| Soybean is one kind of widely distributed agricultural products. Its protein plays an active role in modern food industry and new food resource researches. Relative research shows most of the functional soybean peptides are the low weight mass hydrolysates, and those peptides can improve the absorbability of zinc. This paper studied the optimum hydrolysis conditions of soybean protein with single enzyme and compound enzymes, and the zinc chelating condition with low weight mass hydrolysates. Furthermore the Bio-availavility of peptide-zinc chelate and its antioxidant activity were explored. The results are showed as following:1, Study on the effect of Acid or heat pre-treatment on the DH showed that the heat pre-treatment facilitated enzymatic hydrolysis of SPI by increasing the degree of hydrolysis (DH) than Acid (0. 05N, 0.1N, 0. 2N) pre-treated . 2 , Among the papain , neutral proteinase As1.398, alkaline proteinase 2709, and Flavourzyme, The degree of hydrolysis of Flavourzyme is bigger than 2709, than papain , and As1.398; and 2709+Falvourzyme is bigger than Papain +2709, and Asl. 398+2709. Bisides the 2709+Falvourzyme, both 2709+Falvourzyme and Asl. 398+2709 have the bigger DH than their single enzyme. 3, The result of the study on distribution of hydrolysis says the group of Flavourzyme has more low molecular weight peptides , than Papain +2709, than Asl. 398+2709, or 2709. but because the hydrolysis of Asl. 398+2709 has more clear content than others , so it is choosed as the material of peptide-zinc. 4, The optimum chelating conditions of soybean peptides with zinc acetate is the concentration of peptides is 4%(W/V), the ratio of peptide to zinc 2.25: 1(mol/mol), pH 5.0, temperature 60*C, time 40min. 5, With the polarity increasing of solution , the solubility of peptide-zinc is enhancing; and has the most solubility of 0.1055 g/100ml in water at pH4. 6, High performance liquid chromatography (HPLC) was introduced to analysis the peptides-zinc chelate , and the mobile phase was optimized , the optimumconditions were as follow: Lichrospher C18 column (15cm 4.6mm, 5um); The gradient elution method changed from 5% acetonitrile(0.1% formic acid/ acetonitrile) (V/V) to 60% (0.1% formic acid/ acetonitrile)in twenty minutes; UV detection wavelength: 280nm and 220nm; flow rate:lml/min; column temperature 20 .Injection volume lOul, sensitivity 0.02. under this mobile phase the chelate can be divided to 10 fractions according to the retain time . ultraviolet spectrometry (UV) and infrared spectrometry (IR) indicates the peptide-zinc is a new compound different from zinc acetate and peptide.7, The biological activities of peptide-zinc were analyzed. Among the parallel panel: Zinc sulfate, zinc glucose, zinc met and peptide-zinc , they have no different effect in the weight of Wistar rats' liver .kidney, brains , and testicle; But organic zinc can improve the weight of spleen, and the groups of peptide-zinc have more great influence than other groups. 8, Because of The groups of peptide-zinc having less fat than other groups, so it indicated the peptide-zinc also has the function of losing weight. 9, The groups supplying peptide-zinc with 20ppm {low dose zinc, LDZ}and 40ppm(high dose zinc, HDZ) zinc have the same zinc aggradation , both of them can improve the zinc utility than other zinc supplements. LDZ has the same effect with the ones with 40ppm, such as Zinc sulfate, zinc glucose and zinc met groups.10, The activity of AKP in HZ is higher than others, and the activity is depend upon the peptide-zinc' s concentration. The HDZ and 30ppm peptide-zinc (moderate dose zinc, MDZ ) have a lower MDA content , and a higher activity of SOD in liver plasm , the value of T-AOC are also bigger than others . All these indicate that peptide-zinc have the antioxidant activity.
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