cooperation with Mr. J. T. Curry and J. P. Scherb of the California Olive Growers Association in the factory of the California Cooperative Canneries at Visalia, 5 pounds of Cerelose sugar was added to a 50-gallon barrel of Manzanillo olives before fermentation. No sugar was added to the remaining 144 barrels. The barrels were stored in a warm room. On January 4, after 2% months fermentation the brine of the barrel to which sugar had been added contained 1.16 grams of acid as lactic per 100 cc whereas the acidities of brines of four untreated barrels were .48, .44, .44 and .42 grams of acid per 100 cc. None of the 144 untreated 26 University of California — Experiment Station barrels possessed acidities above .6 grams per 100 cc of brine. The flavor, color and general quality of the treated olives were superior to those of the untreated. Sugar Added After Primary Fermentation. — A number of experi- ments were made on this point but in order to conserve space only two will be presented. In a laboratory experiment 50 gallons of Manzanillo olives pre- pared during the 1927 season were shipped to Berkeley late in May, 1928. Fermentation had practically ceased, analysis showing the olives and brine to contain less than .1 per cent of fermentable mate- rial. The olives were transferred to 10-gallon kegs and treated as indicated in table 11. The kegs were stored in a warm room (75° to 80° F). TABLE 11 Effect on Acid Formation of Addition of Cerelose Sugar to Manzanillo Olives After Fermentation Has Ceased Keg and treatment Total acidity as lactic, grams per 100 cc June 4 June 23 July 26 .25 .47 .38 .28 .76 .64 35 *4. 1 pound Cerelose to 10-gallcn keg, May 8, 1928 1 05 .70 " Acidity at time of addition of sugar .27 per cent in all samples. In addition. to being much higher in acid, the olives in keg 4 were much superior in color and flavor to those in keg 1. The olives in keg 5 were intermediate between the other two in flavor and about equal to those in number 4 in color. Some of each was packed in fresh brine in vacuum sealed glass jars. One year later the olives from keg 1 had become gray in color and were too low in acid to be palatable. Those from kegs 4 and 5 were satisfactory in every respect, although those from number 4 were somewhat superior to those of number 5. A large scale factory experiment was made in cooperation with C. W. Hutton at Palermo during the 1925-26 season, who treated enough Sevillano and Ascolano olives, about equal amounts of each, to fill 120 50-gallon second hand olive shipping barrels. He placed the barrels in a well sealed room and maintained the temperature at 75° to 80° F by means of a large stove. Fermentation was rapid but ceased about December 13. There was no increase in acid between the sampling dates of December 13, Bul. 498] Pickling Green Olives 27 1925, and January 13, 1926. It was suggested that 2 pounds of Cerelose sugar be added to each barrel. This was done on January 15. On February 15, titrations of brine samples showed that fer- mentation had been resumed with marked increase in acid. A further addition of 2 pounds of Cerelose was made to many of the barrels. On January 13, the average acidity was .34 grams per 100 cc and on February 15, one month after addition of sugar, it had increased to an average of .45. Several samples to which a total of 4 pounds of sugar per 50-gallon barrel were added, were found to contain in excess of .75 grams acid as lactic per 100 cc. All of the olives were disposed of successfully. A quart jar of Ascolano olives from one of the barrels was taken to Berkeley on December 22. To the brine was added 2 grams of pure dextrose sugar per 100 cc and the jar was stored at 85° F in an incu- bator. At intervals acid determinations were made and dextrose was added on the following dates : December 22, 2 grams per 100 cc ; February 28, 1 gram per 100 cc ; March 17, 2 grams per 100 cc ; and May 8, 1 gram per 100 cc. The acidities on dates of titration were : December 22, .12 per cent ; January 10, .40 per cent ; February 28, .48 per cent ; March 17, .63 per cent; March 26, .77 per cent; May 8, .81 per cent and July 8, 1.12 per cent. EFFECT OF FILM YEAST AND MOLD ON ACIDITY The flavor and keeping quality of green olives depend in very marked degree on the acidity of the brine. The experiments proved that the film yeast often found on the brine in incompletely filled barrels of olives or in open containers rapidly destroys the acid and if unchecked will reduce the acid to the point where spoilage occurs. Blue Penicilliiim mold also was found to destroy the acid of the brine about as rapidly as the film yeast. The results given in table 12, are typical of all the experiments made to determine the effect of mold and film yeast on the acidity of green olives. The olives in the open jar became soft and spoiled in about a month ; those in the open keg became moldy in taste within two months and were soft and unfit for use after 80 days. Those in the sealed jar and sealed keg kept perfectly. The acidity in these two containers increased by fermentation until the forty-second day ; film growth in 28 University of California — Experiment Station the small head space created by removal of brine samples for analysis caused a slight decrease toward the end of the storage period. Pure cultures of a Mycoderma (film yeast) and a Penicillium (blue mold) destroyed most of the acid in olive brine