Kinetics of Total Volatile Basic Nitrogen and Trimethylamine Formation in Stored Rohu (Labeo rohita) Fish

Abstract

ABSTRACT Fish freshness estimation has been mostly studied in terms of total volatile basic nitrogen (TVB-N) and trimethylamine nitrogen (TMA-N) determination and partially addresses the kinetics, which limits its practical utility. In this study, TVB-N and TMA-N content of Rohu stored under limited refrigerated (5 and 0°C) and frozen (−5°C) conditions for 42 days showed an increasing trend, respectively. TVB-N and TMA-N formation in stored Rohu was higher at higher temperature and their initial and final values were found 4.57 ± 0.321, 0.14 ± 0.047 mg/100g and 46.56 ± 0.994, 3.24 ± 0.112 mg/100g, respectively. The volatile formations in Rohu at −5°C were slow, as the frozen storage arrests the enzymatic and microbial activities in comparison to 0°C and above. The kinetics of TVB-N and TMA-N were investigated using zero, first, and nth-order reaction model. First-order kinetics exhibited the best fit model for TVB-N (R2 = 0.98; χ2 = 0.045), whereas TMA-N formation showed nth-order kinetics (n = −0.4608, R2 = 0.96, χ2 = 0.028) as best fit model. The first-order kinetic reaction contributed activation energy of 58.16 kJ/mol for TVB-N and 10.86 kJ/mol for TMA-N. TVB-N and TMA-N formations were influenced by storage temperature and duration as expected. Kinetic parameters were also significantly (P ≤ 0.05) affected by storage temperatures.