filf.?f* /I Htfcrxrg g * ^ # U. S. DEPARTMENT OF AGRICUL I i RE, BUREAU OF PLANT [NDU8TRY- BOLLBTLfl NO, 871 ts SOUK EFFECTS OF REFRIGER; ON SULPHURED AM) I X S U L- PHURED IIUI'S. BT W W. STOGKBERQEB, Physiologist, AND FI1ANK UAKAK, Chemical BiolOffitt, Drug Plant, PoitOnOUt-Plant, Phytiologioal, and Fermentation Investigations. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1912. U. S. DEPARTMENT OF AGRIC1 Ml RE. BUREAU OF PLANT INDUSTRY BULLETIN NO. 871 it 1. ■. \I . l.t i\\ V, | RM, SOME EFFECTS OF REFRIGERATION ON SULPHURED AND UNSUL- PHURED HOPS. BT TV. W. STOCKBEBGER, PhyaMagU*, AND FRANK ItAUAK. Chemical BiolOffitt, Drug-Plant, Poisonous-Plant, Physiological, and Fermentation Investigation*. "SsssSXnSra^ w vstrrvi, TOW: GOVFRNMF.NT PRINTING OFFICE. 1912. BUREAU OF PLANT INDUSTRY. Chief of Bureau, Beverly T. Galloway. Assistant chief of Bureau, William a. Taylor. Editor, J. E. Rockwell. Chief Clerk, James E. Jones. Drug-Plant, Poisonous-Plant, Physiological, and Fermentation Investigations. scientific staff. Rodney H. True. Physiologist in Charge. A. B. Clawson, Heinrich Hasselbring. C. Dwight Marsh, \V. W. Stockberger, and Walter Van Fleet, Physiologists. Carl L. Alsberg, H. H. Bartlett, Otis F. Black, H. H.. Bunzel, Frank Rabak, and A. F. Sievers, Chemical Biologists. W. W. Eggleston, Assistant Botanist. S. C. Hood, G. F. Mitchell, James Thompson, and T. B. Young, Scientific Assistants. Hadleigh Marsh, Assistant. G. A. Russell, Special Agent. 271 ADDITIONAL COPIES of this publication XL may be procured from the Supebintenb- ENt of Documents, Government Printing Office , Washington, D. C, at .1 cents per copy LETTER OF TRANSMITTAL U. S. I >i l'\ici mini OF A.GHK i 1 i 1 KB, l'.i i;i \i in Pl.w I [NDU8TBT, Ollli I m| I HI (ll III'. Washington, />. <.. September, 18, 1912. Sn:: I have tin- honor to transmit herewith and to recommend for publication a< Bulletin NO. -71 of the series oi this Bureau a manuscript by Dr. W. W. Stockberger, Physiologist, and Mr. Prank Rabak, Chemical Biologist, entitled "Some Effects of Refrigeration on Sulphured and Dusulphured Hop-." submitted by Dr. R. II. True, Physiologist in Charge of the Office of Drug-Plant, Poisi is-Plant, Physiological, and Fermentation Investigations. In this paper is discussed some of the changes which occur in im- portant constituents of hops under different conditions of storage and i comparison is made of the relative efficacy of certain methods for pn>\ enting undesirable changes in hop constituents. This bulletin shows thai both refrigeration and sulphuring retard changes in the volatile constituents oi imp- and that the determina- tion of the value of hops From the aroma varies according to indi- vidual preference for or dislike of one or the other of the aromatic constituents. The conclusions drawn from a comparison of valua- tions made from both physical and chemical standpoints will be of practical importance to all interested in the hop industry. Respect fully. 13. T. ( i W.l.uWAY. CkU ] of Bureau. Hon. .1 \mi> Wilson, St cretary of Agru idture. 271 3 Digitized by the Internet Archive in 2013 http://archive.org/details/effhopoOOunit C X T E N T S Paee. Introduction 7 Preparation of the hops studied 8 Physical changes in the hope in cold and in ordinary storage 8 Changes in the volatile constituents of hops in cold and in ordinar) storage 11 Changes ID the hop resins 1 > Physical and chemical valuation compared 16 i .en. t.iI significance of the results 19 Summary 20 L'Tl 5 u p i 788 SOME EFFECTS OF REFRIGERATION ON SULPHURED AND UNSULPHURED HUPS. INTRODUCTION. Opinions arc greatly divided as to the desirability or general ex- pediency of the practice of treating hops with the funic- <»f burning sulphur during the process of drying. This process, which in the United States is termed "sulphuring," has been Long in vogue and has come to be regarded as an essential pari of the method of prepar- ing hops for market. The use of sulphur as an adjunct to hop drying apparently originated in England and from the first was regarded as a more or Less effective mean- of checking the tendency of newlj packed hops to heat and -pod in the bale. Later, other virtue- were claimed for sulphuring in addition to thai of pre- servative action, and tho-e who advocate the use of sulphur uow believe that it favorably affects the hops by changing and improv- ing the color, by hastening the drying through causing the rapid deatli of the cells, and by preventing fermentation, thereby improv- ing the keeping qualities. Aside from sulphuring, a number of other expedients have been resorted to for the purpose of delaying or retarding the changes which normally occur in the chemical constituents of hops after they have been dried and baled. Of these expedient- refrigeration is the most widely used and from many considerations it i- perhaps the most efficient and generally satisfactory method of preservation that has as yet been employed. The sulphuring of hop- is such a common practice in the United State- that practically all hops placed in cold storage may he re- garded as having absorbed a varying quantity of sulphurous acid, depending to a certain extent upon the quantity of sulphur used at the time of drying. Since both sulphuring and cold storage are held to he efficient agents in retarding changes in the essential con- stituent.