High Molecular Weight Starch Research Articles

The high molecular weight and large particle size and high crystallinity of starch increase gelatinization temperature and retrogradation in glutinous rice

The gelatinization and retrogradation properties of glutinous rice starch are important factors that affect its quality. In this study, the thermal properties, viscosity properties and retrogradation of starch from 152 natural glutinous varieties were investigated, and further explored the effects of starch structure on gelatinization temperature (GT) and retrogradation. The results demonstrated a strong positive linear correlation between thermal properties and retrogradation of glutinous rice. The high molecular weight, high crystallinity and large particle size of starch have significant positive effects on the thermal properties and retrogradation of amylopectin. Varieties of glutinous rice with high molecular weight starch, large starch particle sizes, and high crystallinity exhibited high GT and retrogradation rates (R%). Additionally, there was a significantly negative correlation between the range of gelatinization temperature and gelatinization enthalpy in raw starch, while a larger temperature range in retrograded starch corresponded to greater gelatinization enthalpy. The recrystallization of retrograded starch exhibited higher crystal heterogeneity and a broader range of melting points compared to raw glutinous starch. These findings provide valuable insights for breeding glutinous rice varieties with desirable retrogradation traits, particularly those with low R%.

New insights into the glass transition of dried fruits and vegetables and the effect of pulsed electric field treatment

Pulsed Electric Field (PEF) pre-treatment has been recently studied to be applied to fresh apple, carrot, and potato tissue as novel food technology to improve the drying performances and the quality of final products. Although the modification induced by PEF and the related reactions have been studied as a function of many parameters and related to several quality aspects, no relationship has been investigated with glass transition temperature (Tg) modification of solid products. This study aims to evaluate the effect of PEF treatment on the Tg of different vegetable tissues. Obtained thermograms revealed the existence of two Tg (TgI, and TgII), the first one mainly dependent from the presence of small molecules, such as sugars, organic acids and small amount of amino acids, while high molecular weight starch, fibers and small amount of proteins are associated to higher temperature values of TgII. PEF treated samples of dried apple, carrot, and potato compared to the untreated ones showed a TgII shift at 0.22 aw to a lower temperature, from 45.12 to 43.37, from 45.15 to 31.04 and from 90.23 to 85.81 °C for apple, carrot and potato respectively. The TgII shift confirmed the mobility raise of the system promoted by PEF treatment, creating a less stable matrix.

Cytoreductive surgery with intraperitoneal chemotherapy in the management of peritoneal surface malignancy: a pharmacist's perspective

ObjectivesTo explore the use of intraperitoneal chemotherapy in conjunction with cytoreductive surgery for the treatment of peritoneal surface malignancy and highlight the challenges this provides for the hospital pharmacist.MethodsA literature...

Multidomain Carbohydrate-binding Proteins Involved in Bacteroides thetaiotaomicron Starch Metabolism

Human colonic bacteria are necessary for the digestion of many dietary polysaccharides. The intestinal symbiont Bacteroides thetaiotaomicron uses five outer membrane proteins to bind and degrade starch. Here, we report the x-ray crystallographic structures of SusE and SusF, two outer membrane proteins composed of tandem starch specific carbohydrate-binding modules (CBMs) with no enzymatic activity. Examination of the two CBMs in SusE and three CBMs in SusF reveals subtle differences in the way each binds starch and is reflected in their K(d) values for both high molecular weight starch and small maltooligosaccharides. Thus, each site seems to have a unique starch preference that may enable these proteins to interact with different regions of starch or its breakdown products. Proteins similar to SusE and SusF are encoded in many other polysaccharide utilization loci that are possessed by human gut bacteria in the phylum Bacteroidetes. Thus, these proteins are likely to play an important role in carbohydrate metabolism in these abundant symbiotic species. Understanding structural changes that diversify and adapt related proteins in the human gut microbial community will be critical to understanding the detailed mechanistic roles that they perform in the complex digestive ecosystem.