in flasks plugged with cotton in less than 30 days at room temperature. In commercial experiments the acidity of the brine decreased rapidly when the barrels were not filled frequently owing to growth of film yeast when the level of the brine dropped sufficiently to give a fairly large liquid surface. The acidity remained constant or decreased only very slowly in well filled, sealed barrels. TABLE 12 Effect of Film Yeast and Mold on Acidity Acidity as grams lactic per 100 cubic centimeters Time in days Sealed jar Open jar Sealed 10-gallon keg Open 10-gallon keg .76 .76 .96 .96 10 .76 .31 1 08 .83 16 .76 .13 1.20 .64 21 .81 .83 .09 .07 27 1.26 .65 35 .90 .88 .06 .04 42 1.35 .54 63 .76 .04 1.30 .36 60 .76 .04 1.27 .30 Experience of the past five years has demonstrated that failure to keep the barrels well filled and sealed has caused most of the spoil- age of green olives. A brine 28° to 30° salometer should be used in filling the barrels. Coating the barrels with varnish would undoubtedly reduce loss of moisture by evaporation and thus reduce the danger of spoilage by film yeast. PACKAGING EXPERIMENTS A number of experiments were made to determine the effect of type of container, composition of brine, method of sealing and of pasteurizing on the keeping quality of green olives. Manzanillo and Sevillano olives previously prepared experimentally in 25-gallon barrels were used in the packaging experiments. Dextrose sugar (Cerelose) had been added to these olives before fermentation and at the time of packaging the olives contained from 1.22 to 1.25 per cent acid as lactic. Bul. 498] Pickling Green Olives 29 Olives of each variety were packed in the following ways: in 8-ounce vacuum sealed Anchor jars in filtered brine of 28° salometer from original barrel; in 8-ounce vacuum seal Anchor jars with freshly prepared brine of 28° salometer; in 4-ounce wide mouth Crown cap jars with 28° salometer brine and sealed with lids contain- ing special liners; in 28° salometer brine in 8-ounce jars sealed with Phoenix composition gaskets and metal caps ; three lots packaged as in the three preceding experiments but heated in containers to 175° P before sealing; in 8-ounce vacuum sealed Anchor jars containing brine of 28° salometer to which .5 per cent lactic acid had been added ; 8-ounce vacuum sealed Anchor jars with brine containing .4 per cent acetic acid by addition of distilled vinegar ; 8-ounce plain tin cans with brine of 28° salometer, cans and contents heated 6 minutes in live steam and sealed hot; No. 2% enamel lined tin cans with brine of 28° salometer; and 8-ounce plain tin cans containing brine of 28° salometer and .4 per cent acetic acid by addition of distilled vinegar. At the end of two months' storage at about 85° F the contents of all containers were sound and none of the containers had developed gas pressure. The brine in unpasteurized containers showed consid- erable bacterial growth, resulting in the deposition of some white sediment of bacteria. The olives in the acidified brines were too sour in taste. After 15 months storage the jars of non-pasteurized olives con- tained a considerable deposit of white sediment (on the olives and on the bottom of the jar). The sediment was found to consist of bac- teria. The acetic acid prevented most of the sedimentation but made the olives too sour. The jars of pasteurized olives were nearly free of sediment. Practically all of the plain tin cans had developed a heavy pres- sure of hydrogen gas owing to corrosion of the tin plate. Half of the enamel lined cans had swelled, but the remaining cans were in good condition. The flesh of the olives that had been pasteurized was brown near the pit, and the flavor was ' ' cooked, * ' that is abnormal owing to the effect of the heat. Olives when taken from the tin containers, plain or enameled, soon became bluish-green in color because of oxidation of the dissolved iron to the ferric condition and reaction of the ferric iron with the tannin of the olives. The olives from the enameled cans showed much less of this discoloration than those from plain tin cans. 30 University of California — Experiment Station In a number of other canning experiments the cans swelled from formation of hydrogen gas generated by corrosion of the tin plate ; none of the cans kept beyond 12 months at 85° F. Mr. R. H. Lueck of the research staff of the American Can Com- pany reports 7 that green olives containing after canning less than .5 per cent acid kept well in cans, in their experiments. The process used was as follows : ' * The product is placed, preferably in a new brine, and closed at a temperature of 180° F or more. No process is necessary. The cans should be cooled after closing, and stored in a cool place to retard corrosion of the plate." Number 10 cans of Fig. 6. — Glass containers of olives illustrating the more common caps and seals. Back row, left to right: (1) "Press on" cap; (2) Phoenix Hermetic Vac- uum Band cap; (3) Hazel Atlas aluminum " tar-off' ' cap; (4) Goldy "tear-off" cap, and (5) cork, used commonly for Spanish bottled olives. Front row, left to right: (1) screw top with paraffined cardboard lining; (2) Anchor vacuum cap; (3) Crown cap; (4) Amerseal screw cap with lacquered paper lining; and (5) glass top Atlas E-Z seal jar. olives canned by the American Can Company have been examined in the Fruit Products Laboratory and the olives found to be in