The combined effect of cooking and storing temperatures on the quantities of aerobic, coliform and lactic acid bacteria in cooked sausage

Abstract

A 'plate type' temperature gradient incubator (GradiplateR, Biodata Ltd., Helsinki, Finland) was used to expose raw sausage material to 81 different combinations of cooking (9 levels in the range of 54-69°C) and then cold storage temperatures (9 levels in the range of 54-69°C) and then cold storage temperatures (9 levels in the range of 1-11°C) according to a 92 factorial design. Following these two incubations, the numbers of naturally present aerobic, coliform, and lactic acid bacteria in the sausage material were determined. The bacterial counts were plotted against the corresponding cooking and cold storage temperature to give three-dimensional maps. A six-order polynomial model was fitted to the experimental data. In general low bacterial counts corresponded with high cooking temperatures and low storage temperatures, but the overall pattern of growth was not readily predictable. Therefore the three-dimensional maps can be used as a model to predict the probable numbers of bacteria in cooked and cold stored sausages. With the help of a polynomial model the combined effect of cooking and cold storage temperatures on quantities of coliform and lactic acid bacteria was discovered. This temperature mapping study also confirms that avoidance of post cookery recontamination provides the method of choice for improving the microbiological quality of cooked sausages.