The microparticulate carbohydrate is preferably water soluble, and may for example be selected from hexoses such as glucose, fructose or galactose; disaccharides such as sucrose, lactose or maltose; pentoses such as arabinose, xylose or ribose; and ??-, ??- and ??- cyclodextrins; the term carbohydrate as used herein is also intended to embrace sugar alcohols, e.g. alditols such as mannitol or so