Donut-Shaped Microparticles Prepared from Different C-Type Starch Sources: Characterization and Encapsulation of Gallic Acid

Donut-shaped microparticles were prepared from starches of different botanical sources by heat-mixture-alcoholic treatment. C-type starch allomorphs: pea, Araucaria araucana, and Aesculus hippocastanum were used for the preparation of the microparticles. The microparticles were characterized and evaluated as a carrier of phenolic compounds. The gallic acid encapsulation efficiency was determined, and its antioxidant activity was evaluated using spectrophotometric assays. The starch microparticles exhibited a round to elongated shape, with a central concavity, similar to donut-shaped microparticles. In the loaded and unloaded starch microparticles, B-type and V-type polymorphs coexist. The entrapment of gallic acid in starch microparticles is due to hydrogen-bond formation and not to an amylose inclusion complex. The loaded pea starch microparticles showed lower onset and peak gelatinization temperature with respect to their unloaded counterpart, which is associated with the decreased stability of formed crystallites. The percentage of phenolic compounds encapsulated depended on the native starch precursor. Pea starch microparticles loaded with gallic acid showed the highest encapsulation efficiency around 45%. Gallic acid entrapped in starch microparticles showed no loss of antioxidant activity. Starch microparticles are a food-grade solid matrix suitable as carriers for active compounds.