- of hops, the diminished rate of deterioration of sulphured hop- in cold storage must he due to the combined action of these two processes. Bowever, the relative efficacy of these two proa 271 7 8 SOME EFFECTS OF REFRIGERATION ON HOPS. or the extent to which the one or the other alone would accomplish the desired result, is usually a subject of approximate estimation only. For the purpose of obtaining some experimental data upon the pre- servative action on hops of sulphuring and cold storage, singly and in combination, suitable material was prepared and held under observation for several years. The results of this study, which are given in some detail in this bulletin, indicate that both cold storage and sulphuring tend to delay certain undesirable chemical changes and that the usual trade judgment can not always be relied upon to give an accurate measure of the extent to which these changes have occurred. However, it is fully realized by the writers that further experimentation is necessary before the conclusions drawn from this work can be considered to have a general application. PREPARATION OF THE HOPS STUDIED. The hops which furnished the materials for the observations here recorded were all picked from the same part of a field on a hop ranch in the Sacramento Valley on August 30, 1907, and were dried on the same day under the senior writer's supervision. As the hops were re- ceived from the field they were equally distributed to two duplicate stove kilns until each had received a load of about 4,500 pounds, green weight. The fires were lighted and the temperature of each kiln was gradually raised to a point between 130° and 140° F., between which limits it was maintained until the drying was completed. On one of these kilns 110 pounds of sulphur was burned under the hops during the drying, which required 13 hours; on the other kiln no sulphur was used and the time required for drying was 18 hours. The dry hops from each of these two kilns were separately deposited in the cooling room and on September 2 two bales of the usual com- mercial type were prepared from the unsulphured hops and two from those which had been heavily sulphured. These four bales were con- veyed to Sacramento, where two bales, one of sulphured and one of unsulphured hops, were placed in cold storage at 36° F. in the hop storeroom of the Buffalo Brewing Co., and the two remaining bales, one of which was sulphured and one unsulphured, were placed in ordinary storage in the Clunie warehouse, PHYSICAL CHANGES IN THE HOPS IN COLD AND IN ORDINARY STORAGE. As a rule, it is difficult to correlate the valuation of hops as de- termined from their physical characters with the indications of their value derived from chemical analysis. In the present case, however, 271 rill BIOAJ \ physical valuation. In order t" have the differences in physical condition expressed in the language of the trade and as nearlj as possible from the trade viewpoint, samples were drawn from time t«> time from the four bales and submitted to various trade experts, who were asked i" report their impressions as to the general condition and relative meril of the various samples. Early in April, 1908, after the hops had been in storage for -even months, samples were drawn from each of the four bales and sub- mitted i" five trade experts, all of whom concurred in the following report made by one of t!mir number: We have examined these samples ai to tbeli condition a1 the present time If there was any difference between cold and regularly Btored hops, and we are of the Bame opinion thai there is no difference between 1 1 * « - cold Btored and regularly stored bops. The bales were not dimpled a second time until midsummer, ami during the time which had elapsed since the firsl sampling the hops in ordinary storage had been subject to the influence of tin- hot and dry weather which prevails in the Sacramento Vallej ai this 3ea on of (lie year. Naturally, it was expected that at this time certain dif- ferences would he apparent in the hops under different condition, of Storage. On July 24, L908, -ample- were drawn and submitted to an expert hop buyer, who reported on them a- follows: I'n muI ph u red cold-stored hops, fine fresh hop flavor; good oilj feeling; aroma almost as good as new hops and seems m !»■ about the same a- tbnt of the sulphured cold stored hops. Sulphured cold-stored hops. Fine fresh hop flavor; g l oily feeling; aroma almost as •_" 1 as new hops, but COlOI somewhat lighter than the Color <'f the onsnlpbured sample above described. Unsulphured ordinary-stored hops. Flavor decidedly that of old hops ascom- pared with the c.