Evaluation of aroma of pasteurized and UHT processed milk by aroma extractdilution analysis

For the purpose of examining the influence of pasteurization and UHT proces sing on the aroma of milk, aroma substances from extracts of raw milk, LTLT milk, HTST milk and UHT processed milks which were distilled under reduced pressure were analyzed by gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and aroma extract dilution analysis (AEDA). As a resu lt, 101 compounds were identified or presumed. As the level of heating was increased, there was a significant increase in the concentrations of 2-pent anone, 2-heptanone, 2-nonanone and 2-undecanone. In addition, a large numbe r of pyrazines were newly detected. In all of the milks, hexanoic acid, oct anoic acid and decanoic acid were detected in large quantities. Those acids were from 8% to 24% of the total aroma concentration in each of the milks. Compounds contributing to milk odor according to the AEDA were shown in 70 locations on the gas chromatogram. Of those 70 locations, the flavor dilut ion (FD) factors of 44 were changed due to heating, while 26 were unchanged . Odors of 2,6-dimethylpyrazine, 2-ethylpyrazine, 2-nonanone, 2-ethyl-3-met hylpyrazine, methional, pentanoic acid, an unknown compound (Kovats index 1 747), an unknown compound (Kovats index 1757), benzothiazole and vanillin w ere potent due to heating. Vanillin was potent in HTST milk, the unknown co mpound (Kovats index 1747) and the unknown compound (Kovats index 1757) in UHT milk. These were thought to characterize HTST milk and UHT processed mi lks respectively. The aromas which contribute to the odor of milk were not necessarily large in quantity.