Technolog Optimization For Rice Bran Solid State Fermentation And Its Effects On The Nutritional And Functional Properties Of Rice Bran

Rice bran is the main by-product of rice processing,which contains a variety of nutrients needed by the human body,and is rich in phenols,dietary fiber and other bioactive substances,so it is a kind of agricultural raw materials with great development value.However,due to the high content of insoluble dietary fiber in rice bran,the eating quality of rice bran is poor,which has become an important problem to limit the food utilization of rice bran.Microbial fermentation is a traditional food processing technology.The fermentation treatment of rice bran by using the characteristics of cellulase secreted by some microorganisms is a possible way to improve the eating quality of rice bran.In addition,the previous studies of the project team showed that rice bran was rich in bound phenols covalently bound to dietary fiber,and microbial fermentation treatment could significantly increase the release of bound phenols,thus improving the antioxidant and other biological activities of rice bran.Because of the differences in growth characteristics and enzyme production ability of microorganisms of different species,there will be significant differences in the effects on the quality of fermentation substrates.In order to establish fermentation conditions to effectively improve the nutritional function and quality of rice bran,the effects of different microbial fermentation on the content of free phenols in rice bran were compared,and the solid-state fermentation conditions were established to effectively promote the release of phenols in rice bran.The bioaccessibility of phenols in rice bran during simulated digestion and glycolysis in vitro was analyzed.The purpose of this paper is to provide the basis for the establishment of processing technology to effectively improve the nutritional function and quality of rice bran.The main results and conclusions are as follows:1 ? Optimization of solid-state fermentation process of rice bran and its effect on phenols in rice bran.By comparing the effects of microbial species,fermentation time,fermentation temperature and inoculation amount on the content of free phenols in rice bran,the solid fermentation conditions were optimized as follows: the fermentation strain was Rhizopus oryzae,the fermentation time was 5 days,the fermentation temperature was 30 ? and the inoculation amount was 1%.The phenolic composition spectrum and antioxidant activity of rice bran before and after fermentation were compared and analyzed.Due to the increase of free phenols content,the content of total phenols and total flavonoids in rice bran(FDRB)after solid-state fermentation increased by 59.9% and 42.0%respectively compared with DRB,but there was no significant difference in the content of bound total phenols and total flavonoids in rice bran before and after fermentation.Ten phenolic acids such as Gallic acid,protocatechuic acid,p-hydroxybenzoic acid,vanillic acid,eugenic acid,ferulic acid and caffeic acid were identified by DRB and FDRB.The contents of Gallic acid,protocatechuic acid,p-hydroxybenzoic acid,vanillic acid and syringic acid in rice bran increased significantly after fermentation.Ferulic acid is the main phenolic compound found in fermented and unfermented rice bran,but the content of ferulic acid in fermented rice bran is significantly lower than that in unfermented rice bran(p<0.05).A large number of new components are produced in rice bran fermented by Rhizopus oryzae,and its structure needs to be identified.After fermentation by Rhizopus oryzae,the antioxidant activities of ABTS,FRAP and ORAC of rice bran increased by 31.0%,20.6% and 30.7%respectively compared with DRB.2 ? Effect of solid-state fermentation of Rhizopus oryzae on the digestion and glycolysis of rice bran phenols in vitro.The results showed that solid-state fermentation of Rhizopus oryzae could significantly enhance the bioaccessibility of phenols and flavonoids in rice bran during simulated digestion and colonic fermentation in vitro 32.6% and 46.3% of unfermented rice bran increased to 53.4% and 51.7% of fermented rice bran,respectively.Rhizopus oryzae fermentation changed the composition spectrum of phenols released into digestive juice of rice bran during simulated digestion and colonic fermentation in vitro.The release of protocatechuic acid and syringic acid from FDRB was significantly higher than that of DRB,to coumaric acid and ferulic acid and lower than that of DRB.During in vitro digestion.In the stage of colon fermentation,the dynamic change trend of Gallic acid release of FDRB and DRB was different,but the maximum release was similar.The release of ferulic acid,coumaric acid and erucic acid in DRB was significantly higher than that in FDRB.The antioxidant capacity of FDRB simulated digestion and glycolysis in vitro was significantly higher than that of DRB.During colonic fermentation for 24 hours,FDRB and DRB increased the production of acetic acid,propionic acid,n-valeric acid and isovaleric acid,and the increasing effect of FDRB was significantly higher than that of DRB,but FDRB glycolysis significantly decreased the production of n-butyric acid and isobutyric acid by intestinal microorganisms,while DRB had no significant effect on the production of two kinds of SCFA.To sum up,solid-state fermentation can improve the polyphenol content,antioxidant activity and probiotic activity of rice bran,and improve the nutritional value of rice bran to a certain extent,which provides a theoretical basis for the development and utilization of rice bran-related functional products.