Molecular Weight Of Amylopectin Research Articles

Molecular weight, chain profile of rice amylopectin and starch pasting properties

Differences in fine structure, average molecular size of amylopectin (AP) as well as clarity of the AP solution from indica waxy rice and high amylose (HAM) rice were examined. Despite similar amylose content (AM), rice starches displayed different pasting properties. Waxy APs had higher values of both number–average and weight–average molecular weight (Mn¯ and Mw¯) but lower values of intrinsic viscosity [η], compared to HAM APs. HAM APs had higher values of average chain length (CL¯), average external chain length (ECL¯), and a proportion of DP≥37. Statistical correlations of mol proportions of debranched AP, branching parameters, and molecular weight of AP were calculated. The study showed that starch pasting properties and clarity of AP solutions were influenced by molecular weight and branching characteristics of AP.

Physicochemical Properties of Starch from a Cereal-Based Fermented Food (Tarhana)

Tarhana is a traditional fermented food product in Turkey. There is limited research on starch characteristics of tarhana. In this study, starch properties of various home-made tarhana samples have been investigated. Starch content ranged from 59.64 to 69.95 and there were significant (P<0.05) differences in starch damage (3.78-10.84%). The starch pasting and gelatinization of the tarhana samples also showed significant (P<0.05) differences. Estimated glycemic indexes ranged from 86.16 to 102.54 and are all considered high glycemic index. Amylose content of the tarhana also showed significant (P<0.05) variation (20.70-29.03%). There were significant (P<0.05) differences in the molecular mass of the tarhana starch. The molecular mass of the high molecular weight amylopectin ranged from 2-15 million daltons and the amylose ranged from 300 thousand to 2.4 million daltons. Overall, there were significant (P<0.05) differences in chemical composition and starch characteristics of tarhana samples.

Composition and properties of starches from Virginia‐grown kabuli chickpea (Cicer arietinum L.) cultivars

SummaryComposition and properties of seeds and starches from five Virginia‐grown kabuli chickpea cultivars were investigated. The seeds had the average weight of 4.48 g per 10 g and volume of 641.2 mm3, and were rich in carbohydrate with starch as a principal constituent (59.2–70.9%). Resistant starch accounted for 7.7–10.4% of the total starch content. The composition and properties of the starches among the five cultivars were significantly different (P ≤ 0.05). All starches had a C‐type crystalline structure. The degree of crystallinity ranged from 21.1% to 27.4%, gelatinisation temperature from 7.97 to 11.2 °C and gelatinisation enthalpies from 2.18 to 3.76 J g−1, and water absorption capacities from 90.7% to 117.5%. Different shapes and granule sizes were observed. Molecular weight of amylopectin was in the range of 6.35 × 108–11.6 × 108 Da. Cultivar ‘HB‐14’ was superior to the other cultivars, when combining larger seed size, higher resistant starch level and better properties.

Comparison of the Gelatinization Behavior of Organic and Conventional Spelt Starches Assessed by Thermal and Rheological Analyses

The objective of this study was to compare gelatinization properties and molecular composition of starches extracted from locally grown organic and conventional spelt using thermal, rheological, and SEC analyses, along with Concanavalin A method. Organic and conventional spelt was planted in six replicated plots, and the extracted starch was analyzed for their gelatinization properties. DSC showed that the gelatinization temperature ranged from 56.7 to 68.8 °C with an average peak of 62.4 °C, with no evidence for statistical difference in gelatinization properties between treatments. Rheological behavior variation among samples was more pronounced than that between the two growing conditions. The amylose content ranged from 23.0% to 29.8%. There was no significant difference in the molecular weight of amylose and amylopectin irrespective of the plot locations, although a significant difference was found between the amylopectin molecular weight of organic and conventional spelt starches when analyzed collectively. The organic spelt starch studied may substitute the conventional starch when gelatinization behavior is considered.

Physicochemical, thermal, and rheological properties of acid-hydrolyzed sago (Metroxylon sagu) starch

The effects of acid hydrolysis on physicochemical and rheological properties of sago starch were investigated. Sago starch was hydrolyzed in hydrochloric acid at 50 °C for 6, 12, 18, and 24 h. The molecular weight distribution, physicochemical, thermal, and rheological properties of acid-hydrolyzed sago starch (AHS) were determined. After 24 h of hydrolysis, molecular weight of amylopectin and amylose were decreased to 3.57 × 105 and 6.5 × 104 g/mol, respectively. Differential scanning calorimetry studies showed that the gelatinization temperature and enthalpy of AHS increased with increasing degree of hydrolysis. Hydrolyzed sago starch containing low molecular weight fractions exhibited cold water solubility up to 100%. Setting temperature of AHS decreased with increasing hydrolysis time but amylose content and gel strength increased in the first 12 h of acid hydrolysis but decreased with extended hydrolysis time. Hydrolyzed sago starch in concentrations lower than 8 g starch per 100 g water was cold water soluble and could be used to modify properties of starch for specific applications such as yogurt and concentrated milk processing.

Amylopectin molecular structure and functional properties of starch from three Ugandan cassava varieties

Amylopectin molecular structure is a very important determinant of starch functional properties. The main purpose of this study was to determine the strength of the relationship between the amylopectin structure of starches from cassava varieties and their functional properties. TME14 had the highest (46.63%) proportion of A chains while Bamunanika had the lowest 42.27%. Bamunanika had the highest (23.33%) proportion of B3+ chains while TME14 had the lowest 19.66%. TME14 had the highest amylopectin molecular weight 2.74x108 g/mol while NASE10 had the lowest 2.42x108 g/mol. TME14 had a higher gelatinisation temperature 65.37°C compared to the other varieties. Bamunanika had the highest final viscosity 2477.66 mPa s while NASE10 had the highest set back viscosity (494.50 mPa s). TME14 had the highest pasting temperature 67.80°C while NASE10 had the lowest 65.23°C. There was a significant negative correlation between final viscosity and A chains (r = -0.64), pasting temperature and A chains (r = - 0.77), A, B1 chains and gelatinisation temperature of retrograded starches (r = - 0.82, r = - 0.87), respectively, gyration radius and onset temperature of gelatinisation for the retrograded starch (r = -0.56) and a significant positive correlation between B2 chains and pasting temperature (r = 0.94), amylopectin molecular weight and percentage retrogradation (r = 0.66). These findings revealed possible improvement through breeding for starch with desired qualities. Key words: Amylopectin structure, cassava varieties, functional properties.

Amylose content, molecular structure, physicochemical properties and in vitro digestibility of starches from different mung bean (Vigna radiata L.) cultivars

AbstractPhysicochemical and in vitro digestibility characteristics of starches isolated from six cultivars of mung bean (Vigna radiata L.) were studied. Significant differences (p &lt; 0.05) were observed between the cultivars with respect to amylose content (29.9–33.6%), relative crystallinity (29.0 to 31.7%), particle diameter (16.2–17.1 µm) and molecular weight of amylopectin (260–289 × 106 g/mol). The scanning electron micrographs revealed the presence of large oval to small round shape granules with average particle diameter of 16.2–17.1 µm. The X‐ray diffraction pattern was of the C‐type. The enthalpies of gelatinization and retrogradation were 8.9–10.3 and 4.6–6.3 J/g, respectively. The amounts of slowly digesting and resistant starch of mung bean followed the order: PBM‐1 &gt; SML‐32 &gt; ML‐613 &gt; SML‐134 &gt; ML‐267 &gt; ML‐5 and ML‐5 &gt; ML‐267 &gt; SML‐134 &gt; ML‐613 &gt; SML‐32 &gt; PBM‐1, respectively. The six starches exhibited significant (p &lt; 0.05) differences in their pasting parameters. Correlation analysis showed that amylose content, granule diameter and relative crystallinity values were important in determining thermal, pasting and in vitro digestibility of starches.

