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 (rrms), weight-average molar mass (Mw) and apparent density (ρapp) 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, Mw and rrms 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 ρapp, gelatinization enthalpy, granule size and amylose content