Identification of potential spoilage bacteria in farmed shrimp (Litopenaeus vannamei): Application of Relative Rate of Spoilage models in shelf life-prediction

To study the effect of temperature in spoilage of Litopenaeus vannamei, fresh shrimps were collected from tropical farm and stored at three different temperatures (30 ± 2 °C room temperature, 4 °C refrigerated and 1 °C ice). Sensory, biochemical and microbial evaluation of the samples were carried out at frequent intervals. The shelf life of the samples was estimated as 10 h, 12 days and 16 days at room temperature, refrigerated and ice storage respectively. In ice storage, total volatile base nitrogen values increased at the initial days, followed by a decrease, and again with an increase in value. Leaching out of ammonia by the melt water is considered as the probable reason. Fitness of three Relative Rate of Spoilage (RRS) models was checked to determine the shelf life of L. vannamei, and Arrhenius model was found to be more fitting. Spoilage potential evaluation was carried out by screening the bacterial isolates at the time of sensory rejection and the results revealed that many isolates possess high potential for spoilage. The 16SrRNA gene sequencing analysis identified the predominant potential spoilers as: Enterobacter and Acinetobacter at room temperature, Pseudomonas and Aeromonas at refrigerated storage and, Aeromonas and Enterococcus at ice storage.