Publications by authors named "Eric Bertoft"

45 Publications

Relationship between molecular structure and lamellar and crystalline structure of rice starch.

Carbohydr Polym 2021 Apr 19;258:117616. Epub 2021 Jan 19.

Lab of Food Soft Matter Structure and Advanced Manufacturing, College of Food Science and Engineering/Collaborative Innovation Center for Modern Grain Circulation and Safety/Key Laboratory of Grains and Oils Quality Control and Processing, Nanjing University of Finance and Economics, Nanjing, 210023, China. Electronic address:

The relationship between molecular structure and crystalline and lamellar structures of fifteen types of rice starches was studied. GPC and HPAEC were used for the molecular chain analysis and WAXS, SAXS, and CP/MAS C NMR were employed for aggregation structural analysis. The amylopectin content and the average lengths of fb-chains (the degree of polymerization (DP) 13-24) were positively correlated with the amount of double helices (r = 0.92 and 0.57, respectively). In contrast, amylose content was positively correlated with the amounts of amorphous materials in starch (r = 0.77). The amount of double helices, which constitute a major part of the crystalline matrix, was positively correlated with the lamellar ordering (r = 0.81), and negatively correlated with the thickness of crystalline lamellae (r = 0.90) and lamellar repeat distance (r = 0.84). Conversely, the amount of the amorphous matrix was correlated with these parameters in the opposite way (r = 0.50, 0.75, and 0.75, respectively).
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http://dx.doi.org/10.1016/j.carbpol.2021.117616DOI Listing
April 2021

A Review of Starch Biosynthesis in Relation to the Building Block-Backbone Model.

Int J Mol Sci 2020 Sep 23;21(19). Epub 2020 Sep 23.

Bertoft Solutions, 20960 Turku, Finland.

Starch is a water-insoluble polymer of glucose synthesized as discrete granules inside the stroma of plastids in plant cells. Starch reserves provide a source of carbohydrate for immediate growth and development, and act as long term carbon stores in endosperms and seed tissues for growth of the next generation, making starch of huge agricultural importance. The starch granule has a highly complex hierarchical structure arising from the combined actions of a large array of enzymes as well as physicochemical self-assembly mechanisms. Understanding the precise nature of granule architecture, and how both biological and abiotic factors determine this structure is of both fundamental and practical importance. This review outlines current knowledge of granule architecture and the starch biosynthesis pathway in relation to the model of starch structure. We highlight the gaps in our knowledge in relation to our understanding of the structure and synthesis of starch, and argue that the building block-backbone model takes accurate account of both structural and biochemical data.
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http://dx.doi.org/10.3390/ijms21197011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7582286PMC
September 2020

On the role of the internal chain length distribution of amylopectins during retrogradation: Double helix lateral aggregation and slow digestibility.

Carbohydr Polym 2020 Oct 13;246:116633. Epub 2020 Jun 13.

School of Engineering, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada; Department of Food Science, iFOOD Multidisciplinary Center, Aarhus University, Agro Food Park 48, Aarhus N, 8200, Denmark. Electronic address:

A structure-digestion model is proposed to explain the formation of α-amylase-slowly digestible structures during amylopectin retrogradation. Maize and potato (normal and waxy) and banana starch (normal and purified amylopectin through alcohol precipitation), were analyzed for amylose ratio and size (HPSEC) and amylopectin unit- and internal-chain length distribution (HPAEC). Banana amylopectin (BA), like waxy potato (WP), exhibited a larger number of B3-chains, fewer BS- and B-chains and lower S:L and BS:BL ratios than maize, categorizing BA structurally as type-4. WP exhibited a significantly greater tendency to form double helices (DSC and C-NMR) than BA, which was attributed to its higher internal chain length (ICL) and fewer DP6-12-chains. However, retrograded BA was remarkably more resistant to digestion than WP. Lower number of phosphorylated B-chains, more S- and B-chains and shorter ICL, were suggested to result in α-amylase-slowly digestible structures through further lateral packing of double helices (suggested by thermo-rheology) in type-4 amylopectins.
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http://dx.doi.org/10.1016/j.carbpol.2020.116633DOI Listing
October 2020

Modification of cereal and tuber waxy starches with radio frequency cold plasma and its effects on waxy starch properties.

Carbohydr Polym 2019 Nov 13;223:115075. Epub 2019 Jul 13.

Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, Saint Paul, MN, 55108, USA. Electronic address:

The use of carbon dioxide-argon gas radio frequency cold plasma in modifying waxy rice, maize and potato was explored in this paper. Treatment with plasma at 120 W or 0 W (carbon dioxide-argon gas mixture only) resulted in significant increases in the enthalpy of gelatinization of all three waxy starches. Treatment with plasma or gas resulted in a significant increase in the resistant starch content of maize and potato with rice increasing only after gas treatment. Significant decreases were observed in the setback and final viscosities after 120 W treatment in all starches. Plasma and gas treatment resulted in a 5.5% and 2.8% decrease in crystallinity of potato but not rice and maize starch. NMR results showed the presence of V-type single helices in mostly maize and rice starches. Carbon dioxide-argon radio frequency cold plasma served as a useful tool in modifying the properties of all three waxy starches.
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http://dx.doi.org/10.1016/j.carbpol.2019.115075DOI Listing
November 2019

Effect of diurnal photosynthetic activity on the fine structure of amylopectin from normal and waxy barley starch.