excel- lent condition. However, number 10 cans naturally corrode less rapidly than the smaller cans used in our experiments. For this reason the number 10 cans are still under observation. Glass top jars were found to be satisfactory for green olives and would be suitable for farm packaging of green olives for local sale. Zinc tops on Mason jars corroded badly and much of the zinc dissolved 7 Communication by letter from R. H. Lueck. Bul. 498] Pickling Green Olives 31 in the brine. However, lacquered tin and. aluminum tops were satis- factory. In figure 6 is illustrated ten common kinds of jar closures. In several experiments screw-top 4-ounce jars permitted slow evaporation of the water from the brine. The olives kept well for 6 months at room temperature but at the end of 12 months sufficient head space to permit mold growth had developed. At 18 months many of the olives had spoiled. Larger jars of this variety are, how- ever, in commercial use and appear to be satisfactory. One-gallon wooden kits, such as are used for vinegar pickles, were found unsatisfactory as retail packages for green olives. The lids were not tight enough to prevent evaporation of moisture so that a head space soon formed with growth of mold and film yeast. In prac- tically all experiments green olives stored in these containers spoiled within six weeks. In a typical test the acidity of the brine of Manza- nillo olives in a. 1-gallon wooden kit decreased from .30 to .10 grams per 100 cc in four weeks and had become so moldy that the olives were unfit for food. OBSERVATIONS ON SPOILING AND DETERIORATION OF GREEN OLIVES Bruising. — Olives may be rendered unfit for green pickling by bruising of the fresh fruit. The brown color from bruises does not disappear and is very prominent on the pickled fruit. After lye treatment green olives will not discolor from bruising. Darkening of Color by Exposure. — Olives unduly exposed to air during lye treatment or washing become permanently gray or brown in color and of greatly reduced commercial value. "Gas Pockets" and "Bloating." — During the initial stages of fermentation gas forming organisms occasionally develop in the olives and evolve gas so rapidly that large blisters and air pockets are formed. Sevillano olives are more susceptible than other varieties to this kind of spoilage. The addition of dextrose sugar before fermen- tation has been proven to aggravate this condition in Sevillano olives. Very dilute initial brine also favors it (see fig. 7). Observations by Pitman showed that olives treated with strong lye (2 per cent and 2.47 per cent) blistered and developed gas pockets to a much greater degree than those treated with a lye of moderate strength (1.58 per cent). In two 10-gallon kegs of Sevillano olives treated with 2.47 per cent lye more than 25 per cent of the olives developed gas pockets ; in two other kegs of the same lot of olives treated with 1.58 per cent lye less than 5 olives per keg developed gas pockets. 32 University of California — Experiment Station Softening and Decomposition. — During storage if the brine is too weak, e.g. below 24° salometer, bacteria that produce a "rancid butter" odor are apt to develop or the olives may soften through bacterial action, particularly if the acidity is low. As stated elsewhere if the barrels are not kept well filled, film yeast and mold will develop, destroy the lactic acid and make condi- tions favorable for putrefaction. Mold also imparts a moldy taste to Fig. 7. — "Gas pockets" in Sevillano olives; note line of cleavage. the olives rendering them inedible or of very poor flavor. Also, as recommended elsewhere, if the acidity of the brine becomes low during storage it is advisable to increase it by addition of dextrose sugar and fermentation, or by addition of distilled vinegar or lactic acid. Sediment. — A white sediment often occurs in glass packed green olives. Microscopical examination has proved that the sediment in most cases is composed of bacteria. According to Ayers 8 if the con- tainers are not completely filled or not well sealed much of the sedi- s Ayers, S. H., H. A. Barnby and E. L Voiglit. Clouding of olive brine. The Glass Container, 7(10) :5-7. 1928. Bul. 498] Pickling Green Olives 33 ment may be film yeast that has formed on the surface and has set- tled. He recommends vacuum sealing or complete filling of the jar to exclude air, or pasteurization at 130° as preventive measures. Safety of Deteriorated Green Olives. — Unless the olives have acquired a disagreeable odor they are probably non-injurious to the consumer, even if they may have become somewhat abnormal in color, or show blisters. However, in commercial practice defective olives are removed by sorting and do not reach the consumer. The packer should discard all barrels of olives that have softened or developed a foul odor. In order to reduce sedimentation, Mullen 9 recommends that the brine from the barrels be heated with a decolorizing carbon and fil- tered in a filter press, the filtered water-white brine then to be used in the filling of bottles of green olives. He claims that such brine retains much of its original and desirable flavor and is superior to plain brine in preventing bacterial growth and formation of sediment in the bottles. However, in experiments in this Laboratory, it was found that filtered but not decolorized brine permitted vigorous bacterial growth and formation of a large amount of sediment. OIL CONTENT OF GREEN OLIVESio Ten samples of representative brands of imported green olives and fifteen samples of green olives pickled by the Spanish process in California were analyzed for acidity and oil content. The average oil content of the imported Sevillano olives was 11.73 per cent; of the California Sevillanos, 9.65 per cent; of imported Manzanillo olives, 14.28 per cent; and of California Manzanillo olives, 15.98 per cent. RECOMMENDED PROCEDURE FOR PREPARING AND PACKAGING GREEN OLIVES The following outline is purposely brief ; discussion of the various steps will be found elsewhere in this publication. Picking. — Pick all varieties after they have reached full size but free of pink or red color. Avoid bruising. Use the fruit as promptly after picking as possible. 