Lipolysis-induced dynamic evolution of sensory and volatile profiles in UHT milk supplemented with exogenous lipase over storage

Lipase supplementation improves the flavor profile of UHT milk during storage. • Methyl ketones constitute the primary source of off-flavors in UHT milk during late storage. • Lactones endow UHT milk with enhanced milky and sweet aroma. • Lipase improves milk flavor mainly within the first three months of storage. Lipase-mediated flavor improvement in dairy products has been widely investigated. However, the majority of previous studies have focus on flavor attributes upon completion of enzymatic hydrolysis, with limited attention has been paid to the dynamic flavor changes of lipase-supplemented UHT milk during storage. This study comprehensively investigated the effects of lipase treatment (0, 0.1, 1, and 10 U/L) on quality properties, color variations, sensory profiles, and volatile compound profiles of UHT milk throughout six months of storage. Lipase supplementation reduced the pH value and fat content of UHT milk and shifted its color toward pale yellow. Sensory evaluation revealed that lipase significantly enhanced the milky, sweetness, and fatty flavor attributes of UHT milk within the first three months of storage, while the overall acceptability was also improved during this period. Based on volatile profiling, PLS-DA model and relative odor activity values (ROAV), 2-heptanone, 2-nonanone, 2-undecanone, octanoic acid, hexanoic acid, 1-octanol, 2-furanmethanol, delta-dodecalactone, delta-decalactone, pentanal, and benzaldehyde were identified as key volatile compounds associated with lipolytic changes in UHT milk. Integrating the aromatic characteristics of volatile compounds and dynamic sensory changes indicated that methyl ketones and short-chain fatty acids exert dual effects on aroma enhancement and off-flavor formation in UHT milk, whereas lactones contribute to improving the sensory properties of milk flavor. This study demonstrates the potential of exogenous lipase supplementation to modulate UHT milk flavor, and reveals the patterns of lipase-associated dynamic changes in volatile flavor compounds of UHT milk during storage. Download: Download high-res image (371KB) Download: Download full-size image