Influence of agglomeration on physical characteristics and oxidative stability of spray-dried oil powder with milk protein and trehalose wall material

Sunflower oil has been microencapsulated by spray drying method in the matrix with trehalose and whey protein isolate (WPI) or sodium caseinate (NaCas). The obtained preparations have been subjected to wet fluidized-bed agglomeration with the use of trehalose and polyvinylpyrrolidone (PVP). Agglomeration of fine powders, irrespective of the wetting liquid, enabled obtaining a free-flowing product easily reconstitutable in water. Encapsulation efficiency of oil reached up to 96% and 99% in powder with WPI and NaCas respectively, whereas it decreased to 90-96% after the agglomeration, on account of insufficient agglomerate strength. The lower level of oil oxidation was observed for the agglomerate preparations, especially the agglomerate obtained with the use of the trehalose solution as a wetting liquid. The impact of agglomeration was reflected in a significant decrease of the level of adsorbed water, being sufficient to initiate the transition of amorphous trehalose to the crystalline state. (C) 2013 Elsevier Ltd. All rights reserved.