9 Mullen, G. W. Secondary fermentation in olives. The Glass Packer, 2(12) : 497-500. 1929. io From analyses made by G. A. Pitman of the Fruit Products Laboratory. 34 University of California— Experiment Station Grading. — Grade for size it* a grader thai will doI bruise the olives is available. Otherwise merely sort to remove overripe, bruised and blemished olives and reserve size grading until after pickling. Lye Treatment. — Prepare, for .Manzanillo. .Mission and Barouni olives, a 1.75 to 2 per cent lye solution i.-siin<_ r 11 12 salometer or 234 to 3° Baume at 60°-70° F. For Sevillano and Ascolano olives use a lye of about 1.60 per cent or D'j salometer to minimize blis- tering. The lye required ranges from about - to 2*4 ounces of flake lye per gallon of water. Place the prepared solution on the olives either in ordinary olive pickling vats or in barrels. Stir occasionally. Remove samples frequently and observe depth of lye penetration on the cut surface. When the lye has penetrated half-way to the pit in Sevillanos and Ascolanos, or two-thirds to the pit in Manzanillo, Mis- sion and Barouni olives, remove it. Washing. — Immediately cover with cold water. Let it stand 2-3 minutes and discard it. Repeal this rinsing three times, finally leav- ing the olives covered with fresh water. Change the water every three hours until most of the olives when cut with a knife and treated with a drop of phenolphtbalein solution show no pink or red color. A few of the olives may show some color with phenolphthalein with- out harm to the product. Thirty to thirty-six hours washing should be sufficient. Brining. — Put the olives into oak barrels, after removal of one head. Head up the barrels, drive the hoops and fill at once with brine. Avoid undue exposure to air. Oak barrels with side bung only should be used. For Manzanillo, Mission and Barouni olives use a brine of 44° salometer; for Sevillano and Ascolano one of 20° salometer. For the last two varieties "build up" the brine at 2-day intervals about 5° salometer at a time until the brine will remain permanently at 28°- 30° salometer. If the brine on other varieties drops below 28° salo- meter, increase it to 28°-30° by addition ©f salt. Addition of Sugar.— To each 50-gallon barrel of Manzanillo and of Mission olives add 3 pounds of dextrose sugar, such as Cerelose, dissolved in 1 or 2 gallons of the brine. Add no sugar to other varie- ties at this time. Care During Fermentation,— Store the barrels on their sides in the open in the sun, preferably against the southern wall of a build-, ing so that they will receive all the sunshine possible. Insert the side bung loosely ; do not at this time drive it. Two or three times a week Bul. 498] Pickling Green Olives 35 during the first three to four weeks open the bungs and fill the barrels to overflowing with brine of 28° salometer. After the active gaseous fermentation has ceased, usually in 3 to 4 weeks, drive the bungs in place moderately tightly. Remove the bungs once a week and fill with 28° salometer brine. During the cold winter months it may not be necessary to fill more fre- quently than once in 10 to 14 days. During the following spring and summer, fermentation will resume and run to completion. Occasionally titrate the brine to determine its acidity. If during the spring or summer the acidity ceases to increase before a total acidity of .9 to 1 gram per 100 cc is attained, add dextrose sugar, normally 3 pounds per 50-gallon barrel. If after 6-8 weeks fermentation in warm weather this fails to give the desired acidity, add more of the sugar. In exceptional cases it may become necessary to add one-half to one gallon of 100-grain distilled vinegar per barrel to olives that are very low in acid. Sevillano, Barouni and Ascolano olives, normally should receive no sugar until spring or early summer for reasons given elsewhere. During storage, test the salometer degree of the brine frequently and adjust it to 28°-30° salometer, when necessary, by the addition of salt or water as required. Packaging. — When the olives have developed .9 or more grams acid per 100 cc and the flesh has lost its chalky white, "raw" color and has acquired the well known Spanish green olive flavor the olives are ready for sale or for packaging for the retail trade. If the olives have not been size graded previously, grade them at this time. Sort them carefully and pack into jars. If the olives are to be placed in jars according to a definite pattern, long slender wooden or bronze tongs should be used. For a "jumble" or "throw" pack, the olives are filled into the jars without regard to placing. Fill the jars of olives with water and turn them upside down to drain ; if one rinsing does not remove all adhering white sediment of bacteria, etc., repeat the rinsing. Drain well. Then fill the jars completely with a fresh brine of 30° salometer and seal. Jars to be sealed in vacuum are filled in the above manner and sealed by a special machine. The Crown cap (similar to a soda water cap) and the Goldy Seal (an aluminum cap commonly used for jars of pickles), are also applied by special capping machines without vacuum. 