Food Science and Human Nutrition

ACA-DC 0040 produced an antimicrobial agent, which was named thermophilin T, active against several lactic acid bacteria strains of different species and food spoilage bacteria, such as Clostridium sporogenes C22/10 and Cl. tyrobutyricum NCDO-1754. The crude antimicrobial compound is sensitive to proteolytic enzymes and alpha-amylase, heat-stable (100 degrees C for 30 min), resistant to pH exposure at pH 1-12 and demonstrates a bactericidal mode of action against the sensitive strain Lactococcus cremoris CNRZ-117. The production of bacteriocin was optimized approximately 10-fold in an aerobic fermenter held at constant pH 5.8 and 6.2. Ultrafiltration experiments with culture supernatant fluids containing the bacteriocin, and further estimation of molecular weight with gel filtration chromatography, revealed that bacteriocin in the native form has a molecular weight in excess of 300 kDa. SDS-gel electrophoresis of partially purified thermophilin T showed that bacteriocin activity was associated with a protein band of approximately 2.5 kDa molecular mass.

Growth of and bacteriocin production by Streptococcus macedonicus ACA-DC 198 were assessed and modeled under conditions simulating Kasseri cheese production. Controlled fermentations were performed in milk supplemented with yeast extract at different combinations of temperature (25, 40, and 55°C), constant pH (pHs 5 and 6), and added NaCl (at concentrations of 0, 2, and 4%, wt/vol). The data obtained were used to construct two types of predictive models, namely, a modeling approach based on the gamma concept, as well as a model based on artificial neural networks (ANNs). The latter computational methods were used on 36 control fermentations to quantify the complex relationships between the conditions applied (temperature, pH, and NaCl) and population behavior and to calculate the associated biokinetic parameters, i.e., maximum specific growth and cell count decrease rates and specific bacteriocin production. The functions obtained were able to estimate these biokinetic parameters fo...

... E-mail The Corresponding Author , Ekaterini Moschopoulou , Anastasios Aktypis , Theophilos Massouras , Evaggelia Zoidou , Ioannis Kandarakis and Emmanuel Anifantakis. ... milk (milk lipase), rennet (pregastric esterases) (PGE) and microflora (Collins et al., 2003 and Fox et al ...

In this study the demographic features, various farm characteristics and milk quality parameters were investigated in sheep farms (n =128) from the North West Peloponnese region, using a prescreen questionnaire. The interviewed sheep farmers were under the control of the regional milk control laboratory of the Hellenic Milk Organization ELGO «Dimitra», which provided us with the corresponding milk quality data for the first quarter of 2014. Our findings regarding the demographic data demonstrated that 23% of farmers were 31-40 years old, 64% of them were high school graduates and 28% had received relevant farming general training; namely 17% of them has designated as “young farmers” in the frame of Third Axis of the Operational Program «Rural Development-Regeneration of the Countryside 2000-2006» and 11% have attended briefings by veterinarians and agriculturists. Ιn terms of farm characteristics, it has been revealed that the mean flock size was 148 sheep and regarding the farming ...

ABSTRACT:  In the present study, the spoilage flora of a sliced cooked cured meat product was studied to determine the specific spoilage organism (SSO). The physicochemical changes of the product during its storage in a temperature range of 0 to 12 °C were also studied. Among the primary models used to model the temperature effect on SSO growth, the modified Gompertz described better the experimental data than modified logistic and Baranyi. The derived growth kinetic parameters, such as maximum specific growth rate (μmax) and lag phase duration (LPD), were modeled by using the square root and Arrhenius equation (secondary models). The latter described better the data of μmax and LPD; therefore, this model was chosen for correlating temperature with kinetic parameters. The selection of the best model (primary or secondary) was based on some statistical indices (the root mean square error of residuals of the model, the coefficient of multiple determination, the F-test, the goodness of fit, the bias, and accuracy factor). The validation of the developed model was carried out under constant and dynamic temperature storage conditions. To validate its usefulness to similar products, another sliced cooked cured meat product stored under constant temperature conditions was also used. The log shelf life model was used for shelf life predictions based on the evident (visual defects) or the incipient spoilage (attainment of a certain spoilage level by SSO and/or chemical spoilage index). The possibility for shelf life predictions constitutes a valuable information source for the quality assurance systems of meat industries.

Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442, isolated from dry fermented sausages, produce bacteriocins antagonistic towards closely related species and pathogens, such as Listeria monocytogenes. The bacteriocins were inactivated by proteolytic enzymes and lipase but not by catalase and lysozyme. They were also heat stable, retaining activity after heating at 100 °C for 60 min. The bacteriocins were stable at pH values ranging from 2.0 to 8.0. Bacteriocin production was observed at low temperatures (10 and 4 °C) and in meat juice. The maximum bacteriocin activity was observed at the end of the exponential growth phase. The bacteriocins were produced in media with initial pH values ranging from 5.0 to 7.5, but not in media with a pH lower than 5.0 (weak bacteriocin activity of the antibacterial compound produced by Ln. mesenteroides L124 was observed at pH 4.5). Both bacteriocins exhibited strong bactericidal activity following cell/bacteriocin contact.

Lactic acid bacteria (LAB) strains, isolated from dry fermented sausages were tested as protective cultures in vacuum- or modified atmosphere-packaged sliced cooked cured pork shoulder at 4°C. The inhibitory capacity of the bacteriocins produced by Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442 against different strains of Listeria monocytogenes and L. innocua were also studied. In samples inoculated with the LAB, the listeriae population decreased by about 1.5log10cfug−1. Addition of bacteriocins in samples reduced the listeriae population below the enumeration limit (102cfug−1). Similar results were obtained with samples stored in modified atmosphere. Acetate concentration was increased in all samples. Thus, these lactic acid strains may be used as protective cultures to inhibit growth of L. monocytogenes or their bacteriocins in meat.

The microbial flora of naturally fermented sausages was studied. Lactic acid bacteria were the dominant species at the end of fermentation in all 3 batches (ca. 10(8) cfu g(-1)). Enterobacteria, Pseudomonas, yeasts and aerobic spore-formers decreased during fermentation and the ripening process and were below the detection limit in the end product. Enterococci exceeded 10(4)-10(5) cfu g(-1) during fermentation and remained constant at this level during ripening. Gram-positive, catalase-positive cocci exceeded 10(5) cfu g(-1), except for batch 1, during the first days of fermentation and then decreased until the end of ripening (10(2)-10(4) cfu g(-1)). No pathogenic staphylococci, sulfite reducing clostridia or Salmonella spp. were detected. Listeria spp. occurred in the first days of fermentation but were eliminated by the end of whole process in all batches. Identification showed that the majority of lactobacilli isolated from MRS agar strains were assigned to the species of Lactobacillus plantarum and Lb. plantarum/pentosus. All the isolated strains from the mannitol salt agar belonged to the genus of Staphylococcus. The predominant species were Staphylococcus saprophyticus, Staphylococcus xylosus and Staphylococcus simulans. The tests used to characterize the lactic acid bacteria and staphylococci as well as their distribution on the three batches were also discussed.

Lactobacillus curvatus, isolated from a spoiled vacuum-packaged 'pariza' type meat product, was used to inoculate modified MRS broth containing sodium lactate, sodium acetate and potassium sorbate in different concentrations, alone or in inter se combinations. Two commercial preparations (MIX 1 and MIX 2) were also used containing combinations of the above antimicrobials. Results from the preservatives addition to the culture medium showed highest antimicrobial activity in the case of the sodium lactate (2%, 3% or 4%), sodium acetate (0.5%) and potassium sorbate (0.15%) combination. Results from the preservatives addition to two types of thermally processed meats showed that sodium lactate and the combination of sodium lactate, sodium acetate and potassium sorbate were the most effective; extending the products shelf life an additional 10 days. Finally, MIX 1 and MIX 2 suppressed the lactic acid bacteria (LAB) growth in the culture medium but not in the final product.

The aim of this study was to investigate the effect of complex nutrients on microbial growth and bacteriocin production, in order to improve bacteriocin synthesis during the growth cycle of Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442. The fermentations were conducted at the optimum pH and temperature for bacteriocin production (pH 5.5±0.1 and temperature 25±0.1 °C). Because of their association with the final biomass, conditions favouring the increase of the produced biomass resulted in the increase of bacteriocin activity in the growth medium. Since the produced final biomass and the final concentration of the bacteriocins were associated with the amount of the carbon (glucose) and nitrogen source, better growth of the lactic acid bacterial strains favoured the increase of the specific bacteriocin production. Additionally, the bacteriocin production was influenced by carbon/nitrogen ratio.