54F-12

G. TOVAR-HERNÁNDEZ¹, H. R. Peńa¹, G. Velazquez², J. A. Ramírez³, and J. A. Torres⁴. (1) Food Science and Technology, Univ. Autónoma de Tamaulipas and Oregon State Univ., UAM-Reynosa-Aztlán, Calle 16 y Lago de Chapala. Col. Aztlán, Reynosa, Tam., 88740, Mexico, (2) Food Science and Technology, Univ. Autónoma de Tamaulipas and Oregon State Univ., UAM-Reynosa-Aztlán, Calle 16 y Lago de Chapala. Col. Aztlán, Reynosa, Tam., 88740, Mexico, (3) Food Science and Technology, Univ. Autónoma de Tamaulipas, UAM-Reynosa-Aztlán, Calle 16 y Lago de Chapala. Col. Aztlán, Reynosa, Tam., 88740, Mexico, (4) Dept. of Food Science and Technology, Oregon State Univ., 100 Wiegand Hall, Corvallis, OR 97331-6602

Pasteurized milk is one of the most consumed foods because of its nutritional value and desirable sensory properties; however, its short shelf-life is considered an important drawback for its distribution in large regional markets. High Pressure Processing (HPP) inactivates pathogenic and spoilage microorganisms without altering the sensorial and nutritional quality of foods. The objective of the present work was to evaluate during refrigerated storage the effect of HPP on the microbial load of refrigerated whole and 1% reduced fat milk. Two repetitions of six combinations of pressure (586 MPa), time (1, 3 and 5 min) and temperature (40 and 55ş C) were used to evaluate the treatment effect on mesophiles, pseudomonas, psychrotrophs and coliforms counts in 1% and 3.25% fat content milk stored at 5ş C. Untreated controls and pasteurized commercial milk were used to compare duplicated samples analyzed at 1, 7, 15, 30 and 45 days. Microbial counts immediately after pressure treatments (day 1) showed that all combinations were able to inactivate the microorganisms analyzed as compared to the control sample. When compared to the commercially pasteurized milk, microbial loads remained lower for all treatments during refrigerated storage up to 45 days. The combination of 586 MPa and 5 min at 55ş C was the best treatment showing larger microbial counts reductions in mesophiles, psychrotrophs and pseudomonas. The results of this research, along with physicochemical characterization studies not reported here, suggest that HPP combined with moderate heating is a feasible alternative to extend the refrigerated shelf-life of 1 and 3% fat milk for up to 45 days.

Session 54F, Nonthermal Processing: General I
2:00 PM - 5:30 PM, Monday PM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana