Abstract: The flavor characteristics of milk undergoing low-temperature long-time (LTLT) pasteurization (62, 65 and 68 ℃; 20, 25, 30 and 35 min) or high-temperature short-time (HTST) pasteurization (72, 75, 80, 83, and 85 ℃; 15, 20, and 30 s) were evaluated by electronic tongue, gas chromatography-mass spectrometry (GC-MS) and automatic amino acid analyzer, in order to study the effect of different heat treatment conditions on the flavor of pasteurized milk. The results showed that compared with LTLT pasteurization, HTST pasteurization could better retain the flavor of raw milk. By GC-MS, a total of 19 volatile flavor compounds were identified in raw milk, and 11 of these disappeared after heating, but 42 compounds were newly produced. In the LTLT pasteurized milk, the volatile flavor substances were mainly alcohol, ester, acid and alkane; in the HTST pasteurized milk, phenols, aldehydes and ketones were more abundant. It was found that LTLT pasteurization was beneficial to the production of flavor amino acids, while HTST pasteurization increased the content of bitter amino acids in milk, and the content of sweet amino acids reached the maximum value after treatment at 75 ℃ for 20 s, which basically did not change with varying sterilization conditions. This study provides a theoretical basis for improving the quality of pasteurized dairy products and the pasteurization process.

Key words: pasteurized milk; heat treatment; electronic tongue; gas chromatography-mass spectrometry; automatic amino acid analyzer