Effect of Acid Modification on the Physico-Chemical Properties of North Sulawesi’s Giant Swamp Taro (GST) Starch (Cyrtosperma merkusii)

Abstract

Giant swamp taro (GST, Cyrtosperma merkusii) is an underutilized tropical endemic crop of North Sulawesi. GST starch has the potential to be utilized in various food products such as dry noodles, artificial rice, bioplastic and various other applications. This study aimed to determine the effect of acid modification on the physico-chemical properties of GST starch. Starch was extracted from GST corms by maceration in 2% sodium chloride solution. GST starch was modified by acid hydrolysis using 0.2 M citric acid solution, followed by neutralization in 1 M sodium hydroxide solution. The starch samples (native and modified) were analysed for the following physicochemical parameters; pasting properties, viscosity, total starch content, swelling power. The Fourier transform infrared (FTIR) spectroscopic analysis and Field emission scanning electron microscopy (FESEM) of the starch were also carried out. The results revealed that acid modification of GST starch has significant effect on its physico-chemical properties, microstructure and FTIR spectrum. Native GST starch had high amylose and amylopectin contents with a high ratio of amylopectin to amylose. Acid modification of the GST starch resulted in a starch with lower amylose and amylopectin content. Consequently, lowering the viscosity and gelling properties of the starch. Therefore, modification of GST starch by acid hydrolysis could result in starch product with better physic-chemical properties that could be employed as food thickeners. However, for applications where a more stable and stronger gel matrix is required, other modification methods such as the cross-linking and heat moisture treatment (HMT) methods should be considered.