Amylose Chain Length Research Articles

Characterisation of starch quality from barley varieties grown in South Africa

SummaryStarch is a major determinant of grain quality in cereals but the variation in starch structure has yet to be fully explored in its relation to processing impacts. This study examined the starch properties of South African grown malting barley varieties. Starch amounts, amylose content, covalently bound phosphate, starch granule size, starch molecular structure and pasting properties were examined. There was no difference in amylose content but there was variation in the amylose chain length distribution, despite all barleys showing similar granule parameters. The longer amylose chain length resulted in increased pasting temperature. There was no difference in phosphate content for these samples. Starch properties for the brewing industry are important in the context of the production of fermentable sugars. The variation in starch structure was not observed when measuring content and could impact on fermentation efficiency through variation in fermentable sugars hydrolysed from the starch.

Variation in maltose in sweet wort from barley malt and rice adjuncts with differences in amylose structure

Starch from malt and solid adjuncts provides the majority of fermentable sugars for fermentation. However, there is no current data on the variation in starch structure (particularly long chained amylose) and its impact on the final wort composition of fermentable sugars, specifically maltose. This is the first study to report variation in amylose structure from barley malt and rice used as an adjunct and how this impacts the production of maltose. We compared four commercial malts with two rice adjuncts mashes, in solid and liquid additions, with an all-malt mash used as a control. All combinations of malt and rice adjuncts were tested under two grist-to-liquor (G:L) ratios (1:3 and 1:4) in a 65°C ramped mash. After mashing, the wort original gravity and maltose concentration were measured. The commercial malts had different malt quality but very similar gelatinisation temperatures (~65°C). The malts varied in starch and amylose contents but had only minor variations in average amylose chain lengths. The two rice adjuncts also had similar average amylose chains lengths, but quite different amylose contents, and hence different gelatinisation temperatures. The results showed that liquid adjunct mashes had higher original gravity and maltose concentration for both G:L ratios. However, there was no consistent result in original gravity or maltose between G:L ratio or adjunct type, suggesting interactions between each malt and rice adjunct. Knowing amylose chain length could improve understanding of the potential maltose levels of the sweet wort prior to fermentation.

How amylose molecular fine structure of rice starch affects functional properties

Starch molecular fine structure can have significant effects on pasting and thermal properties of rice flour. This study investigates the mechanistic explanation of these effects, by obtaining data for rice flour with different starch fine structures. Starch structural parameters for both amylose and amylopectin were obtained using size-exclusion chromatography (SEC, a type of gel-permeation chromatography, GPC), and the data fitted with methodologies (one of which is new) based on the underlying biosynthetic processes. It is found that the setback viscosity of rice starch measured by the rapid viscosity analyzer (RVA) depends not only on amylose content but also on the amount of long amylose chains and the size of whole amylopectin molecules. Conversely, long amylose chains and large amylopectin molecules are found to be responsible for the lower peak and trough viscosities. Other results for the effects of amylopectin chains are consistent with the literature. Mechanistic explanations for all observations are put forward. The novel findings about the influence of the distribution of amylose chain lengths and whole amylopectin size, in addition to amylose content alone, can provide guidance for rice breeders and food scientists in the selection of rices with improved functional properties.

Identification of novel mutations in the rice starch branching enzyme I gene via TILLING by sequencing

