Abstract
Native potato proteins consisting mainly of patatin and protease inhibitors were isolated from industrial potato fruit water by expanded bed adsorption (EBA) chromatography. The EBA-refined proteins were dried by different methods and the effect of drying-conditions on solubility, extent of denaturation, rheology and emulsifying properties was investigated. Drying methods include spray drying at varying outlet temperatures, vacuum freeze drying, fluid-bed and atmospherical freeze drying. Solubilities measured in the range pH 4-6 showed that the higher solubility was at pH 6 of around 65%, except for spray drying using an outlet temperature of 165 degrees C, which showed low solubility for all pH values. Spray drying at 90 degrees C and atmospheric freeze-drying emerged as the least deleterious methods with respect to retaining esterase and protease inhibitor activities, comparable to the vacuum freeze drying. The values obtained for the complex modulus suggest that potato protein is not a good gel former even when the protein was vacuum freeze dried. Emulsions prepared with xanthan as stabilizer were more stable at pH 6 compared to pH 4 judged from oil particle sizes. This study showed that potato proteins obtained under gentle isolation and drying conditions will provide interesting functional properties for potential application in food systems. (c) 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.