High iron bioaccessibility from co-microencapsulated iron/ascorbic acid using chelating polypeptides from brewers' spent grain protein as wall material

Iron fortification is an important and difficult task since most of the bioavailable iron sources are reactive against food matrix. Microencapsulation technology can prevent iron interaction with food matrix. Co-microencapsulation of iron and ascorbic acid was carried out by spray-drying using a protein concentrate obtained from brewers' spent grain (BSG-PC) and locust bean gum as chelating wall materials. Microcapsules were formulated using a 2(2) factorial design. The effect of BSG-PC/wall material (8.6 and 17.2 g protein 100 g(-1)) and ascorbic acid/iron molar ratio (0.9:1 and 1.8:1) on iron encapsulation yield (FeE), ascorbic acid encapsulation (AAE), iron chelated by wall material (FeC), iron bioaccessibility (FeB), particle size, zeta potential, and surface hydrophobicity of the microcapsules were assessed. Higher level of BSG-PC increased FeB at low ascorbic acid/ iron molar ratio due to the high iron-chelating activity of BSG proteins (IC50: 7.9 +/- 1.2 mg mL(-1)). At low levels of BSG-PC, FeB was promoted by ascorbic acid in a dose response way. A multiple response maximization of FeE, AAE, FeB, and FeC was performed and validated. Optimal microcapsule formula resulted with 29% of FeB after simulated gastrointestinal digestion. The optimization procedure allowed obtaining a fortifier with the higher iron bioaccessibility and iron content.

Automated summary

The study focused on microencapsulation of iron and ascorbic acid using protein concentrate and locust bean gum as wall materials. A factorial design was used to assess the effects of different factors on iron encapsulation yield, ascorbic acid encapsulation, iron chelation, bioaccessibility, particle size, zeta potential, and surface hydrophobicity of the microcapsules. An optimal microcapsule formula was obtained with high iron bioaccessibility after gastrointestinal digestion, maximizing multiple responses such as iron encapsulation, ascorbic acid encapsulation, iron bioaccessibility, and iron chelation.