Starch branching enzymes (SBEs) incorporate α-1,6-branched glucosidic linkages into α-1,4-glucan chains. Rice has three SBE isoforms (SBEI, SBEIIa, and SBEIIb), which differ in the amylose chain lengths that they transfer to amylopectin. SBEI mutants characterized to date have had little or no effect on starch structure or content. In this study, TILLING by sequencing was employed to identify SBEI mutations in a population of chemically induced mutants of the cultivar Nipponbare (n = 4096), resulting in the detection of 37 putative mutations. After removing mutations in introns or predicted to be synonymous, Sanger sequencing of M2 and M3 generation mutants confirmed six mutations and homozygous lines for four of these mutations were isolated. Only one line, NM-4936, exhibited a visible grain phenotype and produced sufficient M4 seeds for morphological and physicochemical analyses. In contrast to Nipponbare, NM-4936 grains are opaque due to rounded, loosely packed starch granules, and consequently, grain hardness was significantly reduced. NM-4936 grains exhibited significantly reduced width and thickness, which is reflected in reduced grain weight. Physicochemical analysis revealed significant differences in apparent amylose content (15 vs. 19%) and protein content (9.2 vs. 4.8%). Amylopectin chain-length distribution analysis indicated that the mutant has a slight but significant decrease in B3 chains [degree of polymerization (DP) ≥ 37, P < 0.01] and a very slight but significant increase in B1 chains (DP 13–24; P < 0.05). Identification of novel SBEI mutations will be useful in elucidating its function and may provide useful germplasm for breeding novel quality traits.

New insight into the determination of amylose content for maize starches through digital image analysis

Many efforts to characterize amylose content have been reported in the patent and research bibliography. All reported methods are dependent upon the different chain length of amylose and amylopectin, e.g., iodine binding capacity, molecular weight, and complexing ability with phospholipid. In the present study, we report a method of measuring amylose content by a polarized microscope (PM). This method involves shooting images of the chosen fields both under normal and polarized light with the same parameter settings. After processed by IPP-6, the statistic results (amylose content calculated by the IOD method, AmIOD) can be obtained quickly by two computer processing. The results showed a good correlation with the results (amylose content, α) of the ISO method, AmIOD=−1.433−0.146α+0.018α2, (R2 = 0.9703). The novel method has potentialities in various aspects, quick, inexpensive, and less affected by human factors.

Characterization of amylose nanoparticles prepared via nanoprecipitation: Influence of chain length distribution

The influence of chain length distribution of amylose on size and structure of the amylose nanoparticles (ANPs) prepared through nanoprecipitation was investigated. Amylose with different chain length distributions was obtained by β-amylase treating amylose paste for different times and measured by size exclusion chromatography (SEC) and fluorophore-assisted carbohydrate electrophoresis (FACE). ANPs prepared via precipitation were characterized by using dynamic light scattering (DLS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results showed that the β-amylase treatments led to decrease in chain length of amylose, and it was the most important factor affecting size of ANPs. When hydrolysis degree of amylose was 52.8%, mean size of ANPs decreased from 206.4 nm to 102.7 nm. All the ANPs displayed a V-type crystalline structure and the effect of amylose chain length on crystallinity of the precipitated ANPs was negligible in the investigated range.

Parameterizing amylose chain-length distributions for biosynthesis-structure-property relations.

Amylose, one of the components of starch, is a glucose polymer consisting largely of long, linear chains with a few long-chain branch points. The chain-length (molecular weight) distribution (CLD) of the component chains of amylose can provide information on amylose biosynthesis-structure-property relations, as has been done previously by fitting amylopectin CLDs to a model with physically meaningful parameters. Due to the presence of long chains, the CLD of amylose can currently best be obtained by size-exclusion chromatography, a technique that suffers from band-broadening effects which alter the observed distribution. The features of the multiple regions present in amylose chain-length distributions are also difficult to resolve, an issue that combines with band broadening to compound the difficulty of analysis and subsequent parameterization of the structural characteristics of amylose. A new method is presented to fit these distributions with biologically meaningful parameters in a way that accounts for band broadening. This is achieved by assuming that band broadening takes the form of a simple Gaussian over a relatively small region and that chain stoppage is a random process independent of the length of the substrate chain over the same region; these assumptions are relatively weak and expected to be frequently applicable. The method provides inbuilt consistency tests for its applicability to a given data set and, in cases where it is applicable, allows for the first nonempirical parameterization of amylose biosynthesis-structure-property relations from CLDs by using parameters directly linked to the activities of the enzymes responsible for chain growth and chain stoppage. Graphical abstract Model calculation illustrating the method described and showing the division between the three characteristic regions of a typical amylose chain-length distribution.

Amylose and amylopectin molecular fractions and chain length distribution of amylopectin in 12 varieties of Ghanaian sweet potato (Ipomoea batatas) flours

ABSTRACTSweet potato (Ipomoea batatas) is a commonly cultivated root crop in tropical and subtropical regions, including Ghana. Different varieties of sweet potato have been bred, in order to expand its utilisation within the food and industrial sector. This study analysed flours made from 12 recently developed Ghanaian sweet potato varieties in terms of their amylose and amylopectin molecular fractions and amylopectin chain length distribution. Starch content of the sweet potato flours ranged from 49 to 77 g/100 g dry matter, with 11 of the varieties containing above 60 g/100 g dry matter. An orange-fleshed variety, Apomuden, had the lowest amount of starch (48.9 g/100 g dry matter), while the cream-fleshed variety Histarch had the highest (77.3 g/100 g dry matter). The flours from the 12 sweet potato varieties had intermediate amounts of amylose, within the range 10–30 g/100 g dry matter, and showed typical molecular distribution according to size-exclusion chromatography (SEC). The fine structures of amylopectin, as revealed by anion-exchange chromatography, contained features common for starches of C-type X-ray pattern, but some structural differences were also observed.

Structure, physicochemical characteristics, and functional properties of starches isolated from yellow (Curcuma longa ) and black (Curcuma caesia ) turmeric rhizomes

Starch, a dominant component of the turmeric rhizomes, has been traditionally used as a food coloring and functional foods. The objective of this study is to investigate the structure and physicochemical characteristics and functional properties of the yellow (Curcuma longa) and black (Curcuma caesia) turmeric starches. The C. longa and C. caesia starches contained the triangular to oval shaped granules, which exhibited similar B-type crystalline structure and amylose content. However, the C. longa starch had higher chain length of amylose and more short branching chains of amylopectin resulting in lower gelatinization temperature but higher transition enthalpy as compared to the C. caesia starch. Both C. longa and C. caesia starches showed broad peak viscosities with no breakdown indicating greater stability of these starches under heat and shear conditions, in which the C. longa had significantly higher viscosity than did the C. caesia starch. The resistant starch contents of the C. longa and C. caesia starches were 24 and 20%, respectively. Moreover, the C. longa starch contained higher amounts of total phenolics and curcumin resulting in stronger antioxidant capacity as compared to the C. caesia starch. As a result, the C. longa and C. caesia starches could be used as a functional food in both food and pharmaceutical industries.

Impact of amylose content on starch physicochemical properties in transgenic sweet potato

The intrinsic relationship between amylose content and starch physicochemical properties was studied using six representative starch samples (amylose content 0–65%) produced from transgenic sweet potato (cultivar Xushu22). The transgenic lines (waxy and high-amylose) and wild-type (WT) sweet potatoes were analyzed for amylose content, particle size and chain length distribution, X-ray diffraction analysis, thermal characteristics, pasting and rheological property. Compared to the WT starch, the waxy and high-amylose starches showed larger average granule sizes and had fewer short chains and more medium and long chains. X-ray diffractogram analysis revealed that high-amylose starches show a type-B crystal form with a markedly decreased degree of crystallinity in contrast to the type-A crystal form of the WT and waxy starches. In the high-amylose sweet potato starches, the rise of setback value and the reduction of breakdown value led to the high shear resistance as indicated by the higher G′, G″, and tanδ from the oscillation test. ΔH was not found to be decreased with the reduction of crystallinity. The shear stress resistance of starch gel after gelatinization was also enhanced as amylose content increased. Principal component analysis also confirmed that the amylose content greatly influenced the starch structure and properties, e.g., storage modulus, setback value, and average chain length. Thus, our study not only shed light on how amylose content affects starch properties but also identified novel starches that are available for various applications.

