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

Alcohol precipitate polysaccharides (i.e. EpH2, EpH4.5 and EpH7) 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 EpH2 were higher followed by EpH4.5 and EpH7. FTIR analysis showed that EpH2 and EpH4.5 gave comparable pattern compared to CP with DE values of 83% and 64%, respectively, whereas EpH7 was slightly different. EpH2 obtained a lower solubility (∼60–70%) compared to other extracts (>90%) whereas EpH7 obtained the highest oil holding capacity (OHC) value (3.9 g/g). Flow analysis showed that EpH2 produced a higher viscosity gel solution at pH 2 followed by EpH4.5 and EpH7, 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. EpH2 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 (%DPPHsc) of 47.5% whereas EpH4.5 and EpH7 consisted of 294.8 and 74.5 mg GAE/100 g sample, respectively, and gave %DPPHsc 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.