The scientific interest for the search of natural means of microbial inhibitors has not faded for several years. A search of natural antibiotics, so-called bacteriocins which are produced by lactic ...acid bacteria (LAB), gains a huge attention of the scientists in the last century, in order to reduce the usage of synthetic food additives. Pure bacteriocins with wide spectra of antibacterial activity are promising among the natural biopreservatives. The usage of bacteriocin(s) producing LAB as starter culture for the fermentation of some food products, in order to increase their shelf-life, when synthetic preservatives are not allowable, is also possible. There are a lot of studies focusing on the isolation of new bacteriocins from traditional fermented food, dairy products and other foods or sometimes even from unusual non-food matrices. Bacteriocins producing bacteria have been isolated from different sources with the different antibacterial activity against food-borne microorganisms. This review covers the classification of bacteriocins, diversity of sources of bacteriocin(s) producing LAB, antibacterial spectra of isolated bacteriocins and analytical methods for the bacteriocin purification and analysis within the last 15 years.
The prevalence of enteropathogenic Yersinia spp. in pigs at farms and slaughter in relation to potential farming risk factors in Lithuania was examined. Pig faeces and carcase swab samples from 11 ...farms were studied at slaughterhouses. Nine of the 11 farms were visited again 3–5months later, and pooled feacal samples and environmental samples were collected. Pathogenic Yersinia enterocolitica was found in 64% and Yersinia pseudotuberculosis in 45% of the sampled pig farms. All obtained isolates belonged to bioserotypes 4/O:3 and 2/O:3, respectively. Low biosecurity level was associated with a high prevalence of Y. enterocolitica on farms. Characterization with PFGE of 64 Y. enterocolitica and 27 Y. pseudotuberculosis isolates revealed seven and two different genotypes, respectively. Dominant enteropathogenic Yersinia spp. genotypes were obtained in both pig feacal and carcase samples. The high contamination of pig carcases (25%) with enteropathogenic Yersinia spp. may be an important factor contributing to the high incidence of human yersiniosis in Lithuania.
The objective of this study was to determine risk factors for Campylobacter infection in broiler flocks in Lithuania. Each broiler flock was tested for the contamination with Campylobacter spp., and ...various broiler farm, flock and abattoir as well as the weather-associated characteristics were analysed using the statistical package SPSS. Study revealed that 59.3% of the examined broiler flocks were contaminated with Campylobacter spp. Statistical analysis revealed that broiler flock contamination with Campylobacter was abattoir- and farm-dependent. Among a number of risk factors (e.g. the number of broiler houses at the farm, the type of ventilation system, the presence of the anteroom and boot security, etc.) identified, two broiler health-associated characteristics: (i) broiler age and (ii) the average weight per bird at abattoir had the highest impact on the increased prevalence of Campylobacter spp. in broilers. According to our results broiler health status has a major negative effect on broiler flock contamination with Campylobacter. Thus, it needs to be considered when improving control of Campylobacter spp. in broilers.
In the present study fatty acid (FA) composition in four main groups of dairy products was determined to investigate their development during processing and storage. Fresh cheese, sour cream, butter, ...and ultra-high temperature (UHT) milk representing differences in technological approach were chosen for the study. Fatty acids methyl esters (FAME) were quantified using a gas chromatograph (GC) equipped with a mass spectrometer (MS) and a capillary column SP-2560. The concentrations and profile of FA in final products were primarily dependent on the FA content of raw milk for UHT milk and fresh cheese production or in the raw cream for sour cream and butter. The shelf life had a significant impact (P<0.05) only in UHT milk and butter, whereby unsaturated fatty acids (UFA) and polyunsaturated fatty acids (PUFA) decreased significantly in UHT milk, while PUFA decreased significantly in butter.
The main task of the present study was to evaluate an impact of three nisin Z-producing
Lactococcus lactis
bacteria newly isolated from raw goat milk for some fresh cow cheese characteristics during ...the storage. Microbiological evaluation for
Listeria monocytogenes
,
Staphylococcus aureus
, and viable lactic acid bacteria counts and determination of pH, titratable acidity, and lactic acid concentration of produced cheese were performed after 0, 24, 48, 72, and 96 h. Sensory analysis for the evaluation of acidity, flavor intensity, color intensity, bitterness, and crumbliness of prepared cheese was performed. The changes of volatile compounds in fresh cheese were evaluated using headspace solid phase microextraction (SPME) coupled with gas chromatography-mass spectrometry. Chemometric methods were applied for the data analysis. Study showed that tested bacteria are suitable for the manufacturing of fresh cheese and possible application for fresh cheese biopreservation, as pathogenic bacteria did not grow during 4 days (96 h); chemometric analysis revealed that
L. lactis
strain LL56 was the most similar to commercially available
L. lactis
ATCC11454.
