Characterization of quality degradation during chilled shrimp (Litopenaeus vannamei) supply chain.
Loss of quality in white shrimps (Litopenaeus vannamei) during a cold supply chain (0-8oC for 96 hours) was measured and modeled at constant and variable temperature conditions. Quality parameters such as color, Texture Profile Analysis (TPA), Total Viable Count (TVC), Total Non-Volatile Basic Nitrogen (TVB-N), and Sensory Index (SI) were selected as indices of quality. A bulk mean temperature (Tbm) function was calculated to describe the effect of storage time and temperature, to which the shrimp were subjected, on the quality indices using stepwise multiple linear regressions (R2 = 0.88-0.99, SEE = 0.045-15.63). Color degradation (L*, a*, b* index), SI, and TVC (CFU/g) in cold chain were adequately described by a zero order reaction with R2 values > 0.9. In order to reduce the number of variables obtained in TPA, hardness (H), springiness (S), gumminess (G), cohesiveness (Co) and chewiness (Ch), were subjected to multiple linear regression. The hardness, H, turned out to be the most significant parameter (P < 0.05). Using the Arrhenius equation kinetic parameters, reaction rates (k, min.-1) and activation energy (Ea, KJ. Mole -1.oK) were calculated for all the textural properties. The developed models were used to estimate remaining shelf life in terms of H, TVC, TVB-N and SI at 4 different distribution stages of a supply chain. The predicted values showed a good relationship (R2 ≥ 0.9) with the experimental data for all the quality parameters. The correlation matrix of the dependent variables showed that color parameters (L*,b*), pH, and sensory index were positively correlated (P < 0.05) with H, TVC, and TVB-N, respectively. However, after 84 hours of storage in variable temperature conditions, the level of TVB-N was still within the acceptable range (≤ 25 mg/100 gm N), but samples were unacceptable due to high microbial growth (> 7.5).