Relationships among molecular, physicochemical and digestibility characteristics of Andean tuber starches.

This study aimed to determine and correlate the physicochemical, thermal, pasting, digestibility and molecular characteristics of native starches, such as mashua (Tropaeolum tuberosum R. and P.), oca (Oxalis tuberosa Mol.), and olluco (Ullucus tuberosus C.), which were extracted via successive washing and sedimentation. The morphology of native starches was determined by scanning electron microscopy, granule size distribution, thermal properties, pasting properties, X-ray diffraction (XRD), amylopectin chain-length distribution and amylose and amylopectin molecular weights. Mashua starch was smaller in size than oca and olluco starches. Moreover, the granules of mashua starch were round in shape, whereas those of oca and olluco starches were ellipsoidal in shape. The B XRD spectra showed similar profiles for the three Andean tuber starches. Mashua and olluco starches exhibited the lowest gelatinization temperatures and enthalpy values, and olluco amylopectin exhibited a longer chain length than mashua and oca starches. The resistant starch of gelatinized and ungelatinized samples exhibited a positive and strong correlation with the molecular properties of amylose and amylopectin, gelatinization enthalpy and molecular order.