Critical evaluation of commonly used objective functions to optimize overall quality and nutrient retention of heat-preserved foods

Two objective functions—volume average retention and volume average cook-value—commonly used to optimize the overall quality and nutrient retention of heat-preserved foods, were studied and optimal processing conditions based on the two approaches were compared. Case studies from the literature were run and tested for the two objective functions. The influence of the decimal reduction time (at the reference temperature, Dref value) of the quality factor on the optimal processing temperature was evaluated. For high Dref values, e.g. for vitamins, the two objective functions give the same results and the Dref value has a minor influence on the optimum processing conditions. For low Dref values, such as for texture and colour, the optimal sterilization temperature is affected by this parameter and the use of volume average cook-value, as objective function, does not take this effect into account, which may result in underestimation of the optimal processing temperature.