Proteolysis During Manufacture And Ripening/Storing Of "Olomoucke Tvaruzky" Cheese (Pgi)

Twenty-two free amino acid (FAA) concentrations were observed during manufacture (1st, 3rd and 7th days of production) and ripening period (42 days storing at 8 degrees C) of "Olomoucke tvaruzky" (PGI, smear acid cheese). Sensory attributes were also analysed during ripening period. The free amino acids were determined by means of ion-exchange chromatography. The development of the individual FAA content positively correlated with the ripening period (r = 0.7734-0.9229; P < 0.01). The results gave information about the development precursors (FAA) of typically sensory active compound in "Olomoucke tvaruzky" (PGI) during its production and especially ripening. In conclusion, we found that free amino acid concentration as finally products of proteolysis are positive with improved flavour.National Agency for Agriculture Research [QJ1210300]; Internal Grant project of Tomas Bata University in Zlin [IGA/FT/2012/026

Formulation, characterization and properties of hemp seed oil and its emulsions

The formulation, characterization, and anticipated antibacterial properties of hemp seed oil and its emulsions were investigated. The oil obtained from the seeds of Cannabis sativa L. in refined and unrefined form was characterized using iodine, saponification, acid values, and gas chromatography, and was employed for the preparation of stable oil-in-water emulsions. The emulsions were prepared using pairs of non-ionic surfactants (Tween, Span). The effects of the emulsification method (spontaneous emulsification vs. high-intensity stirring), hydrophilic lipophilic balance (HLB), type and concentration of surfactant, and oil type on the size and distribution of the emulsion particles were investigated. It was found that the ability to form stable emulsions with small, initial particle sizes is primarily dependent on the given method of preparation and the HLB value. The most efficient method of emulsification that afforded the best emulsions with the smallest particles (151 ± 1 nm) comprised the high-energy method, and emulsions stable over the long-term were observed at HBL 9 with 10 wt % concentration of surfactants. Under high-intensity emulsification, refined and unrefined oils performed similarly. The oils as well as their emulsions were tested against the growth of selected bacteria using the disk diffusion and broth microdilution methods. The antibacterial effect of hemp seed oil was documented against Micrococcus luteus and Staphylococcus aureus subsp. aureus. The formulated emulsions did not exhibit the antibacterial activity that had been anticipated. © 2017 by the authors.MOE, Ministry of EducationMinistry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; Czech Science Foundation [17-05095S]; TBU in Zlin [IGA/CPS/2017/001

Decarboxylase-positive Enterococcus faecium strains isolated from rabbit meat and their sensitivity to enterocins

Background: The objective of the study was to determine sensitivity of Enterococcus faecium strains from rabbit meat to enterocins. Results: Twenty-five decarboxylase-positive strains (from rabbit meat) allotted to the species E. faecium by genotypization and by MALDI TOF MS spectrometry identification (evaluation score value range 2.104–2.359; in the range for highly probable species identification-score value 2.300–3.000 and secure probable species identification/probable species identification-2.000–2.299) were studied. Seventeen strains were gelatinase positive. Although they did not produce histamine (HIS), spermidine, and spermine, they produce at least one among seven tested biogenic amines (BAs) in small amounts (2–10 mg/L) or up to very high amounts (>1000 mg/L). Putrescine was produced by two strains. These decarboxylase-positive strains were sensitive to enterocins (Ents). All strains were sensitive to Ent 2019 and Ent 55 (inhibitory activity from 200 to 819 200 AU/mL). Twenty-two strains were inhibited by Ent A(P) and Ent 4231; 20 strains were sensitive to Ent M. Conclusion: Our results have spread the basic knowledge related to inhibitory spectrum of enterocins showing sensitivity of decarboxylase-positive strains to enterocins. Protective possibilities of enterocins in meat processing were also indicated. © 2016 The Authors. Food Science & Nutrition published by Wiley Periodicals, Inc.Slovak Scientific Agency VEGA [2/0004/14]; Slovak Research and Development Agency [SK-HU-0006-08

Quantitative Real-time PCR detection of putrescine-producing Gram-negative bacteria

