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

• Agglomeration of oil powders is proposed to improve their functional characteristics.
• Agglomerates demonstrate free-flowing and good reconstitutability in water.
• Encapsulation efficiency of oil decreases after the agglomeration.
• Application of trehalose in agglomeration increases the oxidative stability of microencapsulated oil.
• Application of trehalose determines high hygroscopicity of material and its susceptibility to caking.

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.