Dynamic changes in Thai-style fermented fish: Low-salt, short fermentation with autochthonous starter culture

Abstract

Thai-fermented fish (Pla-ra), a popular seasoning for Thai cuisine, is rich in free amino acids, but its high salt content and long fermentation time limit its applications. Autochthonous starter culture for Pla-ra production has been developed to accelerate the fermentation, improve safety and quality, and achieve a product similar to traditional Pla-ra. Herein, we investigated the potential of the starter culture for low-salt Pla-ra fermentation, assessing the physical, chemical, and safety properties of low-salt fermented fish (LSFF, using 5% salt with starter culture) compared to traditional fermented fish (TFF, using 20% salt) using local Nile Tilapia (Oreochromis niloticus). Within four weeks, LSFF acquired Pla-ra characteristics with the main volatile compounds: methyl butyric acid, methanethiol, and ethyl hexanoate, while no volatile compounds were detected in TFF at this stage. The LCMS/MS analysis showed that the free amino-acid content in LSFF tripled by the second week, while histamine remained lower than the safety limit (<200 mg/kg). Furthermore, Staphylococcus aureus, a salt-tolerant pathogen, was significantly lower in LSFF than TFF. Thus, the LSFF process with autochthonous starter culture yielded desirable Pla-ra with shorter and safer fermentation compared to the traditional process. This study revealed LSFF's potential for fermented fish product innovation.