Biogenic amines are indispensable components of living cells; nevertheless these compounds could be toxic for human health in higher concentrations. Putrescine is supposed to be the major biogenic amine associated with microbial food spoilage. Development of reliable, fast and culture-independent molecular methods to detect bacteria producing biogenic amines deserves the attention, especially of the food industry in purpose to protect health. The objective of this study was to verify the newly designed primer sets for detection of two inducible genes adiA and speF together in Salmonella enterica and Escherichia coli genome by Real-time PCR. These forenamed genes encode enzymes in the metabolic pathway which leads to production of putrescine in Gram-negative bacteria. Moreover, relative expression of these genes was studied in E. coli CCM 3954 strain using Real-time PCR. In this study, sets of new primers for the detection two inducible genes (speF and adiA) in Salmonella enterica and E. coli by Real-time PCR were designed and tested. Amplification efficiency of a Real-time PCR was calculated from the slope of the standard curves (adiA, speF, gapA). An efficiency in a range from 95 to 105 % for all tested reactions was achieved. The gene expression (R) of adiA and speF genes in E. coli was varied depending on culture conditions. The highest gene expression of adiA and speF was observed at 6, 24 and 36 h (RadiA 3, 5, 9; RspeF 11, 10, 9; respectively) after initiation of growth of this bacteria in nutrient broth medium enchired with amino acids. The results show that these primers could be used for relative quantification analysis of E. coli. © 2017 Potravinarstvo Slovak Journal of Food Sciences

Vegetable oil based emulsions in milk

Milk and dairy products represent an important part of functional food in the market. Based on their positive health and nutritional benefits, they have gained popularity and their consumption as well as production is on the rise in the last few decades. As a result of this trend, milk-based products are being used for the delivery of bioactive food ingredients. This study is devoted to the formulation of stable emulsions containing grape seed oil dispersed with several emulsifiers (Tween 80, monocaprylin, and lecithin) in milk. Photon correlation spectroscopy was used to evaluate the characteristics of the emulsions in terms of mean droplet size, droplet size distribution and polydispersity index. Emulsions were prepared using 2% and 5% w/w grape seed oil, and 3%, 5%, or 8% w/w emulsifier, and these were homogenized at two different rates of 1050 and 13400 rpm. Parameters influencing emulsion particle size and particle size distribution were identified, which included emulsifier type, its HLB value, oil type (virgin, refined), homogenization rate and the fat content in the milk. Homogenization at 13400 rpm for 10 min. produced fine emulsions with small mean particle sizes and monomodal distribution of droplets. Regarding emulsifier type, the smallest droplet sizes were obtained with formulations containing Tween 80 (250-315 nm), whereas lecithin primarily accounted for the monomodal particle size distributions. © 2014 Potravinarstvo

The monitoring of biogenic amines in the raw food

The aim of this work was to evaluate microbial quality and the presence of biogenic amines in raw bars. This study was focused on microbiological research in order to determine the presence of selected indicator groups of microorganisms depending on the composition of raw food. Identification of microorganisms was carried out by MALDI-TOF MS. In the second part of the experiment, biogenic amines and polyamines were analyzed using high performance liquid chromatography with UV/VIS detection. An increased incidence of mold has been reported in the samples, which is associated with a risk of mycotoxin production. After identifying microorganisms, it was found out that genera Micrococcus, Bacillus and Staphylococcus were the most represented. The highest concentration of biogenic amines (tyramine 42.2 ±4.8 mg.kg-1; putrescine 54.0 ±2.9 mg.kg-1) was found in a sample containing the vegetable component. The average concentration of biogenic amines in the tested raw bars was &lt; 30 mg.kg-1 and therefore they do not pose a serious health hazard to a consumer. © 2019 Potravinarstvo Slovak Journal of Food Sciences

Factors affected decarboxylation activity of Enterococcus faecium isolated from rabbit

  Biogenic amines (BA) are basic nitrogenous compounds formed mainly by decarboxylation of amino acids. There are generated in course of microbial, vegetable and animal metabolisms. The aim of the study was to monitor factors affected production of biogenic amines by Enterococcus faecium, which is found in rabbit meat. Biogenic amines were analyzed by means of UPLC (ultrahigh performance liquid chromatography) equipped with a UV/VIS DAD detector. Decarboxylation activity of E. faecium was mainly influenced by the cultivation temperature and the amount of NaCl in this study. E. faecium produced most of the monitored biogenic amines levels: tyramine ˂2500 mg.l-1; putrescine ˂30 mg.l-1; spermidine ˂10 mg.l-1 and cadaverine ˂5 mg.l-1

Antimicrobial effect of selected lactic acid bacteria against microorganisms with decarboxylase activity