Int J Biol Macromol 2017 Sep 28;102:924-932. Epub 2017 Apr 28.

Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA. Electronic address:

The impact of diurnal photosynthetic activity on the fine structure of the amylopectin fraction of starch synthesized by normal barley (NBS) and waxy barley (WBS), the latter completely devoid of amylose biosynthesis, was determined following the cultivation under normal diurnal or constant light growing conditions. The amylopectin fine structures were analysed by characterizing its unit chain length profiles after enzymatic debranching as well as its φ,β-limit dextrins and its clusters and building blocks after their partial and complete hydrolysis with α-amylase from Bacillus amyloliquefaciens, respectively. Regardless of lighting conditions, no structural effects were found when comparing both the amylopectin side-chain distribution and the internal chain fragments of these amylopectins. However, the diurnally grown NBS and WBS both showed larger amylopectin clusters and these had lower branching density and longer average chain lengths than clusters derived from plants grown under constant light conditions. Amylopectin clusters from diurnally grown plants also consisted of a greater number of building blocks, and shorter inter-block chain lengths compared to clusters derived from plants grown under constant light. Our data demonstrate that the diurnal light regime influences the fine structure of the amylopectin component both in amylose and non-amylose starch granules.
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http://dx.doi.org/10.1016/j.ijbiomac.2017.04.107DOI Listing
September 2017

Influence of diurnal photosynthetic activity on the morphology, structure, and thermal properties of normal and waxy barley starch.

Int J Biol Macromol 2017 May 29;98:188-200. Epub 2017 Jan 29.

Department of Food Science and Nutrition, University of Minnesota, St Paul, MN 55108, USA. Electronic address:

This study investigated the influence of diurnal photosynthetic activity on the morphology, molecular composition, crystallinity, and gelatinization properties of normal barley starch (NBS) and waxy barley starch (WBS) granules from plants cultivated in a greenhouse under normal diurnal (16h light) or constant light photosynthetic conditions. Growth rings were observed in all starch samples regardless of lighting conditions. The size distribution of whole and debranched WBS analyzed by gel-permeation chromatography did not appear to be influenced by the different lighting regimes, however, a greater relative crystallinity measured by wide-angle X-ray scattering and greater crystalline quality as judged by differential scanning calorimetry was observed under the diurnal lighting regime. NBS cultivated under the diurnal photosynthetic lighting regime displayed lower amylose content (18.7%), and shorter amylose chains than its counterpart grown under constant light. Although the relative crystallinity of NBS was not influenced by lighting conditions, lower onset, peak, and completion gelatinization temperatures were observed in diurnally grown NBS compared to constant light conditions. It is concluded that normal barley starch is less influenced by the diurnal photosynthetic lighting regime than amylose-free barley starch suggesting a role of amylose to prevent structural disorder and increase starch granule robustness against environmental cues.
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http://dx.doi.org/10.1016/j.ijbiomac.2017.01.118DOI Listing
May 2017

Morphological, Thermal, and Rheological Properties of Starches from Maize Mutants Deficient in Starch Synthase III.

J Agric Food Chem 2016 Aug 19;64(34):6539-45. Epub 2016 Aug 19.

School of Chemical Sciences, University of Auckland , Private Bag 92019, Auckland 1142, New Zealand.

Morphological, thermal, and rheological properties of starches from maize mutants deficient in starch synthase III (SSIII) with a common genetic background (W64A) were studied and compared with the wild type. SSIII deficiency reduced granule size of the starches from 16.7 to ∼11 μm (volume-weighted mean). Thermal analysis showed that SSIII deficiency decreased the enthalpy change of starch during gelatinization. Steady shear analysis showed that SSIII deficiency decreased the consistency coefficient and yield stress during steady shearing, whereas additional deficiency in granule-bound starch synthase (GBSS) increased these values. Dynamic oscillatory analysis showed that SSIII deficiency decreased G' at 90 °C during heating and increased it when the paste was cooled to 25 °C at 40 Hz during a frequency sweep. Additional GBSS deficiency further decreased the G'. Structural and compositional bases responsible for these changes in physical properties of the starches are discussed. This study highlighted the relationship between SSIII and some physicochemical properties of maize starch.
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http://dx.doi.org/10.1021/acs.jafc.6b01265DOI Listing
August 2016

On the molecular structure of the amylopectin fraction isolated from "high-amylose" ae maize starches.

Int J Biol Macromol 2016 Oct 11;91:768-77. Epub 2016 Jun 11.

