Quality, stability and shelf life of ultrapasteurized milk bottled in amber polyethylene terephtalate

Ultrapasteurized (UP) milk has been marketed to consumers as a product that has a longer refrigerated shelf life than high temperature short time (HTST) pasteurized milk, and less cooked flavor than that of ultra high temperature (UHT) processed milk. The product is sold in amber polyethylene terephtalate (PET) amber bottles. This packaging shares the advantages of other plastic containers, but also provides protection from light-induced oxidation reactions. Little is known about the factors associated with changes in the flavor and aroma of UP-processed PET-bottled (UP-PET) milk over time.; The shelf life of UP milk is mainly governed by its flavor and physicochemical stability, because the product is microbiologically safe and stable.; The Flavor of UP milk does not change perceivably during the first 60 days of refrigerated storage. Degradation of flavor occurs sometime afterwards. Possible causes of flavor changes are lipid oxidation and the formation of protein hydrolysis products.; Specifically, this study focused on changes in volatile compounds which could be related to off-flavors and lipid oxidation products. 2% UP-PET, was stored at several temperatures for periods of up to 75 weeks. A total of 4 studies were conducted: a 60 day study at 5°C, a 90 day study at 5°C, a 30 day accelerated study at 5°C, 25°C, 35°C, and 45°C, and a Sensory Evaluation Study with milk that had been stored under refrigeration for 75 weeks. A SPME-GC-MS method was used to identify volatiles in milk samples. The sensory evaluation was carried out using a paired comparison method, which was evaluated by a binomial distribution. It was possible to determine the maximum shelf life of UP milk packed in PET bottles by correlating changes in flavor detected in the sensory evaluation with changes in selected volatile compounds found in the headspace of the milk samples.; According to the sell by/manufacture date, UP milk packaged in amber PET bottles has a refrigerated shelf life of 60 days, but the results of this study indicate that the shelf life of this product could be extended beyond 90 days without detectable changes in flavor or quality.