Comprehensive Chemical Characterization of POP

The phenol-sulfuric acid method was used to determine the total polysaccharide content of POP extract, using D-glucose as the standard[22 ]. Protein content of POP extract was determined by Lowery method, using BSA as the standard[23 (link)]. The m-hydroxybiphenyl assay was used to measure uronic acid content of POP extract, using glucuronic acid as reference material [24 ]. The moisture content of POP was measured, referring to the method outlined in Kong et al (22). The pH values of the POP at the 2 mg/mL of POP were determined using a pH meter and the relative viscosity of POP (10 mg/mL) was determined using viscometer (Thermo Scientific HAAKE, 388–0100) at 25°C[25 (link)].