Abstract:

Three natural preservatives like Nisin, lysozyme and lactoferrin were tested for minimum inhibitory concentration (MIC) against common food-contaminating bacterial species using the agar diffusion method and for inhibitory zone diameter against Staphyloccocus aureus. To minimize total number of bacteria in chilled pork, the preservatives were complexed and the optimal formulation and the optimal pH were investigated using response surface methodology based on a central composite design involving 31 experiments at 5 levels. Results showed that the optimal complex preservative formula consisted of 0.2773% of Nisin, 0.46% of lysozyme and 0.604% of lactoferrin and the optimal pH was 5.16. Significant interaction effects between pH and either Nisin, lysozyme or lactoferrin and between lysozyme and either Nisin or lactoferrin on total number of bacteria in chilled pork were observed (P＜0.01), whereas the interaction effect between Nisin and lactoferrin was not significant (P＞0.05). These factors affected total number of bacteria in chilled pork in the decreasing order: Nisin＞lysozyme＞pH＞lactoferrin.

Key words: chilled pork, complex preservative, Nisin, lysozyme, lactoferrin, pH, total number of bacteria