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

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 (aw 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.