>id stored samples; feeling dry: lupulin not very sticky: color about the same as the color of the unsulphured -ample above. Sulphured ordinary-stored hops. Fine fresh flavor; good oily feeling; aroma almost as good as new hops, but the color somewhat lighter than the color of the unsulphured sample above described. At this time it is decidedly noticeable that the cold Stored hops have by far the besl flavor and that they feel almost as oily as new hops, while the ordinary Stored hops are becoming poorer. This Judgment was taken within an hour after the hales had hem Sampled, ami on coming Into the room where the samples had been placed I thought that the excellent aroma was dif i" new hops. I was really surprised at the -roar difference in the aroma between the ordinary timed and cold-stored bops, but g:.i.:; - 12 2 3 S M 35 10 SOME EFFECTS OF REFRIGERATION ON HOPS. mi comparing color I can Dot notice any serious difference between sulphured and unsulpbured bops in either case. These same samples were next submitted to a second expert, who made the following statement : The difference between the ordinary-stored ami the cold-stored hops is now very noticeable. The unsulpbured cold-stored sample has a very good flavor and looks fresh and bright. The unsulpbured ordinary-stored sample has not such ;i good flavor as the former, is very much drier, and is becoming rapidly aged. The difference between these two is particularly noticeable in the appearance of the sides of the samples, the side of the cold-stored sample showing up much brighter and fresher than that of the other. The sulphured cold-stored sample has a fine fresh flavor and is a particu- larly well kept hop. while the sulphured ordinary-stored sample lias a musty. old flavor and is rather dried out. The difference between these two samples is not so much in the appearance as in the aroma. On the day following, these samples were submitted to a brew- master, who delivered the following opinion : The cold-stored hops have a lighter color as compared with the ordinary- stored hops, the lupulin is bright and shiny, the hops have a very oily and sticky feeling, and the aroma is almost like that of new hops. The ordinary-stored hops have a dull, dry color; the lupulin is not so bright and appears to be hard and dry, with very little oil as compared with the cold- stored hops; the flavor is decidedly different and very much like that of old hops. The hales were not sampled again until February 13. 1009, eighteen months after they were first placed in storage. The samples drawn on this date were first submitted to the brewmaster previously men- tioned, and his judgment as to their relative merit was stated thus: The sulphured and unsulphured cold-stored samples are respectively superior in flavor to the corresponding ordinary-stored samples. The sulphured samples in cold and ordinary storage are far superior both in flavor and color to the unsulphured samples. The samples were next submitted to a trade expert, who gave the following opinion : There is a very great difference between the cold-stored and ordinary-stored hops. The cold-stored samples are much brighter in appearance, have much more flavor, contain much more moisture, and their lupulin is much brighter than the ordinary-stored samples. The cold-stored samples would pass for new hops, while the ordinary-stored samples show their age and could not pass for anything else than " olds." By new hops I mean the 1CK)S crop. Of the cold-stored hops the unsulphured sample seems to have a trifle more flavor than the sulphured one, but the latter has a sweeter flavor, which I believe would be preferred. The lupulin in both these samples is very fresh and moist, but that in the sulphured sample is a trifle the brighter. The sul- phured sample, though in appearance fresher than the unsulphured sample, is not as moist as the latter. Of the ordinary-stored hops the unsulpbured sample has much more flavor than the sulphured sample, the latter having very little flavor at all. The 271 OHANGEfl I \ \t'i \ i 11 I CON8TIT1 1 WTS 01 BOPti i\ 3TOKAOB. 11 i iipni in in iii<- sulphured sample la n trifle brighter In the other. The uneulphnred sample li much more motat than the Rulphured anmple thougli the latter, before o detailed examination, appears to i" the freeher "i the two, m c lltton that can be traced to the brlghtenli f the aulphur. Since the Bulphured cold-stored hops natural]} conformed mosl closely m appearance and general i ondition to the hops usually found in the t rade it was expected that the> would be ranked first in quality, nnd such proved t<> be the case when the several expressions of judg iiii'iu l>\ the trade experts were analyzed. With respect to the other lots of hop-, however, opinion was divided and the usual difference* in trade judgment of quality are here well illustrated. The rank in order of merit as fixed by four of the judges wag as follows: Sulphured cold-stored hops i i l. 1. Unsulphnred cold-stored bopa 2 2 •".. '_'. Sulphured ordlnarj Btored bops :: i -. l. rjnsnlphured ordlnarj Btored bops 4, 3 I, CHANGES IN THE VOLATILE CONSTITUENTS OF HOPS IN COLD AND IN ORDINARY STORAGE. On September 1<>. 