Prediction of Colour Deterioration in Strawberry Juice

Abstract

The rate of colour change from red to brown in reconstituted strawberry juice at temperatures of 20, 35 and 45 °C was investigated over 12 weeks. A model was developed to explain the increase in degradation product concentration, using first order reaction kinetics. With this model, the increase in brown colour over time was studied at storage temperatures of 35 and 45°C. The loss in red colour was found to follow first order kinetics at 20, 35 and 45°C. The ratio of red colour to brown colour, often referred to as a degradation index, gradually declined with storage time but could not be modeled using empirical methods. Reaction rate constants for both the increase in brown colour and the loss in red colour were higher at 45 than 35°C. The first order model developed was accurate in predicting the rates of brown colour increase at 35 and 45°C and the rates of red colour loss at 20, 35 and 45°C.