Sorption isotherms of potato slices dried and texturized by controlled sudden decompression

Abstract

Controlled sudden decompression to a vacuum (DIC) was used to confer a porous structure to partially dehydrated foods by expanding them and facilitating the drying process at lower water content. Moisture sorption isotherms of Bintje potato slices hot-air dried and texturized by DIC were determined and compared using a gravimetric method. The samples were stored in a temperature-controlled chamber at 20, 30 or 40 °C; and relative humidity was controlled between 5% and 90%. Both adsorption and desorption isotherms had a sigmoidal shape (type II). The sorption capacity decreased with increasing temperature at a given water activity. Hysteresis was more pronounced for texturized potatoes than for hot-air dried samples. Non-linear regression analysis was used to fit five moisture sorption isotherm models. The Peleg, Kats and Kutarov, GAB and BET ( a w less than 0.5) equations all accurately characterized the sorption behaviour. Texturizing by DIC increased the surface area of potato slices by ≈45% relative to heat air drying. The net isosteric heat of sorption was found to increase with decreasing moisture content and was higher for texturized potatoes than hot-air dried samples.