Pre-inoculation enrichment procedure enhances the performance of bacteriocinogenic Lactococcus lactis meat starter culture

Sodium nitrite and sodium chloride may inhibit growth and bacteriocinogenes is of protective starter cultures. To reduce sensitivity of a lacticin 3147 -producing starter culture to nitrite, prior to production of salami. Lacto coccus lactis DPC 4275 was placed in a number of pre-inoculation treatments , containing (a) 1% glucose, (b) 2.5 ppm manganese (Mn), (c) 250 ppm magnes ium (Mg), (d) 2.5 ppm manganese + 250 ppm magnesium (Mn + Mg), and held at ambient temperature for 30 min and 4 degreesC for 2 h. The growth, pH reduc tion, and bacteriocin production was monitored in beaker sausage over a per iod of 10 days at 28 degreesC, corresponding to typical salami production t ime, and compared to untreated starter culture. The effect of 1% tryptone a nd inoculum level on growth and bacteriocin production was also determined. Challenge tests were performed using Listeria innocua DPC 1770 and Staphyl ococcus aureus MMPR3 as target strains. All treatments gave a significantly higher (P < 0.05) initial starter level than the untreated starter. Beaker sausage inoculated with either low (10(7)) or high (10(9)) levels of start er culture. treated with Mn + Mg reached significantly (P < 0.05) higher le vels by day 10 than other treatments. Trends indicate that Mn + ME also gav e best pH reduction in sausage containing the low-level starter culture. sa usage and significantly lower (P < 0.05) values for sausage produced with h igher inoculum. Bacteriocin production was also higher in starter culture t reated with Mn, or glucose. Pre-treatment with Mg gave a 2-fold increase in bacteriocin, the addition of Mn augmenting this increase further. The inco rporation of tryptone gave no additional effect. In beaker sausage, both L. innocua and S. aureus populations showed significant reductions (P < 0.05) in the presence of the bacteriocinogenic strain compared to a non-bacterio cinogenic control strain. (C) 2001 Elsevier Science B.V. All rights reserve d.