1909, portions <>f the four bales of hops under consideration were withdrawn from storage and subjected to steam distillation to remove the volatile oils, which were then dried and purified and later examined to determine their degree of acidity and ester content. These factors, together with the percentage of yield of volatile oil, are given in Table I. Tabu I. Comparison of rolatih oih from nulphured and unsulphured li"/^ in cold and in ordinal} vtoragt for two years. mined. oil. nuiiilxT. number. Rulpnured roUtatoreri hops Unsulphured raid-stored hops 9.0 Sulphured ordinary-stored hops • lj."> Unsulpbured ordln hope 103 16] Aii inspection of this table reveals the following interesting facts: i 1 1 The yield of oil is twice as great in the cold-stored hops as in those in ordinary storage. (2) The acidity lit' the oil from the cold-stored hop- is fai than that of the hops in ordinary storage. (3) The <>il from the sulphured hop- in ordinary storage -how- an increase of 71.2 per cent in acidity over that from the hop- in cold -!'i aire, while the oil from the un-ulphured hop- in ordinary storage -how- an increase of ~:).:) per cent in acidity over that of the oil from those in cold storage. 271 12 SOME EFFECTS OF BEFBIGEEATION OX HOPS. (4) The oil from the unsulphured cold-stored hops shows an in- crease of 23.2 per cent in acidity over that from the hops that were sulphured, while the oil from the unsulphured, ordinary-stored hops shows an increase of 24.8 per cent in acidity over that from the hops that were sulphured. (5) The oil from the unsulphured ordinary-stored hops shows an increase of 113.6 per cent in acidity over the oil from sulphured cold- stored hops. (6) The ester content of the oil from the sulphured hops is much less than that of the oil from the unsulphured hops. (7) The oil from the unsulphured ordinary-stored hops shows an increase of 23 per cent in ester content over that from the hops in cold storage, while the oil from the unsulphured hops in ordinary storage shows an increase of 46.0 per cent in ester content over the oil from those in cold storage. (8) The oil from the unsulphured cold-stored hops shows an in- crease of 32 per cent in ester content over the oil from the sulphured cold-stored hops, while the oil from the unsulphured ordinary-stored hops shows an increase of 57.2 per cent in ester content over that from the sulphured hops in ordinary storage. (9) The oil from the unsulphured ordinary-stored hops shows an increase of 93.5 per cent in ester content over that of the oil from the sulphured cold-stored hops. This analysis gives an index of the relative efficacy of sulphuring and cold storage in controlling changes in acidity and ester content of the hop oils during the first two years of storage. The percentages of increase in acidity as between cold and ordinary storage are approximately three times the corresponding increase as between the sulphuring and nonsulphuring. This would apparently indicate that cold storage is three times as effective as sulphuring in retarding increase in acidity. With respect to ester content, the increase, as between the oils from cold and ordinary stored hops, is twice as great in unsulphured as in sulphured hops; also as between sulphured and unsulphured hops the increase in the ester content of the oil is twice as great in ordinary storage as in cold storage. This would seem to show that cold storage and sulphuring are about equally effective in retarding the increase in the ester content and that the two combined exert double the effect of either acting alone. On December 1. 1910, fifteen months later, a second set of samples was taken from the four bales in storage and the volatile oils removed by distillation. The results of the examination of these oils, which are given in Table II, show little harmony with those of the first analysis. 271 OHANGEB IN VOLATILE CONSTI! I HOI'S IN STOKAUE. 13 Taiili ll Comparison o) volatih oils from tulphured and unsulphured /■ cold and in ordinary it and Ihra s B Sii'|.'i ;.liur.W urd I !»■ -1 • - An inspection of the table shows in this case the following rela- tions : (1) 'l'lic aciditj of the oil from the cold stored hops is greater than thai of the <>il from the hop- in ordinary storaj (2) The acidities of the oils from the In * i *~ '" ordinarj storage are the same, (3) The oils from the unsulphured col hops are highest in acidity. (4) Tin 1 ester contenl of the oils from the cold-stored hop greater than that of the oils from the ordinary stored hops. (5) The oils from the sulphured hops in cold storage are highest in ester content. The oils from the unsulphured hops in cold and in ordinary storage, respectively, are higher in ester content than the <>il from iln> sulphured hops in ordinary storage. It is now evident that the apparent effects of sulphuring and cold Btorage as shown by the second analysis are almost the reverse of those indicated by the Brst analysis. How these seeming discrepan- cies may be harmonized can be seen from an inspection of Table III. in which the results of the two analyses are directly compared. Tm:i i [II. — Comparison of tin acidity and ester content of the ',;/, froti phwed and unsulphured hops wi cold and in ordinary storage. Sulphured hops. ralphnred bops. Kind of r. IVr- pont- age ..f Ester num- ber. Per- 1910 - 1910. 