Moisture sorption properties of two varieties of dehydrated mango slices as determined by gravimetric method using Guggenheim–Anderson–de Boer model

Abstract

The moisture sorption isotherms for oven dried mango were constructed gravimetrically at three different temperatures of 25°C, 30°C, and 35°C, and relative humidity ranging 8.3%–97.0%. The Guggenheim–Anderson–de Boer model was used to fit sorption data and constant equations determined using nonlinear regression analysis. The isotherms had J-shaped curve that represents type III isotherms characterized by sugar-rich products. At increased temperatures, it was observed that equilibrium moisture content increased and crossing effect of isotherm curves was observed with a corresponding increase in water activity. A substantial increase in equilibrium moisture content was observed above water activity of 0.6. Monolayer moisture content of between 8 and 9.6% was predicted for dried slices where the lowest value indicated that moisture content should not be lower than 8.0% to avoid unnecessary energy consumption. For assured microbiological stability, the safe storage moisture content for dried mango should be maintained at approximately 15% or less that corresponded to 0.6 water activity. Practical applications Dehydration of fruits has been utilized as one of the most effective value addition procedures for extending their shelf-life. However, exposure to high drying temperature and significant loss of moisture in fruits cause irreversible stresses in the cellular structure of the fruits and may lead to robust textural changes especially during storage. This research finds practical application in shelf-life estimation and prediction of storage stability of the mango varieties. Additionally, the results can be used as a guide in product development and process design for dried mango slices.