Structural and physicochemical characteristics of starch from sugar cane and sweet sorghum stalks

The starch present in sugar cane and sorghum juice has been considered a problem to the sugar industry. The objective of this work was to study the structural and physicochemical characteristics of the starch present in sugar cane and sweet sorghum. Sugar cane and sweet sorghum starches presented small granules (maximum 5.9 and 7.9μm), A-type diffraction pattern, high degree of relative crystallinity (44.4 and 42.0%), and low amylose content (17.5 and 16.4%), respectively. Sugar cane starch presented more uniformity in granule shape and size, more homogeneity in amylose chain length, higher number of long lateral chains of amylopectin, and higher susceptibility to enzymatic digestion. Besides being in higher amount in the juice, sweet sorghum starch presented lower values for thermal properties of gelatinization, as well as higher swelling factor, which can cause more problems during processing. Additional studies are needed to evaluate the variety and maturity influence on these properties.

Effects of amylose chain length and heat treatment on amylose–glycerol monocaprate complex formation

Aqueous mixtures of amylose with different chain lengths (DP 23–849), which had been enzymatically synthesized or isolated from potato and maize starches, and glycerol monocaprate (GMC, 5:1 weight ratio) were analyzed by using a differential scanning calorimeter (DSC). The mixtures were thermally treated (first DSC scan: 20–140°C, 5°C/min and prolonged heat treatment: 100°C for 24h) and its effect on the amylose–GMC complex formation was analyzed by DSC and X-ray diffractometer. The amylose, especially short ones, readily associated in the dispersion forming the amylose–amylose crystals but the presence of GMC inhibited the crystal formation. The longer amylose had the greater possibility for the complex formation with GMC, and the prolonged heat treatment facilitated the amylose–GMC complex formation. Both type I and type II complexes were formed during quenching after the initial DSC heating. However, only the type II complexes were formed after the prolonged heat treatment with improved crystallinity and thermostability.

Influence of molecular structural characteristics on pasting and thermal properties of acid-methanol-treated rice starches

Rice starches from TKW1, TNG67 and TCS17 varieties, differing widely in amylose contents (0.1, 18.3 and 29.2%) were treated at 45 °C for 1 h in methanol containing various amounts of HCl. The recovery, pasting properties, thermal behaviors, molecular size and chain length distribution of starch were observed. Starches exhibited widely different pasting and thermal behavior upon acid-methanol treated (AMT). Degradation of starches upon AMT affected the leaching extent and chain length of amylose. No obvious changes were found on chain length and content of chain fractions of amylopectin. The pasting viscosity of rice starch decreased with increasing concentration of HCl, and the pasting profiles depended on the variety of rice. The pasting profile of AMT-TNG67 starch showed a two-step increasing pattern during heating, while TKW1 and TCS17 starches showed smoothly increasing pasting curves. The relationship between pasting patterns of AMT-TNG67 starches with amylose leaching and two stages of swelling behavior of starch granules was investigated. Results indicated that the pasting of starch granules depend on the amount, as well as the chain length, of amylose in granules.

Production of tailor made short chain amylose–lipid complexes using varying reaction conditions

When amylose was synthesized using potato phosphorylase in the presence of amylose complexing lipids, monodisperse populations of amylose–lipid complexes were formed. Enzyme dosage and glucose-1-phosphate (glc-1-P)/primer ratio influenced the reaction rate of the enzymic synthesis, presumably by changing the balance between amylose synthesis and amylose–lipid complexation and precipitation, and impacted the molecular weight of the complexes. Lipid characteristics affected the dissociation properties and amylose chain lengths of the amylose–lipid complexes presumably by determining the minimal amylose chain length necessary for complexation and precipitation. Tailor made short chain amylose–lipid complexes can hence be produced by choosing the appropriate reaction conditions. We propose a synthesis mechanism in which the primer is elongated until an amylose chain is obtained which is of sufficient length to complex a first lipid. Further chain extension then occurs, together with subsequent complexation until the complex becomes insoluble and precipitates.

