Rheological properties of Prunus persica exudate: Potential effects of proteins and polyphenols

This study was to investigate the rheological properties of graded Prunus persica exudates (peach gums). Graded peach gums were extracted by hot water and precipitated by ethanol to obtain white peach gum polysaccharide (WPGP) and yellow peach gum polysaccharide (YPGP). Chemical analysis showed that YPGP had 0.11% proteins and 0.23% polyphenols, which were not detected in WPGP. Molecular weight of WPGP and YPGP were determined as 6.09 × 103 kDa and 5.82 × 103 kDa, respectively, by using HPGPC. Monosaccharide analysis revealed that WPGP and YPGP were mainly composed of arabinose and galactose in an approximate molar ratio of 2: 1. These results suggested that WPGP and YPGP might have the same polysaccharide composition. Rheological analysis revealed that peach gum aqueous solutions (10% w/w) exhibited the non-Newtonian shear-thinning behavior and gel structure. Apparent viscosity and viscoelasticity of peach gums were slightly decreased in alkaline solution (pH = 11), high temperature (40 °C) and the presence of salt ions. YPGP solution possessed higher viscosity and storage modulus than WPGP solution at all the tested conditions, which suggested that conjugates of proteins and polyphenols might be involved in the gel network of YPGP solution, resulting in an increase in apparent viscosity.