54F-23 |
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F. SAN MARTIN1, F. Cubas, J. Welti-Chanes, and H. S. Garcia4. (1) Departamento de Ingeniería Química y Alimentos, Universidad de las Américas, Puebla, Cholula, Puebla, 72820, Mexico, (2) UNIDA, Instituto Tecnologico de Veracruz, M.A. de Quevedo #2779, Col. Formando Hogar, Veracruz, Ver, 91897, Mexico Consumers demand for fresh-like products impose challenges for food processors. In some countries, fresh cheeses are still made with raw milk, thus posing a health risk for consumers. Technologies other than thermal treatment are being investigated for decreasing microbial population in milk while retaining cheese-making properties. The objective of this study was to evaluate the effect of high pressure homogenization (HPH) on the native microflora of milk and on wet yield of fresh cheese, and to compare the effects against low temperature-long time (LTLT) pasteurized milk. Raw milk from a local dairy farm was either homogenized at 100MPa (0-4 times), for holding times at treatment pressure equivalent to 0, 15, 30, 45 and 60 s or pasteurized at 63oC for 30min. Samples from each treatment were serially diluted in 0.1% peptone water. Pour plate method was used to determine aerobic mesophiles and coliforms. Fresh cheeses were made according to a standard procedure. Wet yield was determined as the amount of cheese obtained per 100 kg of milk. Results show that coliforms and aerobic mesophiles in milk decreased with increasing holding times. Holding times of 60s reduced 3.6 log cycles of aerobic mesophiles and 3.7 log cycles of coliforms and resulted in milk with microbial populations comparable to LTLT pasteurized milk (3.4 and 3.0 log cycles in aerobic mesophiles and coliforms respectively). Wet cheese yield for raw milk cheese was 16.3% whereas HPH milk at residence time 60s resulted in significantly higher wet yield 19.6%. No significant difference in yield was observed between raw, pasteurized, 15, 30 or 45s. Homogenization of milk by high pressure resulted in microbial inactivation comparable to LTLT pasteurization while increasing cheese yield, therefore HPH constitutes a feasible alternative for reducing microbiological risks in fresh cheese.
Session 54F, Nonthermal Processing: General I
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |