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Principal components present in fruits are low molecular weight sugars and some organic acids. They have low glass transition temperature (T g ) and are very hygroscopic in their amorphous state, so the dry product becomes sticky. Water acts as a plasticizer and decreases the glass transition temperature of the product with the increase in moisture content and water activity. To overcome this problem, ingredients having high T g value, such as maltodextrin, and food grade anti-caking agents were added to prepare vacuum dried fruit powders. The relationship between T g and a w provides a simple method for prediction of safe storage temperature at different relative humidities environment. Food powders namely, mango, pineapple, and tomato (3-4% w.b moisture content) were produced by mixing with maltodextrin and tri calcium phosphate at predetermined levels before drying. The relationship among glass transition temperature (T g ), sticky point temperature (T s ), moisture content and water activity of the three powders was represented in a stability/mobility diagram to find out safe storage conditions. Glass transition temperature of the fruit powders were interpreted in terms of the Gordon-Taylor model for verification. Glass transition and sticky point temperatures were compared by plotting them in a graph against moisture content.

Three brands of ready to serve mango drinks namely ‘Frooti’, ‘Real’and ‘Slice’that are available in the market were used for sensory evaluation along with the vacuum dried reconstituted mango powder drink. Mango powder was produced from mango pulp of ‘Totapuri’variety with addition of Maltodextrin, Glycerol monostearate and Tri calcium phosphate at rate of 0.62, 0.015 and 0.015 kg per kg dry mango solid, respectively. These ingredients were added for getting a nonsticky free flowing powder. The pulp along with the ingredients was dried in a vacuum drier at 70 ± 2C and 710–750 mm Hg vacuum. Fuzzy logic analysis was used for finding out the best of the three market mango drinks. BrimA index (a criterion for acceptance of fruit juice) and total solid (kg per kg drink) of the reconstituted mango drink was adjusted based on the BrimA index and total solid values of the best market drink. The reconstituted mango drink satisfied the quality criteria set for ‘mouth feel’but not the color, smell and taste.

Vacuum-dried mango powder was produced from mango pulp through the addition of glycerol monostearate and tricalcium phosphate at 0.015 kg each per kg mango solids and maltodextrin at 0.62 kg per kg dry mango solids. The mango powder was packed in aluminum foil-laminated pouches and stored in an accelerated storage environment maintained at 90% relative humidity (RH) and 38 ± 2C. The sticky-point moisture content at 38 ± 2C was considered as the maximum moisture content to which the mango powder would remain stable. The shelf life of the powder predicted from this consideration and the Guggenheim-Anderson-de Boer (GAB) model for the water activity moisture content relationship was 114.68 days, whereas the actual shelf life was 105 days. The color change of the powder during storage followed first-order reaction kinetics with a rate constant of 0.038 per day.