ovalbumin and Salmonella-Food-Poisoning

The thermal death time kinetics of Salmonella Enteritidis (SE) was measured in buffer, egg yolk, and albumen using thin layer plastic sleeves. The sleeves allowed for the loading and sampling of liquids of high or unusual viscosity, as in the case of yolk and albumen, and accepted relatively large volumes (2 to 3 ml) of fluid. The sleeves maintained the volume of the fluid in a thin layer and could be easily handled for heat exposure. The thin layer maintained one-dimensional heat transfer and minimized temperature gradients, thus preventing parts of the fluid from experiencing different heating rates. A representative strain of SE associated with an egg-based salmonellosis outbreak was used in this study. The D- and z-values of the chosen strain, H7037, were measured in buffer, yolk, and albumen. In buffer, SE had the following mean (±standard deviation) D-values: D(55°C) = 3.51 ± 0.30 min, D(57°C) = 1.75 ± 0.13 min, and D(60°C) = 0.25 ± 0.06 min. In yolk, D(58°C) = 0.90 ± 0.05, D(60°C) = 0.26 ± 0.03, and D(62°C) = 0.20 ± 0.02. In albumen, D(55°C) = 1.26 ± 0.31, D(56°C) = 0.68 ± 0.10, and D(57°C) = 0.44 ± 0.04. The z-values for SE calculated from these D-values were 4.29 ± 0.39°C in buffer, 6.12 ± 0.26°C in yolk, and 4.63 ± 1.14°C in albumen. The sleeves allowed one consistent approach to determining thermal death time kinetics regardless of viscosity.

Topics: Animals; Consumer Product Safety; Egg Yolk; Eggs; Food Preservation; Hot Temperature; Humans; Microbial Viability; Ovalbumin; Salmonella enteritidis; Salmonella Food Poisoning; Viscosity

The effect of a low-temperature, extended-time, in-shell pasteurization process on the protein quality of egg albumen was evaluated. Ten dozen fresh chicken eggs were pasteurized in a hot-air oven at 55 C for 180 min. The eggs were refrigerated and broken out for analysis on Days 0, 7, 14, 28, 42, and 56 following pasteurization. There were no significant differences in total or soluble protein over the experimental period for the pasteurized or unpasteurized albumen. Mean protein content was 80.6 +/- 0.5% for the pasteurized albumen and 80.9 +/- 0.5% for the unpasteurized albumen. In vitro digestibility, as measured by the AOAC method, was 82.4 +/- 0.7% for the pasteurized albumen and 81.7 +/- 0.6% for the unpasteurized albumen. There were no significant differences over the experimental period in the digestibility of the samples. Free amino acids and discriminant-computed protein efficiency ratio (DC-PER) also did not differ between the pasteurized and unpasteurized albumens or over the experimental period. The in-shell pasteurization process used had no effect on the protein quality of albumen.

Topics: Amino Acids; Animals; Chickens; Digestion; Disinfection; Egg Shell; Female; Food Handling; Hot Temperature; Nutritive Value; Ovalbumin; Protein Denaturation; Quality Control; Salmonella Food Poisoning; Time Factors

The incidence of food-poisoning caused by Salmonella serotype Enteritidis PT4 has increased. Implicated food products display pH levels between 4 and 9. Accordingly, the effect of growth at extremes of pH on the presence of surface structures and the carriage of a 38-MDa plasmid was determined by growing a clinical isolate of Enteritidis PT4 in a chemostat. Steady-state growth was possible over the pH range 4.35-9.45, corresponding to the pH extremes associated with key reservoirs implicated in outbreaks. Without pH control, cultures stabilised at pH 7.10. Growth at extremes of pH had significant effects on the distribution of cell surface structures; at pH 9.45, only 3% of cells were fimbriate compared with 52% at pH 7.10 and 20% at pH 4.35. The proportion of motile cells and the presence of flagella was also reduced at extremes of pH. A 38-MDa plasmid was present in cells grown in the chemostat at pH 7.10, but not in cells grown at pH 4.35 or pH 9.45. Thus, environmental pH may have a significant impact on the virulence potential of Enteritidis PT4.

Topics: Bacteriophage Typing; Cell Movement; Culture Media; DNA, Bacterial; Feces; Humans; Hydrogen-Ion Concentration; Meat; Microscopy, Electron; Ovalbumin; Plasmids; Salmonella enteritidis; Salmonella Food Poisoning; Serotyping