| A variety of biochemical reactions that participate the flavor formation during cured meat products processing are usually catalyzed by various endogenous enzymes, such as proteases, lipases, lipoxygenase etc. Process temperature and salt content are closely related to the endogenous enzyme activities. It is possible to find out the optimal temperature and salt content that influencing the enzyme activity under the premise of ensuring the flavor quality of cured meat products, so as to achieve the objectives of enhancing enzymatic activities, promoting protein degradation to form flavor compounds and shortening the process time. In this study, alanine aminopeptidase(AAP) was purified from turkey skeletal muscle, in order to explore the regulation mechanism of AAP activity, improve the production process and product quality during dry-cured turkey ham processing, the characteristics of AAP and interactions of processing factors on its activity were studied, and investigating the correlations between AAP activity, its product amino acids and processing regulation factors. The detailed contents and results of this study were as follows.1、The enzymatic characterisation of an alanine aminopeptidase from turkey skeletal muscle and the effect of salt and its hydrolysis products to enzyme activityAlanine aminopeptidase was purified from turkey skeletal muscle by using45%～65%ammonium sulphate fractionation, its enzymatic properties and the effect of salt and its hydrolysis products to enzyme activity was studied, the results showed that AAP optimum reaction temperature was37℃～39℃, and the optimum pH was approximately7.0.0.8mol/L NaCl inhibited the activity of AAP by10%, salt had a weak inhibition function to AAP activity. Alanine(Ala) which was the major hydrolysis product almost had no inhibition to AAP, while the other product amino acids had significant feedback inhibition (P<0.05) to AAP,100mmol/L phenylalanine(Phe)、lysine(Lys)、leucine(Leu) and methionine(Met) separately reduced the activity of AAP by69.7%、81.6%、55.8%and67.6%. 2、The study on the regulation method of the alanine aminopeptidase activityThe alanine aminopeptidase was extracted from the turkey ham and the interaction of temperature, pH and NaCl concentration to AAP activity from turkye muscle was studied by response surface experiments. Multiple regression equation getting by multiple regression method was to predict the actual AAP activity during air-drying mature process. The results showed that:temperature and pH had a significant influence on the activity of AAP, and there was a significant interaction (P<0.05) between them. The critical value influencing the AAP activity of temperature decreased with the increasing of pH values; the effect of NaCl to the AAP activity was not significant(P<0.05), and the interactions between NaCl concentration and temperature, pH, were not found. The optimal reaction conditions for AAP were reaction temperature38.17℃, the buffer system pH6.67, and the salt content24.56mM,and the AAP corresponding activity was8.551U/g.3、The study on the air-drying ripening processing of dry-cured turkey ham and the effect on the alanine aminopeptidaseThe turkey ham was processed to dry-cured turkey ham through intensifying high-temperature ripening process. The parameters of intensifying high-temperature ripening of dry-cured turkey ham was optimized by orthogonal test. The order of all factors was:air-dried days> temperature of the intensifying high-temperature> salt amount of dry-cured; and the optimal processing was:100g meat with3g salt, intensifying high-temperature temperature50℃, air-drying ripen nine days. The actual AAP activity was predicted by multiple regression equation getting from response surface test, and the correlation analysis of actual AAP activity and process parameters and product amino acids were studied. The results showed that:predicted AAP activity,total free amino acids (∑FAA), air-dried days showed a significant positive correlation (P<0.01), but with no correlation to the temperature of intensifying high-temperature and the amount of cured salt;∑FAA and sensory scores showed a significant positively correlation (P<0.01). This meant extending air-dried days could increase AAP activity and intensifying high-temperature temperature had no influence on the activity of AAP. These results indicated that AAP acting during the air-dryin ripen stage, appropriate increasing air-drying ripen temperature can increase the AAP vitality with a conditions of low pH, and raising the temperature before air-drying ripen stage could not increase in AAP activity. |
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