Preparation And Properties Of Chicken Feet Collagen Peptide And Its Application To Improving The Storage Quality Of Chicken Breast Meat

Collagen is a kind of important structural proteins in animal tissues.Collagen peptide with relatively low molecular weight can be formed by biological,chemical and physical means,aiming at completely open the three helical structures of collagen.A large number of collagen-rich by-products（chicken feet,skin,bones,etc.）are produced during broiler processing.At present,the chicken feet considered not edible are chicken carcasses in some western countries.Some of chicken feet are used as pet feed,while most of them are wasted.Chicken feet have a huge consumer market in China,but the molecular weight of collagen is difficult to absorb.So,using chicken feet and its byproducts as raw materials for collagen peptide extraction by enzyme can not only increase its added value,but also reduce waste of resources and environmental pollution.This thesis with chicken feet（bone）as experimental material,the first step adopts the single factor experiment and response surface optimization（Box-behnken）experiments.The best enzyme hydrolysis conditions were determined,and the preparation of the chicken feet collagen peptide,and its physical and chemical properties,basic secondary structure and antioxidant activity in vitro were studied.The collagen peptide extracted from chicken feet was applied to meat,and its improvement effect on meat quality was studied during the storage period of 4℃（cold）and-18℃（frozen）,the aim is to provide theoretical basis for developing new methods to improve meat quality.The purpose of this study is to provide relevant theoretical basis for the application and development of chicken feet collagen peptide in the food and medicine industry,cosmetics and beauty fields,and have certain practical reference significance.The research results are as follows:1.Determination of basic components of chicken feet and screening of enzymesChicken feet（boneless）contain 16.66%moisture,48.68%protein,13.21%ash and 19.87%fat.They are high in protein and low in fat,so they are a good source of collagen peptide.Papain,epsin,alkaline protease,complex protease and trypsin were used to extract chicken feet（bone）,and an enzyme suitable for the extraction of collagen peptide from chicken feet was screened out.In the enzyme extraction experiment,the solid-liquid ratio needs to be controlled at 1:15（w/v）,the ultrasonic time and ultrasonic power were set at 30 min and 200 W,respectively.The extraction temperature was 45℃with the addition of complex protease at 55℃,and the extraction time was 6.0 h with the addition of 4000～7000 U/g,collagen peptide yield of chicken feet was used as the index.Therefore,appropriate enzymes could be screened out for the following experiments by measuring the content of collagen peptide in the enzymatic hydrolysate.To mention the collagen enzyme peptide yield as index,five kinds of chicken feet collagen peptide enzyme extraction ability of high and low order as:alkaline protease>trypsin>protamex>pepsase>papain,the most significant of alkaline protease（P<0.05）,the extraction rate of collagen peptide from chicken feet was 45.46%,so this enzyme was selected to extract collagen peptide from chicken feet.2.Results of single factor and response surface optimization experimentsOn the basis of single factor experiment,with chicken feet collagen peptide yield as the measuring standard,according to Box-behnken experiment design principle,the auxiliary alkaline protease enzyme hydrolysis extraction of ultrasonic and chicken feet collagen peptide,The optimum technological conditions of chicken feet were as follows:solid-liquid ratio of 1:25.87（w/v）,ultrasonic power and extraction time of 249.50 w and 3.83 h,respectively.The estimated yield of collagen peptide was 50.1514%.Considering the actual process conditions in enterprises,the process parameters were adjusted as follows:ultrasonic power,enzyme extraction time and solid-liquid ratio were 250 W,4 h and 1:26（W/V）respectively.In order to further test the credibility of the model,three parallel tests were carried out under the optimal technological conditions,and the yield of collagen peptide was 49.2438%,which was close to the theoretical value.In another word,the response surface model can be used to optimize the extraction of chicken feet collagen peptide.At the optimum extraction time of 4 h,the hydrolysis of chicken feet collagen peptide reached 28.65%.3.Physical and chemical properties and functional characteristics analysisThe basic physical and chemical properties of chicken feet collagen peptide were tested.The molecular weight distribution of chicken feet collagen peptide is in line with the standard of collagen peptide,and it contains abundant amino acids.Polyacrylamide gel electrophoresis,ultraviolet spectroscopy,Fourier infrared spectroscopy,X-ray diffraction spectroscopy,circular dichromatography and other images were used to reflect the secondary structure of collagen peptide,and its microstructure was expressed by scanning electron microscopy.The electrophoresis analysis of polypropylene gel showed that the electrophoresis bands were basically belowα₂ chain.The characteristic absorption peak of collagen peptide was found at the wavelength of 200～230 nm by ultraviolet spectrum analysis.Fourier infrared spectrum analysis,which can get its amideⅠ,Ⅱ,A,B and amideⅢcomposition;The first two peaks of the X-ray diffraction spectrum were obvious,while the third peak was not.There was no positive absorption peak at the wavelength of 220～224 nm in the circular dichrogram,and no obvious turning point in the positive and negative absorption bands.These results indicate that its structure meets the basic structure of collagen peptide.Nitrogen solubility index was used to represent the solubility of collagen peptide.The maximum solubility of chicken feet collagen peptide was 97.5%when the p H was 7 and the extraction time was 4 h.The antioxidant activity of the chicken feet collagen peptide prepared by the optimized technology was studied.The IC₅₀ of ABTS+·radical and hydroxyl radical（·OH）scavenging ability of the chicken feet collagen peptide was 8 mg/m L and 6～8 mg/m L,the reducing ability was lower than VC,but it had better metal chelating ability.Therefore,it can be applied to cosmetics and food additive industries to enhance the added value of chicken feet and its by-products and improve the efficiency of resource utilization.4.Analysis of the effect of improving the quality of chicken breast by chicken feet collagen peptideThe chicken breast meat at 4℃and-18℃was subjected to blank treatment,soak in deionized water,ultrasound-assisted deionized water immersion,soak in chicken feet collagen peptide solution,ultrasound-assisted chicken feet collagen peptide solution treatment（five groups）during storage（4℃0/1/3/5/7 d;-18℃0/5/10/15/20d）.With blank treatment as control,cooking loss,drip loss,low field nuclear magnetic resonance index,myofibrillation index,texture index and tissue structure of chicken breast were measured.The results showed that with the prolongation of storage time,the moisture composition of both storage temperatures changed greatly.In the 4℃group,a large amount of non-mobile water was converted to free water,and the rising rate of changes in cooking loss and drip loss was faster.The water migration degree of samples in the-18℃group was smaller,and the water retention in the 4℃group was worse.The texture parameters of the ultrasonic treatment group were significantly improved（hardness decreased,elasticity increased）,and the color of meat was not significantly affected,indicating that the combined treatment of ultrasonic and chicken feet collagen peptide can significantly improve the quality of chicken breast meat in storage period.The results of this study were expected to provide technical support for the optimization of meat quality during the cold and freezing process of chicken breast meat,and also provide reference for the research and development of chicken feet collagen peptide in meat products.