Rheology and microstructure of basil seed gum and β-lactoglobulin mixed gels

Abstract

Gelling profiles and interaction between basil seed gum (BSG) and β-lactoglobulin (BLG) were characterized using dynamic rheology and scanning electron microscopy. Sequence of experimental sweeps of time–temperature, frequency, and strain were applied for BSG, BLG and BLG–BSG mixtures in the ratio of 10:1, 5:1, 2:1 & 1:2. Rheological behavior of BLG was found to be different from that of BSG and gelling point was raised during the heating period. By increasing BSG concentration, storage and loss moduli were increased and gel point was determined at about 80 °C, which was dependent of concentration and occurred during cooling period. Upon heating–cooling period (temperature sweep) of BLG–BSG mixture from 20 °C to 90 °C and coming back to original temperature, mixed gels presented a biphasic profile: the first phase, characterized by a sharp increase in the storage modulus in which gelation of BLG happened and the second phase exhibiting an increase in the storage modulus, corresponded to the build-up of a BSG network. Strain sweep results obtained for mixed gels at the end of the temperature sweep tests supported the biphasic hypothesis. The SEM results showed that BLG has a globular structure in comparison with BSG which has fibril and globular structure and the mean diameter of its globular structure was higher than that of BLG. Increasing the ratio of BSG to BLG resulted in a finer microstructure, which could retain higher water to form gel. In addition, microstructural study showed that BLG–BSG mixed is a bicontinuous network in which BSG dispersed in BLG continuous phase.