36 University of California — Experiment Station Corks are now used less commonly than formerly in America, by green olive packers. If the olives are deficient in acid, that is, if the original brine contains less than .5 grams of acid as lactic per 100 cc, pure, edible lactic acid should be added to the fresh brine at the rate of % to % ounce per gallon of brine, or distilled 100-grain vinegar should be added at the rate of 3 to 5 ounces per gallon of brine. TABLE 15 Kelation Between" Baume Degree and Salometer Degree Per cent salt (Also approxi- mately Baum6 degrees) Salometer degree Ounces salt per gallon 1 3 8 1.3 2 7.6 2.6 3 11.3 4 4 15 1 5 3 5 18 9 6.7 6 22.6 8 1 7 26.4 9.6 8 30 2 11.1 9 34 12.7 10 37.7 14 2 11 40 5 15 8 12 45.3 17.5 13 49.1 19.1 14 52.8 20.8 15 56.6 22.6 16 60.4 24.4 17 64.2 26.2 18 68 28.1 19 71.7 30 20 75.5 32.0 21 79.2 34 22 83 36.1 23 86.8 38.2 24 90 6 40.4 25 94.3 42.7 26 5 100 46 1 USE OF HYDROMETERS The Baume hydrometer indicating approximately the per cent of salt and the salometer hydrometer indicating "per cent of satura- tion' ' are both very useful; one or the other is indispensable in pre- paring green olives. Four degrees salometer at low concentrations of salt are roughly equal to 1 degree Baume, but at high concentra- tions this relation does not hold very closely. The relationship is given in table 15. Bul. 498] Pickling Green Olives 37 In using" the hydrometer for preparing lye solutions and brines pour a sample of the solution into a tall cylinder in such manner that formation of bubbles is avoided. Insert the hydrometer and take the reading at the general level of the liquid, not at the top of the menis- cus (the meniscus is the curved surface extending up the stem above the general level of liquid). For testing the brines in barrels a long, slender metal cylinder with perforated bottom is very useful. This is inserted through the bung; liquid rises in it and floats the hydrometer which may then be read easily (see fig. 4). When the temperature of the brine or lye solution varies greatly from the usual standard temperature of 68° F a correction should be made in the hydrometer reading since low temperatures cause the indicated reading to be too high and high temperatures cause it to be too low. For practical purposes the following rule may be applied. For every 10° above 68° F add 0.2° Baume or 0.8° salometer to the observed reading and for each 10° below subtract a similar amount. Example : Observed reading 28° salometer at 59° F. Correction % x .8 or approximately .7 salometer. Corrected reading is 28° + .07 = 28.7°. In most California factories, except during the cold winter months, temperature correction will usually be unnecessary. Other "Standard" Temperatures. — Many hydrometers are stand- ardized for use at 60° F instead of 68° F. In correcting for tem- perature for instruments standardized at 60° F follow the rule given above but use 60° F as basis for calculation of correction. Thus if the reading is 30° salometer at 70° F, the correction is 10x.8 = .8. Corrected reading is then 30+ .8 = 30.8°. DETERMINATION OF ACIDITY It is necessary to determine the acidity of the green olive brine since acidity is the best index of progress of fermentation and of the keeping quality of the olives. For the convenience of those unfamiliar with the process, the following directions are added : Equipment and Solutions Needed. — The following equipment and solutions will be needed (see fig. 8). 1. A 50 cc burette graduated in y m cc divisions and fitted with a glass tip connected by a short piece of soft rubber tubing to the burette. A large pinch cock is fitted on the tubing. 38 University of California — Experiment Station 2. A 10 cc pipette. Several should be purchased as breakage may occur. 3. A ring stand and clamp to hold the burette. 4. Several glass tumblers. 5. Several glass stirring rods. t I Fig. 8. — Equipment used for titrating acidity of brines. A, burette ; B, burette stand ; C, pipette ; D, phenolphthalein indicator solution ; and E, glass tumbler and stirring rod. 6. A one-gallon bottle of tenth normal sodium hydroxide. 