Encapsulation of vitamin E in edible orange oil-in-water emulsion beverages: Influence of heating temperature on physicochemical stability during chilled storage

This study investigated the effects of thermal processing (63 ºC for 30 min, 80 º C and 90º C for 45 s) on the stability of orange oil (3.5% w/w) beverage emulsions containing vitamin E during chilled storage. The physical stability of the whey protein-stabilised emulsions was monitored by multiple light scattering (Turbiscan) and optical microscopy and the vitamin E content was determined by RP-HPLC analysis. The extent of heat-induced protein denaturation was also investigated. Heat treatment had a significant beneficial effect on emulsion stability as indicated by the Turbiscan Stability Index (TSI) (Control: 1.17; 63 ºC: 0.57, P=0.00; 80 ºC: 0.80; P=0.01; 90 ºC: 0.83, P=0.03). This was attributed to mild denaturation which enabled whey proteins to effectively rearrange their structures at the interface. All heated beverages were fairly stable during the storage period (4 weeks) with the sample heated at 63 ºC for 30 min being more susceptible to destabilization phenomena (146.6% ↑TSI). The main cause of instability during storage is likely to be Ostwald ripening. Flocculation induced by droplet-droplet and droplet-serum protein interactions may also account for the instability of the sample heated at 63 ºC. Vitamin E retention was considerably higher for all heated beverages (≥85%) under the specified storage conditions. These data have important implications for the processing and storage conditions of emulsion beverages applied by the food industry.