New freeze-thaw method for improved extraction of water-soluble non-starch polysaccharide from taro (Colocasia esculenta): Optimization and comprehensive characterization of physico-chemical and structural properties

This study investigated the effects of an improved extraction method that utilized freeze-thaw, termed improved conventional extraction (ICE), on the yield and properties of the water-soluble non-starch polysaccharide of taro (Tc-WS-NSP) and compared this method to the conventional extraction (CE) method. The freeze-thaw condition was optimized using response surface methodology (RSM) based on yield. The use of the ICE method resulted in a 227.8% increase in yield of Tc-WS-NSP compared to the CE method. The Tc-WS-NSP-ICE had higher purity, lighter color, larger particle size, and higher ζ-potential than Tc-WS-NSP-CE. Both of the samples contain the sugar arabinose, galactose, glucose, and mannose and exhibited comparative FTIR, 1H, and 13C NMR spectra. The Tc-WS-NSP-ICE had a semi-crystalline structure resulting in higher thermal stability and had a higher consistency index than Tc-WS-NSP-CE. Overall, the use of the ICE method provided a simple, efficient, and green alternative to CE for the extraction of Tc-WS-NSP.