In vitro digestibility, structural and functional properties of starch from pigeon pea (Cajanus cajan) cultivars grown in India

Abstract Starches isolated from two pigeon pea cultivars (AL-15 and AL-201) were evaluated for their in vitro digestibility, structural and functional properties. Both the cultivars exhibited a characteristic C-type diffraction pattern with relative crystallinity values of 31.9% and 34.2%, for AL-15 and AL-201, respectively. The structural characterization obtained using high performance size exclusion column chromatography revealed that molecular weight of amylopectin and amylose was higher for AL-201 (396 and 3.92 × 106 g/mol, respectively) in comparison to AL-15 starch (354 and 3.31 × 106 g/mol, respectively). AL-201 exhibited higher values for transition temperatures, enthalpy of gelatinization, pasting temperature and percentage retrogradation in comparison to AL-15 starch. Slowly digestible starch, readily digestible starch and resistant starch contents of AL-15 and AL-201 cultivars were observed to be 31.0, 8.1 and 60.9% and 29.6, 5.2 and 65.2%, respectively. The hydrolysis index and RS values indicated that pigeon pea starches were highly resistant to digestion.

Structure and Physicochemical Properties of Starches from Sieve Fractions of Oat Flour Compared with Whole and Pin‐Milled Flour

ABSTRACTOne oat cultivar grown in Idaho (three field sites) was pin‐milled and separated by sieving to investigate whether starch from oat bran differs from the remainder of kernel. Ground oat particles were classified into three sieve fractions: 300–850 μm, 150–300 μm and &lt;150 μm). β‐Glucan content in sieve fractions was analyzed and starch was extracted from kernels without milling and from kernels of each sieve fraction. β‐Glucan contents of 300–850, 150–300, and &lt;150 μm sieve fractions were 4.2, 2.3, and 0.8%, respectively. Therefore, starch in bran (300–850 μm sieve fraction) and endosperm (&lt;150 μm sieve fraction) were separated. Starch isolated from entire kernels had significantly higher apparent and absolute amylose content than starch from the 300–850 μm sieve fraction. Starch from different sieve fractions was not significantly different in the apparent amylose, absolute amylose, amylopectin molecular weight, gyration radii, starch gelatinization, and amylose‐lipid complex thermal transition temperatures. Starch from the 150–300 μm sieve fraction had significantly lower peak, final, and setback viscosity compared with the starch isolated from the 300–850 μm and &lt;150 μm sieve fractions. Starch removed from the oat bran fraction during β‐glucan enrichment may have different applications compared with starch obtained from other kernel compartments. Because pin‐milling decreased apparent amylose content and shortened amylopectin branch chains, its potential to alter starch structure should be considered.

Starch‐graft‐(synthetic copolymer) latexes initiated with Ce4+ and stabilized by amylopectin

AbstractA method is presented for synthesizing surfactant‐free latexes comprising starch‐graft‐(vinyl polymer) starting with a suspension of amylopectin, either native or modified, then using cerium(IV) with either potassium persulfate or glucose to create grafting sites on the starch. Latex particles comprising polystyrene, poly(styrene‐co‐(n‐butyl acrylate)) and poly(vinyl acetate) grafted onto high molecular weight amylopectin were developed, with up to 80% of the starch effectively grafted to the particles. These latexes were colloidally stable against electrolyte (several months in 4 M NaCl). Reaction rates of Ce4+ with simple sugars and polysaccharides were investigated, as well as the gelation mechanism of the latex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4185–4192, 2007

Characterisation of oat bran products with and without supercritical carbon dioxide extraction

SummaryMorphology, starch structures and thermal and pasting properties of oat bran concentrate (OBC) and Nutrim‐OB (NOB), a jet‐cooked oat bran product, with or without supercritical carbon dioxide extraction (SCD) were studied. Oil composition was analysed. OBC had three thermal transitions, starch gelatinisation and two amylose–lipid complex transitions. NOB only had amorphous amylose–lipid transition. SCD significantly decreased gelatinisation temperatures of OBC. Pasting properties, showed NOB had significantly higher peak viscosity and breakdown, with significantly lower final viscosity, setback and pasting temperature compared with OBC. SCD increased peak viscosity for NOB and final viscosity for OBC. Thermogravimetric analysis showed NOB had higher water‐holding capacity (WHC) than OBC, while SCD decreased WHC. Amylopectin molecular weight was 3.4 × 108 for OBC and was significantly lower for NOB (1.4 × 108). Predominant fatty acids were oleic (41%), linoleic (38%) and palmitic (16%). Study showed NOB had different properties from OBC thereby expanding industrial applications.

