Functional properties of modified starch of arrowroot, cassava, and kimpul starch by autocla ving-freeze-drying and chemical treatments

Abstract

Studies on the functional properties of resistant starch (RS) receive much attention in recent years due to its promising beneficial effect for health known as prebiotic. Many local varieties of tubers contain high amylose and amylopectin which have the potential to be modified as resistant starch (RS). Many methods to modify the starch properties as RS have been developed. In this study starches of three varieties of tubers i.e. arrowroot (Marantha arundinacea L), cassava (Manihot esculenta Crantz), and kimpul (Xahnthosoma violaceum Schott) were modified to obtain two types ofRS type III and IV. RS type III were prepared by autoclaving the starches at 121°C for 30 min and then freeze-dried, while RS IV were prepared using cross-linking method by addition of POCb. After physical and chemical treatments, modified starches were analyzed for RS type III and IV contents, amylose content, digestibility, and dietary fiber. Either physical or chemical treatments could significantly increase RS contents in all modified tuber starches. The formation of RS type III was higher than RS type IV ranging from 6.52 to 8.67%, and 4.3 to 5.2%, respectively. The highest content ofRS type III (8.67%) was found in modified kimpul starch followed by arrowroot (6.65%) and cassava (6.52%). Digestibility of all modified tuber starch either containing RS III or RS IV were relatively low (15.96% - 29.31 %), excluding cassava starch RS III (53.78%). No significant difference of amylose contents between native and modified starches were found which ranging from 26.54% to 31.76%. Prebiotic activity potential were also determined based on the viability of Lactobacillus casei subsp. rhamnosus, Lactobacillus plantarum sa28k, and Bifidobacterium bifidum in medium MRSB-minus glucose containing modified starch. All modified starches either containing RS type III or IV could be utilized by the three tested bacteria with the production of SCFA (short chain fatty acids) i.e. acetic acid, whilst formic, butyrate and propionate acids were not detected. Dietary fiber contents of all modified starches containing RS type IV were relatively high (7.5 - 8.7 gil 00 g starch). Generally, the modified tuber starches resulted in this study produced higher RS and dietary fiber contents but low digestibility that will support the prebiotic properties.