Physicochemical and structural properties of starch from five Andean crops grown in Bolivia

Three Andean grains - amaranth (Amaranthus caudatus), quinoa (Chenopodium quinoa), canihua (Chenopodium pallidicaulle) - and two Andean roots starches - achira (Canna indica), maca (Lepidium meyenii) - were studied. Physicochemical properties such as granule size, crystallinity, pasting properties among other as well as structural properties such as root-mean-square radius (r_rms), weight-average molar mass (M_w) and apparent density (ρ_app) were analyzed in order to evaluate the relation between them. Grains were similar in most of their characteristics as roots in their i.e. granule size, shape, type of crystallinity, M_w and r_rms varied according to botanical source. The starch granules from grains were in a narrow diameter range (0.5 to 2 μm) and displayed A-type X-ray diffraction pattern (XRD). Roots starch had a wide granule diameter range (1 to 100 μm) and displayed a B-type XRD. The amylose content varied between 0 and 48% where amaranth had the lowest value and achira had the highest. Furthermore, quinoa and canihua starches had very low breakdown in pasting properties, indicating high stability during cooking. A model is proposed that relates pasting properties i.e. peak viscosity and final viscosity with ρ_app, gelatinization enthalpy, granule size and amylose content.