A study on the microbiological and biochemical changes in flavour compounds during ripening of Xinjiang specialty cheese

Abstract

Xinjiang specialty cheese is produced by natural fermentation of milk. During fermentation, a complex succession of changes takes place in the milk, including pH decline, protein denaturalisation, whey discharge, and etc. The ripening process of Xinjiang specialty cheese was studied for 50 days. Microbial count showed that Lactobacillus helveticus was the dominant strain in the cheese during ripening. The contents of pH 4.6 soluble nitrogen and 12% TCA soluble nitrogen gradually increased during the ripening process of the cheese. An electrophoretogram showed that the degree of protein degradation was high after 30 days of ripening. The contents of total organic acids and free fatty acids were determined by high performance liquid chromatography (HPLC). The results showed that the contents of total organic acids and free fatty acids in the flavour compounds increased significantly (p< 0.01). Twenty-five compounds were detected by gas chromatography-mass spectrometry (GC-MS), mainly alkanes, ketones, alcohols, esters, aldehydes, and acids. The sensory evaluation scores increased with ripening, and reached the highest value after 50 days.