Calculating the degradation kinetic parameters of thiamine by the isothermal version of the endpoints method

Abstract

Thiamine (vitamin B1)'s degradation during thermal processing and storage of foods is known to follow first-order kinetics, where the rate constant's temperature-dependence can be described by the two-parameter Arrhenius equation. In agreement with previous reports, a simpler two-parameter exponential model could replace the Arrhenius equation in thiamine degradation without sacrificing the fit. Theoretically, the exponential model's two parameters can be estimated from the concentration ratios after two isothermal exposures by solving a pair of simultaneous nonlinear algebraic equations of which they are the two unknowns. Once calculated, these two parameters can be used to reconstruct the entire degradation curves to which the two endpoints belonged, and to predict those at any other exposure in a pertinent temperature range. The concept and mathematical calculation procedure were implemented in a freely downloadable interactive Wolfram Demonstration, with which the user solves the equations by moving sliders on the screen to match the reconstructed degradation curves with the experimental endpoints. The method was tested with computer simulations and with published experimental data on thiamine's degradation in a model solution, beef, pasta and salmon, over large temperature ranges and exposure times, and validated by comparing thiamine's predicted final concentration ratios with those reported at temperatures not used in the kinetic parameters calculation. The described method and interactive calculation program can facilitate and economize the study of thiamine degradation in stored foods by eliminating the need to record entire sets of isothermal degradation curves.