Physico-chemical properties of alcohol precipitate pectin-like polysaccharides from Parkia speciosa pod

Alcohol precipitate polysaccharides (i.e. E_pH2, E_pH4.5 and E_pH7) from Parkia speciosa were extracted at 95 °C for 5 h using 0.1 M citrate phosphate buffers of pH 2, pH 4.5 and pH 7, respectively. Comparison between the extracts and commercial citrus pectin (CP) was also performed. Uronic acid and protein content of E_pH2 were higher followed by E_pH4.5 and E_pH7. FTIR analysis showed that E_pH2 and E_pH4.5 gave comparable pattern compared to CP with DE values of 83% and 64%, respectively, whereas E_pH7 was slightly different. E_pH2 obtained a lower solubility (∼60–70%) compared to other extracts (>90%) whereas E_pH7 obtained the highest oil holding capacity (OHC) value (3.9 g/g). Flow analysis showed that E_pH2 produced a higher viscosity gel solution at pH 2 followed by E_pH4.5 and E_pH7, however the gelling properties decreased as pH increased. Different colour of the gels was also found, ranging from yellowish to purplish colour; and the colour changed with the alteration of pH. Antioxidative properties were also shown in the extracts. E_pH2 consisted of 382.8 mg gallic acid equivalent (GAE)/100 g of samples and exhibited percent of 2,2-diphenyl-1-picrylhydrazyl free radical scavenged (%DPPH_sc) of 47.5% whereas E_pH4.5 and E_pH7 consisted of 294.8 and 74.5 mg GAE/100 g sample, respectively, and gave %DPPH_sc values of 42.8 and 6.0, respectively. Therefore, it was suggested that P. speciosa has the potential in producing functional polysaccharides that could be imparted into the food system.