Physicochemical properties, total bacterial counts and volatile flavor compounds of fermented yak meat sausages with 0.0%, 1.5%, 3.0% and 4.5% NaCl were evaluated in this experiment. The results showed that the pH and lightness value of the sausage with 4.5% NaCl were significantly higher than those of the other three groups (P < 0.05). The hardness, adhesiveness and chewiness decreased with decreasing amount of added NaCl, while the storage modulus and total bacterial count increased. Additionally, the water-holding capacity and resilience of the sausage with 3.0% NaCl were significantly higher than those of the other groups (P < 0.05), and the yellowness value was the lowest among the four groups. As NaCl content decreased from 4.5% to 1.5%, the thiobarbituric acid reactive substances (TBARS) value and sulfhydryl content showed an upward trend, and the protein carbonyl content showed a downward trend, while the redness value, elasticity, and cohesiveness did not significantly differ. Seven categories of volatile flavor compounds including aldehydes, alcohols, and acids were detected in fermented yak meat sausages. Three principal components were identified by principal component analysis (PCA), and 12 key volatile flavor compounds with relative odor activity values (ROAV) ≥1) such as hexanal, nonanal, and isovaleraldehyde were obtained. The relative contents of volatile flavor compounds and the key flavor substances of fermented yak meat sausage varied with NaCl level. With decreasing NaCl content from 4.5% to 1.5%, the relative content of aldehydes derived from lipid oxidation increased. Sensory evaluation showed that with the decrease in NaCl content from 3.0% to 0.0%, the appearance, texture, taste, and overall acceptability showed a downward trend, while there was no significant difference in sensory scores between the sausages with 3.0% and 4.5% NaCl.

To explore the effect of reducing the sodium content on the lipid oxidation and flavor quality of naturally fermented yak meat sausages, low-sodium and control sausages were prepared by adding 2% and 4% sodium salt and natural ripening or constant temperature ripening, respectively. Physicochemical indicators were measured during the ripening process. The results showed that regardless of the ripening method used, the water content, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and hydroxyl radical scavenging capacity of the low-sodium group were significantly lower than those of the control group (P < 0.05), and the pH was significantly higher than that of the control group (P < 0.05). The degrees of lipid hydrolysis and oxidation in the four treatment groups increased with ripening time, being significantly higher in the low-sodium group than in the control group for each ripening method (P < 0.05). There was no significant difference in lipoxygenase activity between the two groups of natural maturation (P > 0.05), while at the late stage of constant-temperature ripening, the lipoxygenase activity in the low-sodium group was significantly higher than that in the control group (P < 0.05). In addition, a total of 69 volatile flavor compounds were detected from the sausages, and the cumulative contribution rate of the first three principal components was as high as 96.206%. Principal component analysis (PCA) showed that on the 9th and 17th (end) day of maturation, the relative contents of alcohols, aldehydes and other substances generated by lipid oxidation in the low-sodium group were higher than those in the control group. Different sodium contents had a significant effect on the hydrolysis and oxidation of lipids in sausage. Directly reducing the sodium content to 2% may promote the oxidation of lipids.