Succinylated Dioscorea cayenensis starch: Effect of reaction parameters and characterisation

Abstract

AbstractStarch was extracted from Dioscorea cayenensis (yield, 87.2%) and it was subjected to succinylation under different reaction conditions. The succinyl amount and the degree of substitution (DS) in starch increased as the concentration of succinic anhydride, time and temperature increased. Optimal DS (0.217) and % succinyl content of 11.82 could be achieved at starch: catalyst (pyridine) ratio of 1:1, succinic anhydride concentration of 4% w/w at 120°C and 4 h of reaction. Succinylation did not alter starch crystallinity remarkably. Native starch granules appeared oval, round and spherical with sizes in the range 15–31 µm (length) and 10–20 µm (width). Both swelling capacity and solubility improved after succinylation. Succinylation increased paste clarity and it was dependent of the DS and storage time for the paste. Pasting temperature was reduced after modification and as the DS increased among the starch derivatives. The peak viscosity of the native starch was lower than the viscosities of all the modified starches. Succinylation reduced setback values but increased breakdown. Percentage syneresis was reduced after succinylation and progressive increases in percentage syneresis were observed as the number of cycles of freezing–thawing increased. In vitro enzyme digestibility reduced after succinylation and progressively as the DS of the modified starch increased.