1910 Ugg 1910 ■ 1910. 1900 1910 1910. rvi.i B0.8 Ml n 78 9.3 9.0 53.8 1M.1 Ordinary U.E B2.0 16.6 24.0 IB 109.0 Regarding, first, the acidity, the data in this table show that the percentage of increase in acidity was least in the oils from the hops which yielded oils that were highest in acidity in 100° and greatest 271 14 SOME EFFECTS OF BEFBIGBBATIOM 03S HOPE. in those lowest in acidity in 1009. Further, all the percentages of increase in acidity in 1010 are inversely proportional to the acidities in L909. It is evident from the first analysis that the rate of change in the volatile constituents under consideration was greatest in the oils from the unsulphnred hops in ordinary storage. These changes would continue until a maximum was reached, after which, owing to the interaction between the oxidation products of the various organic constituents of the hops and to the direct loss through vola- tilization, a decline in acidity would be the normal result. Assum- ing that this maximum was reached between the time of the first and the second analysis and applying this explanation to the data on acidity in Table III, the oils from the hops in ordinary storage may be regarded as having passed the maximum and as being in the declining phase with respect to acidity. Since the changes in the unsulphnred hops in ordinary storage were not artificially retarded, the oils from these would naturally be nearer than the others to the maximum acidity at the time of the first analysis, and hence the per- centage in increase in 1010 would be smallest. Of the hops in cold storage, the oils from those that were unsul- phnred may be regarded as being at or near the maximum of acid- ity in 1010. thus accounting for the high figure of actual acidity and for the relatively large percentage of increase in acidity during this year. On the other hand, the oils from the sulphured cold-stored hops had apparently not reached the maximum acidity in 1010. owing to the slower rate of change in acidity in these oils due to the combined effect of sulphuring and cold storage. When viewed from this standpoint, the apparent discrepancy between the two analyses disappears and the balance of evidence is in favor of the conclusion (1) that under the four conditions of this experiment the acidity of the oil of hops increases to a maximum and then de- clines; (2) that sulphuring and cold storage merely retard but do not inhibit changes in acidity; and (3) that sulphuring and cold storage combined are more effective in retarding changes in acidity than either alone. With respect to the esters, the data indicate that, in general, the changes in ester content have been similar to the changes in the acidity, although complicated by some other factors which make the relations of these changes to the conditions of storage less clear. The first analysis show.- that the greatest changes in ester content occurred in the oils from the unsulphnred hops and also that the oils from the hops in ordinary storage had undergone a i \Mi !. I 0N8TIT1 i N I - OF HOPS IN STORAGE. L5 sulphur inhibits the development of estei beyond >i certain point, in which case two maxima might be expected one for the oil from sulphured hops and a higher one for 1 1 » * - oil from unsulphured hops. The data of Table MI agree with this assumption, for i< appears that the «'il- of the unsulphured ordinary stored hopa were at or near tli< maximum of ester content in L909, which thereafter rapidlj declined, as shown li\ the figure reached in 1910. The ml from the unsulphured cold stored hops, which was below the probable maximum of ester content :ii the time of analysis in 1!M>'.». shows an apparent increase of 22.4 per cent in 1910; but, since the figure reached in 1910 is less than the probable maximum as indicated l>\ the ester content of the oils fr the hops in ordinary storage in L909, it seems evident that the oils in the hops in cold storage had reached the maximum and entered upon the declining phase before the analysis in L910. This vie* receives further sup port from the fact that the oil from the sulphured cold stored hops, in which tlic chemical changes were most retarded, was higher in ester content in 1910 than the oil from those which were unsulphured. The oils of the sulphured hop- in ordinary storage appear to have pa>s,-(l their maximum of ester content and to be in the declining phase in L910, while those of the Imps that were sulphured ami which show the greatest increase in ester content in 1910 appeal- to he at or near their maximum. The conclusion- which are to he drawn with respect to the ester