Effect Of Solid-state Fermentation With Agaricus Blazei On Polyphenols Of Cereal

Polyphenols are a class of compounds containing many phenolic hydroxyl groups,and have a wide range of bioactivities including antioxidant activity,anti-cancer,bacteriostasis,and prevention of cardiovascular diseases and type II diabetes.Whole cereals are good sources of polyphenol compounds,which are mostly concentrated in the germ,bran,and chaff.However,these polyphenols are lost in the separation of the seeds during the refining of the grain.As many biochemical changes are produced in the process of fermentation,fermentation has long been considered as one of the best processes to obtain products with a high quality and a high activity.In this paper,in order to investigate the effect of solid-state fermentation(SSF)with Agaricus blazei on polyphenol of selected cereals(wheat,rice,corn,oats,finger millet,proso millet and sorghum),the contents of free polyphenols,bound polyphenols and total polyphenols after SSF by A.blazei and the carbohydrates hydrolases enzymes activities of fermented products were determined.As well as the correlations between these enzyme activities and polyphenols contents in fermented products were analyzed.Then,the SSF conditions for A.blazei were optimized.Finally,the effects of different processing methods and storage conditions on the polyphenol content of fermented products were studied.Firstly,the effect of SSF with A.blazei on polyphenol of selected cereals was investigated.The result indicated that the content of free and total polyphenols of wheat,rice,corn,oats,finger millet and proso millet increased with the prolonging of fermentation time.In contrast,the content of conjugated polyphenols decreased.The results of sorghum were opposite.In general,the activities of cellulase and ?-amylase of wheat,rice,corn,oats,finger millet and proso millet increased as the time increase initially and decreased afterwards.The activities of ?-glucosidase kept growing in 5~30days.The carbohydrates hydrolases enzymes activities of sorghum increased with the prolonging of fermentation time.Moreover,correlation analysis showed that in addition to oats and finger millet,significant negative relationships were observed between conjugated phenols against the activities of ?-glucosidase.Also,there was a significant negative correlation between the content of polyphenols in oat,millet and mica and theactivity of cellulase.It indicated that ?-glucosidase plays an important role in releasing of conjugated polyphenols from cell wall.Secondly,through measuring the effect of inoculum size,loading amount,fermentation temperature on the content of free polyphenols,the results showed that the inoculum size had the significant effect on the content of free polyphenols.The optimum conditions for SSF of A.blazei determined by orthogonal experiment was the following: inoculum size of 10%,loading amount of 125 g/bottle,fermentation temperature of 28 ?.Finally,the content of polyphenols from fermented products as influenced by processing and storage condition was evaluated.Physicochemical properties of the 7fermented products significantly changed after processing.Open-pan boiling and microwave-heating significantly reduced the content of free polyphenols,while the same was increased by roasting.There was not change in the content of free polyphenols after microwave-heating of corn.Thus,roasting was better than boiling and microwave-heating at retaining and improving the free polyphenols content of fermented products.Open-pan boiling caused greater loss on free polyphenols than microwave-heating.After the seven fermentation products were stored at different temperatures for 28 days,we found that the free polyphenols in proso millet were stable and not affected by the temperature.The contents of free polyphenols in wheat and sorghum stored at-20 ? had no significant change.Finger millet could be stored at low temperature and normal temperature,and the free polyphenols in rice and corn were stable in storage at 25 ?.The stability of free polyphenols in oats was poor.The longer the storage time was,the lower the content of free polyphenols was.