Study Of Molecular Modification And Characteristics Of Soy Bean Protein

Processing characteristics of soy bean protein could be changed by molecular modification.Molecular modification of protein is to change one or more physical or chemical properties of protein and to change processing characteristics.Now molecular modification of protein include physical modification,chemical modification,enzymatic modification and biological modification.1. SPI was hydrolysed as soybean peptides by enzyme and soybean peptide chelation-ZincRelative research shows most of the functional soybean peptides are the low weight mass hydrolysates; and those high hydrolysis 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-utilization of peptide-zinc chelate and its antioxidant activity were explored. The results showed as following:(1)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 Asl.398,alkaline proteinase 2709,and Flavourzyme, Flavourzyme has the highest DH. The enzymatic hydrolysis products of Flavourzyme and 2709 step by step has more higher DH than papain and 2709,or 2709 and As1.398, whose average peptide chains are about 2 amino acid units.(3)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: l(mol/mol), pH 5.0, temperature 60℃, time 40min.(4) 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.(5)High performance liquid chromatography (HPLC) was introduced to analysis the peptides-zinc chelate , and the mobile phase was optimized , the optimum conditions were as follow: Lichrospher C18 column (15cmx4.6mm, 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 10ul,sensitivity 0.02. under this mobile phase the chelate can be divided to 10 fractionsaccording to the retain time .ultraviolet spectrometry (UV) and infrared spectrometry(IR) indicates the peptide-zinc is a new compound different from zinc acetate andpeptide.2. Evuation of soybean peptide chelation-Zinc functionsThe 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. Besides the peptide-zinc has the function of losing weight.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.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 palsm ,the value of T-AOC are also bigger than others .3.Molecular modification ang processing characteristics of soybean 7S globulinThis paper focused on modifying the soybean 7S globulin through acetylation, phosphonation and protease. The functions of them were estimated by the capacity of holding water, emulsification and absorbency of oil. The results indicated that both the modifications of chemistry and enzyme methods could take some meliorations to the function of Soybean 7S globulin. The capacity of holding water and the emulsification stability of soybean 7S globulin could be greatly advanced by appending acid anhydride (15%v/w), the absorbency of oil could be evidently advanced by the accession of STP(l%w/w). The capacity of holding water, emulsification and emulsification stability of soybean 7S globulin modified by pawpaw protease were evidently advanced while the hydrolyze index was 10.78%. Soybean 7S globulin could be hardly advanced by Asl.398 protease.Modification research of soybean 7s globulin and soy protein isolate (SPI) hydrolyzed by papain (DH%=3.7% and DH%=8.9%) was made separately usingascorbic acid and sodium alginate. The optimal sample was obtained by adopting five physics and chemistry indexes: viscosity, foaming property, foaming stability, emulsifying property, emulsifying stability. The result showed: the soybean 7s globulin and ascorbic acid in a ratio of 5 to 0.3,the SPI(DH%=3.7%) and ascorbic acid 3 to 0.3, the SPI(DH%=8.9%)and ascorbic acid 3 to 0.1, the SPI(DH%=3.7%) and sodium alginate 7 to 0.1,the SPI(DH%=8.9%)and sodium alginate 3 to 0.1 are preferable.the effect of the soy protein modified by ascorbic acid is more notable than by sodium alginate. sodium alginate only promote the foaming stability and emulsifying stability property of the soy protein isolate enzymed(DH%=3.7% and DH%=8.9%), but have the certainly negative action to foaming property.From the economy and appliance angle of the actual production, synthetically evaluating the five preferable samples: the soybean 7s globulin and ascorbic acid in a ratio of 5 to 0.3 is optimal.4.Molecular modification ang processing characteristics of soybean US globulinThe effect of three factors, including soaking time, precipitation pH and ice-bathing time, on the yield of soybean 1 IS globulin was studied and its mechanism was analyzed. The result of multiple linear regression analysis was : y=0.02738xST-0.4875xPH+0.028893xIT+3.8617(y: yield; ST: soaking time; pH: precipitation pH; IT: ice-bathing time; R2=0.9805). Phosphated US globulin (11SP) was prepared by modifying US globulin with sodium triphosphate (STP). It was validated by Infrared Spectrum Analysis that -PO43" was indeed imported. Compared with soybean protein isolate(SPI), functional properties of both modified and non-modified US globulin were evaluated, including solubility, emulsifying capacity, emulsifying stability and oil-holding capacity. Functional properties of phosphated US globulin were improved in different extents.5.Acidity and rheological behaviour of yogurt mixed with enzymatic soy-protein hydrolysateAcidity change and apparent viscidity change of yogurt mixed with different amount and different hydrolytic degree pea-protein hydrolysate by neutral protease As 1.398 were studied in this paper. Rheological shear stress, parameter and viscosity index in different shear rate were studied in yogurt.The result showed that to mix enzymatic soy-protein hydrolysate with milk would contributed to acidic forming in yogurt. It took shortest time to be the fermentive end for yogurt when milk was mixedwith 7.5-10% enzymatic soy-protein hydrolysate which hydrolytic degree was 5.61%. The apparent viscidity of fermented yogurt was increased when milk was mixed with 7.5% DH3.76% enzymatic soy-protein hydrolysate. Flexibility of yogurt was reduced when milk mixed with soybean hydrolysate and the yogurt was non-newtonian fluid. Shear stress of yogurt in high shear rate was far higher than CK when milk was mixed with DH8.89% enzymatic soy-protein hydrolysate.