Functional and dynamic rheologicai properties of acetylated starches from two cultivars of cassava

摘要

The starches derived from two different cultivars of cassava were modified with acetic anhydride. The increase in swelling power and solubility of the cassava starch (CS) pastes treated with different acetic anhydride concentration could be attributedto easier hydration, resulting from reduction of interaction between starch chains due to the substitution. The transition temperatures (To, Tp and Tc) and enthalpy of gelatinisation (AH) of acetylated CS, were determined. The values were lower than those of native starches. Rheologicai properties of CS pastes (5% w/w) as a function of the degree of substitution were evaluated in dynamic shear force measurements. Magnitude of storage modulus (G'), loss modulus (G") and complex viscosity (Eta*) of acetylated CS pastes were determined also. Dynamic moduli (G', G" and Eta*) values of acetylated sweet cultivar pastes were generally higher than those of native starch whereas the acetylated samples of the bitter cultivar were lower than those of native starch. The magnitudes of G' were greater than those of G" and Eta* at all frequencies (l). The fact that all the tan 8 (ratio G"/G') values (0.7-0.48 and 0.25-0.44) were less than one is an indication that the samples are more elastic than viscous. The acetylated starches could find promising industrial uses in food products like Lemon curd and Mayonnaise and other non-food applications.