Improvement of oxidative stability of dry emulsion containing antioxidants by modifying process conditions

The encapsulation of polyunsaturated fatty acids (PUFAs) in powder by spray drying oil-in-water (O/W) emulsion containing antioxidant is used both to modify their handling properties and to preserve their functional properties. In this study, the influence of the process conditions (e.g. during production of emulsion and drying) on the oxidative stability of encapsulated sunflower oil and on the antioxidant activity of alpha-tocopherol was investigated in relation with the microstructure and morphology of the dry particles produced. High drying rate conditions were found to be detrimental to the encapsulation efficiency since giving rise to hollow particles with the inner vacuole acting as an oxygen reservoir. Furthermore, the contamination of the initial emulsion by metal ions favoured a pro-oxidant behaviour of alpha-tocopherol. The control of the process conditions to limit both the iron content in the initial emulsion and the drying rate is therefore essential to take advantage of the antioxidant character of alpha-tocopherol and to ensure an efficient protection of PUFAs in dry emulsion.