Amylose and Amylopectin Content of Starches Determined by their Iodine Complex Formation¹

Abstract

For many years the chemical literature has contained references to starch fractionation. The methods employed have been numerous and the products obtained by different methods have generally been at variance in their chemical and physical properties.2Recently, however, three methods of fractionation have been developed which appear to give nearly identical results. The methods are (a) hot water extraction of one component,* (b) selective adsorption of this same component on cellulose,4 and (c) the selective precipitation of this component by butanol and other alcohols.6In each case one fraction stains blue with iodine, is converted almost completely to maltose by /3-amylase, retrogrades easily, and furnishes good quality X-ray diffraction patterns in "A," " " and "V" modifications. The other fraction stains purple to red with iodine, is only partially converted to maltose by (3-amylase, retrogrades with difficulty or not at all, and yields poor or even amorphous diffraction patterns regardless of treatment.Meyer has made a thorough study of the two components of his fractionation,6 and has concluded that the hot-water extracted fraction is straight-chain starch, i. e,, glucose residues united exclusively by a-l,4-glucosidic linkages, the other fraction is similar but highly branched, probably through a-l,6-glucosidic linkages.7 He has used the term, "amylose" to designate the straightchain fraction, and "amylopectin," the branchedchain fraction.* At the present time the proof of the structure of the two starch components is based almost entirely upon quantitative methylation studies. These are executed only with difficulty and can

Physico-chemical characterisation of sago starch

“…For amylopectin fractions the iodine binding capacity was around 0.3%. The amylose contents for sago starches found in this study agree well with the published values of 22%-31.7% (Bates et al, 1943;Howling, 1980;Kawabata et al, 1984;Sim et al, 1991).…”

Nanocomposites Based on Cassava Starch and Chitosan-Modified Clay: Physico‑Mechanical Properties and Biodegradability in Simulated Compost Soil

“…4,5 Cassava starch is composed mainly of two types of polysaccharides, amylose and amylopectin. 1,6 Even though amylose to amylopectin ratio might not be constant depending on the cassava species, it is usually around 1:4, respectively.…”

“…4,5 Cassava starch is composed mainly of two types of polysaccharides, amylose and amylopectin. 1,6 Even though amylose to amylopectin ratio might not be constant depending on the cassava species, it is usually around 1:4, respectively. 7 While both polysaccharides are constituted by the same monomer unit called α-D-glucopyranose, amylose possesses almost exclusively 1-4 α linkages, originating short linear chains ( Figure 1a).…”

A comparison of spectrophotometric and denuder based approaches for the determination of gaseous molecular iodine

“…By covering the inner walls of the tube with a substrate that binds with the analyte of interest, the analyte may be trapped for subsequent determination. Molecular iodine forms a stable complex with the amylose helices in starch (Calabrese and Khan, 1999;Bates et al, 1943), so in principle a starch coating may be used to trap iodine from the gas phase (Chen et al, 2006). Chen et al (2006) used amber glass denuder tubes (6 mm internal diameter, 9 mm external diameter, 500 mm length) coated using 2 mL of starch in ethanol (2 g L −1 ) to detect molecular iodine in air.…”

“…Consequently, the protocol used to isolate amylose from starch influences the ability of the amylose to interact with iodine (Rendleman, 2003), and thus the exact type and brand of starch used is likely to affect iodine recovery by the denuder. Amylose was used here, as it is the component of starch with the highest iodine binding capacity (Bates et al, 1943) and preliminary trials using ground starch (Fluka) as per the method of Chen et al (2006) gave low recoveries and poor reproducibility. However, it is possible the amylose had undergone retrogradation from the "V" form at some stage, rendering it less reactive to iodine.…”