Ivana Filipović

Microbial and physicochemical succession in fermented sausages produced with bacteriocinogenic culture of Lactobacillus sakei and semi-purified bacteriocin mesenterocin Y

The influence of the bacteriocinogenic culture Lactobacillus sakei (10(5)/g) and semi-purified bacteriocin mesenterocin Y (2560AU/kg) on the safety and quality of traditional Croatian fermented sausages was investigated. The addition of Lb. sakei and/or mesenterocin Y reduced microbial counts (P<0.05) in the final products. After 28 days of ripening, coagulase-negative cocci decreased 1.5-2.0log, yeasts 1.2-1.4log and enterococci 1.7-2.7log. In the case of the addition of Lb. sakei, the lactic acid bacteria count was significantly (P<0.05) higher at day 7 of ripening, and was accompanied by a lower pH and a higher amount of lactic acid (P<0.05). In the final product the amount of acetic acid was significantly lower. More intensive proteolysis and an increase in ammonia content were found at the beginning of fermentation, and in the second phase of ripening in the control samples, respectively. The free fatty acid concentration was significantly lower during the entire ripening process compared to the control (P<0.05). Semi-purified mesenterocin Y did not affect the sensory properties of the sausages, whilst the addition of Lb. sakei enhanced them.

The hygiene and quality of hare meat (Lepus europaeus Pallas) from Eastern Croatia

This research was conducted over two seasons (winter and spring) and comprised a total of 71 samples of hares shot in the eastern region of Croatia, and was aimed at examining the quality and hygiene of the meat. The degree of usefulness in relation to the total average weight of the shot hares was 66.54%. Chemical tests showed that the average amount of water in the meat of the hares amounted to 75.34%, protein 23.19%, fats 1.12% and ash 1.16%. Of the 71 samples examined, as many as 44 (61.97%) did not meet the requirements of the rules on microbiological food standards, of which in 19 samples (26.76%) this was due to the high level of aerobic mezophilic bacteria/g, 2 samples (2.82%) contained Staphylococcus aureus/g, and 37 samples (52.11%) were not satisfactory because they contained enterobacteria/g. In terms of heavy metals in kidney and meat samples, 17 (23.94%) did not meet the provisions of the rules on toxins, metals, metaloids and other harmful substances which may be found in food. Of these 15 kidney samples (88.24%) contained cadmium, and 2 samples (11.76%) mercury in amounts greater than the permitted concentration. Tests on liver samples from the hares (n=71) did not show organophosphorus pesticides, nor organochlorinated pesticides or polychlorinated biphenyls.

The antimicrobial effect of lactobacilli on some foodborne bacteria.

The aim of this study was to determine the inhibitive effect of eleven lactobacilli strains from traditional fermented sausages on Listeria (L.) monocytogenes NCTC 10527, three strains of L. monocytogenes from food, L. welshimeri, Yersinia (Y.) enterocolitica, Pseudomonas (P.) aeruginosa, Staphylococcus (S.) aureus NCBF 1499, Salmonella Enteritidis and Salmonella spp. by use of the agar spot and agar diffusion tests. The most sensitive indicator bacteria were L. monocytogenes 1 (inhibited by ten of eleven strains of lactobacilli) and L. monocytogenes NCTC 10527 (8/11), whilst the most resistant was L. welshimeri (3/11). Six lactobacilli strains inhibited Salmonella spp., five P. aeruginosa and four inhibited the growth of Y. enterocolitica, S. aureus and Salmonella Enteritidis. The broadest spectrum of inhibition was confirmed for Lactobacillus (Lb.) paracasei subsp. paracasei, and the narrowest for Lb. curvatus. The preliminary results indicate a significant antimicrobial activity of selected lactobacilli, which is one of the important characteristics of the potential functional starter cultures.

Influence of protective cultures on Listeria monocytogenes in fermented sausages : a review

Within the concept of protective technologies in the production of fermented sausages, in addition to known hurdles such as nitrites, NaCl, low water activity and low pH, of great importance is also the biopreservation procedure. This procedure involves the use of lactic acid bacteria, their metabolites and protective substances for the purpose of achieving antagonistic effect on the undesirable microflora. The importance of biopreservation is optimally manifested in the bacteriostatic and/or bactericidal action of protective cultures and bacteriocins on L. monocytogenes in various foods, including fermented sausages. Biopreservation is an additional factor in the production of safer food, but it alone can not warrant microbiological safety, and in order to have purport and effect, this method must be a superstructure to good manufacturing and good hygienic practice.

Microbiological quality of soft, semi-hard and hard cheeses during the shelf-life

Abstract Cheeses as ready-to-eat food should be considered as a potential source of foodborne pathogens, primarily Listeria monocytogenes. The aim of present study was to determine the microbiological quality of soft, semi-hard and hard cheeses during the shelf-life, with particular reference to L. monocytogenes. Five types of cheeses were sampled at different time-points during the cold storage and analyzed for presence of Salmonella and L. monocytogenes, as well as lactic acid bacteria, Escherichia coli, coagulase-positive staphylococci, yeasts, molds, sulfite-reducing clostridia and L. monocytogenes counts. Water activity, pH and NaCl content were monitored in order to evaluate the possibility of L. monocytogenes growth. Challenge test for L. monocytogenes was performed in soft whey cheese, to determine the growth potential of pathogen during the shelf-life of product. All analyzed cheeses were compliant with microbiological criteria during the shelf-life. In soft cheeses, lactic acid bacteria increased in the course of the shelf-life period (1.2-2.6 log increase), while in semi-hard and hard cheeses it decreased (1.6 and 5.2 log decrease, respectively). Soft cheeses support the growth of L. monocytogenes according to determined pH values (5.8-6.5), water activity (0.99-0.94), and NaCl content (0.3-1.2%). Challenge test showed that L. monocytogenes growth potential in selected soft cheese was 0.43 log10 cfu/g during 8 days at 4°C. Water activity in semi-hard and hard cheeses was a limiting factor for Listeria growth during the shelf-life. Soft, semi-hard and hard cheeses were microbiologically stable during their defined shelf-life. Good manufacturing and hygienic practices must be strictly followed in the production of soft cheeses as Listeria-supporting food and be focused on preventing (re)contamination.