Preparation and morphological, rheological, and structural characterisation of proanthocyanidin coated starch granules

Abstract Proanthocyanidins are known to interact with carbohydrates, impacting their physicochemical properties providing beneficial attributes for food and industrial applications. To harness these advantageous properties, starch granules were coated with proanthocyanidins (condensed tannins) using an aqueous process yielding a dry product by freeze-drying, vacuum drying, or co-spray drying. Confocal microscopy showed localisation of condensed tannins on the starch granule surface, while SEM indicated retention of starch morphology. Rheology and DSC revealed minimal changes to the pasting or gelation properties, with no loss of molecular order exhibited by FTIR and NMR spectroscopy. The water stability of the coating was enhanced through the use of 1% carrageenan as a coating additive. The methodology was transferrable across various proanthocyanidins, sourced from radiata pine, mimosa, and quebracho. However for starches of different biological origin (maize, amaranth, oat, and potato) optimisation of the coating process would be required.