Studies On The Two Steps Enzymatic Hydrolysis Of Pigskin Protein And Properties Of Its Hydrolysate

Pigskin was a high-quality animal protein resource which was rich in collagen. However, there were some problems such as narrowly applicated, low rate of utilizating and value-added despite of rich pigskin resources in China. In my paper, pigskin as the material was bought from market which was defatted and dried to make the pigskin protein powder. Then Alcalase alkali protease and papain protein were used to prepare smaller relative molecular mass peptide by hydrolysising pigskin protein and optimal hydrolyze process was determined. Besides, the antioxidant effect in vitro of deffirent compositions of pigskin hydrolysate which were got by membrane grading were studied as well as their processing characteristics, especially their emulsification properties in order to provide theoretical bases for the application of pigskin peptide food, health products of antixidant and new emulsifier and improve value-added of pigskin processing. This article was mainly studied as follow:1. Two-step enzymatic hydrolysis of efficient preparation of pigskin protein peptide. To optimize the preparation of small molecular weight peptide from protein pigskin by sequentially hydrolyzing, Alcalase and Papain were used and different hydrolysis time, temperature, pH and enzyme were investigated, which respectively affected the pigskin protein degree of hydrolysis (DH) and ammonia nitrogen concentration of hydrolyzate. The results showed the first step, temperature and enzyme addition significantly effected on the DH (P< 0.05). Besides, temperature and hydrolysis time significantly affacted on the ammonia nitrogen concentrations in the second step (P< 0.05). Considering the various factors to determine the optimal conditions were as follow: the pigskin proteins were hydrolyzed by Alcalase, dosage of 2100 U/g substrates, in the condition of pH 9.5,55℃for 4 hours, and then, Hydrolyzed continuously by Papain in the condition of pH 5.0,50℃and 22500 U/g adding amount of Papain for 4 hours. The degree of hydrolysis and ammonia nitrogen concentration of hydrolyzates respectively reached 16.79% and 0.956 mg/mL.2. Purification of pig skin protein hydrolysates and the molecular weight distribution of their products:To use anion exchange resin and cation exchange resin mixed bed to remove the salt in pigskin protein hydrolysates, with the peptide recovery and desalting ratio as the indicators, analyzing the effect of column temperature, elution rate, the volume ratio of anion and cation exchange resins, the initial pH of sample hydrolysates protein hydrolysates of peptides in pigskin recycling and desalination effect; Used of hollow fiber membrane desalination products were graded by three components, compared three components of molecular weight distribution. The results showed that the column temperature, elution rate and the volume ratio of anion and cation exchange resins are desalination recovery rate of the peptide had significant effects (P<0.05); on the kind of peptide hydrolysates on the recovery of the initial pH had significant effect (P<0.05), but the impact of desalination was no significant difference (P> 0.05). Determine the mixed-bed anion and cation exchange resins for the desalting of the best conditions: column temperature is 15℃, anion and cation exchange resin volume ratio of 3:1. the initial sample pH 4.0, flow rate of 10 BV/h,71.35% salt rejection at this time, peptide recovery was 96.33%. Therefore, the anion and cation exchange resins mixed bed was an effective way of desalination. The three components of the molecular weight concentrated in the less 6000 Da after desalination and classification by membranes, which existed as the form of small peptides.3. Studies on the antioxidant effect of different components of pigskin protein hydrolyzate in vitro:After the desalination, membrane classification of the three components, comparison of scavenging, ABTS radical, anti-superoxide anion, and the ability to handle different processing conditions on the ABTS radical clearance rate; analysis of amino acid composition of three components and in vitro antioxidant activity relationship. The results showed that, (1) different components of pig protein hydrolyzate with good in vitro antioxidant, antioxidant activity of different components of the size of the size of its molecular weight distribution, amino acid composition close relationship. Hydroxyl Radical Scavenging Components 1,2,3, and in turn increases were significantly different between each other (P< 0.05); the ability of resistance were superoxide anion component 2> component 3> component 1. with the significant difference between each other (P< 0.05); component between 2 and 3 the ability to remove ABTS radical difference was not significant (P> 0.05), but were significantly higher than that of component 1 (P< 0.05). (2) Pigskin protein hydrolyzate in the process of each component of its antioxidant affected to varying degrees. Among them, the component 2 clearing ABTS radicals by temperature, pH, storage time, addition of divalent ions, the amount of sugar added significant difference (P< 0.05); component 1 by pH, storage time, divalent ions concentration significantly different (P< 0.05): component 3 by pH, storage time significantly different (P< 0.05). Three, component 3 can be in the process to maintain a good antioxidant activity. 4. Studies on the processing properties of the different components of pigskin hydrolyzate. Oil absorption and solubility was compared between pigskin protein and its hydrolysate before and after pigskin protein enzymatic hydrolysis, as well as three components of hydrolysates water absorption, emulsification, emulsion stability, surface hydrophobicity and the relationship between surface hydrophobicity and emulsion. The results showed that the pigskin protien enzymatic hydrolysising before and after, its solubility and oil absorption have undergone significant changes (P<0.05). Hydrolysis products were more superior solubility and oil-absorbing than pig protein. Different components of pigskin protein hydrolysates have shown good water absorption. Comparing absorption rate among the three components, component 1 was the worst, component 3 the best and centering component 2. Emulsifying properties of different components were effect by different levels of pH, protein concentration, oil content, ionic strength and other factors. Including components of the emulsifying properties of 2 and 3 significantly better than component 1 (P< 0.05). The surface hydrophobicity index of different components had significant differences among them (P< 0.05), with the order component 2> Segment 3> component 1. Besides, the surface hydrophobicity of protein affected the emulsifying properties may be an important factor.5. Studies on the properties high-protein emulsions propared by the different components of Pigskin hydrolyzate:High-protein emulsions of Components 1,2.3 were prepared, and viscosity, elastic modulus, and morphology were compared. The results showed that the three high-protein emulsions have shown the nature of pseudoplastic fluid, shear thinning; at low speed, the three high-protein emulsions modulus changed significantly affected by the angular frequency, as the frequency increases sharply. Also, the variation shown three similar:When the angular frequency in the 0.1～1.5 rad/s, G"> G', emulsion system showed the nature of the liquid, dominant; when the angular frequency in the 1.8～100 rad/s, G'> G", the emulsification system showed flexibility advantage. Microscopy showed the formation of component 2 and component 3 is more homogeneous and delicate emulsion system, components 1 of the emulsion system formed a coarse system, which may be related to the size of each component on its emulsifying capacity.