The Role of D-enzyme in Starch Metabolism in Plants

D-enzyme (EC 2.4.1.25) is believed to be involved in starch metabolism, but the function in vivo is not known. In order to investigate the role of D-enzyme, several approaches have been undertaken. A biochemical analysis of the purified potato D-enzyme suggested that high molecular weight starch (amylose and amylopectin) can serve as donor and acceptor, and very long α-1, 4-glucans or even highly branched glucans can be transferred by the enzyme. Transgenic potato plants with dramatically reduced D-enzyme activity were obtained by introducing sense and antisense D-enzyme cDNA sequences with the appropriate promoter sequence. The tubers from these plants sprouted later and the growth of sprouts was slower than the wild type. However, no significant difference was found in starch produced in tubers, either in its quantity or quality. From these results, the possible role of Denzyme in starch metabolism is discussed.

Flocculation of calcite dispersions induced by the adsorption of highly cationic starch

The interactions between highly cationic starch and likewise cationic calcite were investigated by determining the adsorption isotherms and the flocculation of the calcite dispersions at different concentrations of starch. Starch of varying degree of substitution (DS), 0.2, 0.35, and 0.5, and molecular weight (MW), ∼3800 and ∼2×10 6 g mol −1 , were used. The experiments were in addition made at three different temperatures; 25, 35, and 45 °C. It was found that the interactions in most cases were of fairly low character. Consequently, the entropy and low solubility of the starch are expected to be the dominant driving forces for adsorption. The cationic character of both the untreated calcite and the starch generate an electrostatic repulsion that counteracts a possible adsorption. There is also repulsion between the cationic substituents in the starch, which among others factors controls the solubility of the starch in the aqueous phase. The repulsion can be affected by adding electrolytes. NaCl was used for this purpose in this investigation. As a result of the changes in the electrostatic repulsions the adsorbed amount of starch onto calcite did also change. The adsorption did increase with increasing NaCl concentrations, as did the degree of flocculation. The high MW starches did in all the conditions examined adsorb to a higher degree than did the low molecular ones. Increasing the temperature from 25 to 45 °C causes changes in the adsorption and flocculation behavior of the dispersions, especially in systems where starch with DS of 0.2 is present. The starches of higher charge are less affected by the temperature due to stronger internal repulsion. The low MW starches did not flocculate the calcite dispersions, while the starches of high MW initially flocculated the dispersions and restabilized them at higher concentrations. The high MW starch with DS 0.2 induced the strongest flocculation.

The structure and expression of the wheat starch synthase III gene. Motifs in the expressed gene define the lineage of the starch synthase III gene family.

The endosperm of hexaploid wheat (Triticum aestivum [L.]) was shown to contain a high molecular weight starch synthase (SS) analogous to the product of the maize du1 gene, starch synthase III (SSIII; DU1). cDNA and genomic DNA sequences encoding wheat SSIII were isolated and characterized. The wheat SSIII cDNA is 5,346 bp long and contains an open reading frame that encodes a 1,628-amino acid polypeptide. A putative N-terminal transit peptide, a 436-amino acid C-terminal catalytic domain, and a central 470-amino acid SSIII-specific domain containing three regions of repeated amino acid similarity were identified in the wheat gene. A fourth region between the transit peptide and the SSIII-specific domain contains repeat motifs that are variable with respect to motif sequence and repeat number between wheat and maize. In dicots, this N-terminal region does not contain repeat motifs and is truncated. The gene encoding wheat SSIII, designated ss3, consists of 16 exons extending over 10 kb, and is located on wheat chromosome I. Expression of ss3 mRNA in wheat was detected in leaves, pre-anthesis florets, and from very early to middle stage of endosperm development. The entire N-terminal variable repeat region and the majority of the SSIII-specific domain are encoded on a single 2,703-bp exon. A gene encoding a class III SS from the Arabidopsis genome sequencing project shows a strongly conserved exon structure to the wheat ss3 gene, with the exception of the N-terminal region. The evolutionary relationships of the genes encoding monocot and dicot class III SSs are discussed.

