Reduction in salt fermentation time of Indian mackerel (Rastrelliger kanagurta) using Halobacterium salinarum as a starter culture

Abstract

Salt fermentation is a preservation technique in which higher salt concentrations are introduced to inhibit the growth of most spoilage microbes. This process takes several months to attain maturity. The present study was designed to accelerate the fermentation rate and shorten the maturation time employing the haloarchaeal strain Halobacterium salinarum (HS1). H. salinarum was inoculated in the salt fermentation medium and the fermentation time and quality were compared to the control salt fermentation without inoculation of HS1. The lot inoculated with HS1 matured by the 60th day with higher sensory scores, whereas the control (C) took 120 days for maturation, indicating that the salt fermentation process can be accelerated using haloarchaea. The final moisture content at the end of 120 days in the control and HS1 were 56.31 and 56.78% respectively. pH showed decreasing trend initially and was found to be stable in later phases. Protein content reduced from 24.29 to 18.95% and 15.03% in control and HS1 respectively. Fat content fluctuated throughout the fermentation period (6.99 to 8.81%) showing an increasing pattern initially and then a reduction during later stages of fermentation. Trimethylamine (TMA, 3.12 to 14.09 mg%), total volatile base nitrogen (TVBN, 18.23 to 38.35 mg%), alpha-amino nitrogen (AAN, 31.87 to 126.43 mg%) and non-protein nitrogen (NPN, 0.18 to 0.83%) contents increased throughout the salt fermentation process but were found to be within limits suggesting controlled degradation. Present results suggest that H. salinarum (HS1) as a starter culture can accelerate salt fermentation and maturation can be attained by 60 days compared to 120 days of maturation time taken by control without HS1.