FAT ENCAPSULATION IN SPRAY-DRIED FOOD POWDERS

The surface composition of spray-dried sodium caseinate/lactose emulsi ons having different oil phases were estimated using electron spectros copy for chemical analysis (ESCA), and the particle structure was stud ied using scanning electron microscopy (SEM) both before and after sto rage under humid conditions. After spray-drying, powders in which the oil phases consisting of fats with intermediate melting points, such a s hardened coconut oil and butter fat, had the highest surface coverag e of fat, approximately 34%. The powder with soybean oil as the oil ph ase had a surface coverage of fat of approximately 15%. The high-melti ng hardened rapeseed oil was almost completely encapsulated after spra y-drying. After storage in a humid atmosphere, fat was released onto a ll the powder surfaces (surface fat after storage, between 50-65%) exc ept for those with hardened rapeseed oil in which the fat remained enc apsulated. These observations are consistent with the powder structure observed by SEM. The surface composition estimated by ESCA for spray- dried sodium caseinate/lactose-containing emulsions with different amo unts of soybean oil and a constant lactose/sodium caseinate ratio show ed an almost completely encapsulated oil-phase after drying. Storage o f these powders in a humid atmosphere leads to a release of fat onto t he powder surface even if the soybean oil content is low (1% of the dr y weight). Powders made from soybean oil emulsions with sodium caseina te alone exhibit a much lower degree of encapsulation than in the syst em where lactose is present.