| The Xuefeng black-bone chicken is famous for the name of the “five black”, which can be used in medicine and food as a kind of chicken. It is rich in protein, and also rich in many essential amino acids, vitamins and trace elements. Rich small peptides will be created after hydrolysis. These small peptides were absorbed rapidly and have high biological activity; which were good for the health of human, so this is the hot topic in the development of health food at present. In this paper, the Xuefeng black chicken are used as raw material, and were subjected to ultrasonic assisted enzymatic pretreatment of high pressure water extraction, hydrolyzed protein with protamex. Among them, bitterness value is used as a reference index to get more short peptides. The residues after hydrolysis were mixed with chicken to ferment with lactic acid bacteria in order to obtain highest content of short peptides. Then we determined the antioxidant ability of peptide from protein hydrolyzed. The main conclusions are as follows:The Xuefeng black-bone chicken are used as raw materials, the conditions were explored using ultrasonic combined with the technology of high pressure water extraction. In order to improve the efficiency of hydrolysis, the pre-treatment to active peptide of enzymatic extraction of Xuefeng black-bone chicken were made. The content of short peptides and amino nitrogen were used as indicators to explore the optimal conditions of ultrasonic power and time. The results showed that: The fowl meat were hydrolyzed and extracted by high pressure under the condition of ultrasonic at 320 W for 30 min, the highest content of short peptide is 9.366mg/m L, and amino nitrogen content is up to 0.587 mg/m L. At the same time, the control group peptide content is 5.297 mg/m L, and the content of amino nitrogen is 0.291 mg/m L.The pretreated Xuefeng black-bone chickens were optimized using the composite protease(Protamex), to get more short peptides considering bitterness value in a reasonable range. Single factor experiment on the substrate concentration, reaction time and enzyme dosage were done, and explored the optimum conditions for enzymatic hydrolysis process by orthogonal experiment. The results showed that the sequence of effect on the content of short peptide: substrate concentration > reaction time > enzyme dosage, the optimum conditions of enzymatic reactor is substrate concentration of 9.0%, hydrolysis time of 1.5h, enzyme dosage of 4.0k U/g. In this condition, the content of short peptide is 44.643 mg/m L, and bitter taste is less than 5.With the mixture of bones and meat of Xuefeng black-bone chickens as the raw material, the lactic acid bacteria fermentation formula and the optimal fermentation conditions were researched and determined. The additive amount of the optimal fermentation formula was determined as 1.0% under the condition of adding lactobacillus casei, Lactobacillus bulgaricus and Streptococcus thermophilus bacteria at the ratio of 3:1:1, inoculation amount of 5.0%, 37 ? for 24 h fermentation, the substrate concentration of 4.0%. And in this condition, the short peptide content is 20.194 mg/m L. Furthermore, the optimal fermentation condition was determined by using the orthogonal experiment. The results showed that the affecting elements could be arranged in the descending order of importance: the loading quantity, the substrate concentration, followed by the fermentation temperature. It can be concluded that the optimal fermentation condition is the substrate concentration of 6.0%, temperature of 39?, and the loading quantity of 25 m L. On this condition, the short peptide content is 23.894 mg/m L.The antioxidant function test of Xuefeng black-bone protein hydrolyzed: the supernatant of supernatant were obtained by optimal solutions described above. The results showed that the active peptide of Xuefeng black-bone possess the ability of scavenging and reducing capacity, and the percent of scavenging and reducing capacity enhanced with the increasing of active peptide concentration. Among them, the scavenging rate of hydroxyl radical was 89.79% at the concentration of 15mg/m L; the scavenging rate of DPPH radical was 89.74% at the concentration of 20mg/m L; the scavenging rate of superoxide anion radical was 52.76% at concentration of 5mg/m L. At the concentration of 20mg/ml, the absorbance value was 0.750, whose reducing capacity was equivalent to VC at the concentration of 0.12 mg / m L.In summary, in order to get the highest content of short peptide under the premise of bitterness value of less than 5, the best conditions of ultrasonic pretreatment with high pressure water extraction and enzymatic hydrolysis were determined to get the active peptide of Xuefeng black-bone chicken. The residues after enzymatic hydrolysis were mixed with chicken to fermentative, and the best fermentation formula and fermentation conditions were got, and determining the fact that the active peptide of Xuefeng black-bone chicken hydrolyzed had the antioxidant function. The paper provides a theoretical basis and technical guidance for the utilization of Xuefeng black-bone chicken and development of Xuefeng black-bone chicken functional foods. |
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