Efeito da refrigeração em leite de ovelha - evolução da flora microbiana e efeito na aptidão tecnológica para queijo

Mestrado em Engenharia Zootécnica - Produção animal - Instituto Superior de AgronomiaThe objective of this study was to investigate the effect of the cooling on ewe’s milk. After an initial characterization, the raw milk was refrigerated at 4 °C and 8 °C for seven days, through what was studied the evolution of the microbial population (total mesophilic (ISO/DIS 6610) and psychrotrophic (ISO/ IS 8552)), pH and the ability to coagulation, through clotting tests with the Optigraph. After three days of cooling, there were increases in the population of mesophiles, 10 and 52, and 15 and 87 times the values of psychrotrophic, at 4 °C and 8 °C, respectively. The pH decreased very significantly along the cooling, especially at 8 °C and from 2nd day, which influenced the start of the micellar aggregation. The cooling at 4 °C showed no significant effect on the ability to clotting and allowed the control of development of microbial populations (particularly the psycrotrophic population) for a period of 48 hours. The results presented in this study reinforce the belief that when the cooling is at inadequate temperatures and storage times, microbial populations can be selected favoring psychrotrophic bacteria that may have a negative effect on manufacture of the cheese from raw milk