- Top of page
- Materials and methods
- Bacterial cultures and media
- Lyophilized preparations of the bacteriocin-producing strains
- Sausage manufacture
- Sausage sampling and analysis
- Statistical analysis
- In vitro antimicrobial activity testing
- Sausage manufacture
- Microbiological study
- Enumerations of LAB
- Behaviour of L. monocytogenes in dry-fermented sausages.
Aim: Study of the effectiveness of in situ bacteriocin production by lactic acid bacteria (LAB) to control Listeria monocytogenes in dry-fermented sausages.
Methods and Results: Two bacteriocin-producing strains: Lactococcus lactis subsp. lactis LMG21206 and Lactobacillus curvatus LBPE were grown in a pilot scale fermentor and lyophilized to be directly used in dry sausage fermentation. A commercial starter culture (Bel'meatTM SL-25) not inhibitory to L. monocytogenes (Bac− starter) was mixed (1 : 1) with each of the two lyophilized bacteriocin-producing strains to obtain starters active against the pathogen (Bac+ starter). Anti-Listeria effectiveness of the Bac+ starters was studied in dry-fermented sausages. The meat batter was experimentally contaminated with a mixture of four different strains of L. monocytogenes (102–103 CFU g−1). The results showed that L. monocytogenes did not grow in any of the contaminated batches, but no significant decrease (P > 0·05) was observed either in the positive control (no added starter culture) or in samples fermented with the Bac− starter culture during the fermentation period and up to 15 days of drying. When the Bac+ starter contained Lb. curvatus LBPE, cell counts of L. monocytogenes decreased to below the detectable limit (<10 CFU g−1) after 4 h of fermentation and no survivors could be recovered by enrichment beyond day 8 of drying. When the Bac+ starter culture containing Lc. lactis LMG21206 was used, a decrease in Listeria counts to below the detectable limit was achieved after 15 days of drying.
Conclusions: The bacteriocin-producing strains studied may be used as adjunct cultures for sausage fermentations to control the occurrence and survival of L. monocytogenes.
Significance and Impact of the Study: Addition of the Bac+ strains, especially the Lb. curvatus strain would provide an additional hurdle to enhance the control of L. monocytogenes in fermented meat products.