Esterase activities of autochthonous starter cultures to increase volatile flavour compounds in Chinese traditional fermented fish (Suan yu)

Suan yu, a type of Chinese traditional fermented freshwater fish in solid form, is cheered among consumers due to its characteristic sensory flavour, primarily taste and smell. The purpose of this study was to investigate the presence of esterase activity of Lactobacillus plantarum 120, Staphylococcus xylosus 135, and Saccharomyces cerevisiae 31, in selecting appropriate processing means to accelerate the formation of the desired flavour in Suan yu. The results showed that all strains exhibited esterase activities in both intracellular and extracellular fractions against p-nitrophenyl (p-NP)-acetate, p-NP-butyrate, and p-NP-octanoate, and also that the maximum activity was observed in the intracellular fraction with p-NP-octanoate. Esterase activities of all strains were inhibited by low pH and low water activity (Aw), with the exception of L. plantarum 120 exhibiting an increase in intracellular activity with decreasing Aw. Moreover, L. plantarum 120 and S. xylosus 135 esterase were negatively affected by decreasing temperature, while a positive influence was observed on the intracellular esterase of S. cerevisiae 31. The results suggested that a low pH, a low Aw and a high temperature would be more appropriate for Suan yu processing to produce more flavour compounds which are acceptable by consumers.