Structures and physicochemical properties of starch from immature seeds of soybean varieties ( Glycine max (L.) Merr.) exhibiting normal, low-linolenic or low-saturated fatty acid oil profiles at maturity

Soybean varieties bred for normal (NM), low-linolenic (LL) or low-saturate (LS) fatty acid composition were collected 20 d prior to harvest. Seed starch structure and functional properties were studied. Soybean starch had small granules (0.5–4.5 μm diameter), and C B-type crystallinity. LL and LS soybean starch had significantly lower absolute amylose than NM soybean. Weight-average amylopectin molecular weight, measured by HPSEC, ranged from 5.91 × 10 8 g/mol for LL to 8.92 × 10 8 g/mol for NM. Soybean amylopectin had short average branch chain-length (DP 19.9–21.9) and LS amylopectin had significantly larger percentage of DP 6–12 than LL and NM soybeans. No significant differences among soybean varieties were observed for starch thermal and pasting properties, with onset gelatinization temperature (51.0–51.8 °C) and peak viscosity (79–100 RVU, 8% starch suspension). Further research is needed to understand if amylose content or amylopectin fine structure in developing soybean seeds relates to fatty acid composition of soybean oil at maturity.

Changes in structure and properties of starch of four botanical sources dispersed in the ionic liquid, 1-butyl-3-methylimidazolium chloride

Ionic liquid (IL) has gained industry attention, especially in green chemistry. Researchers have utilized IL for dispersing cellulose, but no report using IL for other polysaccharides. In this study, corn, rice, wheat and potato starches were dispersed in hot water (DIHW) or IL, 1-butyl-3-methylimidazolium chloride and morphology, amylopectin molecular weight (APMw) and thermal properties (TP) were analyzed. For starch DIHW, corn and potato had gelatinized aggregates, whereas rice and wheat had granular clumps. Starch heat-dispersed in IL (HDIIL) had clumps composed of < 1 μm diameter particles. Starch DIHW had little effect on APMw. Cereal starches had APMw greatly reduced by HDIIL (4-6 peaks observed). Potato amylopectin was degraded less by IL (two peaks) probably because charged phosphomonoesters covalently bonded to imidazolium rings or repelled IL chloride ions and large granule size impeded IL penetration, reducing reaction efficiency. TP showed potato starch incompletely gelatinized by HDIIL.

Lipid oxidation and amylopectin molecular weight changes occurring during storage of extruded starch samples

Using thermomechanical extrusion, waxy maize starch and 4% (w/w) lipid were formed into strips. The lipids used were free fatty acids (mostly linoleic) and antioxidant stripped sunflower oil (either previously oxidised or fresh, with and without copper ions). By altering their water content it was possible to store, at the same temperature, sample strips in the glassy and rubbery states. Lipid oxidation was monitored by determining hexanal in the headspace above all stored samples. The molecular weights of the amylopectin in the samples of extruded products (dissolved in dimethylsulfoxide, precipitated and redissolved using a pressure cell) were determined by asymmetric flow-field-flow fractionation, analytical ultracentrifugation and light scattering. The initial rate of hexanal generation was higher in samples stored in the glassy state compared with those in the rubbery state. Waxy maize and extruded samples, at the start of the storage period and after 42 days, were used to establish the molecular weight of the amylopectin. A significant fall (a decrease of ∼40%) in molecular weight was found on storage of samples containing sunflower oil and copper ions and those containing free fatty acids, irrespective of the method used for molecular weight determination.

Maltogenic amylase has a non-typical impact on the molecular and rheological properties of starch

The effects of different amylases on the rapid visco analysis rheological properties of starch were studied and the accompanying changes in the starch molecular properties were analyzed with high performance size exclusion chromatography. Different amylases affect the rheological properties of starch slurries and the molecular weight of the starch molecules to a degree depending on their mode of action and properties such as thermostability. Endo-amylases generally reduced the viscosity and the amylose and amylopectin molecular weight (MW) whereas an exo-amylase had little effect. In contrast, a maltogenic amylase from Bacillus stearothermophilus had a markedly different effect on the rheological and molecular properties of starch. Remarkably, the cold paste viscosity (CPV) exceeded that of the control slurry even at high enzyme dosages. Furthermore, this enzyme specifically affected the amylose population, which gained in monodispersity while largely maintaining its MW. In addition, an interesting relationship between CPV and amylose peak degree of polymerisation was found. These results may contribute to a better understanding of amylase functionality in bread making.

