Lyophilized preparations of bacteriocinogenic Lactobacillus curvatus and Lactococcus lactis subsp. lactis as potential protective adjuncts to control Listeria monocytogenes in dry-fermented sausages

Authors


Noreddine Benkerroum, Département des Sciences Alimentaires et Nutritionnelles, Institut Agronomique et Vétérinaire Hasssan II, BP. 6202, Institut, 10101-Rabat, Morocco (e-mail: n.benkerroum@iav.ac.ma).

Abstract

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.

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