7. A small bottle of 1 per cent phenolphthalein indicator in dena- tured alcohol. The equipment and chemicals may be had from any chemical sup- ply house. Addresses of such firms can be obtained from farm advis- or's offices, or from the Fruit Products Laboratory, University of California. Bul. 498] Pickling Green Olives 39 Procedure. — (1) By means of a small hose or by inserting a pipette through the bung obtain a small sample of brine from near the center of the barrel. (2) Place the large end of the pipette in the mouth and draw the pipette full of the brine. Quickly place the index finger over the large end of the pipette and by gently releasing the pressure let the brine level drop exactly to the mark on the stem. Then let the 10 cc of the brine flow into a clean glass tumbler. (3) Add a little distilled water, possibly 40-50 cc. The exact amount is of no consequence. (4) Add 3-5 drops of the phenolphthalein indicator solution. (5) Fill the burette with the tenth normal alkali solution making certain that all air bubbles are removed from the tip and rubber tub- ing connection and that the tip is filled completely with the solution. Let enough solution drain from the burette to bring the level to or to any convenient number on the scale. (6) Allow the solution to flow slowly, a few drops at a time, into the tumbler; stop the titration (additions of hydroxide) when a permanent but rather faint pink color is obtained. If the solution turns a deep red permanently the titration has gone too far and must be repeated. (7) Take readings on the burette scale of levels of the hydroxide solution before and after titration and subtract one from the other. The resulting figure multiplied by 0.09 gives the grams of acid as lactic per 100 cc, that is, approximately the per cent of acid. Example : First reading 1.4 Second reading 9.3 9.3-1.4 = 7.9 7.9 x .09 = .711 grams acid as lactic per 100 cc. PRICES FOR GREEN OLIVES It is probable that competition with imported olives in the eastern United States would be keen and profits small in spite of the tariff on imported olives. The wholesale prices f.o.b. Chicago for March 4, 1930 11 varied from $1.50 a gallon for olives of 80 to 90 per kilogram (36 to 41 per pound) to $.50 a gallon for those counting 180 to 200 per kilogram (81 to 90 per pound). Allowing 25 cents a gallon for transportation and handling charges the gross returns f.o.b. Chicago based on the above prices 11 From quotations in the Canner, March 4, 1930. 40 University of California — Experiment Station would range from $1.25 a gallon for the largest Sevillano olives to 25 cents a gallon for the smallest listed Manzanillo olives. Based on a yield of 380 gallons of green olives per ton of fresh olives the gross return per ton would range from $95 to $465. The cost of pickling must be deducted. This includes cost of barrels (about 10 cents a gallon for oak barrels), lye, salt, labor, etc., probably a total of at least 20 cents a gallon. Therefore there would probably be very little profit in shipping the smaller sizes of green olives to the eastern markets. A large packer of imported green olives in San Francisco stated that it should be possible to realize on the average a price of 75 cents a gallon for green Sevillano olives of the sizes commonly used for ripe pickling, that is, Jumbo, Mammoth and Colossal sizes. He would make no estimate of possible returns from Manzanillo olives. How- ever, Manzanillo olives packed experimentally in 1925 and 1926 were sold wholesale for 60-75 cents a gallon, depending on the size. Retail prices in Berkeley at present, April, 1930, for green olives in glass are higher than prices of ripe olives in corresponding sizes of tin containers. SUMMARY 1. All commercial varieties of olives grown in California were found satisfactory for green pickling and ranked in suitability in the following order: Sevillano, Barouni, Manzanillo, Ascolano and Mission. 2. All varieties gave better results when picked full size, but still green to partial straw yellow, than when picked at full straw yellow to pink in color. 3. Olives stored in brine several weeks before use were found unsuitable for green pickling because of darkening of the color. 4. The lye concentration found best was from 1.7 to 2 per cent, or 10° to 12° salometer for the Manzanillo, Mission, Barouni and Ascolano; and 1.6 per cent or slightly less, for the Sevillano. .... 5. The depth of lye penetration found best was one-half to a scant two-thirds to the pit for Sevillano and Ascolano and full two- thirds to the pit for other varieties. 6. The time required for lye penetration varied with the size of the fruit, lye concentration and temperature but for a 2 per cent lye solution the time averaged about 5 hours for Manzanillo and about 6 hours for Sevillano olives under factory conditions. Bul. 498] Pickling Green Olives 41 7. The time required for washing lye from the olives sufficiently for barreling averaged about 30 hours but ranged from 20 to 48 hours, depending on depth of lye penetration, concentration of lye used, frequency of changing the wash water and the size of fruit. 8. Color formed by undue exposure during washing was per- manent and greatly decreased the commercial value of the product. 9. Olives stored in oak barrels were superior in flavor to those stored in paraffin-lined spruce barrels. Barrels with large head bungs leaked badly and permitted mold growth. Barrels with a single small bung on the side were found best, 10. For the Manzanillo, Mission and Barouni varieties the initial brine concentration found best was 44° salometer; but for Sevillano and Ascolano olives it was found desirable to first place a brine of 20° salometer in the barrels and to increase the salt content progressively and slowly to 28°-30° in order to avoid excessive shriveling. Brine of 44° decreased to 30° or less during fermentation. 11. Addition of a starter of active green-olive brine aided fermen- tation, as did also the addition of a small amount of vinegar or lac- tic acid. 12. Addition of dextrose sugar aided fermentation and resulted in increased acidity. By this means it was found possible to obtain any desired degree of acidity. 