Effects Of Solid-state Fermentation With Agaricus Bisporus On Nutritional Components And Antioxidant Properties Of Cereals

Wheat,rice,corn,millet,broomcorn millet and oat are the most common gramineous plants in our province,which can provide protein,fatty acids,vitamins,minerals and other nutrients.In recent years,the cereals were processed excessively to get better taste,which resulted in a great loss of nutrients.In addition,a large amount of active ingredients,such as polyphenols,are existed in the valley skin and the aleurone layer of cereals and can not be absorbed adequately.Many researches showed that fermentation could improve the nutritional value of cereals,and most studies use yeast,small filamentous fungi and bacteria as starter cultures and had achieved certain results.Agaricus bisporus contains rich polysaccharides,nucleotides,vitamins,flavonoids,polyphenols and high quality protein.Moreover,A.bisporus contains 8 kinds of essential amino acids,especially lysine and tryptophan,which is lacking in many cereals.However,there are few studies about the solid-state fermentation with A.bisporus on the cereals medium.Solid-state fermentation（SSF）of wheat,rice,corn,millet,broomcorn millet and oat with A.bisporus were carried out.The polyphenols contents of fermentation products were determined and phenolic acids were isolated and identified.The effects of SSF on antioxidant properties of cereals were analyzed.The effects of SSF on carbohydrates and protein of cereals were determined.The protein nutritional value of fermentation products were evaluated according to the amino acid score（AAS）,essential amino acid index（EAAI）,nutrition index（NI）and fuzzy identification method.This study can provide a theoretical basis for improving the nutritional value of cereals and enriching cereals fermentation food.The main results are as follows:1.The contents of free polyphenols,conjugated polyphenols and total polyphenols of cereals were determined after SSF.The result showed that the conjugated polyphenols contents decreased significantly（P<0.05）,and free polyphenols contents and total polyphenols increased significantly（P<0.05）.In the control,free polyphenols contents of weat,rice,corn,broomcorn millet and oat were 1.093,0.005,0.022,0.009 and 0.015mg/g,total polyphenols contents were 1.665,0.066,0.691,0.210 and 0.350 mg/g,after SSF of 30days,free polyphenols contents were 3.908,0.462,1.932,3.033 and5.782mg/g,which were 2.58,94.84,88.84,326.65 and 383.86 times higher than that of control respectively,total polyphenols contents were 4.228,6.99,2.329,3.197and 5.938mg/g,which were 1.54,2.37,14.25 and 15.98 times higher than that of control respectively.However,the contents of free polyphenols and total polyphenols of millet reached the maximum after SSF of 20 days,which were 0.82 and 0.67 times higher than that of control respectively.After SSF with A.bisporus,the phenolic acids were more abundant in the fermentation products of six cereals.2.The effect of SSF on antioxidant properties was determined.The result showed that the antioxidant properties（DPPH radical scavenging capacity,reducing power,ferrous ion chelating ability and superoxide anion radical scavenging ability）of fermented careals were improved significantly.The improvement degrees of corn in DPPH radical scavenging capacity and superoxide anion radical scavenging ability were the highest after SSF of 30days,which the EC₅₀0 value in DPPH radical scavenging capacity decreased from11.02 to 0.08 mg/mL and superoxide anion radical scavenging ability decreased from 26.18 to 2.24mg/mL,the improvement degrees of oat in reducing power and ferrous ion chelating ability were the highest after SSF of30 days,which the EC₅₀0 value in reducing power decreased from 28.06 to0.13 mg/mL and ferrous ion chelating ability decreased from 18.72 to 2.60mg/mL.3.The effects of SSF on carbohydrates contents and the activity of carbohydrates hydrolases in the SSF process were determined.The result showed that the content of reduce sugar of six cereals increased significantly（P<0.05）and the oat were the highest,which was 77.12 times of control.The content of total sugar and starch decreased significantly（P<0.05）,total sugar contents in corn fermented with A.bisporus and starch contents in oats were the lowest,which were 87.5%and 61.6%of control respectively.The hydrolase of carbohydrates（α-amylase,β-glucosidase and xylanase）were produced in the SSF process of six cereals,and with the change of time,the activity of three hydrolytic enzymes present different trends.4.The effects of SSF on the content of water soluble protein and crude protein of six cereals were determined.The result showed that crude protein and water soluble protein contents increased significantly after SSF（P<0.05）.In the control,water soluble protein contents of wheat,rice,corn,millet,broomcorn millet and oat were 13.00,5.07,18.15,5.96,8.78 and 12.9mg/g,after SSF of 30 days,the contents were 58.36,31.77,43.16,33.61,60.06 and 73.14 mg/g,which was 4.51,6.30,2.42,5.59,6.82 and 5.66 times of control respectively.5.The effects of SSF on the content of amino acids and the nutritional value of protein of six cereals were determined.The result showed that the variety of amino acids of cereals were more complete after SSF with A.bisporus,the essential amino acid（EAA）,total amino acids（TAA）and EAA/TAA were higher than that of control,in addition,the AAS,EAAI,NI and the close degree（CD）of cereals were higher than that of control after SSF.These results showed that fermentation can improve the nutritional value of grain protein.