Digestibility of Sweet Potato Raw Starches by Glucoamylase

Abstract

Three crude glucoamylase preparations from Rhizopus sp., Chalara paradoxa and Aspergillus sp. K‐27 were used to determine the digestibility of raw starches from eight sweet potato varieties. Granule sizes and amylose contents were also measured. The average granule sizes ranged between 10.5 and 14.2 μm. The amylose contents varied between 18.2 and 21.8%. The hydrolysis rates for the raw starches by any of the three glucoamylases were similar. However, starch of the variety Hi‐starch had a slightly lower hydrolysis rate than other starches when Rhizopus sp, enzyme was used.

Modelling starch digestion in sweetpotato with biphasic digestograms

“…amylose, crystallinity) of the sweetpotato samples, amylose content (within a narrow range) did not exercise any significant effects on the sweetpotato samples studied by Noda et al (1992). However, with maize starches of 0-80% amylose, and using the in vitro procedure in the present study, Sopade (2009) revealed starch digestion reduced with an increase in amylose content.…”

“…Also, maize starch digestograms changed from monophasic to slightly biphasic digestogram when amylose content increased. Unlike amylopectin that is branched (a-1,4 and a-1,6 glucosidic bonds), the essentially linear (a-1,4 glucosidic bonds) amylose is more difficult to digest (Noda et al, 1992). However, since biphasic digestogram was exhibited by all the samples in the present study, it could be that, even though possibly different, the effects of amylose on the digestion pattern or configuration of the sweetpotato, rather than on the rate and extent of digestion, were not substantial.…”

“…While some studies have been published on the characteristics of sweetpotato starch (e.g. Noda et al, 1992Noda et al, , 1997Noda et al, , 2008, studies are limited or non-existent on the manner in which sweetpotato starch is digested (Ly et al, 1999;Sarikaya et al, 2000). Sopade and co-workers have published the starch digestograms of some cultivars of sweetpotato, which they noted could differ in configuration from those of cereals (Sopade et al, 2008;Chen et al, 2009;Liu et al, 2010).…”

Physicochemical Properties of Starches from Sri Lankan Rice Varieties

“…Amylose content The amylose content was estimated by the blue value method as described by Noda et al (1992) without defatting the starch. A 2% starch suspension was prepared by dissolving starch in dimethyl sulfoxide (DMSO) at 70ºC for 3 h and diluting the mix into a 0.1% starch suspension using distilled water.…”

“…(Oriental Yeast Co., Ltd., Tokyo, Japan) for 4 h at 40ºC according to the modified method of Noda et al (1992). The amount of glucose released during enzyme digestion was estimated by the phenol-sulfuric method (Dubois et al, 1956), and enzyme digestibility was calculated as the percentage of glucose released during incubation with the enzyme to the total amount of sugar in the starch on a weight basis.…”