A kinetic model and endpoints method for volatiles formation in stored fresh fish

• Power-law model described isothermal TMA and TVBN formation in stored fresh fish.
• Exponential model described the temperature-dependence of model's rate parameter.
• Endpoints method was developed to estimate the volatiles formation kinetic parameters.
• Free interactive program reconstructed and predicted isothermal volatiles formation.
• Rate equation used to simulate volatiles formation patterns under varying temperature.

Based on experimental data reported by Koutsoumanis and Nychas (2000), the rise in the trimethylamine (TMA) and total volatile basic nitrogen (TVBN) concentrations during fish fillets isothermal storage is described by a power-law model. This model has a fixed exponent (m ~ 2), and a temperature-dependent coefficient that follows the two-parameters exponential model, a substitute for the Arrhenius equation. The model's two adjustable parameters were calculated by the endpoints method, i.e., from a pair of final concentrations determined at the end of storage at two temperatures, with an interactive program posted as freeware on the Internet. Their values were then used to reconstruct the entire formation curves at the two temperatures and predict the curves at two other temperatures that were not used in their calculation. A dynamic version of the model was also developed, based on the assumption that the momentary volatiles formation rate is the rate at the momentary temperature at the time which corresponds to their momentary concentration. It was tested for consistency and used to simulate volatiles formation patterns under rising and fluctuating temperatures.

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