Recrystallisation behaviour of native and processed waxy maize starch in relation to the molecular characteristics

Molecular characteristics were determined for native waxy maize starch and maize starch modified in different way (by mechanical treatment or/and acid hydrolysis). Recrystallisation behaviour was studied. Methods used in this study were MALLS, HPAEC-PAD, NMR, DSC, SEM, light microscopy. Five starch materials were subjected to storage under the same conditions in the presence of water (70 w/w%). Molecular weight, radius of gyration, initial crystallinity, and degree of polymerisation, degree of branching, chain length distribution profiles, were related to nucleation rate during the recrystallisation process, rate of recrystallisation, thermal stability and amount of obtained crystallinity. This allowed the following connections between the molecular characteristics and kinetic of recrystallisation to be proposed: Amylopectin molecular weight appeared to affect the number of starch crystallites formed and amount of crystallinity but not the stability of the rebuilt crystallites. The stability of rebuilt crystallites can be controlled by degree of polymerization, degree of branching and unit chain length distribution, characteristics which were similar for the starches. A mixture of two starches, with and without crystalline structure in initial state but with molecular weight in same range, were stored and scanned in order to understand possible cocrystallisation effects.

The molecular deposition of transgenically modified starch in the starch granule as imaged by functional microscopy

The molecular deposition of starch extracted from normal plants and transgenically modified potato lines was investigated using a combination of light microscopy, environmental scanning electron microscopy (ESEM) and confocal laser scanning microscopy (CLSM). ESEM permitted the detailed (10 nm) topographical analysis of starch granules in their hydrated state. CLSM could reveal internal molar deposition patterns of starch molecules. This was achieved by equimolar labelling of each starch molecule using the aminofluorophore 8-amino-1,3,6-pyrenetrisulfonic acid (APTS). Starch extracted from tubers with low amylose contents (suppressed granule bound starch synthase, GBSS) showed very little APTS fluorescence and starch granules with low molecular weight amylopectin and/or high amylose contents showed high fluorescence. Growth ring structures were sharper in granules with normal or high amylose contents. High amylose granules showed a relatively even distribution in fluorescence while normal and low amylose granules had an intense fluorescence in the hilum indicating a high concentration of amylose in the centre of the granule. Antisense of the starch phosphorylating enzyme (GWD) resulted in low molecular weight amylopectin and small fissures in the granules. Starch granules with suppressed starch branching enzyme (SBE) had severe cracks and rough surfaces. Relationships between starch molecular structure, nano-scale crystalline arrangements and topographical–morphological features were estimated and discussed.

Extrusion of Cross‐Linked Hydroxypropylated Corn Starches II. Morphological and Molecular Characterization

ABSTRACTA series of cross‐linked hydroxypropylated corn starches were extruded with a Leistritz micro‐18 co‐rotating extruder. Extrusion process variables including moisture (30, 35, and 40%), barrel temperature (60, 80, and 100°C), and screw design (low, medium, and high shear) were investigated. Scanning electron microscopy (SEM) of extruded starches showed a gel phase with distorted granules and granule fragments after extrusion at 60°C. After extrusion at 100°C only a gel phase was observed with no granular structures remaining. High performance size exclusion chromatography (HPSEC) equipped with multiangle laser light‐scattering (MALLS) and refractive index (RI) detectors showed extruded starches degraded to different extents, depending on extrusion conditions. The average molecular weight of the amylopectin of unextruded native corn starch was 7.7 × 108. Extrusion at 30% moisture, 100°C, and high shear reduced the molecular weight of amylopectin to 1.0 × 108. Hydroxypropylated normal corn starch extruded at identical conditions showed greater decreases in amylopectin molecular weight. With the addition of cross‐linking, the amylopectin fractions of the extruded starches were less degraded than those of their native and hydroxypropylated corn starch counterparts. Similarly, increasing moisture content during extrusion lowered amylopectin degradation in the extruded starches. Increasing temperature during extrusion of cross‐linked hydroxypropylated starches at high moisture content (e.g., 40%) lowered amylopectin molecular weights of the extruded starches, whereas increasing extrusion temperature at low moisture content (30%) resulted in less degraded molecules. This difference was attributed to the higher glass transition temperatures of the cross‐linked starches.