New methods to determine the extent of reaction of epichlorohydrin with maltodextrins

The reaction of epichlorohydrin with maltodextrins has been studied using novel methods for determining free glycerol and glycerol monoethers. Glycerol is determined by enzymatic analysis and glycerol monoethers by a modified oxidative method involving the HPLC separation and the determination of formaldehyde as the 2,4 dinitrophenylhydrazone derivative. Chloride is determined by a standard gravimetric assay involving silver precipitation. These methods permit the deduction of the overall yield of grafting and the degree of cross-linking in the crude reaction medium with no need for further purification thus allowing the study of the reaction of epichlorohydrin with polysaccharides other than high molecular weight starch or dextrans. Other reaction intermediates such as chloropropanediol and glycidol can also be concluded to be produced, based on the kinetics of the hydrolysis reaction.

Effects of pentafraction and hetastarch plasma expansion on lung and soft tissue transvascular fluid filtration

Hetastarch and pentafraction are high molecular weight starch solutions designed to augment plasma oncotic pressure. Although clinical utilization of hetastarch has been limited by reported coagulation abnormalities, pentafraction is a newer derivative that appears to have few adverse hemostatic effects. We examined the ability of pentafraction to modulate lung and soft tissue transvascular fluid filtration under hypoproteinemic conditions compared with hetastarch and Ringer's lactate (LR). Awake, protein-depleted sheep (n = 19) were prepared with lung and soft tissue lymph fistulas, and comparable infusions of 5% pentafraction (n = 6), 6% hetastarch (n = 6), or LR (n = 7) were administered. Plasma and lymph samples were collected during 24-hour period to determine changes in protein concentrations, plasma-to-lymph oncotic gradients, and lung (QL) and soft tissue (QS) lymph flows. QL and QS rose nearly twofold after protein depletion alone. LR infusion increased QL and QS to 8.7 +/- 1.7 and 3.1 +/- 0.6 times normoproteinemic baseline, respectively (p < 0.05). In contrast, hetastarch and pentafraction infusion limited the increase in QL to 4.2 +/- 1.1 and 4.0 +/- 0.8 times normoproteinemic baseline, respectively (p < 0.05 versus LR) and did not significantly increase QS. Hetastarch and pentafraction infusions increase plasma oncotic pressure by nearly 6 mm Hg, which significantly widened the plasma-to-lymph oncotic pressure gradients above preinfusion baseline by 4.7 +/- 0.7 and 3.4 +/- 0.4 mm Hg in lung and 4.6 +/- 0.7 and 3.2 +/- 0.4 mm Hg in soft tissue, respectively (p < 0.05). Both hetastarch and pentafraction limit transvascular fluid filtration under hypoproteinemic conditions by augmenting plasma oncotic pressure and the plasma-to-lymph oncotic pressure gradient. Because of fewer adverse hemostatic effects pentafraction may be an improvement over current therapies in critical care fluid management.

Composition and Structure of Starch from Taproots of Contrasting Genotypes of Medicago sativa L.

The objective of this study was to examine the composition and branch chain lengths of alfalfa (Medicago sativa L.) taproot starch during starch utilization and reaccumulation in response to defoliation. Genotypes were propagated vegetatively and well-established plants were sampled at defoliation and at weekly intervals thereafter. Starch granules from root tissues were dispersed in dimethyl sulfoxide and starch components separated using gel permeation chromatography. Root starches also were debranched enzymically, and branch chain lengths were examined. Results indicate that, irrespective of starch concentration, starch from taproots of the high starch genotype was composed of approximately 80% high molecular weight starch with I(2)-Kl absorbance characteristics similar to amylopectin. The remaining 20% of the starch was low molecular weight with I(2)-Kl absorbance characteristics similar to amylose. Starches of the low starch genotype contained approximately 85% high molecular weight polysaccharide at high root starch concentrations (>50 grams per kilogram). At low root starch concentrations (<10 grams per kilogram), starch from the low starch genotype had nearly equal proportions of low and high molecular weight polysaccharide. The I(2)-Kl absorbance properties of the low molecular weight starches from roots of the low starch genotype indicated that some branching may be present. The distribution of chain lengths from amylopectin did not change during starch degradation and reaccumulation for the high starch genotype. In the low starch genotype, the proportion of low molecular weight branches having a degree of polymerization between 1 and 30 was decreased at the very low starch concentrations observed on the 14th day of regrowth. Higher concentrations and/or quantities of starch in roots of the high starch genotype were not associated with greater rate of herbage regrowth, when compared to the low starch genotype.