Spray dried flaxseed oil powdered microcapsules obtained using milk whey proteins-alginate double layer emulsions

Spray-dried flaxseed oil microcapsules were produced by designing O/W double-layer emulsions using a whey protein concentrate (WPC) and sodium alginate (SA). The influence of homogenization pressure (5-15 MPa), pH (4-7) and maltodextrin concentration (0.8-7 wt%) on stability of primary and secondary emulsions was investigated, through droplet size and zeta potential measurements. Powders obtained after spray drying were characterized through scanning electron microscopy, encapsulation efficiency and water activity determinations. Flaxseed oil oxidative stability was assessed by measuring peroxide values (PV) and thiobarbituric reactive substances (TBARS) at different microencapsulation processing steps and during powders storage. Droplet sizes of primary emulsions were reduced when increasing homogenization pressures (up to 10 MPa). Zeta potential measurements evidenced double WPC-SA layer formation around oil droplets at pH 5. Encapsulation efficiencies up to 84% were obtained in powdered microcapsules with the highest MD content. Microencapsulation process produced a gradual increment on PV, whereas TBARs slightly increased. Nevertheless, these values were maintained relatively constant after powders storage at -18 and 4 °C for 6 months, and at 20 °C up to 6 weeks and PV did not exceed the maximum allowed for cold pressed oils.