부산대학교 도서관

The determination of the optimum conditions for the conversion of ergosterol to vitamin D2 in shitake mushrooms (Lentinula edodes) was studied using response surface methodology (RSM). The effects of the three main variables, including ambient temperature (20-40℃), exposure time (60-180 min), and irradiation intensity (0.6-1.8 W/m2), were investigated. According to the RSM ridge analysis, the optimum conditions were as follows: ambient temperature of 34.2℃, exposure time of 175.6 min, and irradiation intensity of 1.41 W/m2. Under these optimum conditions, the maximum vitamin D2 content of 117.93 μg/g was obtained, which agreed fairly well with the predicted value of 122.60 μg/g. According to the proximate analysis, no nutritionally or toxicologically significant changes occurred in shitake mushroom composition, which means these parameters can be used in commercial production. 5’-nucleotides were analyzed to investigate the influence of drying methods and UV-B irradiation on flavor 5’-nucleotides and total 5’-nucleotides in shitake mushrooms. In general, levels of 5’-nucleotides in freeze-dried mushrooms were significantly higher than those in hot air dried mushrooms. Besides, to freeze-dried mushrooms with or without UV-B irradiation, there was no significant change of flavor 5’- nucleotides (1.80 mg/g to 1.82 mg/g) or total 5’- nucleotides (9.47 mg/g to 9.29 mg/g). For better practical application, the effect of hot air drying temperature on vitamin D2 conversion in shitake mushrooms was studied. The maximum retention of vitamin D2 was achieved at 45℃. In addition, different treatments were conducted to improve vitamin D2 preservation during hot air drying. In conclusion, it indicated that vitamin D2 easily degraded in acidic condition, and vitamin D2 content in shitake mushrooms increased modestly after hot water processing for some time, compared with the negative control. The changes of vitamin D2 contents in UV-B irradiated shitake mushrooms during 4 weeks’ storage at 4℃ and room temperature (25℃) were also studied. Both the two cases were on an obvious downward trend, a 35% decrease for the 25℃ preserved mushrooms, and a 28% decrease for the 4℃ preserved ones. To cell proliferation, sterols treatments significantly increased the cell proliferation up to 120% of the basal value of the vehicle control. While too high doses of sterols mixture (10 ng/mL or more) inhibited MC3T3-E1 cell growth, with a decrease of up to 15% of basal value. The effect of sterols extract from mushroom on calcium deposition in MC3T3-E1 cells was studied. Both the UV-B irradiated group and the control group had positive effects on calcium absorption in osteoblast cells. At the same dose of treatment (2 ng/mL), the UV-B irradiated group exhibited a remarkably higher stimulatory effect on calcium deposition in MC3T3-E1 cells than the group without ultraviolet irradiation.