Department of Food Science and Nutrition, University of Minnesota, St Paul, MN 55108, USA. Electronic address:

The amylopectin fractions from starch of a series of amylose-extender (ae) maize samples (HYLON(®) V, VII and VIII starches) were isolated and analysed for their molecular composition and structure. The fractions from all samples contained both a high and a low molecular weight fraction (HMF and LMF), of which LMF increased with the amylose content of the starch and appeared to have substantially more of long chains than HMF. A normal amylose-containing maize starch (NMS), which served as a reference sample, contained very little LMF, which suggested that LMF was the inherent result of the effect of the loss of starch branching enzyme IIb activity in the ae mutants. Clusters were isolated from the amylopectin fractions using Bacillus amyloliquefaciens α-amylase, which effectively hydrolyses long internal chain segments between clusters. During the hydrolysis process, clearly more of small dextrins were released from the ae starches in comparison to NMS. It appeared that some of these small dextrins did not precipitate in methanol together with the majority of the clusters. Nevertheless, isolated clusters from the HYLON starch samples were smaller than in NMS and the clusters possessed a lower density of branches with longer chains. The composition of small, branched building blocks was also clearly different: HYLON starch samples possessed much more of single-branched blocks and less multiple-branched blocks than NMS.
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http://dx.doi.org/10.1016/j.ijbiomac.2016.06.029DOI Listing
October 2016

Structure of clusters and building blocks in amylopectin from African rice accessions.

Carbohydr Polym 2016 Sep 14;148:125-33. Epub 2016 Apr 14.

Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave, St Paul, MN 55108, USA. Electronic address:

Enzymatic hydrolysis in combination with gel-permeation and anion-exchange chromatography techniques were employed to characterise the composition of clusters and building blocks of amylopectin from two African rice (Oryza glaberrima) accessions-IRGC 103759 and TOG 12440. The samples were compared with one Asian rice (Oryza sativa) sample (cv WITA 4) and one O. sativa×O. glaberrima cross (NERICA 4). The average DP of clusters from the African rice accessions (ARAs) was marginally larger (DP=83) than in WITA 4 (DP=81). However, regarding average number of chains, clusters from the ARAs represented both the smallest and largest clusters. Overall, the result suggested that the structure of clusters in TOG 12440 was dense with short chains and high degree of branching, whereas the situation was the opposite in NERICA 4. IRGC 103759 and WITA 4 possessed clusters with intermediate characteristics. The commonest type of building blocks in all samples was group 2 (single branched dextrins) representing 40.3-49.4% of the blocks, while groups 3-6 were found in successively lower numbers. The average number of building blocks in the clusters was significantly larger in NERICA 4 (5.8) and WITA 4 (5.7) than in IRGC 103759 and TOG 12440 (5.1 and 5.3, respectively).
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http://dx.doi.org/10.1016/j.carbpol.2016.04.057DOI Listing
September 2016

Impact of full range of amylose contents on the architecture of starch granules.

Int J Biol Macromol 2016 Aug 22;89:305-18. Epub 2016 Apr 22.

Department of Food Science and Nutrition, University of Minnesota, USA.

The effects of amylose deposition on crystalline regions of barley starch granules were studied in granules containing zero to 99.1% amylose using "waxy" (WBS, 0% amylose), normal (NBS, 18% amylose) and amylose-only barley lines (AOS, 99.1% amylose). The effects were probed after hydrolysis of amorphous regions of starch granules in dilute HCl generating lintners, which typically represent the crystalline lamella of starch granules. Compared to NBS and WBS, AOS granules exhibited an irregular, multilobular morphology with a rough surface texture. AOS displayed lower rates of acid hydrolysis than WBS, and AOS reached a plateau at ∼45wt% acid hydrolysis. High-performance anion-exchange chromatography of lintners at equivalent levels of hydrolysis (45wt%) revealed the average degree of polymerization (DP) of AOS lintners was 21, substantially smaller than that of NBS and WBS (DP 42). AOS lintners contained the lowest number of chains (NC) per molecule (1.1) compared to NBS (2.8) and WBS (3.3) and the average chain length of AOS, NBS and WBS lintners was 19, 15 and 13, respectively. Hence, both NC and the average chain length correlated with amylose content. The size distribution profile of AOS lintners revealed a repeat motif in the molecules corresponding to 5-6 glucose residues.
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http://dx.doi.org/10.1016/j.ijbiomac.2016.04.053DOI Listing
August 2016

Small differences in amylopectin fine structure may explain large functional differences of starch.

Carbohydr Polym 2016 Apr 13;140:113-21. Epub 2015 Dec 13.

Whistler Center for Carbohydrate Research and Department of Food Science, Purdue University, 745 Agricultural Mall Dr., West Lafayette, IN 47907-2009, USA.

Four amylose-free waxy rice starches were found to give rise to gels with clearly different morphology after storage for seven days at 4°C. The thermal and rheological properties of these gels were also different. This was remarkable in light of the subtle differences in the molecular structure of the amylopectin in the samples. Addition of iodine to the amylopectin samples suggested that not only external chains, but also the internal chains of amylopectin, could form helical inclusion complexes. It is suggested that these internal helical segments participate in the retrogradation of amylopectin, thereby stabilising the gels through double helical structures with external chains of adjacent molecules. Albeit few in number, such interactions appear to have important influences on starch functional properties.
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http://dx.doi.org/10.1016/j.carbpol.2015.12.025DOI Listing
April 2016

Unit and internal chain profile of African rice (Oryza glaberrima) amylopectin.

