Molecular Size Of Amylopectin Research Articles

Starch fine molecular structures as driving factors for multiphasic starch gelatinization property in rice flour

AbstractBackground and ObjectivesAlthough the gelatinization property of isolated rice starch has been investigated in terms of its relationship to starch fine molecular structures, it remains unclear how these structures determine the gelatinization property of rice flour. The gelatinization properties of 10 rice flours with varying chain‐length distributions were thus studied.FindingsRice flours with larger amylose molecules, longer and higher amount of amylopectin intermediate chains showed double gelatinization peaks. The onset and peak temperatures of gelatinization for the peak having a lower gelatinization temperature showed a positive correlation with the molecular size of amylopectin. Conversely, the conclusion temperature of gelatinization for the peak with a higher gelatinization temperature exhibited a negative correlation with the molecular size of amylose and a positive correlation with the quantity of amylose and amylopectin intermediate chains. These correlations were largely different compared with those for rice flours with a single gelatinization peak.ConclusionsThese results supplied the first associations between gelatinization property of rice flour and starch fine molecular structures, which were different from those for pure rice starches.Significance and NoveltyThese results have the potential to assist the food industry in developing rice products with improved quality, depending on the molecular structure of the starch.

Genotype diversity in structure of amylopectin of waxy rice and its influence on gelatinization properties

A set of 13 waxy rice genotypes prepared by chemically-induced mutation of non-waxy rice variety TNG67 and 7 waxy rice varieties widely planted in Taiwan were screened for various structural and gelatinization properties of starches. Wide variation on physicochemical properties and molecular structure of amylopectin for the 20 waxy rice starches were obtained and relationship between gelatinization properties and molecular structure of starch were discussed. More attributes on swelling and gelatinization thermal properties, comparing to pasting attributes, showed significant correlation with molecular structure parameters. The swelling and gelatinization thermal properties of waxy rice starch did not show significant correlation with molecular size of amylopectin, while significant correlations were found between the swelling or gelatinization thermal properties and chain length of amylopectin. Results suggest that the swelling and pasting of waxy starch is essentially dominated by granule architecture and is dependent on the interactions among amylopectin chains.

Structural properties and gelatinisation characteristics of potato and cassava starches and mutants thereof

The molecular size of amylopectin (AP) and amylose (AM), AP chain length distribution, crystallinity and granular structure (morphology and granule size distribution) of five wild type potato starches (wtps), five AM free potato starches (amfps), four high-AM potato starches (haps), one wild type cassava starch (wtcs) and one AM free cassava starch (amfcs) were investigated and related to their gelatinisation characteristics. Starches with higher levels of short chains [degree of polymerisation (DP) 6–9 and DP 10–14)] had lower gelatinisation onset ( T o), peak ( T p) and conclusion ( T c) temperatures, whereas higher contents of longer chains (DP 18–25 and DP 25–80) led to higher gelatinisation temperatures. Gelatinisation enthalpies (Δ H) increased with degree of crystallinity. The granules of wtps were larger than those of amfps and haps, respectively. No differences in morphology were observed between wtps and amfps granules, but the haps granules had more irregular surfaces and showed multi-lobed granules.

Molecular Structure of Starches from Cassava Varieties having Different Cooked Root Textures

Starches from 12 cassava varieties with different cooked root texture; i.e. mealy, firm and mealy and firm, were investigated with a particular focus on aspects of molecular structures of amylose and amylopectin. Structural elements of amylopectin were essentially constant in terms of unit chain distributions and chain lengths. All cassava amylopectins displayed two distinct chain length peaks, at DP 40–46 and at DP 11–13, with a shoulder at DP 17–19, and average chain length (CL) of amylopectins was 17–20. A fraction of extra-long chains in the range of 0.24–1.78% was found. Amylose and amylopectin from four varieties with different textures of cooked root were isolated. Data from C-chain distributions indicated that the molecular size of amylopectin from M-hanatee (Hanatee), a locally adapted cassava variety, was 2.5–2.9 times smaller than those of the other varieties. Three of the four amylose samples, except that from M-hanatee, were very similar in average DP (4120–4390), chain length (530–550) and number of chains (7.1–7.5), and composed of nearly equal numbers of linear and branched molecules. The amylose from the M-hanatee variety showed a unique characteristic: it had smaller size (2050), shorter chain length (450), fewer chains (4.7) and a higher content of linear fraction (58%), when compared with other amyloses.

Irradiation of maize and bean flours: effects on starch physicochemical properties

AbstractIn an earlier study (Rombo GO et al, J Sci Food Agric 81: 497–502 (2001)) it was found that the in vitro starch digestibility of raw and cooked maize and bean flours was increased by irradiation of the flours at 2.5 kGy, but there was a reduction in starch digestibility at doses above 2.5 kGy. Experiments were performed to determine what effects irradiation had on the molecular properties of the starch in maize and bean flours. Increasing irradiation dose caused an increased proportion of β(1–3)‐ and β(1–4)‐bonded starch in bean and maize flours. Starch containing β‐bonds is only partially digestible by porcine pancreatic α‐amylase, and this may in part explain the reduction in starch digestibility at higher doses. Size exclusion–high‐performance liquid chromatography showed that higher irradiation doses led to a reduction in the molecular size of amylopectin in both bean and maize starches, which presumably involved debranching and an increase in the production of short, straight‐chain molecules. With increased irradiation dose there was an increase in the crystallinity of the amylopectin fraction of the bean starch as shown by differential scanning calorimetry, presumably at least in part due to β‐bonding and amylopectin depolymerisation. These two factors and their interrelated effects are probably responsible for the observed slight reduction in maize and bean porridge starch digestibility reported previously. Copyright © 2004 Society of Chemical Industry

Modification of barley starch by α-amylase and pullulanase

The hydrolysis of the amylopectin of gelatinized waxy barley starch by Bacillus licheniformis α-amylase occurred in a non-random way, showing accumulation of smaller-size hydrolysis products. The hydrolysis of barley starch by Bacillus acidopullulyticus pullulanase also began with a rapid decrease in the molecular size of amylopectin, indicating that the enzyme was capable of hydrolyzing the α-1,6-linkages in the middle of the amylopectin molecule.