Okra polysaccharide: Effect on the texture and microstructure of set yoghurt as a new natural stabilizer.

Four plant-derived polysaccharides including okra polysaccharide (OP), apple pectin (AP), sodium alginate (SA) and konjac glucomannan (KGM) were studied in yoghurt formulation to investigate their effect on gelling characteristics. The results indicated that OP, KGM and AP enhanced the water-holding capacity, firmness and elasticity of yoghurt while SA demonstrated the opposite effects. Gel structure was better improved with OP, the firmness of yoghurt increased from 9.01 g to 14.86 g when 0.08% OP was added. The yoghurt with OP achieved the closest transverse relaxation time (T2) to the control. The free water area (A23) decreased from 1592 for control to 1414 for yoghurt with 0.08% OP addition. All samples exhibited shear-thinning behavior, both apparent viscosity and elastic modulus (G', G″) increased with increasing concentrations of OP and KGM, with peak values at 0.06% OP and 0.015% KGM. Both G' and G'' reduced significantly as pectin concentration rose to 0.1%, while modules went up with the increasing concentration of SA. Microscopy results showed that addition of OP and AP reduced the porous structure of gel and promoted formation of larger protein clusters, which eventually led to more compact protein network. This study provided new insights for food application with plant-derived polysaccharides.