Carbohydr Polym 2016 Feb 10;137:466-472. Epub 2015 Nov 10.

Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave, St Paul, MN 55108, USA. Electronic address:

High-performance anion-exchange chromatography was used to study the unit chain profiles of amylopectins and their φ,β-limit dextrins from two African rice (Oryza glaberrima) accessions-TOG 12440 and IRGC 103759. The samples were compared with two Asian rice (Oryza sativa) samples (cv Koshihikari and cv WITA 4) and one O. sativa × O. glaberrima cross (NERICA 4). The ratio of short:long chains ranged between 12.1 and 13.8, and the ratio of A:B-chains was ∼ 1.0 in all samples. A significant difference was observed in the distribution of internal chains with regards to the proportion of short "fingerprint" B-chains (Bfp-chains), which in the φ,β-limit dextrins have a degree of polymerization (DP) 3-7. The African rice starches and NERICA 4 had higher levels of Bfp-chains, but the major group of short B-chains (DP 8-25) was similar to that of the Asian rice samples. The average chain length (CL), internal chain length (ICL), and total internal chain length (TICL) were similar in all samples. However, the external chain length (ECL) was longer in the African rice samples and NERICA 4. ECL correlated positively and significantly (p<0.05) with gelatinization transition temperatures and enthalpy suggesting differences between the two rice types in cooking properties.
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http://dx.doi.org/10.1016/j.carbpol.2015.11.008DOI Listing
February 2016

Starch structure in developing barley endosperm.

Int J Biol Macromol 2015 Nov 8;81:730-5. Epub 2015 Sep 8.

Department of Food Science, Swedish University of Agricultural Sciences, P.O. Box 7051, S-750 07 Uppsala, Sweden. Electronic address:

Barley spikes of the cultivars/breeding lines Gustav, Karmosé and SLU 7 were harvested at 9, 12 and 24 days after flowering in order to study starch structure in developing barley endosperm. Kernel dry weight, starch content and amylose content increased during development. Structural analysis was performed on whole starch and included the chain-length distribution of the whole starches and their β-limit dextrins. Karmosé, possessing the amo1 mutation, had higher amylose content and a lower proportion of long chains (DP ≥38) in the amylopectin component than SLU 7 and Gustav. Structural differences during endosperm development were seen as a decrease in molar proportion of chains of DP 22-37 in whole starch. In β-limit dextrins, the proportion of Bfp-chains (DP 4-7) increased and the proportion of BSmajor-chains (DP 15-27) decreased during development, suggesting more frequent activity of starch branching enzymes at later stages of maturation, resulting in amylopectin with denser structure.
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http://dx.doi.org/10.1016/j.ijbiomac.2015.09.013DOI Listing
November 2015

Thermal properties of barley starch and its relation to starch characteristics.

Int J Biol Macromol 2015 Nov 2;81:692-700. Epub 2015 Sep 2.

Department of Food Science, Swedish University of Agricultural Sciences, P.O. Box 7051, S-750 07 Uppsala, Sweden. Electronic address:

Amylopectin fine structure and starch gelatinization and retrogradation were studied in 10 different barley cultivars/breeding lines. Clusters and building blocks were isolated from the amylopectin by α-amylase from Bacillus amyloliquefaciens and their structure was characterized. Gelatinization was studied at a starch:water ratio of 1:3, and retrogradation was studied on gelatinized starch at starch:water ratio of 1:2, by differential scanning calorimetry. Three barley cultivars/breeding lines possessed the amo1 mutation, and they all had a lower molar proportion of chains of DP ≥38 and more of large building blocks. The amo1 mutation also resulted in a higher gelatinization temperature and a broader temperature interval during gelatinization. Overall, small clusters with a dense structure resulted in a higher gelatinization temperature while retrogradation was promoted by short chains in the amylopectin and many large building blocks.
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http://dx.doi.org/10.1016/j.ijbiomac.2015.08.068DOI Listing
November 2015

Structure of Arabidopsis leaf starch is markedly altered following nocturnal degradation.

Carbohydr Polym 2015 Mar 17;117:1002-1013. Epub 2014 Oct 17.

Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave, St Paul, MN, USA.

Little is known about the thermal properties and internal molecular structure of transitory starch. In this study, granule morphology, thermal properties, and the cluster structure of Arabidopsis leaf starch at beginning and end of the light period were explored. The structural properties of building blocks and clusters were evaluated by using diverse chromatographic techniques. On the granular level, starch from end of day had larger granule size, thinner crystalline lamellae thickness, lower free surface energy of crystals, and lower tendency to retrograde than that from end of night. On the molecular level, the starch had lower amylose content, larger cluster size, and higher number of blocks per cluster at the end of day than at end of night. It is concluded that the core of the granules contains a more permanent molecular and less-ordered physical structure different from the transitory layers laid down around the core at daytime.
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http://dx.doi.org/10.1016/j.carbpol.2014.09.092DOI Listing
March 2015

Branching patterns in leaf starches from Arabidopsis mutants deficient in diverse starch synthases.

