Determination of the minimum integral entropy, water sorption and glass transition temperature to establishing critical storage conditions of beetroot juice microcapsules by spray drying

The aim of this work was to microencapsulate beetroot juice (BJ) (Beta vulgaris L.) by spray-drying using as protective colloid gum Arabic. The adsorption isotherms of the microcapsules and the minimum integral entropy (∆S int)T were determined at 25, 35 and 40 ◦C. The glass transition temperature (Tg) was measured by differential scanning calorimetry and modeled by GordonTaylor equation. The water contents-water activity (M-aW ) sets obtained from (∆S int)T , and critical water content (CWC) and critical water activity (CWA) from the Tg were similar, being in the range of water content of 5.11-7.5 kg H2O/100 kg d.s. and in the water activity range of 0.532-0.590. These critical storage conditions were considered as the best conditions for increase the stability of the microcapsules, where the percentage of retention Betanin in the microcapsules was higher compared with other storage conditions in the temperature and aw range studied. Keywords: beetroot juice, microcapsules, minimum integral entropy, glass transition temperature, critical water content, critical water activity