content, therefore, arc that sulphuring re- tards the increase in ester content and inhibits it beyond a certain maximum, that cold storage retards but doe- not inhibit increase in ester content, and that sulphuring and cold storage combined are more effective in retarding changes in ester content than either alone. CHANGES IN THE HOP RESINS. In further pursuance of the plan of securing trade opinions with respect to the changes which had taken place in the four bales of hops under different condition- of treatment, portions of these bales were sent to a firm which is a large consumer of hops, with the re- quest that the content of soft and hard re-in- lie determined in each. The first analysis was made by the chemist of this firm iii January, 1910, two year- and four month- after the hale- had been first placed in storage. One year later a second lot of -ample- was sent to the same chemist anil by him duly analyzed. The results of these two analyses are given in Table IY\ 1171 16 SOME EFFECTS OF REFRIGERATION ON ITOPS. Table IV. — Changes in resin content in .sulphured and unsulphured hops in colli and in ordinary storage. Previous treatment of the hops analyzed. Percentage of resins. Soft resins. 1910 1911 Hard resins. 1910 1911 Total resins. 1910 1911 Sulphured, cold stored Unsulphured, cold stored Sulphured, ordinary stored... Unsulphured, ordinary stored 10.5 10.6 9.8 9.9 10.3 8.7 7.5 7.8 5.5 5.3 5.5 7.0 5.6 6.2 6.4 16.0 15.9 If). 4 16.9 15.9 14.9 15.0 14.2 The figures in the foregoing table give an index to the changes which occurred in the resin content of these hops during the third year of storage. The slightest change in total resins, 0.1 per cent, took place in the sulphured cold-stored hops, while the greatest change, 2.7 per cent, is evident in the unsulphured hops in ordinary storage. The loss in soft resins was least in the sulphured cold- stored hops, 0.2 per cent, and greatest in the sulphured ordinary - stored hops, 2.4 per cent. The loss in soft resins of the unsulphured hops was 1.9 per cent in cold storage and 2.1 per cent in ordinary storage. As far as the evidence from these analyses goes, it indi- cates that sulphuring diminishes the less of total resins, but does not diminish the loss of soft resins except when followed by cold storage. The greatest loss in soft resins was in the sulphured hops in ordinary storage, and. since the soft resins alone are intrinsically valuable, from this standpoint these hops must be regarded as the poorest of the lot. With respect to these particular samples, the balance of evidence indicates that there is a distinct advantage in both sulphuring and cold storage. However, the margin of differ- ence in the results of the analyses is relatively small, and if the soft resins were regarded as the only measure of value, the advis- ability of incurring the expense of long-continued cold storage might be questioned. PHYSICAL AND CHEMICAL VALUATION COMPARED. Great difficulty is experienced not only in harmonizing the results of the physical and chemical estimations of the value of hops, as pointed out on a previous page, but also in bringing into accord the different individual judgments of quality, determined on a purely physical basis. This point has been discussed at some length in a previous publication 1 and will not be dwelt upon here further 1 Stockberger, W. W. The Necessity for New Standards of Hop Valuation. 33, Bureau of Plant Industry, TJ. S. Dept. of Agriculture. 1909. 271 Circular PHYSICAL AND CUEMICA1 VALUATION COMPARED 17 than to Btate thai it is well nigh impossible to find two pei one who will assign the same rani in value to -i\ samples of commercial Imps selected at random. Some light i- thrown on these differenct judgment by a study of the different opinions rendered ss t<> the relative value «>f the four h>t- of hops, all from the Bame Bource but subject to different conditions of treatment and storage. In order ti> bring out clearly Borne of the contrasts in these opinions, a table was prepared in which the physical and chemical valuations are compared. In this table the relative rank given each l"t of Imps by the four expert judges is indicated by the corresponding numeral. The relative rank in acidity of 1 1 u* oils, which is similarly indi- cated; was determined from the results of the first analysis, since this analysis was made nearest in point of time to the physical filia- tions. The hops having the oils lowest in acidity were given the highest rank, those with oils next in acidity second rank, and SO on, tin- order being determined by the fact that the hops having oils lowest in acidity had changed least from the original condition at the lime of first storage. The relative rank with respect to ester content \\;i- determined in the same manner. The relative rank with respect to resins was determined from the content of soft . as these alone are considered to he the only resins of value in the utilization of hop-. Since keeping quality, as indicated by a slow rale of change in the chemical constituents, is an important factor of value it was made the basis <»f relative rank in this case rather than the absolute quantity of -oft resin. This relative keep- ing quality was determined from the difference in the content of soft resin.