key: cord-0862920-ictid6e0
authors: Jiang, Qiyong; Zhang, Min; Mujumdar, Arun S.
title: UV induced conversion during drying of ergosterol to vitamin D in various mushrooms: Effect of different drying conditions
date: 2020-09-22
journal: Trends Food Sci Technol
DOI: 10.1016/j.tifs.2020.09.011
sha: bf82de1d8abbaa68937838300cd7567cb2bf041e
doc_id: 862920
cord_uid: ictid6e0

BACKGROUND: Mushrooms are increasingly popular around the world as a nutritional food which is an excellent source of vitamin D(2). Although natural mushrooms often contain very little vitamin D(2) as many are grown in the dark, they are rich in ergosterol, a precursor to vitamin D(2). Ergosterol can be converted to vitamin D(2) under ultraviolet radiation. Due to the high water content of fresh mushroom, its quality deteriorates rapidly after harvest, and drying is the most commonly used technology to extend the shelf life. The vitamin D(2) content of dried mushrooms depends on the drying conditions used. SCOPE AND APPROACH: In this review, the chemistry of the photo-conversion process of ergosterol to vitamin D(2) under ultraviolet radiation is introduced. The ergosterol and vitamin D contents in different mushroom varieties are discussed. The effects of several drying methods and the influence of different drying conditions are reviewed. Key findings and conclusions: Thermal drying in the presence of UV has been proven to convert ergosterol into vitamin D and enhance the nutritional content of all types of edible mushrooms. Solar drying, hot air drying, freeze drying, microwave drying and infrared drying can be used for mushrooms drying under selected operating conditions. A critical evaluation of published literature demonstrates the importance of applying appropriate drying methodology to maximize the nutritional value of various types of edible mushrooms.

It is now recognized that exposure to sunlight and dietary foods are the most 74 important ways for humans to obtain vitamin D. Due to lifestyle changes, however, Table 2 shows ergosterol and vitamin 194 D 2 contents in some fresh mushroom samples. 195 It was found that although the natural vitamin D content in mushrooms is very Table 3 shows effects of UV irradiation on contents of vitamin D 2 in mushrooms. In 210 addition, it was also found that ergosterol decreased in mushrooms exposed to UV dehydration is equipped with a solar panel with a total exposed surface of 10 square 252 meter, electrical resistances and paraffin wax as phase change materials, which also 253 achieve energy-saving effect in mushroom drying (Reyes, Mahn, & Vásquez, 2014). Currently, freeze drying is considered one of the best drying methods due to its 301 excellent performance in maintaining the quality of dried products (Duan, Zhang, Li, 302 Nevertheless, despite its many advantages, freeze drying has long been known as the 306 most expensive process for producing dehydrated products. Freeze drying is an 307 energy-consuming operation because it requires freezing fresh products at very low 308 temperatures. In addition, some processes involve reducing the pressure in the drying 309 chamber to a certain degree of vacuum, sublimating water vapor by heating, and It is easy to convert ergosterol into vitamin D following ultraviolet radiation, which 434 makes mushrooms become a rich source of vitamin D, as shown in Table 3 . Therefore, 435 in evaluating different drying methods for mushrooms, consideration should be given 436 to optimization of the conditions to facilitate this conversion process as much as 437 possible. Although the photo-conversion kinetics of ergosterol to vitamin D 2 in 438 mushrooms is not fully understood, UV exposure is an important condition. In various produced 45 μg/g d.m. of vitamin D 2 . However, sliced mushrooms before being 480 exposed to UV-B light and then dehydrated produce 406 μg/g d.m. of vitamin D 2 , 481 about 10 times more than when the whole fruit is exposed to UV light (Nölle, et al., Lee, & Park, 2008). Whether sliced or exposed to the sun on both sides, the tissue area 497 of mushrooms exposed to ultraviolet light increases, resulting in an increase in 498 vitamin D production. Similar results were obtained by Wu et al., that compared with 499 intact fresh mushrooms, homogeneous mushroom powder significantly increased the 500 exposure surface area, thus greatly increasing the ergosterol conversion efficiency. In 501 addition, the opening of mushroom cap also affects the formation of vitamin D 2 when 502 the whole mushroom is irradiated by ultraviolet light. This is of practical importance 503 for some mushrooms that are harvested according to their maturity, such as button 504 mushrooms, which has different stages of maturity as button, cup and open flat. As 505 the mushroom cap opens, more gills are exposed, which helps to receive ultraviolet shown that dried mushrooms can also boost vitamin D 2 levels after exposure to 598 ultraviolet light, which could also be used as an alternative. Therefore, with the 599 demand for vitamin D 2 production, drying can be expected to become a commercial Table 1 Proximate composition of some edible mushrooms (% of dry matter) 1000 Table 2 Ergosterol and vitamin D 2 contents in some fresh mushroom samples 1001 Table 3 Effects of UV irradiation on contents of vitamin D 2 in mushrooms 

Vitamin D 2 content and antioxidant properties of 732 fruit body and mycelia of edible mushrooms by UV-B irradiation

Freeze-Drying of the Black 735 Currant Juice

The effect of 737 ultrasound-assisted immersion freezing on selected physicochemical properties of 738 mushrooms

Accelerated drying of 740 button mushrooms, Brussels sprouts and cauliflower by applying power ultrasound 741 and its rehydration properties

Kinetics of the conversion of 743 ergosterol in edible mushrooms