Predicting Concomitant Denaturation of Vitamin as Influenced by Combined Process Temperature and pH in Batch and Continuous Flow Sterilization of Liquids

Thermal sterilization is widely used in the food industries because of its reliability and, generally, economy. Process design is based on a knowledge of the inactivation rate of the contaminating micro-organism of interest. For many liquids, denaturation of vitamin will occur during the exposure time necessary for sterilization. A mathematical model is used to develop a practical procedure to predict the concomitant denaturation of vitamin during sterilization as influenced by combined temperature and liquid pH over a range of exposure times in batch thermal processing. The procedure is illustrated using published data for denaturation of thiamine (vitamin B 1 ), and ascorbic acid (vitamin C). The effect of processing is expressed as per cent denaturation. The model on which the procedure is developed explained more than 94% of the variance accounted for (% V ) in these independent data. The model has fitted all available data without exception. The continuous flow simulation consists of combined thermal-pH denaturation kinetics and a residence time distribution function of a non-Newtonian liquid in a tube. Simulation uses the spores of the pathogen Clostridium botulinum as the contaminant together with a sterilization process requirement (i.e. the reduction in the number of viable spores) of 10−12. The value of the flow behaviour index and shear regime simulate conditions used in commercial sterilization. The influence of pH on vitamin denaturation is shown to be highly variable, indicating no simple rules of thumb. The procedure could readily be applied to a range of vitamins in different liquids. It should provide a convenient tool for the assessment of vitamin denaturation during thermal processing and, the design and evaluation of sterilizer design and process operations.