Incorporation of hydroxytyrosol alkyl esters of different chain length as antioxidant strategy in walnut oil spray-dried microparticles with a sodium alginate outer layer.

Omega-3 rich vegetable oils, such as walnut oil, are gaining interest because of their health benefits. Synthetized homologous series of hydroxytyrosol alkyl esters (HTEs) with different alkyl chain lengths (C4-C18) were incorporated in purified walnut oil (PWO) spray-dried microparticles, designed with Capsul® (C) as encapsulating agent and sodium alginate (SA) as outer layer (PWO-C/SA). The encapsulation efficiency (>87%) and Tg of PWO-C/SA microparticles were not affected by the HTEs. The incorporation of HTE-C10 increased the melting point (185.0 ± 1.3 °C), decreasing the formation of Dimers + Polymers (1.12 ± 0.05% at day 35 of storage) and the crystallinity of the microparticles (>170 °C). The highest stability of PWO-C(HTE-C10)/SA suggests a specific location of HTE-C10 at the oil:water interface. The SA layer delayed the release of fatty acids during in vitro digestion. The incorporation of HTEs of medium chain length can be a suitable strategy to protect unsaturated oils encapsulated by spray-drying.

Influence of the Location of Ascorbic Acid in Walnut Oil Spray-Dried Microparticles with Outer Layer on the Physical Characteristics and Oxidative Stability.

Purified walnut oil (PWO) microparticles with Capsul® (C, encapsulating agent), sodium alginate (SA) as outer layer and ascorbic acid (AA) as oxygen scavenger were obtained by spray drying using a three-fluid nozzle. AA was incorporated in the inner infeed (PWO-C(AA)/SA), in the outer infeed (PWO-C/SA(AA)) and in both infeed (PWO-C(AA)/SA(AA)). PWO-C(AA)/SA (4.56 h) and POW-C(AA)/SA(AA) (2.60 h) microparticles showed higher induction period than POW-C/SA(AA) (1.17 h), and lower formation of triacylglycerol dimers and polymers during storage (40 °C). Therefore, AA located in the inner infeed improved the oxidative stability of encapsulated PWO by removing the residual oxygen. AA in the SA outer layer did not improve the oxidative stability of encapsulated PWO since oxygen diffusion through the microparticles was limited and/or AA weakened the SA layer structure. The specific-location of AA (inner infeed) is a strategy to obtain stable spray-dried polyunsaturated oil-based microparticles for the design of foods enriched with omega-3 fatty acids.