| In order to research the characteristics of duck heart protein, the duck heart muscle tissue protein was studied. The duck heart protein was divided into non protein nitrogen, myofibrillar protein, matrix protein and sarcoplasmic protein. The protein accounts for duck heart protein proportion and amino acid composition was analysised. In order to optimize the duck heart protein enzymolysis condition, the response surface experiment was carried out based on the single factors. 3K and 10 K hollow fiber ultrafiltration membrane module were used to separate duck heart protein peptides. Part I(less than 3KD), part II(3-10KD) and part III(more than 10KD) were obtained. The processing properties was researched of part I, part II and part III, including solubility, emulsifying and emulsion stability, foaming and foaming stability, viscosity, composition of free amino acid. The weak luminescence analyzer was used to analysis antioxidant capacity of different parts of duck heart protein peptides including scavenging rate of superoxide anion, scavenging rate of hydroxyl radical and DNA damage protection. The scavenging power of DPPH and reducing force were determined, too. And the inhibitory effect of different components of duck heart protein polypeptide on cholesterol micelles and the antibacterial activity were determined.Duck heart protein was consisted by the sarcoplasmic protein, myofibrillar protein, matrix protein and non protein nitrogen. The ratio of each proteins was as follows: The sarcoplasmic protein accounted for 40.57%. The matrix protein accounted for 30.99%. The myofibrillar protein accounted for 21.99%. And non protein nitrogen accounted for 1.94%. The duck heart protein separation is completely.The papaya protease, neutral protease, trypsin and alkaline protease were used as protease to enzymolysis duck heart protein. DPPH clearance and hydrolysis degree as indicators, the neutral protease was screened out for the enzymatic hydrolysis of duck heart protein as the best enzyme. The enzymatic hydrolysis time, the amount of enzyme, enzymatic hydrolysis temperature and pH were chose as single-factors. Based on the single-factor experiments, the response surface methodology was carried out. The optimal conditions were as follow: hydrolysis time of 3.90 h, enzyme amount of 0.31%, hydrolysis temperature of 45.5 °C, pH value of 7.15. The hydrolysis degree can reach 17.51% in theory. Considered the feasibility of the test, the optimal conditions were modified as follows: enzymolysis time of 4.0 h, enzyme amount of 0.30%, hydrolysis temperature of 45 °C, pH value of 7.0. The confirmatory test was carried out three times and the hydrolysis degree could reach 17.49%.The viscosity of duck heart peptides were measured. The order of viscosity was as follows: part I< part II< part III; The duck heart peptides have good solubility. When the pH value is 5, the solubility of each part are relatively low, which indicated that isoelectric point of duck heart peptides is around pH=5. The order of solubility of each part is part I>part II>part III. When the pH value is 5, emulsification and emulsion stability of each parts were rapidly decreased to the minimum. And the order: part I> part II> part III; The foamability and foam stability are also determinated, and the results showed that part I has no foamability and foam stability. The foamability and foam stability of part II was weak. The part III has good foamability and foam stability. The foamability of part III was 180% and foam stability was 30%. The order of foamability and foam stability was as follows: part III >part II>part I. With the decrease of the molecular weight of the duck heart peptides, the viscosity decreased, the solubility increased, the stability of the emulsion and the emulsion showed an upward trend, and the foamability and foam stability decreased.Amino acid analysis found that essential amino acid of part I, part II and III was 36.91%, 33.23% and 29.17%, respectively. Essential amino acid of part I is the highest. The antioxidant amino acid of part I, part II and III was 9.12%, 6.43% and 5.97%, respectively. Thus the antioxidant activity of part I may best. The flavor amino acid of part I, part II and part III were 23.21%, 24.68% and 20.14%. The flavor amino acid of part II is highest. The branched chain amino acids of part I is highest which was 19.13%. And part II was the lowest, only 13.06%.The antioxidant capacity, cholesterol micelle inhibition rate and antibacterial activity of part I, part II and part III were compared and analyzed.DNA damage and antioxidant activity test showed that with the increase of sample concentration, removal rate increased, in a dose- effect relationship. The reducing power of Vc, part I, part II and part III was 2.2720, 0.4107, 0.3437 and 0.2130, respectively. The reduction order: part I >part II> part III, but they were significantly lower than that of VC; In the DPPH scavenging test, duck heart peptides' DPPH clearance rate was significantly lower than that of Vc. The clearance rate of DPPH order: part I > part II> part III; The duck heart peptides has superoxide anion scavenging ability. The IC50 of part I, part II and part III were 25.06mg/mL, 33.18mg/m L and 48.02mg/m L, respectively; The order of superoxide anion scavenging ability is as follows: part I > part II>part III; The IC50 of hydroxyl radical of part I, part II and part III were 279.92ug/mL, IC50 388.28ug/m L and 2.89mg/m L, respectively. The order of scavenging ability of hydroxyl radical is as follows: part I > part II>part III. The IC50 of DNA injury protection of part I, part II and part III were 2.65mg/m L, 4.34mg/m L and 4.23mg/m L, respectively. The order of DNA protection is as follows: part I > part II>part III.The cholesterol solubility inhibition rate of each part of Duck heart protein peptides were 33.43% and 14.49% and 2.58%, respectively. Bacteriostatic test showed that the part III had no inhibitory effect. Part I and part II had some inhibitory effect. The inhibition effect of part I was significantly higher than that of part II. Part I can inhibit Staphylococcus aureus obviously, Enterobacter sakazakii, Salmonella, and Bacillus cereus. Part II can inhibit the growth of Enterobacter sakazakii and Salmonella in certain degree. All parts had no inhibitory effect to Proteus. Thus, duck heart peptides in small molecular weight have good function. |
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