Modification of mechanical, rheological and structural properties of agar hydrogel using xanthan and locust bean gum

Agar is a valuable seaweed hydrocolloid that can form a high-firmness thermoreversible gel. With the increasing demand for vegetarian meals, agar can be used as a gelatin substitute with some modifications. In this study, we investigated the structural, mechanical, and rheological properties of a compound hydrogel using the agar/locust bean/xanthan gum (ALX). The different concentrations of hydrocolloids were optimized based on comparing the results of texture profile analysis of samples with high-bloom gelatin. Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy tests confirmed the interaction between agar, locust bean and xanthan gum. The textural analysis results showed that the addition of locust bean gum (LBG) and xanthan gum (XG) to agar could significantly increase the springiness of agar hydrogel (AG) from 0.92 +/- 0.00 to 1.00 +/- 0.00, also decrease its hardness from 702.11 +/- 5.99 to 343.31 +/- 20.23 g (p < 0.05). Moreover, a remarkable decrease was shown in the syneresis degree of AG from 2.33 +/- 0.02% to 0.52 +/- 0.00%. All behaviors of the optimum hydrogel indicated the effective interaction of LBG and XG with AG which made the final compound hydrogel a promising alternative to high-bloom gelatin.