APPLICABILITY OF BACTERIAL GROWTH MODELS IN SPREADABLE PROCESSED CHEESE

Background. Food spoilage is a process in which the quality parameters decrease and products are no longer edible. This is a cumulative effect of bacteria growth and their metabolite production, which is a factor limiting shelf life. Thus, the aim of the study was to evaluate whether microbiological growth models for total viable count (TVC) and Clostridium strain bacteria are reliable tools for prediction of microbiological changes in spreadable processed cheese. Material and methods. Investigations were conducted for two types of bacteria: TVC and Clostridium in following temperature: 8 degrees C, 20 degrees C and 30 degrees C. A total number of aerobic bacteria was determined based on standard PN-EN ISO 4833: 2004 and Clostridium was detected by using microbiological procedure for sulphite-reducing anaerobic spore-bacteria with a selective nourishment. During the analysis nonlinear regression and Baranyi and Roberts primary model were used. Results. For temperatures 20 degrees C and 30 degrees C, Baranyi and Roberts model, for total viable count showed determination coefficient of 70%. The models prepared for Clostridium, in these temperatures, showed much lower R-2, respectively 25% and 30%. At the above mentioned temperatures also the expiration of product shelf life was much shorter and amounted 70 days at 20 degrees C and 7 days at 30 degrees C. For both types of bacteria incubated at 8 degrees C the numbers of bacteria decrease until the expiration of product shelf life. Conclusions. Models used in the analyses, Baranyi and Roberts and nonlinear regression, poorly matched the experimental data, hence they are not reliable tools. Nevertheless, they gave information about dynamic of microbiological changes in spreadable processed cheese.