| Popis: |
A number of strains of enterococci was isolated from pasteurized meat products. Two variants of Streptococcus faecium (E1 and E20) took part in the present study. Using these organisms, heating tests in suspensions of pork (sealed plastic pouches) were performed. Mixtures of ingredients ('preparation of cooked ham') were added in the majority of experiments. Dextrose was replaced by sorbitol in one experiment, by glycyrrhizin in another. Following thermal treatment at 68.9 degrees C (various heating times), duplicate pouches were incubated at 8 and 37 degrees C. When the mixture of ingredients were added to the meat suspension, thermoresistance of the test strains was found to increase markedly. For E20, D 68.9 degrees C values of 63 and 2.5 min were measured respectively in the systems with or without ingredients (pH 6.3 in both cases). When dextrose was replaced by one or by the two other sweeteners, the levels of thermoresistance did not show any changes. During incubation at 37 degrees C, the surviving cells almost invariably grew to high counts; however similar results were not observed at 8 degrees C. At this temperature a decrease in viable counts during five months' storage was recorded; this was particularly the case with longer periods of heating. On growth of Streptococcus faecium in the presence of dextrose, the pH of the meat suspension decreased from 6.3 to 4.7-4.9. As a result, the residual nitrite fell to very low levels. These phenomena were not observed in the experiments in which dextrose was replaced by the other sweeteners. |
