Antilisterial bacteriocin-producing strain of Lactobacillus curvatus CWBI-B28 as a preservative culture in bacon meat and influence of fat and nitrites on bacteriocin production and activity.

摘要

The objectives of this study were to evaluate the effectiveness of a bacteriocin-producing Lactobacillus curvatus CWBI-B28 to inhibit the growth of Listeria monocytogenes in de Man, Rogosa and Sharp (MRS) broth and in bacon meat. A co-culture of L. monocytogenes with the Bac+ strain in MRS broth, resulted in a reduction of the pathogen counts by 4.2 log cycles after 24 h of incubation at 37 degrees C. In bacon, the counts of L. monocytogenes was reduced to below the detectable limit (<10 cfu/g) in samples inoculated with the Bac+ strain within 1 or 2 weeks in absence or presence of nitrites (210 mg/kg), respectively. However, a week later, a re-growth of the pathogen has occurred. In contrast, no such reduction in Listeria cfus was observed in samples treated with the Bac- derivative of Lactobacillus curvatus CWBI-B28. Nonetheless, the extent of inhibitory effect of the Bac+ strain against L. monocytogenes in bacon was somewhat reduced in the presence of nitrites. A separate study on the influence of nitrites and fats on growth and bacteriocin production by L. curvatus CWBI-B28 revealed that the curing agent affects the growth of the Bac strain and, thereby bacteriocin production and activity only at concentrations (>5%) far beyond those allowed in the meat industry. Fat content did not affect the bacterial growth even at the highest concentration used (i.e. 50%). However, it interfered significantly with the detection of AUs and the antilisterial activity. The use of the Bac+ L. curvatus CWBI-B28 was proven efficient in controlling L. monocytogenes in bacon despite the slight antagonistic effect of nitrites. However, the efficacy was dramatically reduced upon extended period of storage at 4 degrees C..