Fine Structure Of Amylopectin Research Articles

Corn Dry‐Milled Grit and Flour Fractions Exhibit Differences in Amylopectin Fine Structure and Gel Texture

ABSTRACTCorn starch amylopectin (AP) fine structure and gel textural properties of dry‐milled grit and flour fractions were investigated in 10 corn cultivars. Amylopectin was isolated by fractionating the starch derived from these two milled fractions using size‐exclusion chromatography (SEC). Fine structure was characterized by SEC after thorough debranching with pullulanase. SEC revealed three major fractions of debranched AP from the grit and flour portion. Amylopectin in the grit portion had a significantly higher proportion of long chains (DPn 70–75) and a postulated lower extent of chain branching than its flour counterpart. Texture profile analysis showed that flour gels from the grit fraction had significantly higher values for hardness, gumminess, and springiness compared with gels from the floury fraction. Trends were similar for starch gels of the two dry‐milled fractions, though only springiness was significantly different. The finding that differences in AP fine structure in dry‐milled fractions relate to gel textural differences suggests that dry millers may be able to produce flours of different functionalities that would be suited for different end uses. Additionally, mixing the dry‐milled flour fraction with a grit‐derived flour would result in different product properties.

The fine Structure of Amylopectin in Endosperm from Asian Cultivated Rice can be largely Classified into two Classes

1 The present investigations have been performed to characterize the structure of amylopectin in endosperm of rice plants cultivated in Asian countries, and to determine the relationship between the amylopectin structure and physicochemical properties of the starch. The results indicated that almost all of rice amylopectin was distinctly classified into L-type or S-type. The L-type amylopectin was diffrent from the S-type amylopectin in that the numbers of short α-1, 4-glucan chains of DP ≤ 10 were less than 20% of the total α-1, 4-glucan chains of DP ≤ 24 in a single cluster in the former and those were higher than 24% in the latter, while no significant difference between both types was found in the proportion of B2 and longer chains of DP ≥ 25. Strikingly, among the 129 rice varieties examined, only a single variety cv. Khauk Yoe belonging to the Tropical Japonica rice group had an intermediate amylopectin structure between L-type and S-type, called M-type amylopectin. Apparently, the proportion of chains with DP ≤10 to those with DP ≤ 24 in amylopectin molecules was negatively correlated with the onset temperature of gelatinization of the starch, whereas no such correlation was observed between the amylose content and the thermal properties of starch. All these results show that the varietal difference in amylopectin structure is predominantly due to difference in lengths of A chains of the cluster and plays a critical role in determining the physicochemical properties of starch in the rice endosperm.

Order in maize mutant starches revealed by mild acid hydrolysis

Maize mutants starches cover a broad range of features with respect to apparent amylose content (1–63%), fine structure of amylopectin (short- to long-chain ratios), crystallinity level (19–48%) and polymorphic type (various proportions of A-, B- and V allomorphs). This study subjected starches from single and double maize mutants to mild acid hydrolysis (35 days) with 2.2 N HCl. The crystallinity of these starches before and after 12 days of mild hydrolysis was studied by X-ray diffractometry. The linear chain length distribution of amylopectin and residues was studied after debranching, followed by high-performance anion-exchange chromatography with pulsed amperometric detection. Regardless of amylose content or crystallinity level, starches with a predominant B-crystalline type were less susceptible to acid degradation than others, and initial rates of hydrolysis were lower for B-type than A-type starches. Changes in initial hydrolysis rate may have been due to defective crystallites and/or dangling chains. Branch points were more frequent in residual fractions of A-type starches (normal, wxdu) than in predominant B-type starch ( aewx). Conversely, residual fractions of a pure B-type starch ( ae) appeared to have no branch points, suggesting the involvement of apparent amylose in crystallites.

Amylopectin Fine Structure and Rice Starch Paste Breakdown

Ten rice starches with a fairly narrow range of amylose content, but wide variation in RVA pasting curves, were selected to study a possible relationship between amylopectin fine structure and RVA paste viscosity parameters. Amylopectin fine structure was found to significantly correlate with paste breakdown. Proportion of long chains of amylopectin (FrI) was negatively correlated (r=0·84, p<0·01) and proportion of short chains of amylopectin (FrIII) was positive correlated (r=0·89, p<0·001) with paste breakdown. The findings imply that amylopectin fine structure relates to the extent of breakdown of swollen granules and the viscosity after gelatinised starch granule structure is disrupted. The results suggest the possibility that lines can be selected with high proportion of amylopectin long chains for reduced paste breakdown.

