Encapsulation of wheat germ oil in alginate-gelatinized corn starch beads: Physicochemical properties and tocopherols' stability

Microencapsulation by production of polymer beads from ionic gelation is a useful method to improve the stability of nutritional compounds. Wheat germ oil is a nutritional source of unsaturated fatty acids and phytonutrients, such as tocopherols (α and β), phytosterols, carotenoids, and phenolic compounds. This work studied the development of alginate-starch beads over the stability of encapsulated wheat germ oil. The beads contained sodium alginate and gelatinized corn starch in proportions of 2:0, 1:1, 1:2, and 1:4. The addition of small amounts (1:1) of gelatinized starch in the alginate emulsions improved the physicochemical properties and stability during storage. The emulsions had oil droplets with mean sizes ranging from 4.5 to 12.2 µm. The 1:1 samples showed more disperse oil droplets, explained by the molecular interaction between the starch chains and oil. The encapsulation efficiency was higher than 91%, and the beads' mean diameters were between 383.22 and 797.45 µm. The proportion of 1:1 alginate-starch also enhanced the beads' microstructures, avoiding oil oxidation. Six days accelerated stability (65 °C) evidenced higher tocopherols amounts (0.66 mg/g oil) and a lower oxidation (2.52 meq.O₂ /kg oil) for the 1:1 samples compared to the remained samples. PRACTICAL APPLICATION: Alginate-gelatinized corn starch beads loaded with wheat germ oil can be used as an ingredient in functional food products for the enrichment of nutrients. The use of starch decreased the oil oxidation and the loss of tocopherols during storage, indicating that the quality of the wheat germ oil will be desirable for longer durations of food storage.