13. Elevation of the temperature to 70°-80° F during fermenta- tion proved beneficial but is unnecessary except for olives that are to be "cured" quickly for early marketing. Fermentation was found to proceed satisfactorily during October, early November and during the spring and summer months when the barrels were placed in the sun. 14. Film yeast and mold were found to destroy the acidity of the brine very rapidly and when their growth was unchecked spoilage ensued. Exclusion of air by keeping the barrels completely filled and sealed prevented their growth. 15. Several kinds of glass containers proved satisfactory. It was found necessary to fill them as completely as possible and to seal them tightly (unless vacuum sealed jars were used) in order to prevent growth of film yeast. Wooden 1-gallon kits permitted evaporation, mold growth and spoilage. Green olives kept well in cans for a few months but on exposure to air soon turned greenish blue in color. On prolonged storage the cans swelled from formation of hydrogen gas by action of the brine on the tin plate. 42 University of California — Experiment Station 16. The oil content of California green olives compared favorably with that of imported green olives. The green Manzanillo olives were considerably higher than the Sevillano and Ascolano in oil content. ACKNOWLEDGMENT Sincere thanks are due Mr. S. A. Kaloyereas of the Department of Agriculture of Greece for use of data obtained by him as a grad- uate student and research assistant in this laboratory in 1927, and to G. A. Pitman for results of oil determinations and observations on causes of blistering. It is desired to acknowledge also the coopera- tion of J. P. Scherb, J. T. Curry and C. E. Weikert, formerly of the California Olive Growers Association at Visalia; the Mt. Ida Olive Packing Corporation and the Wyandotte Olive Association of Oro- ville ; the A. Adams Jr. Olive Company of Sunland ; the Maywood Packing Company, Glick Brothers Packing Company and Corning Olive Growers Association of Corning; the Sylmar Packing Corpora- tion of San Fernando ; the Gifford Olive Company of San Diego ; and the Lindsay Olive Growers, for conducting factory experiments and in supplying fruit used in these investigations. STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION BULLETINS No. No. 253. Irrigation and Soil Conditions in the 408. Sierra Nevada Foothills, California. 409. 263. Size Grades for Ripe Olives. 277. Sudan Grass. 279. Irrigation of Rice in California. 283. The Olive Insects of California. 410. 304. A Study of the Effects of Freezes on Citrus in California. 412. 310. Plum Pollination. 313. Pruning Young Deciduous Fruit Trees. 331. Phylloxera-resistant stocks. 414. 335. Cocoanut Meal as a Feed for Dairy Cows and Other Livestock. 415. 343. Cheese Pests and Their Control. 416. 344. Cold Storage as an Aid to the Market- ing of Plums, a Progress Report. 418. 346. Almond Pollination. 347. The Control of Red Spiders in Decid- 419. uous Orchards. 348. Pruning Young Olive Trees. 420. 349. A Studv of Sidedraft and Tractor Hitches. 421. 353. Bovine Infectious Abortion, and Asso- 423. ciated Diseases of Cattle and New- born Calves. 425. 354. Results of Rice Experiments in 1922. 426. 357. A Self-Mixing Dusting Machine for 427. Applying Dry Insecticides and Fun- gicides. 428. 361. Preliminary Yield Tables for Second Growth Redwood. 362. Dust and the Tractor Engine. 430. 363. The Pruning of Citrus Trees in Cali- 431. fornia. 364. Fungicidal Dusts for the Control of 432 Bunt. 366. Turkish Tobacco Culture, Curing, and 433. Marketing. 367. Methods of Harvesting and Irrigation in Relation to Moldy Walnuts. 434 368. Bacterial Decomposition of Olives During Pickling. 435 369. Comparison of Woods for Butter Boxes. 370. Factors Influencing the Development of Internal Browning of the Yellow 435 Newtown Apple. 371. The Relative Cost of Yarding Small 43g and Large Timber. 373. Pear Pollination. 374. A Survey of Orchard Practices in the 4dy * Citrus Industry of Southern Cali- fornia. 380. Growth of Eucalyptus in California Plantations. 885. Pollination of the Sweet Cherry. 440. 386. Pruning Bearing Deciduous Fruit Trees. 388. The Principles and Practice of Sun- 444. Drying Fruit. 389. Berseem or Egyptian Clover. 445. 390. Harvesting and Packing Grapes in California. 446. 391. Machines for Coating Seed Wheat with 447. Copper Carbonate Dust. 392. Fruit Juice Concentrates. 448. 393. Crop Sequences at Davis. 394. I. Cereal Hay Production in California. 449. II. Feeding Trials with Cereal Hays. 395. Bark Diseases of Citrus Trees in Cali- 450. fornia. 396. The Mat Bean, Phaseolus Aconitifolius. 397. Manufacture of Roquefort Type Cheese 451. from Goat's Milk. 400. The Utilization of Surplus Plums. 405. Citrus Culture in Central California. 452. 406. Stationary Spray Plants in California. 453. 