Prediction of the glass transition temperature of fruit juice powders : a thesis presented in partial fulfilment of the requirements for the degree of Doctor in Philosophy in Process Engineering at Massey University, Manawatu, New Zealand. EMBARGOED until 1 July 2021.

Abstract

To overcome the limited shelf life of fresh fruit juice, manufacture aim to reduce the juice to a powdered form that can be available all year around. One technique of powder formulation is the use of spray dryer. However fruit juices are rich in fruit sugars and organic acids, which make them difficult to spray dry. Their low glass transition temperatures lead to stickiness problems in the spray dryer. This work investigates the prediction of the glass transition temperature (Tg) of fruit juice powders and mixtures including high molecular weight components often used as drying aids of their mixtures. The ability to predict glass transition temperatures enables optimization of powder formulations and spray dryer operation to avoid sticking problems. A semi-empirical model is presented to predict the glass transition temperature of fruit juice powders on the basis of the chemical composition and the Tg values of the individual pure components.--Shortened abstract