The main purpose of this study was to evaluate the antimicrobial activity of twenty-one bacteriocinogenic lactic acid bacteria (12 strains of Lactococcus lactis subsp. lactis, 4 strains of Lactobacillus gasseri, 3 strains of Lb. helveticus and 2 strains of Lb. acidophilus, LAB) against 28 Staphylococcus and 33 Enterococcus strains able to produce tyramine, putrescine, 2-phenylethylamine and cadaverine. The antimicrobial activity of cell-free supernatants (CFS) from tested LAB was examined by an agar-well diffusion assay. Nine out of twenty-one strains (33%) showed the inhibitory effect on tested enterococci and staphylococci, namely 9 strains of Lactococcus lactis subsp. lactis. The diameters of inhibition zones ranged between 7 mm and 14 mm. The biggest diameter of 14 mm inhibition was obtained with the CFS's from strains CCDM 670 and CCDM 731 on Enterococcus sp. E16 and E28. The cell-free supernatants from Lactococcus lactis subsp. lactis CCDM 71 and from Lactococcus lactis subsp. lactis CCDM 731 displayed the broadest antibacterial activity (52% inhibition of all tested strains). On the other hand, the cell-free supernatants from the screened Lactobacillus strains did not show any inhibitory effect on the tested Staphylococcus and Enterococcus strains. Nowadays, the great attention is given to the antibacterial substances produced by lactic acid bacteria. With the ability to produce a variety of metabolites displaying inhibitory effect, the LAB have great potential in biopreservation of food. © 2017 Potravinarstvo Slovak Journal of Food Sciences

Hydrogen sulfide effects on the survival of lactobacilli with emphasis on the development of inflammatory bowel diseases

The gut microbiota is a complex component of humans that depends on diet, host genome, and lifestyle. The background:The study purpose is to find relations between nutrition, intestinal lactic acid bacteria (LAB) from various environments (human, animal intestine, and yogurt) and sulfate-reducing microbial communities in the large intestine; to compare kinetic growth parameters of LAB; and to determine their sensitivity to different concentration of hydrogen sulfide produced by intestinal sulfate-reducing bacteria. Methods: Microbiological (isolation and identification), biochemical (electrophoresis), molecular biology methods (DNA isolation and PCR analysis), and statistical processing (average and standard error calculations) of the results were used. The results: The toxicity of hydrogen sulfide produced by sulfate-reducing bacteria, the survival of lactic acid bacteria, and minimal inhibitory concentrations (MIC) were determined. The measured hydrogen sulfide sensitivity values were the same for L. paracasei and L. reuteri (MIC > 1.1 mM). In addition, L. plantarum and L. fermentum showed also a similar sensitivity (MIC > 0.45 mM) but significantly (p 0.45 mM). L. paracasei and L. reuteri are more sensitive to hydrogen sulfide than L. fermentum and L. plantarum. L. pentosus was sensitive to the extremely low concentration of H2S (MIC > 0.15 mM). Conclusions: The Lactobacillus species were significantly sensitive to hydrogen sulfide, which is a final metabolite of intestinal sulfate-reducing bacteria. The results are definitely helpful for a better understanding of complicated interaction among intestinal microbiota and nutrition. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Grant Agency of the Masaryk University [MUNI/A/0902/2018

Quality changes of long-life foods during three-month storage at different temperatures

The aim of this study was to describe quality changes of eight long-life foods (instant potato purée with milk, instant goulash soup, canned white-type cheese, pre-baked baguette, szeged goulash meal-ready-to-eat, canned chicken meat, pork pate and canned tuna fish) during three-month storage at 4 different temperatures (-18 °C, 5 °C, 23 °C and 40 °C). These temperatures were chosen to simulate various climatic conditions in which these foods could be used to ensure the boarding during crisis situations and military operations to provide high level of sustainability. Foods were assessed in terms of microbiological (total number of aerobic and/or facultative anaerobic mesophilic microorganisms, number of aerobic and anaerobic spore-forming microorganisms, number of enterobacteria, number of yeasts and/or moulds), chemical (pH-values, dry matter, fat, crude protein, ammonia and thiobarbituric acid reactive substances contents), texture profile (hardness) and sensory (appearance, consistency, firmness, flavour and off-flavour) analyses. Microbiological analyses showed expected results with the exception of szeged goulash, pork pate and tuna fish, which, although being sterilised products, contained some counts of bacteria. The decrease of pH-values and increase of dry matter, ammonia and thiobarbituric acid reactive substances contents were observed during the storage of all foods due to prolonged storage time and/or elevated storage temperature. Furthermore, according to texture profile analysis, hardness of cheese and baguette rose as a result of both storage temperature and time. Finally, the highest storage temperature (40 °C) resulted in a deterioration of sensory quality (especially flavour) of most foods; the exceptions were pate and tuna fish which retained good sensory quality throughout 3-month storage at all temperatures. © 2017 Potravinarstvo Slovak Journal of Food Sciences