Effects of storage time and temperature on the chemical and sensory properties of aseptic milk

Abstract

Our objective was to determine the effects of storage temperature and storage time on the chemical, physical, and sensory properties of ultra-high-temperature–direct steam injection aseptic milk. Milk was collected on 2 different processing dates (2 replicates) at a commercial aseptic milk processing facility immediately as containers came off the processing line. Milk was heat treated by direct steam injection (142°C for 3 s) with a flash vacuum cooling step following the holding tube and packaged aseptically in 946-mL aseptic packages. Packages were randomly assigned to 1 of 2 treatment groups (storage temperature of 4°C or 21°C). Half of the packages of 1% aseptic milk were cooled immediately off the processing line in ice and held at 4°C, and the other half were cooled to 21°C and held at 21°C for 12 mo. An unopened package of 1% aseptic milk that had been stored at 4°C or 21°C was opened and analyzed each month (for 12 mo) by chemical and descriptive sensory analyses. Chemical analyses included volatile compounds, viscosity, furosine, and dissolved oxygen. At 2 wk, 6 mo, and 12 mo, milk samples stored at each temperature were evaluated by consumers along with commercial 1% HTST milk. By descriptive sensory analysis, sulfur-eggy flavor decreased faster and caramelized flavor increased faster in aseptic milk stored at 21°C than in that stored at 4°C. Similarly, relative abundance of sulfur volatiles was lower initially in milk stored at 21°C than in that cooled and stored at 4°C. Furosine concentration was higher in milk stored at 21°C than in milk stored at 4°C. There were differences in consumer liking between the aseptic milk samples stored at the 2 storage temperatures, but they did not translate to an advantage in flavor liking for aseptic milk. Consumers indicated higher liking scores for fresh, refrigerated HTST milk than aseptic milk stored at either temperature at all 3 storage time points. Fluid milk processors need to focus on developing technology to increase the sensory liking scores of aseptic milk to maintain and increase fluid milk consumption as consumer lifestyles increase the demand for shelf-stable beverages.