Assessment of Microbial Contamination in Products of Animal Origin: Stretched-curd Cheese, Yogurt and Fresh Sausage

Abstract Animal products are sources of microbiological contamination when the process has hygienic-sanitary control fails. Therefore, this work aims the evaluation of the pathogenic microorganisms presented in samples from the Brazil southern region of yogurt (N = 101), stretched curd cheese (N = 31), fresh sausage (N = 22) and processing water (N = 63). Analyses of coliforms at 45 °C, Staphylococcus aureus, Salmonella sp. and Escherichia coli were performed. Analysis indicated processing water is an important contamination source to be monitored, because the majority of samples presented results above the regulation limits. Thermal treatment and fermentation such as stretched curd cheese and yogurt appeared to be more stable against contamination during processing. In this study, for coliforms at 45 °C, only one cheese sample and 12% of total yogurt samples exceeded the Brazilian legislation limit. None of sausage samples presented any contamination. On the other hand, values found in both processing water and dairy products indicated failures in application and monitoring of good manufactured practices.

Removal of COD and nitrogen from animal food plant wastewater in an intermittently-aerated structured-bed reactor.

This study evaluated the performance of a continuous flow structured-bed reactor in the simultaneous removal of total nitrogen (TN) and chemical oxygen demand (COD) in the effluent from an animal food plant. The reactor had an intermittent aeration system; hydraulic retention time (HRT) of one day; temperature of 30 °C; and recirculation ratio of five times the flow. An experimental central composite rotational delineation (CCRD) type design was used to define the aeration conditions and nitrogen load (factors) to be studied. Response surface methodology was used to analyse the influence of the factors above the results, the removal of TN and COD. It was observed that the aeration factor showed the greatest significance for the results and that the affluent TKN concentration did not have a significant effect, at a 95% level of confidence, on COD removal. Throughout the experiment, the COD/N ratio remained between 3.2 and 3.8. The best results for COD and TN removal, 80% and 88%, respectively, were obtained with 158 min of aeration on a cycle of 180 min and 255 mg L(-1) of Total Kjeldahl Nitrogen (TKN) in the substrate.