-, a- shown by the two analyses. A direct compari.-on of all these relative rankings may Ik 1 made from Table V. Tabu y. Comparisons of rankings in t tulphured rnge. Previous trentment of the hops. Rank In value determined as noted. By trade experts. A. By acidity. By ester eon- tent. By I quality ot .« ' i f t r s. Sulphured, rold stored- I'nsuiphured. cold stored Sulphured, ordinary stored Unsulphured, ordinary stored. From this table it appear? that the rankings as to value are con- sistent in one case only, that of the sulphured cold-stored hops. How- ever, on taking the judgments of the trade experts singly, that of expert A will be seen to agree with the rankings determined by 18 SOME EFFECTS OF REFRIGERATION OX HOPS. acidity, that of expert C with the rankings with respect to ester con- tent, while the rankings of experts B and D agree with the order determined by the keeping quality of the soft resins. The reason for the differences in the judgments, based largely, if not entirely, upon the flavor or aroma of the hops, seems to lie. in part at least, in the difference of degree of sensitiveness of the individual to the several volatile constituents, which together form the aroma. It is well known that odors which are agreeable to some persons affect others unfavorably, and there is every reason to believe that in the present case the differences in judgment were due to the physiological idiosyn- crasies of the observers. That this point of view is coming into wider recognition is shown by the following statement made by Dr. Albert Fischer: The determination of aroma is an entirely individual matter, depending upon the individual taste, the state of health, and the eventual influence of outside flavors on the person testing. 1 However, since the number of individuals who passed judgment upon the experimental samples was small, the decisions rendered are not necessarily conclusive and certainly do not prove that the aroma should not be used as a factor in the determination of the value of hops. That the aroma is useful in determining the age and sound- ness of hops is conceded even by those who hold that it -is not a proper factor from which to determine intrinsic value. The term " age " may be used to express the time that has elapsed since the hops were harvested or. in a relative sense, to denote the extent to which unfavorable changes have occurred in the hops. The hops under discussion here were of the same actual age. but owing to the different conditions of treatment they were of different relative ages, as shown by the different points to which the changes in the chemical constituents had progressed at the time of analysis. From the several classifications shown in Table V it is evident that the relative age and degree of deterioration as determined from analysis will depend very largely upon which one of the various constituents is selected as the basis of comparison. Similarly, the estimation of age or dete- rioration from the impressions produced by the aroma will vary according to the individual peculiarities of taste or fancy possessed by the observer. It is much to be regretted that there is not a better understanding of the relations between the factors commonly con- sidered in establishing the relative market value of hops and the actual value of the hops in the processes in which they are utilized. The determination of a definite basis of value from which sound standards could be derived would have great practical importance, both for the producers and for the consumers of hops. 1 Fischer, A. Modern methods of hop analysis. Letters on Brewing, vol. 11, 1912, p. 317. 271 i.i \ i I vi BIONIFIOANOB OS PHH BJ 81 i is. !'.» GENERAL SIGNIFICANCE OF THE RESULTS. The material which furnished the basis for the observations dis cussed in tlii- paper was prepared primarily with the view to < l!' sulphuring, to obviate which the dis- continuance of tin' use i>t" sulphur was naturally suggested. It was expected that the unsulphured hops would be received with Less favor by the trade than those which bad been sulphured, owing to the more pronounced variations in the color of the former, but at the time tli«' bales of hops selected for observation were placed in storage the difference in general appearance was comparatively small, although the sulphured hops could be readilj distinguished by their more uniform and somewhal brighter color. A study of the trade opinion- rendered on these hops after they had been for some tune in storage apparently Bhows thai the difference in appearance due to Bulphuring becomes accentuated with age and thai the preference is for the sulphured hop. When freshly cured, the difference in color between sulphured and unsulphured hop- is. as a rule, much more pronounced; and, however