| Our country is rich in peanut and its by-product after extracting oil, peanut meal, is rich, too. There are various kinds of chemical composition in peanut meal whose content of protein is high, composition of amimo acids is reasonable, price is relatively cheap. So peanut meal is a superior kind of protein resource. Its protein involves mang kinds of amino acid which are necessary to human body. Among those protein, the content of Aspartic acid and Glutamate is high, which is close to animal protein. There is no cholesterol in those protein which is easy to digest and with high nutritional value. But the solubility, emulsification and foaming ability of peanut meal are bad, which limit its application in food industry (Wu et al.,2009), so it is used as feed and fertilizer at present.The moderate enzymatic hydrolysis of peanut meal using proteinase can not only improve its physical and chemical properties, but also improve its nutritional value (Kamara et al.,2010). The main components of the enzymatic product were peptides with different molecular mass which were not only easy to be absorbed, but also of stronger antioxidative and other bioactive activities (Chen et al.,2007). So it can be applied to functional food to mitigate the damage of oxygen free radical and reactive oxygen species to human body and be used as antioxidant additive to prevent oxidation of lipid in food (Zhang et al.,2011). This article mainly studied optimization of the production process of antioxidaive peptides from peanut meal using compound enzyme hydrolysis and liquid state fermentation, and also studied the effect of degree of hydrolysis on antioxidative activity, solubility, foaming ability and foam stability.With DPPH radical scavenging ability and yield of peanut peptides as response value, the Box-Behnken experiments were carried out to optimize the production conditions of antioxidative peptides from peanut meal using compound enzyme. Results proved that Alcalase and Neutrase showed the highest hydrolysis ability compared with other commercial proteases. The optimal hydrolysis conditions was50℃, pH8.54and substrate concentration8.34%(w/w) when Alcalase and Neutrase were adopted together with a ratio of2to1. When peanut meal was hydrolyzed for16h under the optimal conditions, the yield of peanut peptides reached65.80%and the DPPH radical scavenging ability of the peanut peptides solution with a concentration of0.55mg/mL reached25.77%, which increased by7.48%and7.66%, respectively, compared with the hydrolysate of Alcalase, and10.29%and22.53%, repectively, compared with the hydrolysate of Neutrase.A large amount of by-product, Neutrase, can be accumulated during the liquid state fermentation of Bacillus subtilis AS1.398to produce antioxidative peptides with peanut meal as raw material. The results of single factor investigations and Central Composite Design show that, the optimum conditions to produce antioxidative peptides and Neutrase at the same time are inoculation amount of1%(v/v), natural pH, fermentation temperature of34℃, fermentation time of71h. Under these conditions, the DPPH radical scavenging ability of fermentation liquid predicted is81.51%and the activity of Neurtase is600U/mLWith the increase of degree of hydrolysis, the solubility of peptides produced by fermentation increased at first and then decreased, foaming ability and foam stability quickly increased at first and then were basically stable, both DPPH radical scavenging ability and reducing power gradually increased. With the increase of degree of hydrolysis, the solubility of peptides produced by enzymatic hydrolysis gradually increased at first and then quickly increased, foaming ability and foam stability at first were basicallly stable and then quickly increased, DPPH radical scavenging ability and reducing power rose at first and then reduced. When the degree of hydrolysis was11.81%and the concentration of peanut peptides was1.00mg/mL, DPPH radical scavenging ability was highest and reached93.2%. |
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