Molecular screening of bovine raw milk for the presence of Shiga toxin-producing Escherichia coli (STEC) on dairy farms

Milkborne transmission of Shiga toxin- producing Escherichia coli (STEC) has raised considerable concern due to recent outbreaks worldwide and poses a threat to public health. The aim of this study was to develop a sensitive and specific multiplex PCR assay to detect the presence of STEC in bovine raw milk. To identify E. coli (ATCC 25922) contamination, the gene uspA was used, and PCR sensitivity and specificity were accessed by testing diluted samples ranging from 2 to 2.0 × 10(6) CFU/mL. To detect STEC, the stx1 and stx2 genes were selected as targets. After reaction standardization, the multiplex assay was tested in raw milk collected from 101 cows on dairy farms. PCR assay for E. coli detection had a specificity of 100% and sensitivity of 79% (P<0.0001), with a lower detection limit of 2 CFU/mL. Multiplex PCR assay had 100% sensitivity for E. coli positive raw milk samples, and 31.1% were contaminated with STEC, 28.3% of stx2, and 1.9% of stx1. The multiplex PCR assay described in the present study can be employed to identify and screen E. coli harboring stx1 and stx2 genes in raw milk on dairy farms and in industries.

Characterization of goat milk and potentially symbiotic non-fat yogurt

Combining prebiotics and probiotic microorganisms improve quality in the formulation of foods. In this paper, the characteristics of goat milk and symbiotic yogurt were studied. Raw goat milk was analyzed and the skimming process was optimized. For the formulation of a potentially non-fat symbiotic yogurt made with skimmed goat milk, inulin, gelatin, sugar, and Streptococcus salivarius subsp. thermophilus, Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus casei subsp. rhamnoshus. Chemical characteristics, acceptability, and viability of lactic acid bacteria and probiotic culture were assessed. The protein and fat content of the raw milk was 2.90 and 3.56 g/100 mL, respectively. The optimum skimming process was obtained at 9,800 rpm and 4 °C for 15 minutes. The product formulated had a protein and fat content of 4.04 to 0.04 g/100 mL, good sensory properties, and acceptability of 95%. The lactic bacteria count was 9 × 10(7) CFU mL- 1, and probiotic culture count was higher than 1 × 10(6) CFU mL- 1, which guarantees their effect and capacity to survive in the digestive tract and spread in the intestine. The yogurt was stable during the 21 days of storage. Therefore, this study shows that goat milk yogurt is an adequate delivery vehicle of the probiotic culture L. casei and inulin.

Peptide separation of commercial fermented milk during refrigerated storage

Milk is an important source of bioactive compounds. Many of these compounds are released during fermentation and refrigerated storage. The aim of this study was to determine the release of peptides by lactic acid bacteria in commercial fermented milk during refrigerated storage. The size and profile of peptides were analyzed by polyacrylamide gel electrophoresis and sizeexclusion HPLC. During electrophoresis, it was observed that the peptides were released from caseins, whereas β-lactoglobulin was the whey protein with the highest degradation. HPLC analysis confirmed the pattern of peptide formation observed in electrophoresis. Two fractions lower than 2 kDa with aromatic amino acids in their structure were separated. These results were consistent with those reported for structures of peptides with antihypertensive activity. Therefore, the presence of aromatic amino acids in the peptide fractions obtained increases the likelihood of finding peptides with such activity in refrigerated commercial fermented milk. In conclusion, during cold storage, peptides with different molecular weights are released and accumulated. This could be due to the action of proteinases and peptidases of the proteolytic system in lactic acid bacteria.

Evaluation of Petrifilm™ system compared with traditional methodology in count of indicators of sanitary-hygienic quality and pathogenic microorganisms in sheep milk

The objective of this study was to evaluate the applicability of the Petrifilm™ plates to enumerate microbial groups in sheep milk. Samples of sheep milk (n = 30) were plated simultaneously, to enumerate mesophilic aerobes, total coliforms, lactic acid bacteria, Staphylococcus aureus and Escherichia coli, using convencional reference protocols and Petrifilm™ plates. The results were compared using McNemar's test, linear regression and ANOVA (p < 0,05). The results demonstrated good significant between conventional methodologies and Petrifilm™ plates. Further, the Petrifim™ STX for counting S. aureus had higher recoverability of bacteria compared with the conventional methodology. Based on the results obtained and in view of the ease and rapidity procedures results, Petrifim ™ plates may be considered as alternatives for microbiological testing in sheep milk.

Lactose hydrolysis potential and thermal stability of commercial β-galactosidase in UHT and skimmed milk

Abstract The commercial enzyme (E.C. = 3.2.1.23) from Kluyveromyces lactis (liquid) and Aspergillus oryzae(lyophilized) was investigated for its hydrolysis potential in lactose substrate, UHT milk, and skimmed milk at different concentrations (0.7; 1.0 and 1.5%), pH values (5.0; 6.0; 6.5 and 7.0), and temperature (30; 35; 40 and 55 ºC). High hydrolysis rates were observed for the enzyme from K. lactis at pH 7.0 and 40 ºC, and from A. oryzae at pH 5.0 and 55 ºC. The enzyme from K. lactis showed significantly higher hydrolysis rates when compared to A. oryzae. The effect of temperature and β-galactosidase concentration on the lactose hydrolysis in UHT milk was higher than in skimmed milk, for all temperatures tested. With respect to the thermal stability, a decrease in hydrolysis rate was observed at pH 6.0 at 35 ºC for K. lactisenzyme, and at pH 6.0 at 55 ºC for the enzyme from A. oryzae. This study investigate the hydrolysis of β-galactosidase in UHT and skimmed milk. The knowledge about the characteristics of the β-galactosidase fromK. lactis and A. oryzae enables to use it most efficiently to control the enzyme concentration, temperature, and pH in many industrial processes and product formulations.

Lactose intolerance and cow's milk protein allergy

Abstract Adverse reactions to food intake have very diverse etiology and symptomatology. Regarding milk, its food allergy is presented as lactose intolerance, the sugar in milk, or allergy to milk protein. Despite having different symptomatology, confusions among allergic conditions to dairy and its mediators are common. Milk protein allergy originates from protein components present in milk, causing reactions to either the protein fractions in emulsion (caseins) or in whey (milk albumin). The allergic reaction is type IV mediated by T lymphocytes. The allergic reaction produces severe cellular damage and it triggers physical, mental and emotional symptomatology that may vary in time, intensity and severity. Lactose intolerance is originated by total or partial absence of the enzyme that digests this disaccharide. Lactose intolerance can be primary or congenital and secondary; the former being more rare and severe, the latter being more common. Lactase deficiency can be diagnosed by symptoms associated with cramping and diarrhea. Thus, the objective of this study was to conduct a review of available literature on cow’s milk protein allergy and lactose intolerance.

7/7/20, [gare d'Orsay], arrivée du roi d'Espagne à Paris [avec la reine Victoria et l'infant don Jaime, et à droite M. Raux, préfet de police] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 59946

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