Water penetration into mixed and un-mixed carbohydrate powders

Many Industrial food-related processes involve the hydration of powders. The penetration of water in both liquid and vapour forms into carbohydrate powders has been studied using the techniques of low-field Time Domain NMR, Dynamic Vapour Sorption, and optical microscopy. A simplified model of water penetration into powders has been produced, principally derived from NMR measurements. No-mixing, mixing and overmixing conditions were studied. There was concurrently a progressive association of solids with the liquid (not necessarily solubilisation) and hydration behaviour approximated by 2 relaxation components in the case of potato flake and 3 components in the case of pre-gelatinised starch. Microscopic evidence is consistent with this behaviour, and the maintenance of structure in potato flake was evident in contrast to the complete dissolution of pre-gelatinised starch. Vapour rather than water sorption removes any capillarity/water meniscus effect and both pre-gelatinised starch and potato flake showed different levels of surface adsorption and penetration behaviour but with the same time course.