| The okara is the by-product of processing tofu or soy milk,which is full of nutrition and rich in dietary fiber,protein,fat,vitamins and minerals.The water content of the okara is as high as 70%~85%,which is very easy to be spoiled,causing most of the okara to be discarded or incinerated,resulting in waste of resources.Therefore,it is necessary to find a new method to utilize the okara.The high content of cellulose and hemicellulose in the okara hinders the release of nutrients from the okara,and selecting the appropriate strains can improve this condition.This research explored the screening of solid fermentation strains of okara,and the changing of nutrients,functional components and antioxidant activities during fermentation.The main results are as follows:1.Ganoderma lucidum,Flammulina Velutipes,Agrocybe cylindracea and Clitocybe maxima as the target strain,with sodium carboxymethyl cellulose,microcrystalline cellulose,filter paper and xylan as single carbon source,screened by Congo red plate staining method Ganoderma lucidum was been selected for its strong hydrolysis ability of cellulose and hemicellulose.2.The solid fermentation process of okara by ganoderma lucidum mycelium can be divided into three stages,the early fermentation period lasts 5 days,the late fermentation period lasts the next four days,and the aging period lasts the last 2 days.The degradation effect of ganoderma lucidum mycelium on okara was different in the three fermentation stages.At the early stage of fermentation,the mycelium had obvious degradation effect on the cell wall of okara;at the late stage of fermentation,the mycelium had obvious degradation effect on the cell contents of okara;at the aging stage,a large number of holes appeared on the surface of okara particles.The qualitative and structural properties of okara were changed by the fermentation.3.The changes of extracellular enzymes during the solid fermentation of okara by ganoderma lucidum mycelium were as follows.In the fermentation process,hemicellulase activity is higher than cellulase and pectinase.Hemicellulase activity reached the maximum value of 97.25 U on the 7th day of fermentation,and pectinase activity reached the maximum value of 27.45 U on the 3th day of fermentation.The maximum activity time of the four cellulases was different: the maximum value of cellulase was reached at the 3rd day of fermentation.the maximum value of cellulase and ?-glucosidase was reached at the 5th day of fermentation,and the maximum value of filter paper enzyme was reached at the 9th day of fermentation.4.The nutritional and functional components of okara during solid fermentation has changed.Compared with unfermented okara,the polysaccharides and oligosaccharides reached the maximum at the third day,which increased by 6.01% and 29.10% respectively.Insoluble dietary fiber at the 5th day reached the minimum,which was reduced by 29.53%.Triterpenes peaked at 90% at the 5th day.On the 7th day after fermentation,soluble protein,amino acid nitrogen and reducing sugar reached the maximum,increasing by 3.57 times,7.57 times and 32.80% respectively.At the 9th day of fermentation,the oligopeptide reached the maximum,with an increase of 64.62%.At the 11 th day of aging,the maximum amount of crude protein and polyphenols was reached,which increased by 15.45% and 50% respectively.Through the above research results,it was found that the accumulation of metabolites was relatively high in post-fermentation of fermented okara by ganoderma lucidum mycelium.5.The in vitro antioxidant activity of fermented okara by ganoderma lucidum mycelium was improved.The scavenging ability of ABTS free radical of ethanol-extraction was the strongest,followed by hydroxyl free radical and DPPH free radical.The scavenging ability of ABTS free radical of water-extraction was the strongest,followed by hydroxyl free radical scavenging ability,total reducing power and DPPH free radical.There was a phase correlation between the components and the four antioxidant abilities. |
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