IMPACT OF BACTOFUGATION ON MILK THERMODURIC AND SPORE COUNTS

As a way of reducing microbiological counts, a dairy industry may use milk bactofugation as a "pre-stage" of processing. Bactofugation is a mechanical treatment of physical separation performed in centrifuges, which are able to eliminate spores that are present in milk. The microbiota remaining in milk bactofugation may be resistant to the treatment of pasteurization, the thermoduric ones. These microorganisms multiply in pasteurized milk and can produce lytic enzymes such as proteases and lipases, which can compromise its quality and lifespan. Sporulated microorganisms are capable of changing their vegetative form in order to survive extreme conditions of the environment, including the thermal resistance to the processes used in milk processing. The objective of the present work was to evaluate the effect of bactofugation in the thermoduric and in the mesophiles, psychrotrophs and thermophilic spore counting. The milk samples were collected before and after the bactofugation process was carried out in a dairy located at Teodoro Sampaio / SP. For thermoduric research, 5mL of milk were submitted to laboratory pasteurization (62.8° C for 30 minutes) and then rapidly cooled in an ice bath at a temperature below 10°C. For spores, 200mL of milk were heated at 80°C for 12 minutes and rapidly cooled in an ice bath. Subsequent serial dilutions were then plated in duplicate by the surface in PCA medium. Each set of plates was incubated at 37°C/48h, 55°C/48h and at 7°C/10days, for enumeration of thermoduric and mesophiles, thermophilic and psychrotrophic spores, respectively. Regarding of the thermoduric, the average counts in the raw and bactofuged milk of mesophiles were 239,700 and 88,665 UFC/mL; psychrotrophic 352 and 47 UFC/mL; and, thermophilic 3 and 0 CFU mL. Thus, bactofugation efficiency was 63.01%, 86.73% and 100% for thermoduric, mesophiles, psychrotrophic and thermophilic, respectively in relation to spores, the counts in raw and bactofuged milk were, respectively, 333 and 17CFU/mL for mesophiles, 2 and 0 CFU/mL for psychrotrophic and 3 and 0 CFU/mL for thermophilic. It was observed, therefore, that bactofugation of the raw milk was able to reduce by 95%, 100% and 100% the mesophilic, psychrotrophic and thermophilic spores, respectively. In the present study, bactofugation proved to be effective in reducing concentrations of microorganisms in raw milk and could, therefore, be used as a tool to improve its microbiological quality and, consequently, its technological potential to produce milk derivatives by the preservation of the integrity of its constituents.