Technology And Physicochemical Properties Of Alfalfa Peptides Prepared By Solid-state Fermentation

Alfalfa is a high quality legume forage with nutrients balance, and rich in protein, fat, minerals and vitamins; and is also a potential protein feed resources. The objects of the study were to decrease the level of cellulose, and increase the content of protein and acid-soluble peptide in Alfalfa meal. The methods were based on solid-state fermentation with the appropriate bacteria, prepared alfalfa protein, and then degradted to Alfalfa prptide by enzyme, we also studied physicochemical properties of Alfalfa peptide. The results were shown: 1. The Alfalfa was fermentated based on solid-state by white rot fungi, and the best process parameters were as follow: Ratio of substrate to water 1:1.2, fermentation time was 72 h, inoculum size was 108 cfu/g, and fermentation temperature was 28 ℃. The content of crude fiber was 11.90% after fermentation, that was decreased 38.34% compared with the unfermented alfalfa. The contents of alfalfa protein and true protein were 29.62% and 22.97%, respectively, compared with the unfermented alfalfa, the contents were increased 42.41% and 28.97%, respectively. The level of acid-soluble peptide was increased 12.59%. Essential amino acids and total amino acids were increased too. 2. The beer yeast was chosen as a fermented strain, response surface analysis was designed based on the single factor test. The regression equation was:Y=4.276667+0.165X1+0.73X2+0.2475X3-0.417083X12-0.3025X1X2+ 0.0025X1X3-0.842083X22-0.3225X2X3-0.577083X32. From the equation, ratio of substrate to water was 1:1.52, fermentation time was 122.6 h, and fermentation temperature was 28.3 ℃, and the content of alfalfa protein was 26.81%. After the verification test, we analyzed the true content of alfalfa protein was 26.65%, relative error to the calculator value by equation was 0.60%. The content of cellulose was 15.73%, that was decreased 18.50% comparing with the unfermented alfalfa cellulose which content was 22.37%. The content of acid-soluble peptide was increased 69.58%. 3. Alkaline extraction and acid precipitation were employed to produce alfalfa protein. Ratio of substrate to water 1:8, alkaline extraction was pH 9.0, extraction time was 30 min, and extraction temperature was 45℃, acid precipitation pH was 4.0. The efficiency of extraction was 41.25%. 4. Foaming and foaming stability of Alfalfa peptide had no significant difference between fermented and unfermented products. The water absorption and oil absorption of alfalfa peptide, which was extracted from fermented Alfalfa were more superior to the unfermented Alfalfa peptide. 4 kinds of polypeptide were contained in fermented alfalfa, the highest content of polypeptide was at retention time 6.37 min. Conclusion: the Alfalfa meal was increased the level of protein, acid-soluble peptide, and decreased the content of crude fiber after fermented with white rot fungi and beer yeast.That improved the feed quality of alfalfa grass powder.