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.

Physicochemical, functional and morphological characterization of starches isolated from three native potatoes of the Andean region.

Three varieties of native potato (Imilla blanca, Imilla negra and Loc'ka) that grow in the Andean region at more than 3800 m.a.s.l. were selected fot the extraction and characterization or their starch. Instrumental techniques such as scanning electron microsocopic (SEM), differential scanning calorimetry (DSC), Fourier transformed infrarred spectroscopy (FTIR), X-ray diffraction, colorimetry and polarized light microscopy were used. The results showed that only Loc'kás starch had a unimodal granule size distribution, whereas Imilla negra and Imilla blanca starches showed two and three granule size populations, respectively. The starch from Imilla negra showed higher apparent amylose content, peak viscosity, phosphorous content and paste clarity. The starch from Imilla blanca showed high relative crystallinity, while Imilla blanca and Imilla negra had higher intensity ratios than that from Loc'ka, suggesting high molecular order. Cooked starch from Imilla negra showed higher resistant starch (RS) fraction than the other starches studied.