Carbohydr Res 2015 Jan 15;401:96-108. Epub 2014 Nov 15.

Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave, St Paul, MN, USA.

This is the first report on the cluster structure of transitory starch from Arabidopsis leaves. In addition to wild type, the molecular structures of leaf starch from mutants deficient in starch synthases (SS) including single enzyme mutants ss1-, ss2-, or ss3-, and also double mutants ss1-ss2- and ss1-ss3- were characterized. The mutations resulted in increased amylose content. Clusters from whole starch were isolated by partial hydrolysis using α-amylase of Bacillus amyloliquefaciens. The clusters were then further hydrolyzed with concentrated α-amylase of B. amyloliquefaciens to produce building blocks (α-limit dextrins). Structures of the clusters and their building blocks were characterized by chromatography of samples before and after debranching treatment. While the mutations increased the size of clusters, the reasons were different as reflected by the composition of their unit chains and building blocks. In general, all mutants contained more of a-chains that preferentially increased the number of small building blocks with only two chains. The clusters of the double mutant ss1-ss3- were very large and possessed also more of large building blocks with four or more chains. The results from transitory starch are compared with those from agriculturally important crops in the context that to what extent the Arabidopsis can be a true biotechnological reflection for starch modifications through genetic means.
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http://dx.doi.org/10.1016/j.carres.2014.09.011DOI Listing
January 2015

Structure of clusters and building blocks in amylopectin from developing wheat endosperm.

Carbohydr Polym 2014 Nov 27;112:325-33. Epub 2014 May 27.

Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA. Electronic address:

Changes in internal structure of amylopectin (AP) during wheat endosperm development were studied by isolating clusters and building blocks of AP from both large A-type and small B-type starch granules at different maturity stages up to harvest time at 49 days after anthesis (DAA). Clusters isolated from B-type granules had a degree of branching (DB) of 16.5-16.8% and were more tightly branched than those isolated from A-type granules (DB 15.7-16.2%). The degree of polymerization (DP) of the clusters increased in both types of granules during the pre-physiological maturity stage up to 28 DAA. Clusters at maturity were smaller with less branches and building blocks than at the end of the pre-maturity stage. It is suggested that this was due to a continuous trimming of the cluster structure after the active period of starch synthesis. Differences were evident between A- and B-type granules with regards to glucan trimming and the type of new chains produced.
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http://dx.doi.org/10.1016/j.carbpol.2014.05.051DOI Listing
November 2014

Evolution of amylopectin structure in developing wheat endosperm starch.

Carbohydr Polym 2014 Nov 14;112:316-24. Epub 2014 May 14.

Food Science and Nutrition, University of Minnesota, 225, 1334 Eckles Ave, St. Paul, MN 55108, USA. Electronic address:

In this study, starches extracted from wheat grains harvested at 7, 14, 28, and 35 days after anthesis (DAA) were used as a means of examining the molecular structure of amylopectin (AP) from developing wheat grain. Scanning electron microscopy of wheat grain cross-sections revealed the presence of endosperm at 7 DAA and contained lenticular-shaped developing large (A-type) granules. From 14 DAA onward, spherical-shaped small (B-type) granules coexisted with large granules in the endosperm. During granule development, the fine structure of AP varied with maturity in both large and small granules. Towards the end of the pre-physiological maturity stage (28 DAA), AP in small and large granules had shortest external chain length (ECL), longest internal chain length (ICL) and lowest amount of A-chains. At physiological maturity (35 DAA), these changes in ECL, ICL and amount of A-chains were reversed when compared to 28 DAA. In both large and small granules, the external AP structure was apparently more organized at physiological maturity than at pre-physiological maturity.
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http://dx.doi.org/10.1016/j.carbpol.2014.05.008DOI Listing
November 2014

Distribution of branches in whole starches from maize mutants deficient in starch synthase III.

J Agric Food Chem 2014 May 8;62(20):4577-83. Epub 2014 May 8.

School of Chemical Sciences, University of Auckland , Private Bag 92019, Auckland, New Zealand.

An earlier study explored the possibility of analyzing the distribution of branches directly in native, whole starch without isolating the amylopectin component. The aim of this study was to explore if this approach can be extended to include starch mutants. Whole starches from du1 maize mutants deficient in starch synthase III (SSIII) with amylose content of ∼30-40% were characterized and compared with the wild type of the common genetic background W64A. Clusters were produced from whole starch by hydrolysis with α-amylase of Bacillus amyloliquefaciens. Their compositions of building blocks and chains were analyzed further by complete α-amylolysis and by debranching, respectively, whereafter the products were subjected to gel permeation and anion exchange chromatography. The size and structure of the clusters were compared with those of their isolated amylopectin component. Whereas the whole starch of the wild type sample had a branched structure similar to that of its amylopectin component, the results showed that the du1 mutation resulted in more singly branched building blocks in the whole starch compared to the isolated amylopectin. This suggested that amylose and/or intermediate materials in whole du1 starches likely contributed to the composition of branches. This study explored an alternative procedure to characterize the composition of branches in the whole starch without fractionating the components.
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http://dx.doi.org/10.1021/jf500697gDOI Listing
May 2014

Hydrothermal treatment and iodine binding provide insights into the organization of glucan chains within the semi-crystalline lamellae of corn starch granules.

