[Evaluation of commercial UHT milk and optimization of industrial process]

From the nutrition al point of view milk is one of the most complete food in the diet of mammals. It contains nearly all the nutrients necessary to sustain life, but milk can deteriorate very easily, either by microbiological contamination or by biochemical reactions during processing and/or storage. The objective of this research study was to design a modified UHT treatment to achieve commercial sterilization and maximize the stabilization of the heat-treated product during storage. To search for a modified UHT process, a mathematical model coupled with an optimization routine (complex method) was developed. The mathematical model considers Kinetics for the inactivation of Bacillus stearothermophilus and several quality factors. To attain the objective function, several commercial UHT milk were analyzed and for the computer search the minimization of hydroxy methyl furfural (HMF) formation was considered and also including constraints for protease and lipase inactivation. The complex optimization procedure was implemented to search for the optimum modified UHT treatment.. One of the optimum modified UHT treatments was the combination of two pre-treatment (3.16 minutes at 62.30 degrees C and 6 minutes at 75 degrees C) in addition with a UHT treatment (0.75 s at 148.8 degrees C). This treatment attains the maximum product stability with a negligible effect on composition and color formation in the treated milk (HMF formation less than 3 mg/mL).