Résumé
Starches with low amylose contents generally exhibit good gel clarity, high swelling power and RVA peak viscosity, large breakdown, and high resistance to retrogradation during gel storage, as compared to some other starches with higher amylose contents. The demand of the food processing industry for new low amylose or even waxy starchy ingredients for the improvement of the quality of end-use products is considerable. Thereby, the objective of this work is to characterize the functional properties of starches isolated from three Dioscorea trifida genotypes (white, purple and black) cultivated in the Venezuelan Amazon. The investigation of the Dioscorea trifida starches revealed very low amylose contents in the three genotypes. DSC and amperometric amylose determinations of the starches fluctuated from 1.4 to 3.6% and 2.2 to 5.9%, respectively, whereas a commercial Dioscorea trifida starch exhibited an amylose content of 8.7% and 9.5%, respectively. All starch granules were large, triangular or shell-shaped, and exhibited a monomodal particle size distribution from 24.5 to 35.5 ?m. Onset gelatinization temperatures varied from 69.1 to 73.4 °C, and quite high gelatinization enthalpies were recorded in the 22.5 to 25.3 J g-1 range. All starches X-ray diffractograms exhibited B-type patterns. The degrees of crystallinity varied from 24% to 40%. The highest crystallinity was found for the starches exhibiting the highest amylose content. At 90°C, solubility and swelling power varied from 2.1 to 4.4% and 20.5 to 37.0%, respectively. Gel clarity was quite variable from 22.4 to 79.2% and a 5% starch suspension induced a high viscosity between 1420 and 2250 cP using RVA. This discovery could present some industrial potential for the food industry. (Résumé d'auteur)