Biopolymers 2014 Aug;101(8):871-85

Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, 55108.

The importance of glucan chains that pass through both the amorphous and crystalline lamellae (tie chains) in the organization of corn starch granules was studied using heat-moisture treatment (HMT), annealing (ANN), and iodine binding. Molecular structural analysis showed that hylon starches (HV, HVII, and HVIII) contained higher proportion of intermediate glucan chains (HVIII > HVII > HV) than normal corn (CN) starch. Wide angle X-ray scattering revealed that on HMT, the extent of polymorphic transition in hylon starches decreased with increasing proportion of intermediate and long chains. Iodine treated hylon starches exhibited increased order in the V-type polymorphism as evidenced by the intense peak at 20° 2θ and the strong reflection intensity at 7.5° 2θ and the extent of the change depended on the type of hylon starch. DSC results showed that the gelatinization enthalpy of CN and waxy corn starch (CW) remained unchanged after ANN. However, hylon starches showed a significant increase in enthalpy with more distinct endotherms after ANN. It can be concluded that tie chains influence the organization of crystalline lamellae in amylose extender mutant starches.
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http://dx.doi.org/10.1002/bip.22468DOI Listing
August 2014

Composition of clusters and building blocks in amylopectins from maize mutants deficient in starch synthase III.

J Agric Food Chem 2013 Dec 6;61(50):12345-55. Epub 2013 Dec 6.

School of Chemical Sciences, University of Auckland , Private Bag 92019, Auckland 1142, New Zealand.

Branches in amylopectin are distributed along the backbone. Units of the branches are building blocks (smaller) and clusters (larger) based on the distance between branches. In this study, composition of clusters and building blocks of amylopectins from dull1 maize mutants deficient in starch synthase III (SSIII) with a common genetic background (W64A) were characterized and compared with the wild type. Clusters were produced from amylopectins by partial hydrolysis using α-amylase of Bacillus amyloliquefaciens and were subsequently treated with phosphorylase a and β-amylase to produce φ,β-limit dextrins. Clusters were further extensively hydrolyzed with the α-amylase to produce building blocks. Structures of clusters and building blocks were analyzed by diverse chromatographic techniques. The results showed that the dull1 mutation resulted in larger clusters with more singly branched building blocks. The average cluster contained ~5.4 blocks in dull1 mutants and ~4.2 blocks in the wild type. The results are compared with previous results from SSIII-deficient amo1 barley and suggest fundamental differences in the cluster structures.
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http://dx.doi.org/10.1021/jf403865nDOI Listing
December 2013

Structural and physical properties of granule stabilized starch obtained by branching enzyme treatment.

Carbohydr Polym 2013 Nov 8;98(2):1490-6. Epub 2013 Aug 8.

Department of Plant and Environmental Sciences, University of Copenhagen, Denmark; KMC, Brande, Denmark.

Chemical cross-linking of starch is an important modification used in the industry for granule stabilization. It has been demonstrated that treatment with branching enzyme (BE) can stabilize the granular structure of starch and such treatment thereby provides a potential clean alternative for chemical modification. This study demonstrates that such BE-assisted stabilization of starch granules led to partial protection from BE catalysis of both amylose (AM) and amylopectin (AP) in their native state as assessed by triiodide complexation, X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The granule stabilizing effects were inversely linked to hydration of the starch granules, which was increased by the presence of starch-phosphate esters and suppressed by extreme substrate concentration. The data support that the granule stabilization is due to the intermolecular transglycosylation occurring in the initial stages of the reaction prior to AM-AP phase separation. The enzyme activity needed to obtain granule stabilization was therefore dependent on the hydration capability of the starch used.
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http://dx.doi.org/10.1016/j.carbpol.2013.07.071DOI Listing
November 2013

Impact on molecular organization of amylopectin in starch granules upon annealing.

Carbohydr Polym 2013 Oct 12;98(1):1045-55. Epub 2013 Jul 12.

Food Science Department, University of Guelph, Canada.

This study investigated the influence of the internal structure of amylopectin on annealing (3h, 24h) of starches from four different types of amylopectin (Bertoft, Koch, & Aman, 2012; Bertoft, Piyachomkwan, Chatakanonda, & Sriroth, 2008). Regardless of the starch source and incubation time, annealing significantly increased the onset gelatinization temperature (To) and narrowed and deepened the amylopectin endotherm. However, the extent of the change in the melting temperature (Tm) and the enthalpy of gelatinization (ΔH) differed among the types. In terms of the To and Tm, starches from type 1 (oat, rye, barley, and waxy barley) showed the most significant response to annealing. The Tm of starches belonging to type 2 (waxy maize, rice, waxy rice, and sago) remained unchanged after 3h of annealing. Type 1 and type 2 starches with the lowest gelatinization temperatures showed the greatest increase in melting temperature after annealing. However, type 3 (tapioca, mung bean, and arrowroot) and type 4 (potato, waxy potato, canna, and yam) starches were not in line with these observations. Instead, starches from type 3 and type 4 showed a pronounced increase in the ΔH. The inter-block chain length (IB-CL) (distance between tightly branched units within a cluster) correlated positively (r=0.93, p<0.01) with the change in enthalpy after 24h of annealing. These data indicate that a short IB-CL affects the optimum registration of double helices within the crystalline lamellae. The relationship between the gelatinization parameters before and after annealing suggests that type 1 and 2 starches might possess a high number of unpacked double helices (type 1>type 2) compared to other types. Longer IB-CLs, which facilitate the parallel packing of splayed double helices, and the lengthening of double helices likely increased the ΔH in type 3 and type 4 starches. It is concluded that annealing can be used as a probe for visualizing the organization of glucan chains (alignment of double helices/degree of perfection) within crystalline lamellae.
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http://dx.doi.org/10.1016/j.carbpol.2013.07.006DOI Listing
October 2013

