Effect of UHT treatment on volatile compounds in milk.

The volatile profile of raw milk and UHT milk was studied by the method of solid-phase micro-extraction and gas chromatography–mass spectrometry(SPME–GC–MS) to determinate the characteristic volatile compounds of UHT milk and to know the change in the volatile profile of milk before and after UHT treatment.A total of 50 compounds were detected in raw milk,in which carboxylic acids were the most abundant volatile compounds.Other volatile compounds include acids,aldehyde,ketones,esters,alcohols and phenol.About 75 volatile compounds were identified and quantified after the heat treatment with 137 ℃,4s.Content of volatile compounds was significantly modified(P 0.05) and the relative total amounts of esters and ketones increased after UHT heat treatment.The most characteristic compounds of UHT milk aroma were some methyl ketones(2-butanone,2-pentanone and 2-heptanone),3-Hydroxy-2-pyranone,δ-Decalactone and γ-Dodecalactone.