Morphological, physicochemical, functional, pasting, thermal properties and digestibility of hausa potato (Plectranthus rotundifolius) flour and starch

The aim of this work was to characterize morphological, crystalline property, physicochemical, functional, thermal, pasting, rheological properties, and in vitro digestibility of starch and flour from Plectranthus rotundifolius (Hausa potato). Chemical composition analysis showed a significant difference (p ≤ 0.05) between the Hausa potato starch and flour, and the amylose content of starch (30.44 %) was substantially greater than that of flour (20.57 %). SEM study showed that Hausa potato starch granule size varies from 3.31 μm to 6.61 μm having a morphology of some truncated circular shapes on a smooth granule surface. Hausa potato starch and flour exhibited a similar FT-IR pattern and A-type crystallinity. Howbeit, the relative crystallinity (obtained from XRD) of starch was significantly higher (p ≤ 0.05) than flour. The functional properties, including water and oil absorption capacity and solubility of flour, were significantly higher (p ≤ 0.05) than starch. RVA analysis observed that Hausa potato starch had a higher value in pasting properties compared to its flour. Enthalpy of gelatinization calculated from DSC showed that Hausa potato starch was significantly higher (p ≤ 0.05) than the flour. Hausa potato flour has a significantly greater (p ≤ 0.05) slowly digestible starch and resistant starch value than its starch. The study showed that starch and flour of Hausa potato significantly differed from each other. Better physicochemical and structural properties of Hausa potato starch can be explored as a non-conventional source of starch for various applications, and flour can be used as a useful functional ingredient in the food industry.