Iodine binding to explore the conformational state of internal chains of amylopectin.

Carbohydr Polym 2013 Oct 29;98(1):778-83. Epub 2013 Jun 29.

Whistler Center for Carbohydrate Research and Department of Food Science, Purdue University, 745, Agriculture Mall Drive, West Lafayette, IN 47907, USA.

Previous studies have found that the proportion of long chains of amylopectin correlates to its functional and nutritional properties. As a possible explanation of this correlation, the iodine binding property of amylopectin internal chains was investigated as an indirect evidence of their ability to form helices for intra- or inter-molecular interactions. Waxy and amylose-extender waxy corn starches were hydrolyzed by β-amylase for varying periods of time to incrementally remove the external chains, and the absorbance and the wavelength of maximum absorbance of iodine binding were examined. Experimental results suggest that iodine can bind with both external and internal chains; a significant amount of absorption comes from the latter, as stepwise removal of external chains only somewhat reduced absorption. Internal amylopectin chains, thus, were concluded to likely pre-exist in helical form, as opposed to a conformational change into helices facilitating iodine binding in the absence of external chains. Such internal chain helical structures possibly drive intermolecular interactions that would explain why amylopectin with high proportion of internal chains form harder gels, create pastes less prone to shear breakdown, and are more slowly digesting.
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http://dx.doi.org/10.1016/j.carbpol.2013.06.050DOI Listing
October 2013

Molecular structure of starches from maize mutants deficient in starch synthase III.

J Agric Food Chem 2013 Oct 4;61(41):9899-907. Epub 2013 Oct 4.

School of Chemical Sciences, University of Auckland , Private Bag 92019, Auckland 1142, New Zealand.

Molecular structures of starches from dull1 maize mutants deficient in starch synthase III (SSIII) with a common genetic background (W64A) were characterized and compared with the wild type. Amylose content with altered structure was higher in the nonwaxy mutants (25.4-30.2%) compared to the wild type maize (21.5%) as revealed by gel permeation chromatography. Superlong chains of the amylopectin component were found in all nonwaxy samples. Unit chain length distribution of amylopectins and their φ,β-limit dextrins (reflecting amylopectin internal structure) from dull1 mutants were also characterized by anion-exchange chromatography after debranching. Deficiency of SSIII led to an increased amount of short chains (DP ≤36 in amylopectin), whereas the content of long chains decreased from 8.4% to between 3.1 and 3.7% in both amylopectin and φ,β-limit dextrins. Moreover, both the external and internal chain lengths decreased, suggesting a difference in their cluster structures. Whereas the molar ratio of A:B-chains was similar in all samples (1.1-1.2), some ratios of chain categories were affected by the absence of SSIII, notably the ratio of "fingerprint" A-chains to "clustered" A-chains. This study highlighted the relationship between SSIII and the internal molecular structure of maize starch.
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http://dx.doi.org/10.1021/jf402090fDOI Listing
October 2013

Characterization of internal structure of maize starch without amylose and amylopectin separation.

Carbohydr Polym 2013 Sep 9;97(2):475-81. Epub 2013 May 9.

Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada.

Normal maize starch was used to characterize the internal structure of starch without separating amylose and amylopectin, and the result was compared with amylose-free waxy maize starch. The clusters in the whole starch were produced by partial hydrolysis using α-amylase of Bacillus amyloliquefaciens, and were subsequently treated with β-amylase to remove the linear amylose and to produce β-limit dextrins of clusters from amylopectin. The clusters were further hydrolyzed extensively with α-amylase to produce building blocks. The compositions of clusters in the form of β-limit dextrins and their building blocks were analyzed by gel-permeation chromatography and high-performance anion-exchange chromatography. The results showed that the structures of clusters and building blocks from whole starch of normal and waxy starches were similar. By number, each cluster contained 9-10 chains and 5-6 building blocks. The inter-block chain length in the clusters of whole starch was around six glucosyl residues. This study explored an alternate procedure to characterize the composition of branches in whole starch without separating amylose and amylopectin components.
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http://dx.doi.org/10.1016/j.carbpol.2013.04.092DOI Listing
September 2013

Influence of amylopectin structure and degree of phosphorylation on the molecular composition of potato starch lintners.

