Effects of a lactoperoxidase–thiocyanate–hydrogen peroxide system on Salmonella enteritidis in animal or vegetable foods

Lactoperoxidase (LPO) from skim milk was purified by ion-exchange chromatography. The purified protein was used to catalyze the oxidation of thiocyanate by H2O2 in an antibacterial system (LPO system). The LPO system was used to inactivate or inhibit Salmonella enteritidis in tomato juice, carrot juice, milk, liquid whole egg, and chicken skin extract under various conditions. The system was found to be more effective against the organism in vegetable juices than in animal products, at low pH than at neutral pH, and at higher temperatures than at lower temperatures. Acid-adapted S. enteritidis cells were more susceptible than nonadapted cells. The system reduced numbers of S. enteritidis in vegetable products by up to 5.4 log units and inhibited growth of the organism in animal-derived foods during 4 h incubation at 30 °C. Sodium chloride (>100 mM) and polyphosphate (0.01–0.5%) enhanced the antibacterial effects of the system in tomato juice and chicken skin extract, respectively. The findings indicate that the LPO system could probably be used to prevent the growth and survival of salmonellae in minimally processed fruit and vegetable products, but combination of the system with other preservatives or treatments would be needed to effectively inhibit growth and survival of salmonellae in animal products.