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

Abstract

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.

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

“…The moisture content (2.0 -4.1%) and water activity (0.133 to 0.196) of the all microparticles were in the range of acceptable values to ensure the microbiological quality of the powder microparticles. The SA outer layer significantly increased the hygroscopicity of the microparticle systems, as reported by Cáceres et al (2020), indicating that hygroscopicity is polymer specific.…”

“…oil, which is the oil fraction more exposed to the environmental oxygen and hence potentially more prone to oxidation. The EE of PWO was significantly lower in PWO-C than in PWO-C/SA with and without HTEs (Table1), showing the important role of the SA outer layer in decreasing the surface PWO, as reported byCáceres et al (2020). In the case of microparticle systems with a SA outer layer, the EE of PWO ranged between 89.1% (PWO-C/SA) and 88.2 % (PWO-C-HTEs/SA), and no significant differences were found between PWO-C/SA and PWO-C(HTEs)/SA microparticles, suggesting that the incorporation of HTEs into the formulation had no effect on the EE.…”

“…The encapsulation of PWO-in-water emulsion with C and SA as outer layer was performed using a three-fluid nozzle, according to Cáceres et al (2020). The preparation of the inner and outer infeed, and the spray-drying conditions were as follows.…”

“…Food Chemistry, 2022Chemistry, , vol. 395, p. 133595. https://doi.org/10.1016Chemistry, /j.foodchem.2022 Inner infeed (35 g): PWO-in-water emulsion was formulated under the optimal conditions reported by Cáceres et al (2020). Firstly, SL (0.06 g) was dispersed in distilled water (3.39 g) at 40 ºC, by stirring at 500 rpm for 20 min.…”

“…https://doi.org/10.1016/j.foodchem.2022.133595 spray-drying may be a suitable strategy for the formation of a SA outer layer coating the microparticles, since the solution sprayed by the external peripheral nozzle covers the solution sprayed by the central nozzle during the atomization process, generating an outer layer (Kondo, Niwa, & Danjo, 2014). In food applications, three-fluid nozzles have been mainly used for the encapsulation of immiscible liquids such as oils (Legako & Dunford, 2010;Cáceres et al, 2020).…”