Assessment of physicochemical and microbiological quality of UHT whole milk and proteolysis determination during storage

Abstract

The aim of this work was aimed to evaluate physicochemical and microbiological quality of UHT whole milk, market in Londrina-PR, Brazil, as well as estimate gelation and proteolysis during storage period of 150 days at room temperature. Physicochemical analyses included determination of fat content; titratable acidity; ethanol stability; total solids; solids-not-fat; pH, density and freezing point. For proteolysis estimative, total nitrogen, non-casein nitrogen and non-protein nitrogen were quantified. Gelation estimation was carried out as well as mesophilic aerobes enumeration. Results obtained in this work demonstrate increase of gelation and proteolysis during storage and samples in disagreement with physicochemical and microbiological standards. The problems found in UHT milk quality standardization associated with increasing proteolysis and gelation during storage could lead to product rejection by the consumer.