407. Yield, Stand, and Volume Tables for White Fir in the California Pine 454. Region. Alternaria Rot of Lemons. The Digestibility of Certain Fruit By- products as Determined for Rumi- nants. Part I. Dried Orange Pulp and Raisin Pulp. Factors Influencing the Quality of Fresh Asparagus After it is Harvested. A Study of the Relative "Value of Cer- tain Root Crops and Salmon Oil as Sources of Vitamin A for Poultry. Planting and Thinning Distances for Deciduous Fruit Trees. The Tractor on California Farms. Culture of the Oriental Persimmon in California. A Study of Various Rations for Fin- ishing Range Calves as Baby Beeves. Economic Aspects of the Cantaloupe Industry. Rice and Rice By-Products as Feeds for Fattening Swine. Beef Cattle Feeding Trials, 1921-24. Apricots (Series on California Crops and Prices). Apnle Growing in California. Apple Pollination Studies in California. The Value of Orange Pulp for Milk Production. The Relation of Maturity of California Plums to Shipping and Dessert Quality. Range Grasses in California. Raisin By-Products and Bean Screen- ings as Feeds for Fattening Lambs. Some Economic Problems Involved in the Pooling of Fruit. Power Requirements of Electrically Driven Dairy Manufacturing Equip- ment. Investigations on the Use of Fruits in Ice Cream and Ices. The Problem of Securing Closer Rela- tionship between Agricultural Devel- opment and Irrigation Construction. I. The Kadota Fig. II. The Kadota Fig Products. Grafting Affinities with Special Refer- ence to Plums. The Digestibility of Certain Fruit By- Products as Determined for Rumi- nants. II. Dried Pineapple Pulp, Dried Lemon Pulp, and Dried Olive Pulp. The Feeding Value of Raisins and Dairy By-Products for Growing and Fattening Swine. Series on California Crops and Prices: Beans. Economic Aspects of the Apple In- dustry. The Asparagus Industry in California. A Method of Determining the Clean Weights of Individual Fleeces of Wool. Farmers' Purchase Agreement for Deep Well Pumps. Economic Aspects of the Watermelon Industry. Irrigation Investigations with Field Crops at Davis, and at Delhi, Cali- fornia, 1909-1925. Studies Preliminary to the Establish- ment of a Series of Fertilizer Trials in a Bearing Citrus Grove. Economic Aspects of the Pear Industry. Series on California Crops and Prices: Almonds. Rice Experiments in Sacramento Val- ley, 1922-1927. BULLETINS— (Continued) No. No. 455. Reclamation of the Fresno Type of 465. Black-Alkali Soil. 466. 456. Yield, Stand and Volume Tables for Red Fir in California. 467. 458. Factors Influencing: Percentage Calf 468. Crop in Range Herds. 459. Economic Aspects of the Fresh Plum 469. Industry. 470. 460. Series on California Crops and Prices: Lemons. 471. 461. Series on California Crops and Prices: Economic Aspects of the Beef Cattle 474. Industry. 462. Prune Supply and Price Situation. 464. Drainage in the Sacramento Valley 475. Rice Fields. Curly Top Symptoms of the Sugar Beet. The Continuous Can Washer for Dairy Plants. Oat Varieties in California. Sterilization of Dairy Utensils with Humidified Hot Air. The Solar Heater. Maturity Standards for Harvesting Bartlett Pears for Eastern Shipment. The Use of Sulfur Dioxide in Shipping Graoes. Factors Affecting the Cost of Tractor Logging in the California Pine Region. Walnut Supply and Price Situation. CIRCULARS No. No. 115. Grafting Vinifera Vineyurds. 269. 117. The Selection and Cost of a Small 270. Pumping Plant. 276. 127. House Fumigation. 277. 129. The Control of Citrus Insects. 164. Small Fruit Culture in California. 278. 166. The County Farm Bureau. 178. The Packing of Apples in California. 279 203. Peat as a Manure Substitute. 212. Salvaging Rain-Damaged Prunes. 282. 230. Testing Milk, Cream, and Skim Milk for Butterfat. 284. 232. Harvesting and Handling California 287. Cherries for Eastern Shipment. 288. 239. Harvesting and Handling Apricots and 289. Plums for Eastern Shipment. 290. 240. Harvesting and Handling California 292. Pears for Eastern Shipment. 294. 241. Harvesting and Handling California 295. Peaches for Eastern Shipment. 296. 243. Marmalade Juice and Jelly Juice from Citrus Fruits. 298. 244. Central Wire Bracing for Fruit Trees. 245. Vine Pruning Systems. 300. 248. Some Common Errors in Vine Pruning 301. and Their Remedies. 302. 249. Replacing Missing Vines. 304. 250. Measurement of Irrigation Water on 305. the Farm. 307. 253. Vineyard Plans. 308. 255. Leguminous Plants as Organic Ferti- 309. lizers in California Agriculture. 310. 257. The Small-Seeded Horse Bean (Vicia faba var. minor). 311. 258. Thinning Deciduous Fruits. 312. 259. Pear By-Products. 261. Sewing Grain Sacks. 262. Cabbage Production in California. 313. 263. Tomato Production in California. 314. 265. Plant Disease and Pest Control. 315. 266. Analyzing the Citrus Orchard by Means of Simple Tree Records. A.n Orchard Brush Burner. A Farm Septic Tank. Home Canning. Head, Cane, and Cordon Pruning of Vines. Olive Pickling in Mediterranean Countries. The Preparation and Refining of Olive Oil in Southern Europe. Prevention of Insect Attack on Stored Grain. The Almond in California. Potato Production in California. Phylloxera Resistant Vineyards. Oak Fungus in Orchard Trees. The Tangier Pea. Alkali Soils. Propagation of Deciduous Fruits. Growing Head Lettuce in California. Control of the California Ground Squirrel. Possibilities and Limitations of Coop- erative Marketing. Coccidiosis of Chickens. Buckeye Poisoning of the Honey Bee. The Sugar Beet in California. Drainage on the Farm. Liming the Soil. American Foulbrood and Its Control. Cantaloupe Production in California. Fruit Tree and Orchard Judging. The Operation of the Bacteriological Laboratory for Dairy Plants. The Improvement of Quality in Figs. Principles Governing the Choice, Oper- ation and Care of Small Irrigation Pumping Plants. Fruit Juices and Fruit Juice Beverages. Termites and Termite Damage. The Mediterranean and Other Fruit Flies. 14m-10.*30