Application Research Of Exogenous Lipase Enzyme On Mature Of Dry-cured Duck Leg

In this study, we take frozen duck leg meat as raw material, which is disposed by enzymolysis of exogenous lipase. After marinating, roasting and smoking, drying preserved duck leg, we make quantitative research on the parameters of the enzymolysis which could shorten the maturation cycle of dry-cured duck. Quality index of the dry-cured duck during the processing is also concerned in our research.Main content of this study is organized as following:At first, we take study on the quality indexes variation of thawing raw material duck legs within24hour. Quality indexes of thawing duck leg, including moisture, water activity, pH, acid value, peroxide value, diene value, thiobarbituric acid value(TBA), carbonyl value, activity of acid lipase, neutral lipase and lipoxidase, are measured under room temperature at1st,6th,12th,18th,24th hour. The results show that pH value, acid value, TBA value are continuous increasing in24hour, these values reach the level of0.8869mg/g,6.36å'Œ0.3216mg/100g respectively at last. At the same time, there is no significant change in moisture, water activity, peroxide value, diene value, carbonyl value, as well as activity of acid lipase, neutral lipase and lipoxidase. Quality index of sampling in12th hour is better than others under room temperature.Then we take study on processing method of enzymatic hydrolysis of dry-cured duck leg. Single factor test and orthogonal test are utilized to determine the best production method of dried duck leg processed by enzymatic hydrolysis:1.65×105U/L neutral lipase,1.5hour hydrolysis,30℃hydrolysis temperature,3%salt content. The score of sensory testing, peroxide value, TBA value are regarded as index to determine the optimum roasting conditions:baking dry-cured duck legs2hour in60℃.As the third part, quality index variation of both enzymolysis dry-cured duck leg and the control group are studied. The dry-cured duck legs are sampled after marinating, roasting, smoking, and drying of the4th,7th,10th,14th,18th,21st,24th,28th day respectively, to make sensory evaluation and to assay physical and chemical indexes which includ moisture, water activity, free fat acid(FFA), pH, peroxide value, thiobarbituric acid value and so on. Sensory evaluation show that the optimal results appeared on the test group drying for14days and control group drying for21days. Physical and chemical indexes implicate that after14days’drying, moisture and water activity decreased to45.9%and0.806, respectively. Saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) in the FFA increased to3.63g/100g fat and2.033g/100g fat respectively. Peroxide value and TBA value increased to0.0326g/100g fat and0.7892mg/100g fat. The parameters of the test group drying for14days are were at the same level with the ones of the control group drying for21days. Results demonstrat that comparing to control group, test group can shorten maturation cycle about a week, to14days’ period.In the final part, we take study on the volatile components of the sampling from enzymolysis dry-cured duck leg, the control group and the product on the market. Sampling is taken from the control group drying for21days, test group drying for14days, and the product on the market drying for21days, then volatile components of these sampling is extracted and quantified. Results demonstrate that sampling of product on the market drying for21days contains9kinds of aldehyde,1kind of alcohol,7kinds of hydrocarbon; Sampling of the control group drying for21days contains7kinds of aldehyde,2kinds of alcohol,9kinds of hydrocarbon. Sampling of test group drying for14days contains7kinds of aldehyde,2kinds of alcohol,9kinds of hydrocarbon. The concentration of aldehyde and hydrocarbon in the product on the market is0.28%,20.07%, while the value of the test group is0.21%,20.29%, and the control group is0.03%,22.27%. Results show that quality of test group drying for14days and product on the market drying for21days are at the same level.