Guinea Grass Seed (Megathyrsus maximus), a Potential Novel Starch Source: Impact of Isolation Methods on Functional, Morphological, Structural, Pasting, and Rheological Properties

Abstract

In the present study, Guinea seed starch (GS) is extracted using four different isolation methods (Sodium hydroxide [NaOH], potassium metabisulphite [KMS], citric acid [CA], and distilled water [DW]) to investigate the effect of isolation methods on different properties of starch. The water and oil absorption capacity range from 0.69 to 1.12 g g −1 and 0.81 to 0.95 g g −1 , respectively. The swelling and solubility of isolated starches are temperature dependent and increase with temperature (70-90 °C). The amylose content also varies with isolation method and all the starch showed typical A-type X-ray patterns. The mean particle size of GS is 9.86-13.36 µm and shows round to polygonal shapes with pores. The isolation method impacts glass transition temperatures and enthalpies, which vary between 73.36-83.67 °C and 0.72-23.69 J g −1 , respectively. The pasting temperature (PT) also varies with the isolation method and follows the pattern of CA (84.80 ± 0.07 °C) > KMS (81.97 ± 0.06 °C) > DW (81.95 ± 0.05 °C) > NaOH (79.82 ± 0.03 °C). All the starches showed shear thinning behavior, and storage modulus is higher than loss modulus, representing that the elastic component is higher than the viscous component.