Antibacterial activity of the lactoperoxidase system against food-borne pathogens in Saanen and South African Indigenous goat milk Eyassu Seifu a, * , E.M. Buys a , E.F. Donkin b , I.-M. Petzer b a Department of Food Science, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa b Faculty of Veterinary Science, University of Pretoria, Onderstepoort 0110, South Africa Received 16 February 2003; received in revised form 7 July 2003; accepted 8 July 2003 Abstract The effect of the lactoperoxidase (LP) system on the growth and survival of Escherichia coli, Staphylococcus aureus, Listeria monocytogenes and Brucella melitensis was determined in goat milk samples kept at 30 °C for 6 h. The LP system exhibited a bactericidal effect against L. monocytogenes and Br. melitensis both in Saanen and Indigenous goat milks. The LP system was bactericidal against S. aureus in Saanen goat milk and bacteriostatic against S. aureus in Indigenous goat milk. However, the LP system was bacteriostatic against E.coli both in Saanen and Indigenous goat milks. The results of this study suggest the potential of the LP system to control the growth of food-borne pathogens in goat milk. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Lactoperoxidase system; Goat milk; Escherichia coli; Staphylococcus aureus; Listeria monocytogenes; Brucella melitensis 1. Introduction Goats are important milk producers in several parts of the tropics and significantly contribute to human nutrition in many developing countries (Devendra, 1999). Goat milk is a very nutritious and acceptable food in many parts of the tropics; however, its produc- tion and handling remains a major problem limiting its consumption. The dispersed nature of production across thediversityofsmallfarms,problemsofcollection,poor handling systems, inadequate transport and refrigera- tion facilities all create a considerable challenge to goat milk production in several developing countries (Chamberlain, 1989; Devendra, 1999). Milk is a highly nutritious food ideally suited for the growth of both pathogenic and spoilage organisms. Outbreaks of milk-borne illness date back from the in- ception of the dairy industry. Various bacterial infec- tions have been linked to consumption of raw goat milk (Vasavada, 1986). Brucellosis for instance is one such disease which can be transmitted to humans through contaminated and untreated milk and milk products. Consumption of goat milk or cheese containing Brucella melitensis is an important source of human brucellosis worldwide and has caused several outbreaks (Garin- Bastuji & Verger, 1994). In developed countries, the bacteriological quality of raw milk is safeguarded during collection, storage and transportation through refrigeration. However, cooling facilities are not available in rural areas of most devel- oping countries. As a result, the lactoperoxidase (LP) system has been recommended for preservation of raw milk as an alternative to cooling (Bj € orck, 1987). The LP system consists of three components: the enzyme lacto- peroxidase, thiocyanate and hydrogen peroxide. LP is normally found in a sufficient amount in milk; however, thiocyanate and hydrogen peroxide are the limiting factors and need to be added from exogenous source to activate the LP system. The enzyme lactoperoxidase catalyses the oxidation of thiocyanate by hydrogen peroxide, and generates the hypothiocyanite (OSCN  ) ion, which has proven antibacterial activity (Reiter, 1985). Activity of the LP system has been shown to inhibit thegrowthofmanybacterialspeciesincowmilk(Naidu, * Corresponding author. Address: Alemaya University, P.O. Box 287, Alemaya, Ethiopia. Tel.: +251-5-11-1399; fax: +251-5-11-4008. E-mail address: eyassu_seifu@yahoo.com (E. Seifu). 0956-7135/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0956-7135(03)00120-8 Food Control 15 (2004) 447–452 www.elsevier.com/locate/foodcont