Nevijo Zdolec

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.

European validation of a real-time PCR-based method for detection of Listeria monocytogenes in soft cheese.

The classical microbiological method for detection of Listeria monocytogenes requires around 7 days for final confirmation, and due to perishable nature of RTE food products, there is a clear need for an alternative methodology for detection of this pathogen. This study presents an international (at European level) ISO 16140-based validation trial of a non-proprietary real-time PCR-based methodology that can generate final results in the following day of the analysis. This methodology is based on an ISO compatible enrichment coupled to a bacterial DNA extraction and a consolidated real-time PCR assay. Twelve laboratories from six European countries participated in this trial, and soft cheese was selected as food model since it can represent a difficult matrix for the bacterial DNA extraction and real-time PCR amplification. The limit of detection observed was down to 10 CFU per 25 of sample, showing excellent concordance and accordance values between samples and laboratories (>75%). In addition, excellent values were obtained for relative accuracy, specificity and sensitivity (82.75%, 96.70% and 97.62%, respectively) when the results obtained for the real-time PCR-based methods were compared to those of the ISO 11290-1 standard method. An interesting observation was that the L. monocytogenes detection by the real-time PCR method was less affected in the presence of Listeria innocua in the contaminated samples, proving therefore to be more reliable than the reference method. The results of this international trial demonstrate that the evaluated real-time PCR-based method represents an excellent alterative to the ISO standard since it shows a higher performance as well as reduce the extent of the analytical process, and can be easily implemented routinely by the competent authorities and food industry laboratories.

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.

Use of Premi®Test for the detection of sulphonamide residues in chicken eggs

The presence of sulphadimidine residues in eggs after a peroral administration of Sulfadimidin PG plv. sol. ad us, vet. (120 mg/hen/day) to laying hens was studied. Premi®Test, four-plate microbiological method, and HPLC were used for the detection of sulphadimidine residues. Positive findings of the Four-plate test (FPT) were confirmed by the results of Premi®Test. Using the FPT, the absence of sulphadimidine residues was confirmed 72 hours after the last sulphadimidine administration. The presence of sulphadimidine residues has been detected by Premi®Test within 8 days and by the FPT within 3 days after the last administration. As compared with the results of Premi®Test, the FPT has reported false-negative results for five days (kappa < 0.6). Conformity of results obtained by both Premi®Test and HPLC was confirmed in this study (kappa = 0.6).

Dietary exposure assessment of streptomycin and tetracycline in food of animal origin on the Croatian market

Residual antibacterials in food constitute a risk to human health, particularly because they can contribute to the transmission of antibiotic-resistant pathogenic bacteria through the food chain. This paper presents dietary exposure assessment of streptomycin and tetracycline, based on combining food consumption data in Croatia with data on the concentration of veterinary drugs in analysed samples of food of animal origin. According to the median values, the estimated daily intake of streptomycin and tetracycline through food is 11.9 and 0.7 µg/person/day, respectively. The largest contribution to streptomycin intake comes from meat (4.8 µg/person/day, i.e. 41%), but milk is the largest source for tetracycline (0.3 µg/person/day, i.e. 46%). The estimated dietary exposure to these veterinary drugs does not exceed relevant toxicological reference values and the level of exposure is assessed to be acceptable.

Prevalence of Cysticercus bovis in slaughtered cattle determined by traditional meat inspection in Croatian abattoir from 2005 to 2010

SummaryThe aim of this work was to evaluate the presence of Cysticercus bovis of slaughtered cattle in a Croatian slaughterhouse between 2005 and 2010. In total, 203 166 carcasses and organs were examined, of which in 228 C. bovis was found (0.11 %). The highest number of cysticercosis was found in cows (0.69 %, n = 13 605), then in steers (0.093 %; n = 134 212), and the lowest in calves (0.014 %; n = 55 349). Among the 228 positive specimens, 129 (56.57 %) came from rural estates and 99 (43.43 %) from farms. The ratio of invaded steers from rural estates (n = 2 790) and from farm breed (n = 131 422) was 1.075 %: 0.064 %, calves (n = 316 and n = 55 033) 0.316 %: 0.012 %, and cows (n = 8 985 and n = 4 620) 097 %: 0.15 %. The number of cysticercosis invaded cattle decreased from the initial 0.37 % to 0.07 %. Despite low prevalence, we consider that each positive result requires an individual epidemiologic study in order to decrease the risk even more.

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.

Lactobacillus plantarum with Functional Properties: An Approach to Increase Safety and Shelf-Life of Fermented Foods

Lactobacillus plantarum (widespread member of the genus Lactobacillus) is one of the most studied species extensively used in food industry as probiotic microorganism and/or microbial starter. The exploitation of Lb. plantarum strains with their long history in food fermentation forms an emerging field and design of added-value foods. Lb. plantarum strains were also used to produce new functional (traditional/novel) foods and beverages with improved nutritional and technological features. Lb. plantarum strains were identified from many traditional foods and characterized for their systematics and molecular taxonomy, enzyme systems (α-amylase, esterase, lipase, α-glucosidase, β-glucosidase, enolase, phosphoketolase, lactase dehydrogenase, etc.), and bioactive compounds (bacteriocin, dipeptides, and other preservative compounds). This review emphasizes that the Lb. plantarum strains with their probiotic properties can have great effects against harmful microflora (foodborne pathogens) to increase safety and shelf-life of fermented foods.

Consumer-perceived quality characteristics of chicken meat and chicken meat products in Southeast Europe

Purpose The purpose of this paper is to analyse consumer perception of quality characteristics of chicken meat and chicken meat products in Southeast European countries (Albania, Bosnia and Herzegovina, Bulgaria, Croatia, FYR of Macedonia, Montenegro, and Serbia). Design/methodology/approach Results were collected from a field survey by using data obtained from a questionnaire directed at 2,368 consumers during 2015. Findings This study identified four consumer segments: “typical”, “selective”, “chicken meat preparers” and “uninterested” chicken meat consumers. Originality/value Older consumers (50 years) have higher interest in chicken meat quality characteristics, while women are “chicken meat preparers”. Chicken meat consumers who prefer particular chicken parts and consume chicken meat because it is nutritious are found among the working population, while the most number of consumers “uninterested” in chicken meat come from Serbia.