The present study was conducted to find the potential of
Lactococcus lactis
strains naturally present in raw and fermented milk as probiotics and to evaluate their safety and some technological ...characteristics. There are numerous studies that evaluated probiotic properties of lactococci, nevertheless, limited studies on the probiotic potential of lactococci isolated from raw milk or dairy products were performed. Strains isolation from raw milk or dairy products and their characterization is important when selection of starter strains for the production of functional dairy foods is performed. Depending on aroma production and acidifying activity, 33
L. lactis
strains were selected out of 169 and evaluated for safety, technological and probiotic properties. These strains were screened for antibiotic sensitivity, enzymatic activity, hemolytic and gelatinase activities. The strains were also assessed for resistance to bile salts and acid, growth in bile acids and cholesterol, cell surface hydrophobicity. Based on the obtained results, two strains with the best probiotic potential were selected. These two
L. lactis
strains, with 51% and 67% survival at low pH and more than 80% resistance to various bile salt concentrations, proved their resistance in vitro to gastric conditions. Also these strains proved to be good acidifiers (the pH of milk was reduced by at least 1 unit in 6 h at 30–37 °C) and can be used in the development of functional dairy foods as starter cultures.
Determination of natural preservatives using electrophoretic or chromatographic techniques in fermented milk products is a complex task due to the following reasons: (i) the concentrations of the ...analytes can be below the detection limits, (ii) complex matrix and comigrating/coeluting compounds in the sample can interfere with the analytes of the interest, (iii) low recovery of the analytes, and (iv) the necessity of complex sample preparation. The aim of this study was to apply capillary zone electrophoresis coupled with contactless conductivity detection for the separation and determination of nisin in fermented milk products. In this work, separation and determination of natural preservative–nisin in fermented milk products is described. Optimized conditions using capillary zone electrophoresis coupled with capacitance‐to‐digital technology based contactless conductivity detector and data conditioning, which filter the noise of the electropherogram adaptively to the peak migration time, allowed precise, accurate, sensitive (limit of quantification: 0.02 μg/mL), and most importantly requiring very minute sample preparation, determination of nisin. Sample preparation includes following steps: (i) extraction/dilution and (ii) centrifugation. This method was applied for the determination of nisin in real samples, i.e. fermented milk products. The values of different nisin forms were ranging from 0.056 ± 0.003 μg/mL to 9.307 ± 0.437 μg/g.
Safety is the most important criteria of any substance or microorganism applied in the food industry. The whole-genome sequencing (WGS) of an indigenous dairy isolate LL16 confirmed it to be
subsp.
...with genome size 2,589,406 bp, 35.4% GC content, 246 subsystems, and 1 plasmid (repUS4). The Nextera XT library preparation kit was used to generate the DNA libraries, and the sequencing was carried out on an Illumina MiSeq platform. In silico analysis of
LL16 strain revealed non-pathogenicity and the absence of genes involved in transferable antimicrobial resistances, virulence, and formation of biogenic amines. One region in the
LL16 genome was identified as type III polyketide synthases (T3PKS) to produce putative bacteriocins lactococcin B, and enterolysin A. The probiotic and functional potential of
LL16 was investigated by the presence of genes involved in adhesion and colonization of the host's intestines and tolerance to acid and bile, production of enzymes, amino acids, and B-group vitamins. Genes encoding the production of neurotransmitters serotonin and gamma-aminobutyric acid (GABA) were detected; however,
LL16 was able to produce only GABA during milk fermentation. These findings demonstrate a variety of positive features that support the use of
LL16 in the dairy sector as a functional strain with probiotic and GABA-producing properties.
Indigenous Lactococcus lactis enriched raisins were incorporated in fresh curd cheese in wet, thermally dried, and freeze-dried form to produce a novel probiotic dairy product. Symbiotic cheese ...represents a rising trend in the global market. The viability of L. lactis cells was assessed in the cheeses during storage at 4 °C for 14 days and the effect of the added enriched raisins on physicochemical parameters, microbiological characteristics, and sugar content, aromatic profile, and sensory acceptance of cheeses were evaluated. Immobilized L. lactis cells maintained viability at necessary levels (>6 log cfu/g) during storage and significantly increased the acceptability of cheese. The addition of raisins enhanced the volatile profile of cheeses with 2-furanmethanol, 1-octanol, 3-methylbutanal, 2-methylbutanal, 2-furancarboxaldehyde, 1-(2-furanyl)-ethanone, 5-methyl-2-furancarboxaldehyde. The obtained results are encouraging for the production of novel fresh cheeses with improved sensorial and nutritional characteristics on industrial and/or small industrial scale.
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