Characteristic physicochemical indexes and flavor compounds in Xinjiang Kazak cheese during ripening

Abstract

Kazak cheese is one of the well-known and uniquely flavored dairy foods found in Xinjiang Uygur Autonomous Region of China. This study focuses on the characteristic physicochemical indexes, non-volatile and volatile flavor compounds observed in Kazak cheese at different stages of ripening. A total of 69 volatile compounds, including 16 acids, 17 alcohols, 19 esters, 4 aldehydes, 6 ketones and 7 other compounds were identified using headspace solid-phase microextraction gas chromatography-mass spectrometric. The acids, as important components of the volatile compounds, tailed off during ripening. The alcohols decreased gradually until the end of the ripening. The esters increased during the first 20 days and then increased significantly during the ripening. In addition, 35 non-volatile compounds, including 18 free fatty acids and 17 free amino acids, were detected using gas chromatography-mass spectrometer and high performance liquid chromatography. Lysine, alanine, threonine and leucine were the most abundant free amino acids observed during the ripening of Kazak cheese, while the other free amino acids were observed in small amounts. The main non-volatile free fatty acids were long-chain fatty acids with hexadecanoic acid the most abundant, followed by tetradecanoic acid, cis-9-octadecenoic acid, tetradecanoic acid and octadecanoic acid. These results provide references for the flavor quality control and improvement of Kazak cheese.