careful the grower might be to harvesl his crop at the stage of maturity besl calculated t<> give the greatest uniformity in color, it is evident that in marketing his product he would have to sees for those consumers who have a preference for the greenish grades of hops. Prom the results of the chemical tests it is apparent thai unsul- phured hops are less suited to the requirements of the consumer than those thai have been sulphured, especially when they are stored for a considerable length of time before they are used. However, the fact should not he 1 « > - 1 sighl of that these tests were made on hops which had been in storage for more than two years, and the changes ob- served are certainly considerably greater than those which occur in hop- which have been stored for a -hotter period. Nevertheless, the greater part of the changes in certain constituents take- place during the tir-t year of storage, a- ha- been shown by Heron-' in the case of the tannin of hop-. Bui from the work of Mo-eiv who found that the tannin content of unsulphured samples was consistently smaller than that of sulphured samples of the same sorts, it is evident that the oxidation of the tannin i- retarded by sulphuring. It may 1 Stnckbrr-'or. W. W. The Bonrci - "f arsenic in certain sampl.s of dripil hup-;. Bulle- tin 121, pi. 4. Bnrei I Plant Industry, r. s Depl "f Agriculture 1908 • Heron, John. The tannin ..f bops Journal of tin- Federated Institutes of Brewing, rol .'. 1896, p 172 ■Cited by Braunpirt in Der Bopfen, Munich, 1901, p. B49. 211 20 SOME EFFECTS OF REFRIGERATION ON HOPS. be safely assumed, however, that sulphuring is an effective means of retarding chemical changes in hops from the time they are cured until they have reached the desirable limit of age, usually determined by commercial conditions, provided such hops are held in cold storage. It is fully realized that the conclusions drawn in this paper are subject to the criticism that the analyses are too few in number and that they are not coordinate in point of time with each other and with the physical valuations. Certain obstacles encountered in the course of the work made it impossible to round out the results as fully as was desired, yet it is believed that the coordinations sug- gested by the facts developed are of sufficient importance to justify this somewhat incomplete presentation, which should be regarded more as a report of progress than as an attempt at a full elucidation of the problem, for which much further experimentation is necessary. SUMMARY. Material for a comparative study of the effects of cold and ordinary storage on sulphured and unsulphured hops was secured from a hop field in the Sacramento Valley, Cal. The green hops were divided into two lots, only one of which was sulphured during the process of drying. Bales from each lot were placed in cold and in ordinary storage, and samples from these bales were drawn from time to time for examination with respect to physical condition and certain chemi- cal constituents. At intervals of 7 and 18 months, respectively, from the time the hops were placed in storage, samples were drawn and submitted to trade experts, who were asked to rate the samples according to their relative quality. All agreed that the sulphured hops in cold storage were best in quality, but opinion was divided as to the relative merit of the three other lots. Determinations were made of the acidity and ester content of the volatile oils extracted from samples of the hops under each condi- tion of storage. The conclusions drawn from these analyses are that both sulphuring and cold storage retard changes in the hops leading to an increase in acidity and ester content of the oils. Cold storage is apparently more effective than sulphuring in retarding the increase in acidity, but is less efficient than sulphuring in retarding increase in ester content. Cold storage and sulphuring combined are much more effective in retarding changes in acidity and ester content than either alone. The percentage of decrease in the content of soft resins was less in the cold-stored hops than in those in ordinary storage. The evi- dence from the analyses goes to show that the sulphuring tends to 271 SI M M 1ST. 21 retard changes in the content <>f Boft rasinB only w hen combined with cold storage. Iiii'lr experts to whom Bamples of the bops under considerat were submitted for physical judgmenl differed widely in their ions of relative merit, except in the case of the sulphured cold Btored hops, which all agreed ranked first. The relative rank in merit as determined From each of the Factors Bought in analysis was Found to give corresponding differences. A comparison <>f these differences in the physical and chemical valuations shows that the determination of the value of hops From the aroma depends upon the pen taste of the observer and is greatlj affected by the in lividual's pref- erence or dislike of one or the other of the several constituents oi" the aroma. o UNIVERSITY OF FLORIDA 3 1262 09216 2154