Proteolysis of UHT milk during storage at room temperature is a major factor limiting its shelf-life. In this work, two lots of 10 samples of raw milk each, and after manufacturing, two lots of UHT milk containing 25 samples each, were obtained from a dairy plant for the psychrotrophic microorganism count (raw milk) and to study the rheological behavior and proteolysis index (UHT milk during 120 days of storage time). The psychrotrophic count was carried out using the standard plate count method. The proteolysis index was determined by the presence of free glicomacropeptide using a spectrofotometer at 470 nm. Rheological parameters were carried out five times the same lot at room temperature, using a cone and plate rheometer. There was an increase in proteolysis during the shelf-life and after 60 days of storage, an increase in the apparent viscosity, probably due to the presence of bacterial proteinases produced by psychrotrophic bacterial contaminants in the raw milk.
UHT milk; apparent viscosity; proteolysis
