Study On The Effect Of Alkaline-enzyme Combined Dehairing On Cowhide Quality And Biological Activity

With the continuous increase in the slaughter of beef cattle in China,the production of by-products—cowhide,has also increased.Actively exploring new ways for the development of cowhide edibles is of great practical significance for solving the problems of low utilization value and poor benefits of leathermaking raw materials caused by the low quality cowhide in China.In this paper,based on the previous method of alkaline-enzyme combined dehairing,the effect of this method on the nutritional content and quality of cowhide was further analyzed.This method was used to dehair the cattle carcass,analysis the impact of microbial contamination and revealed the changes in the antioxidant activity of collagen peptides extracted from cowhide after heating and heating-in vitro simulated digestion.The main findings are as follows:（1）Research on the effect of alkaline-enzyme combined dehairing on the nutritional composition and quality of cowhide.After alkaline-enzyme combined dehairing,the protein content in cowhide decreased by 4.89%,and the content of 16 kinds of amino acids decreased to varying degrees;the saturated fatty acid content in cowhide decreased by 8.06%;and the unsaturated fatty acid content increased by 6.54%.After alkali-enzyme combined dehairing,the cooking loss of cowhide increased from 5%to 30%,the water holding capacity was reduced by 25%,the shearing force value was reduced by 42%,the hardness,adhesiveness and chewiness were significantly reduced,and the gumminess and cohesiveness were reduced.After alkaline-enzyme combined dehairing,although the nutrients in the cowhide are lost to varying degrees,it still maintains a high protein content,and the tenderness of the cowhide has been improved.It can be used as a reference for further processing of edible cowhide.（2）The effect of alkaline-enzyme combined dehairing on microbial contamination of cattle carcass and cowhide quality.On the basis of the traditional slaughtering method,the alkaline-enzyme combined dehairing process was added,and it was found that the cattle carcass with the alkaline-enzyme combined dehairing in the three processes of peeling,evisceration and axe splitting,the number of coliform bacteria reduced by 0.57,0.04,and 0.14 log MPN/100cm²,and the total number of colonies decreased by 1.51,0.19,and 0.26 log CFU/cm²,respectively.The carcass coliform group and the total number of colonies decreased in the peeling process,which were 72.29%,63.44%,64.56%and 30.15%,47.03%,36.48%.During aging,the total number of colonies and the number of coliform bacteria in the alkaline-enzyme combined dehairing group remained lower than those in the control group.During aging,the shearing force value of cowhide increased first and then decreased.By 14 days after aging,the alkali-enzyme combined dehairing and control group cowhide shearing force values decreased by 63.77%and 45.66%,respectively.Cowhide hardness,stickiness and chewiness are all reduced.Compared with the control group,the microbial contamination of the beef with skin removed by the alkaline-enzyme combined method was lighter,and the tenderness of the cowhide is improved to a greater extent,which provides a theoretical basis for the realization of"skin as meat".（3）Study on the effect of heating and heating-digestion on the antioxidant activity of cowhide collagen peptides.After the cowhide is heated,the collagen peptides are extracted and simulated in vitro,it is found that the clearance rate of the cowhide collagen peptides to O₂^-·free radicals is 1.0-1.3 times that of GSH.After heat treatment,the DPPH free radical scavenging rate of cowhide collagen peptides has increased.When the mass concentration is 1 mg/mL,the DPPH free radical scavenging rate increases from 37.62%to 52.94%in the raw state（P<0.05）;O₂-·free radical scavenging rate is significantly reduced（P<0.05）;reducing power,Fe²⁺chelating ability is enhanced by heat treatment.After heating-in vitro simulated digestion,the DPPH free radical scavenging rate of cowhide collagen peptides were reduced from 37.62%to 27.68%in the raw state at a mass concentration of 1 mg/mL（P<0.05）;reducing power、the Fe²⁺-chelating ability and O₂-·free radical scavenging rate were further strengthened.Cowhide has a higher free radical scavenging rate,and the antioxidant activity is further improved by heating and simulated digestion in vitro,indicating that cowhide has the potential as a source of antioxidant peptides.