Use of lactic acid bacteria as protective cultures in pork meat batter to prevent Clostridium spp. growth

Introduction: Food safety and preservation are major priorities for consumers and associated industry. Ancient methods of food preservation are still employed in the production of meat products, such as curing with nitrite or nitrate. Nitrite deriving from nitrate conversion is the real preservative agent. It has several toxic effects to humans, therefore its elimination or reduction is envisaged. Objective: to explore the possibility of using lactic acid bacteria (LAB) as protective cultures to prevent Clostridium spp. growth. Material and Methods: Lactobacillus plantarum PCS20 and Lactobacillus delbruecki DSM20074 were used as protective cultures; Clostridium botulinum DSM1975 and Clostridium perfringens DSM756 were the target pathogens. In-vitro studies (co-culture experiments and spot agar texts) were performed to evaluate the capability of the Lactobacillus strains of inhibiting the Clostridium strains. The survival of both LAB in pork meat batter supplied with NaCl at 2% was checked by using traditional plate counts and RAPD-PCR. Challenge texts were then performed aimed at studying in vivo the antimicrobial activity of the selected LAB inoculated in pork meat batter challenged with Clostridium strains in the presence and absence of 150 mg/kg NaNO3. Results: Both the spot agar texts and the co-culture inhibition assays showed an important antimicrobial activity of the two LAB against both clostridia. L.plantarum PCS20 could survive well in pork meat batter, as shown by RAPD-PCR analyses on colonies isolated from MRS plates. When pork meat batter was inoculated with C.botulinum DSM1975 or with Clostridium perfringens DSM 756, an important reduction of both pathogens was observed both in the presence and in the absence of nitrite. On the contrary, L.delbrueckii DSM20074 strain did not show extensive in vivo antimicrobial activity. Conclusion: The strain L.plantarum PCS20 has the potential of being used as a protective culture against Clostridium spp. in pork meat batter used for sausage production