Effect of Hot-water-soluble Components on the Rheological Properties of Rice Starch

The hot-water-soluble components of 2.5% indica (Taichung Sen 17, TCS17 and Kaohsiung Sen 7, KSS7) and japonica (Tainung 67, TNu67) rice starches were prepared by heating from 45 to 70, 80, and 90 °C, respectively and were analyzed by gel-permeation chromatography. Two major peaks (FI and FII) were detected on the chromatogram. The presence of the FI fraction showed that low molecular weight amylopectin and intermediate fraction were solubilized at 70- 80 °C. The size of the solubilized amylose molecules and the ratio of FI to FII increased as temperature rised. The effects of hot-water-soluble components on the rheological properties of rice starch were evaluated by dynamic rheometry. For clarifying the contributions to starch gelation from starch granules and hot-water-soluble components, suspensions of modified waxy rice starch (Taichung waxy 70, TCW70) with the addi-tion of 2% hot-water-soluble components were used as samples. The addition of hot-water-soluble components retarded the swelling of the starch granules and the gelation was dominated by starch granules dur-ing heating. However, the hot-water-soluble components increased the storage modulus (G ') and decreased tan δ of 10% modified waxy rice starch gel during cooling and aging at 25 °C for 3.5 h. The influence of the hot-water-soluble fractions prepared at high temperature on the rheological properties was more profound than that of the fractions prepared at low temperature. The increments of G ' by adding 80 °C fractions were: TCS17 > KSS7 ETNu67 during aging. However, the differences among the 90 °C fractions of the different varieties were: TCS17 EKSS7 > TNu67. Therefore, it is concluded that the fine structure of the hot-water-soluble components will affect the starch rheological properties, and hot-water-soluble components with high molecular weight promote the starch retrogradation more effectively than those with low molecular weight.

Effect of Hot-water-soluble Components on the Rheological Properties of Rice Starch

The hot-water-soluble components of 2.5% indica (Taichung Sen 17, TCS17 and Kaohsiung Sen 7, KSS7) and japonica (Tainung 67, TNu67) rice starches were prepared by heating from 45 to 70, 80, and 90 °C, respectively and were analyzed by gel-permeation chromatography. Two major peaks (FI and FII) were detected on the chromatogram. The presence of the FI fraction showed that low molecular weight amylopectin and intermediate fraction were solubilized at 70- 80 °C. The size of the solubilized amylose molecules and the ratio of FI to FII increased as temperature rised. The effects of hot-water-soluble components on the rheological properties of rice starch were evaluated by dynamic rheometry. For clarifying the contributions to starch gelation from starch granules and hot-water-soluble components, suspensions of modified waxy rice starch (Taichung waxy 70, TCW70) with the addi-tion of 2% hot-water-soluble components were used as samples. The addition of hot-water-soluble components retarded the swelling of the starch granules and the gelation was dominated by starch granules dur-ing heating. However, the hot-water-soluble components increased the storage modulus (G ') and decreased tan δ of 10% modified waxy rice starch gel during cooling and aging at 25 °C for 3.5 h. The influence of the hot-water-soluble fractions prepared at high temperature on the rheological properties was more profound than that of the fractions prepared at low temperature. The increments of G ' by adding 80 °C fractions were: TCS17 > KSS7 ETNu67 during aging. However, the differences among the 90 °C fractions of the different varieties were: TCS17 EKSS7 > TNu67. Therefore, it is concluded that the fine structure of the hot-water-soluble components will affect the starch rheological properties, and hot-water-soluble components with high molecular weight promote the starch retrogradation more effectively than those with low molecular weight.