Biocontrol of processed cheese by incorporation of probiotic bacteria and its metabolites

Abstract

Background: Processed cheese could be estimated as microbiologically safe, nevertheless microorganisms may gain entrance during all stages of processing especially spore forming bacteria, one way to limit the growth of undesirable microorganisms is incorporation of probiotics which show high antimicrobial activity against these pathogens. Materials and Methods: The antibacterial activity of six different lactic acid bacteria against Bacillus cereus and Clostridium perfringes were studied. Results: Lactobacillus curvatus and Lactobacillus acidophilus were the most effective cultures against B. cereus, while Leuconostoc mesenteroides against C. perfringes. Supplementation of processed cheese with L. curvatus and the mixed culture of the three other probiotics effectively suppressed the growth and survival of B. cereus and it could not be recovered after 14 days of storage and room temperature. While, supplementation of the cheese by metabolites of L. curvatus, L. acidophilus and mixed culture of L. curvatus, L. acidophilus and L. mesenteroides reduce the viable counts of B. cereus and the reduction reached 100% at 14 days using metabolites of L. curvatus and the mixed culture of L. curvatus, L. acidophilus and L. mesenteroides and at 21 days using L. acidophilus when the cheese stored at 25EC. But, cold storage delayed the reduction of B. cereus. Also, a pronounced reduction in viability of C. perfringes was observed with L. mesenterials culture, as C. perfinges could not be recovered after 30 and 21 days at room and refrigerator temperature, respectively. Conclusion: Supplementation of probiotic metabolites of L. mesenteroides and the mixed culture (L. curvatus, L. acidophilus and L. mesenteroides) led to decrease the viability and survival of C. perfringens as it could not be recovered after 30 days at refrigerator temperature for 45 and 30 days respectively, at room temperature.