Evaluation of Lactobacillus casei ATCC 393 protective effect against spoilage of probiotic dry-fermented sausages

The aim of the present study was to investigate potential protective effects of both free and immobilized Lactobacillus casei ATCC 393 on wheat grains against spoilage and pathogenic microbes in probiotic dry-fermented sausages containing reduced or negligible amounts of curing salts. The results showed that the probiotic cultures resulted in significant increase of self-life and the resistance to spoilage was more prominent in samples containing immobilized cells. Although spoilage was mainly due to yeasts/moulds overgrowth, a drastic decrease was observed in enterobacteria, staphylococci and pseudomonads counts. Microbial diversity was further studied applying a PCR-DGGE protocol. Members of Lactobacillus, Lactococcus, Saccharomyces and Kluyveromyces and Debaryomyces hansenii or Priceomyces carsonii were the main microbial populations detected. Noticeably, members of Rhodococcus, Saccharothrix or Micromonospora were only detected in sausages produced with no starter culture. Microbiological and strain-specific multiplex PCR analysis confirmed that the levels of L. casei ATCC 393 in all probiotic samples after 71 days of ripening ranged above the minimum concentration for conferring a probiotic effect (≥6 log cfu/g).