Biopolymers 2014 Mar;101(3):257-71

Department of Biosciences, Åbo Akademi University, FI-20520, Turku, Finland.

Morphology, molecular structure, and thermal properties of potato starch granules with low to high phosphate content were studied as an effect of mild acid hydrolysis (lintnerization) to 80% solubilization at two temperatures (25 and 45°C). Light microscopy showed that the lintners contained apparently intact granules, which disintegrated into fragments upon dehydration. Transmission electron microscopy of rehydrated lintners revealed lacy networks of smaller subunits. The molecular composition of the lintners suggested that they largely consisted of remnants of crystalline lamellae. When lintnerization was performed at 45°C, the lintners contained more of branched dextrins compared to 25°C in both low and intermediate phosphate-containing samples. High-phosphate-containing starch was, however, unaffected by temperature and this was probably due to an altered amylopectin structure rather than the phosphate content. After lintnerization, the melting endotherms were broad with decreased onset and increased peak melting temperatures. The relative crystallinity was lower in lintners prepared at 45°C. A hypothesis that combines the kinetics of lintnerization with the molecular and thermal characteristics of the lintners is presented.
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http://dx.doi.org/10.1002/bip.22344DOI Listing
March 2014

On the importance of organization of glucan chains on thermal properties of starch.

Carbohydr Polym 2013 Feb 23;92(2):1653-9. Epub 2012 Nov 23.

116, Food Science Department, University of Guelph, Guelph, ON N1G 2W1, Canada.

The relationship between the internal structure of amylopectin from diverse plants and thermal properties of the starch granules has been investigated. Correlations were found between structural parameters, such as number of building blocks in clusters, interblock chain length and length of external chains, and gelatinization parameters. Onset gelatinization temperature negatively correlated with number of building blocks (r=-0.952, p<0.01) and positively correlated with inter-block chain length (r=0.905, p<0.01). Enthalpy of gelatinization positively correlated with external chain length (r=0.854, p<0.01). These data showed that the internal structure is predictive of trends in thermal properties. A model is proposed based on the backbone concept of amylopectin structure that explains how the organization of chains in the semicrystalline lamellae of starch granules relates to the thermal properties.
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http://dx.doi.org/10.1016/j.carbpol.2012.11.003DOI Listing
February 2013

On the interconnection of clusters and building blocks in barley amylopectin.

Int J Biol Macromol 2013 Apr 24;55:75-82. Epub 2012 Dec 24.

Department of Food Science, Swedish University of Agricultural Sciences, PO Box 7051, S-750 07 Uppsala, Sweden.

Amylopectin is a highly branched starch component built up of a large number of clustered α-D-glucose chains. A single C-chain possesses the reducing end and carries the rest of the macromolecule. The aim of this study was to investigate the interconnection of clusters and domains (groups of clusters) in barley amylopectin by isolation of the units with α-amylolysis and subsequent labelling of the C-chain in the φ,β-limit dextrins of these structural units with the fluorescent compound 2-aminopyridine. Because these C-chains were formed by α-amylolysis of B-chains in amylopectin, they were designated bc-chains to be distinguished from C-chains in amylopectin. Four barley samples were selected for the study, of which two had the amo1 genetic background. Longer bc-chains were found in domains suggesting their role in cluster interconnection. The average chain length of bc-chains was longer than the average chain length of B-chains and the size-distribution of the bc-chains was unimodal implying that the bc-chains comprise a unique category of chains. Extensive α-amylolysis of labelled amylopectin and clusters revealed the distribution of branched building blocks situated at the reducing end of these molecules. Any type of size group of building blocks can be situated at the reducing end, because the size-distribution of these blocks was similar to the distribution of all building blocks present in the sample. This suggested certain randomness in the distribution of the types of building blocks within the amylopectin macromolecule.
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http://dx.doi.org/10.1016/j.ijbiomac.2012.12.032DOI Listing
April 2013

Effect of amylose deposition on potato tuber starch granule architecture and dynamics as studied by lintnerization.

Biopolymers 2013 Jan;99(1):73-83

Department of Biosciences, Åbo Akademi University, FI-20520 Turku, Finland.

The effect of amylose deposition on the amylopectin crystalline lamellar organization in potato starch granules was studied by mild acid, so-called lintnerization, of potato tuber starch transgenically engineered to deposit different levels of amylose. The starch granules were subjected to lintnerization at different temperatures (25, 35, and 45°C) and to two levels of solubilization, ∼ 45 and 80%. The rate of the lintnerization increased with temperature but was suppressed by amylose. The molecular size of the lintner dextrins increased with temperature, but this effect was suppressed by the presence of amylose. At high temperatures and low-amylose content, the degree of branches was high with the concomitant increase in size in the dextrins. A portion of the branches was resistant to debranching enzymes possibly due to specific structural formations. The effects of temperature suggested a unique granular architecture of potato starch, and a model showing the dependence of temperature on the dynamic arrangement of amylopectin and amylose in the crystalline and amorphous lamellae for the potato starch is suggested.
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http://dx.doi.org/10.1002/bip.22145DOI Listing
January 2013