Effects of lipase-producing lactic acid bacteria on the fatty acid and flavor of Xinjiang traditional cheese

Abstract: Lipase or lipase-producing lactic acid bacteria can be usually added to the cheese production process, in order to improve the sensory and flavor quality of cheese products. Taking the Xinjiang traditional cheese as the research object, this study aims to investigate the effects of lipase-producing lactic acid bacteria on the fatty acid and flavor of the cheese. Four strains of lipase-producing lactic acid bacteria (T1-5 and T1-3 are Weissella fusion, H1-6 is Lactobacillus helveticus, B2-5 is Lactobacillus plantarum) were selected in the previous stage of the experiment as a starter. Three strains were selected as the Lactic acid bacteria compounding for the yogurt cheese, according to the traditional technology. Experimental groups were: Group A T1-5 and T1-3, H1-6 (1:1:1), Group B H1-6, T1-5, B2-5 (1:1:1), Group C H1-6, T1-3, B2-5 (1:1:1), D group T1-3, T1-5, B2-5 (1:1:1); control group (group E): commercial starter. The physicochemical properties of the fermented and matured cheese were then characterized to clarify the effects of lipase-producing lactic acid bacteria on the cheese pH, titer acidity, and fat oxidation indicators. Gas chromatography (GC) was used to detect the fatty acid in the cheese, and gas chromatography-ion mobility spectrometry (GC-IMS) was used to identify the flavor substances in the cheese variety. The results showed that the pH and peroxide values of the cheeses in the four groups A, B, C, and D were significantly lower than those in the E group (control group) (P<0.05), whereas, the cheese titer values in the A and B groups were higher than those in the control E group. (P<0.05). There was no significant difference in the TBARS value between the five groups of cheese (P> 0.05). The contents of saturated fatty acid, monounsaturated fatty acid, and polyunsaturated fatty acid of the cheeses in groups A, B, C, and D were significantly higher than those in group E (P<0.05). The higher saturated fatty acids in the experimental group cheese were the meat Myristic acid (C14:0), palmitic acid (C16:0) and stearic acid (C18:0), as well as butyric acid (C4:0), caproic acid (C6:0), capric acid (C10:0) and Lauric acid (C12:0). The oleic acid (C18:1n9c) in the experimental group cheese was the main component of monounsaturated fatty acids. The linoleic acid (C18:2n6c) in the experimental group cheese was significantly higher than the control group (group E) (P<0.05). The GC-IMS and principal component analysis show that there were many types of volatile flavor compounds in group A and B cheese, indicating the high similarity. Aldehydes and esters were the main volatile flavor substances in the cheese, among which the 2-heptanone content of butyl aldehyde and butyl acetate was relatively high. There were relatively similar flavor substances in the two groups of cheeses C and E. The main volatile flavor substances in Group D were butyl acetate, 3-octanone, and heptanal, indicating a different fragrance from the others. Therefore, there were a better overall flavor and taste of A and B cheeses after the sensory evaluation, indicating the higher scores than the others. The screened lipase-producing lactic acid bacteria can be expected to serve as a starter to improve the quality of traditional Xinjiang cheese.