Microencapsulation of α-tocopherol with zein and β-cyclodextrin using spray drying for colour stability and shelf-life improvement of fruit beverages

alpha-Tocopherol (TOC) has become an important food additive due to its antioxidant effect and capacity to increase shelf-life of products. However, it is a hydrophobically active compound, which compromises its applicability in soft drinks and fruit beverages. The aim of this study was to develop sustained release forms of alpha-tocopherol using zein and cyclodextrin as carriers to be further applied in fruit beverage products for improved shelf-life. For this purpose, the encapsulation of alpha-tocopherol into zein protein was first optimized using a spray-drying technology. Different process conditions, namely temperature (110-180 degrees C) and solids concentration (0.01-0.04 g mL(-1)), were tested aiming at maximizing the encapsulation of alpha-tocopherol and antioxidant capacity using response surface methodology (RSM) following a Face Centred Design (FCD). Results showed that lower inlet gas temperature and lower solids concentration enable the production of alpha-tocopherol: zein forms with a higher antioxidant activity (oxygen radical absorbance capacity > 90 mmol Trolox equivalent antioxidant capacity per g), and the highest encapsulation efficiency (42.05%) was obtained using 0.02 g mL(-1) of solids concentration. beta-Cyclodextrin was further added to the best system to increase the solubility capacity of alpha-tocopherol in fruit juice beverages. Despite the lower antioxidant activity (46.2 mu mol Trolox equivalent antioxidant capacity per g), alpha-tocopherol: zein: cyclodextrin forms reduced colour losses when compared to the normal juice, and this effect was probably related to the suppression of anthocyanin degradation due to the formation of inclusion complexes with beta-cyclodextrin. Importantly, none of these forms induced cytotoxicity in the Caco2 cell model, confirming the safety of these systems.