Physicochemical Properties, Amino Acid Composition and Volatile Components of Fermented Fish (Pla-ra) Accelerated by Starter Cultures

Abstract

Fermented striped snake-head fish, known as Pla-ra, is a popular traditional food that is eaten throughout Thailand. Lactic acid bacteria (LAB) are found as the dominant microorganisms in many fermented fish products. The primary role of LAB is to ferment the available carbohydrates, and thereby causes a decrease in pH. The combination of low pH and organic acids (mainly lactic acid) are the main preservative factors found in fermented fish products. The purpose of this study was to determine the change in physicochemical properties, amino acid composition, and active volatile compounds of Pla-ra, by adding halophilic bacteria and LAB into the fish fermentation. The results revealed that the pH of the 8 Pla-ra treatments were found between 5.33 - 5.63, and the salt content of all Pla-ra treatments, ranged from 20.60 to 22.28 %. The increase in total acidity and the degree of hydrolysis (DH), is generally accompanied by a decrease in pH. The FMP treatment had the highest total acidity, protein, salt, DH and amino acid contents, but had the lowest pH. The important amino acids in all 8 Pla-ra treatments were glutamic acid, lysine, and leucine. There were 43 volatile compounds detected in Pla-ra, and the 7 prime ones were aldehyde, alcohol, ester, furan, pyrazine, sulfur, and ketone. Micrococcus sp., Bacillus subtilis and Pediococcus halophilus strains, and roasted rice powder were added to the fish fermentation, which greatly enhanced the flavour and volatile compounds in Pla-ra. HIGHLIGHTS Halophilic bacteria and lactic acid bacteria (LAB) added into the striped snake-head fish or Pla-Chon fermentation were greatly enhanced the flavour and volatile compounds in Pla-ra Striped snake-head fish fermentation can be accelerated by the addition of halophilic bacteria and LAB, and roasted rice powder 9 Non-essential amino acids and 9 essential amino acids were detected in Pla-ra Dominant amino acids in all 8 Pla-ra treatments were glutamic acid, lysine, and leucine 43 Volatile compounds were detected in Pla-ra with aldehyde, alcohol, ester, furan, pyrazine, sulfur, and ketone were the 7 prime ones GRAPHICAL ABSTRACT