Comparison of physicochemical properties of oca (Oxalis tuberosa), potato, and maize starches.

Oca (Oxalis tuberosa) represents a novel source of starch. Starches from the tubers of two commercial oca varieties were studied for various physicochemical properties. One normal potato starch and one normal maize starch were used for comparison. Oca starches showed lower gelatinization temperatures compared to both potato and maize starches. The pasting, flow, and gelation behaviors of oca starches were intermediate between potato and maize starches. Oca starch pastes were more viscous than maize starch paste and more elastic than potato starch paste. The differences in the properties could be largely due to lower amylose content, intermediate contents of phosphate groups (~400 ppm) and granule size (34.6 μm) of oca starches as compared to the other two starches. The internal unit chains of amylopectin such as the amount of fingerprint B-chains and length of B-chains could also partially explain the different physicochemical properties among oca, potato and maize starches.