Understanding and Influencing Starch Biochemistry

Starch is one of the most important products synthesized by plants that is used in industrial processes. If it were possible to increase production or modify starches in vivo, using combinations or either genetically altered or mutant plants, it may make them cheaper for use by industry, or open up new markets for the modified starches. The conversion of sucrose to starch in storage organs is, therefore, discussed. In particular the roles of the different enzymes directly involved in synthesizing the starch molecules on altering starch structure are reviewed, as well as the different models for the production of the fine structure of amylopectin. In addition, the process of starch phosphorylation, which is also important in determining the physical properties of starches, is reviewed. It is hoped that detailed knowledge of these processes will lead to the rational design of tailored starches. Starch degradation is also an important process, for example, in the cold-sweetening of potato tubers, but outside of cereal endosperm little is known about the processes involved. The enzymes thought to be involved and the evidence for this are discussed.

Understanding and Influencing Starch Biochemistry

Starch is one of the most important products synthesized by plants that is used in industrial processes. If it were possible to increase production or modify starches in vivo, using combinations or either genetically altered or mutant plants, it may make them cheaper for use by industry, or open up new markets for the modified starches. The conversion of sucrose to starch in storage organs is, therefore, discussed. In particular the roles of the different enzymes directly involved in synthesizing the starch molecules on altering starch structure are reviewed, as well as the different models for the production of the fine structure of amylopectin. In addition, the process of starch phosphorylation, which is also important in determining the physical properties of starches, is reviewed. It is hoped that detailed knowledge of these processes will lead to the rational design of tailored starches. Starch degradation is also an important process, for example, in the cold-sweetening of potato tubers, but outside of cereal endosperm little is known about the processes involved. The enzymes thought to be involved and the evidence for this are discussed.

Differences in Amylopectin Structure Between Two Rice Varieties in Relation to the Effects of Temperature During Grain-Filling

The structure of endosperm amylopectin was compared between two rice varieties, Kinmaze (subspecies japonica) and IR36 (subspecies indica), as well as their waxy mutants, all grown under controlled temperature. The distinct varietal difference in chain length distribution of amylopectin was confirmed by high performance anion-exchange chromatography equipped with pulsed amperometric detection. Amylopectin from Kinmaze contains more very short chains with degree of polymerization (DP) between 6 and 10 and less chains with DP from 13 to 22 than amylopectin from IR36, while there is little difference in the distribution of longer chains with DP > 24 between the two varieties. Waxy mutation had little effect on chain length distribution of endosperm amylopectin. The temperature during grain-filling affected the chain length distribution of amylopectin in both varieties in a similar way; grain-filling at lower temperatures lead to an increased proportion of chains of DP 6—13 and decreased the percentage of chains with DP 20—27 and DP 44—54. However, the temperature-dependent changes in chain length distribution of amylopectin were within the range of varietal difference between Kinmaze and IR36. These results strongly suggest that factors regulating the varietal difference in patterns of chain length of amylopectin are dissimilar to those causing the temperature effects on amylopectin fine structure in rice endosperm.

Starch Properties and Stability of Club and Soft White Winter Wheats from the Pacific Northwest of the United States

ABSTRACTBased on examination of 192 club and soft white winter (SWW) wheat samples, club and SWW wheat flours showed comparable levels of starch damage and flour peak viscosity, while differing significantly in starch content. Varietal differences and growing conditions had strong influence on the characteristics of both classes of wheat flour. Club wheat flour exhibited better stability in starch content and starch damage than did SWW wheat flour. A significant correlation between starch damage and cookie diameter in both club and SWW wheat was observed (r = ‐0.480, P &lt; 0.0001 for club wheat and r = ‐0.430, P &lt; 0.0001 for SWW wheat). Sponge cake volume was positively correlated with starch content in both classes of wheat (r = 0.362, P &lt; 0.01 for club wheat and r = 0.181, P &lt; 0.05 for SWW wheat). When wheat samples were grown in one location over three years, club and SWW wheat flours had comparable starch content. However, flour and prime starch peak viscosities were significantly different in club than in SWW wheat. Club wheat flour had lower starch damage and amylose content, as measured by high‐performance size‐exclusion chromatography (HPSEC), than did SWW wheat flour. Crop year and varietal differences had significant effect on amylose content, starch damage, and flour and starch peak viscosities, but not on starch content, in both classes of wheat flour. When wheat samples were grown in one year over seven locations, club wheat flour was higher in starch content, lower in starch damage, and comparable in amylose to SWW wheat flour. Both flour and prime starch viscosities were significantly higher in club wheat than in SWW wheat. Varietal differences and growing location had strong influence on starch properties in both classes of wheat. Peak viscosity of the isolated starch did not correlate well with the corresponding flour, indicating that flour pasting property does not reflect the pasting property of starch. The fine structure of isoamylase‐debranched amylopectins from club and SWW wheats had a similar tri‐modal pattern, with maximum at ≈DP 15 and two valleys at ≈DP 20 and 45, respectively. Although wheat flour samples differed widely in their prime starch peak viscosity, no significant difference between debranching patterns was obtained. These results indicate that the fine structure of amylopectin might not be responsible for the large differences in prime starch pasting property.

Changes in structure of starch and enzyme activities affected by sugary mutations in developing rice endosperm. Possible role of starch debranching enzyme (R‐enzyme) in amylopectin biosynthesis

In maturing endosperms of a variety of sugary mutants of rice, phytoglycogen‐like polysaccharides with highly branched a‐glucans were accumulated instead of amylopectin. while the amylose content greatly decreased. Measurement of activities per endosperm of the 10 major enzymes involved in starch and sucrose metabolism revealed that the activity of starch debranching enzyme (R‐enzyme) was specifically reduced in the sugary mutants. The activity of starch branching enzyme I (Q‐enzyme I) was also significantly decreased, but less so than the R‐enzyme, in the mutants, suggesting some coordination of the expression of the genes coding for R‐enzyme and Q‐enzyme I. Western blot analysis showed that the sugary mutations of rice resulted in a decrease in the amount of R‐enzyme protein, but not in major modification of the enzyme. These findings strongly suggest that R‐enzyme plays a critical role in determining the amylopectin fine structure, since at the extremely low level of R‐enzyme activity as compared with Q‐enzyme activity, as found in sugary mutants, the rice endosperm produced phytoglycogen. We hypothesize that balance of activities or interaction between Q‐enzyme and R‐enzyme may be responsible for the fine structure of a‐polyglucans in plant tissues.

澱粉の構造解明および高度利用技術の開発に関する研究

Researches on structural analysis, physical properties of starch and discoveries of novel starch related enzymes are summarized in this paper as an award address. 1) Physical properties and utilization of various starches Starch phosphate derivatives obtained by chemical synthesis or simple cation substitution of naturally existing phosphate of potato starch are discussed in terms of physical properties and possible utilization. Sago starch as a. neglected starch resource in tropical area and newly developed methodology during the study such as photopastegraphy, Q-amylase/pullulanase method (BAP method) are also described. 2) Fine structure of amylopectin: Fine structures of waxy maize starch were analyzed by structure of a-limit dextrin, X-ray diffraction and enzymic structural analysis of Naegeli amylodextrin, transmission electron microscopy and computer modeling. From the results of these studies, French proposed?gcluster model?hfor amylopectin molecules and Kainuma and French proposed?gdouble helix?hconformation for crystalline part of amylopectin. In 1980, Kainuma represented schematic arrangement of amylopectin molecules within a growth ring. 3) Novel starch related enzymes and oligosaccharides: During structural analysis, exo-maltohexaohydrolase (E. C. 3.2.1.98) was unexpectedly discovered as a contaminant of A. aero genes pullulanase. Since this discovery, our research efforts were concentrated to screen new starch related enzymes and enzymatic preparation of oligosaccharides. As the results, cyclodextrins and branched cyclodextrins, isomaltose, maltohexaose, erythritol -a noncaloric sweetener-were already commercially manufactured. Raw starch hydrolyzing glucoamylase of Chalara paradoxa isolated from sago palm tree in Papua New Guinea is expected for energy-saving saccharification of starch.

The effects of ambient temperature during the grain-filling period on the composition and properties of starch from four barley genotypes

Starch was isolated from four genotypes of barley (one waxy, two normal and one high-amylose) grown at constant ambient temperatures of 10, 15, and 20 °C. There was evidence of physiological stress in grain grown at the higher temperatures, notably reduced starch accumulation, smaller A- and B-granules and fewer B-granules. In the waxy and normal genotypes amylose (AM) and amylopectin (AP) contents were little affected by increasing ambient temperature, but the lipid contents of the starches did show a strong response. No differences in the fine structure of AP in response to temperature were detected. Starch gelatinization temperatures (GT) were 50–55 °C, 52–62 °C and 60–63 °C in starches from grain grown at 10, 15 and 20 °C, respectively. Since the native starches could all be annealed to give similar elevated GT values (72–73 °C, the range of GT in the native starches was probably due to differences in the perfection of AP crystallinity which increased with barley growth temperature. All starches showed marked differences in their swelling curves which clearly related to ambient temperature. Swelling began at the same temperature as gelatinization (loss of crystalline order), At 80 °C, when there was no detectable order, swelling was determined primarily by AP content (45·3–97·6% in the 12 starches) but it was markedly inhibited by lipid (a temperature-dependent variable) probably through a mechanism which involved formation of AM-lipid inclusion complexes.

The fine structure of amylopectin

A critical examination of an enzymic method for determining the ratio of A and B chains in amylopectin leads to a value of ∼ 1:1, and not 2:1 as suggested other workers. Partial debranching with pullulanase gave results consistent with earlier suggestions that A chains are predominantly and selectively removed. The ratio of A and B chains in a partially branched amylopectin has been determined, and the results are discussed in relation to possible structures for amylopectin.

アミロペクチンの微細構造について(第2報)

アミロペクチンの微細構造について(第2報)

アミロペクチンの微細構造について(第1報)

アミロペクチンの微細構造について(第1報)