Physico-chemical and degradative properties of in-planta re-structured potato starch

Starch re-structured directly in potato tubers by antisense suppression of starch branching enzyme (SBE), granule bound starch synthase (GBSS) or glucan water dikinase (GWD) genes was studied with the aim at disclosing the effects on resulting physico-chemical and enzyme degradative properties. The starches were selected to provide a combined system with specific and extensive alterations in amylose and covalently esterified glucose-6-phosphate (G6P) contents. As an effect of the altered chemical composition of the starches their hydrothermal characteristics varied significantly. Despite of the extreme alterations in phosphate content, the amylose content had a major affect on swelling power, enthalpy for starch gelatinization and pasting parameters as assessed by Rapid Visco Analysis (RVA). However, a combined influence of the starch phosphate and long glucan chains as represented by high amylose or long amylopectin chain length was indicated by their positive correlation to the final viscosity and set back (RVA) demonstrating the formation of a highly hydrated and gel-forming system during re-structuring of the starch pastes. Clear inverse correlations between glucoamylase-catalyzed digestibility and amylopectin chain length and starch phosphate and lack of such correlation with amylose content indicates a combined structuring role of the phosphate groups and amylopectin chains on the starch glucan matrix.

Effects of type and concentration of polyols on the molecular structure of corn starch kneaded with pullulanase in a Farinograph

For investigating the effects of type and concentration of polyols on the molecular structure of starch, corn starch (50 g, d.b.) were kneaded in a Farinograph at 60 °C for 3 h with 15 ml polyol solutions (10–100% for glycerol, 10–50% for erythritol, xylitol and sorbitol, and with water as control) and with or without pullulanase (32 NPUN/g starch). The molecular weight and chain length distributions of kneaded starch were determined by high-performance size-exclusion chromatography ( HPSEC). Results showed the average molecular weight and chain length of amylose of the kneaded starch obviously decreased. Starch kneaded with water had lower extent of degradation than that of starch kneaded with polyol solutions. For starch kneaded with the same polyol, the degradation extent of starch decreased with the increasing concentration of polyol solution, but no apparent trend was found for starch kneaded with different polyol solutions at the same concentration. In addition, kneading without pullulanase leads to starch degradation to a similar magnitude as when the starch was kneaded with the enzyme. Results of this study imply that the mechanical force is the main factor on the degradation of starch kneads with pullulanase and different polyol solutions in a Farinograph. Furthermore, starches knead with different polyol solutions have distinct extent of degradation. For the same type of polyol uses, the extent of degradation depends on the polyol concentration.

Enzyme and acid resistance of amylose-lipid complexes differing in amylose chain length, lipid and complexation temperature

To study parameters that influence enzyme and acid resistance of amylose-lipid complexes, complexes were formed between amylose of different average chain lengths [Degree of Polymerisation (DP); DP60, 400, 950] and docosanoic acid (C22) or glyceryl monostearate (GMS) at 60 or 90 °C. Complexes were hydrolysed with hog pancreatic alpha-amylase or acid (2.2 N HCl). DP400- and DP950-complexes were of type I when formed at 60 °C and of type II when formed at 90 °C. Enzyme and acid resistance increased with increasing amylose DP, lipid chain length and complexation temperature. DP60 yielded only type I complexes, independent of the complexation temperature. Enzymic and acid hydrolysis of all complexes gave rise to two or more dextrin subpopulations, which are interpreted to originate from a sequence of lamellar units (the smallest peak DP) with interconnecting, amorphous amylose chains. The peak DP of such lamellar unit increased with increasing amylose DP and complexation temperature, but remained constant when higher enzyme dosages were applied. Synthesis of amylose-lipid complexes from amylose and lipids of variable structure under variable temperature conditions followed by hydrolysis can yield dextrin populations of defined and relatively narrow molecular weight distributions.

Influence of Amylopectin Structure and Amylose Content on the Gelling Properties of Five Cultivars of Cassava Starches

Five cassava genotypes were investigated to identify the fine amylopectin structures and granule chemical compositions, which differentiated the starches into high (T(o) = 63.7 degrees C on average) and low (57.3 degrees C on average) gelatinization temperatures. The amylose contents (15.9-22.4%) and granular dimensions (12.9-17.2 microm) significantly differed among the starches. Diverse amylopectin structural elements resulted in significant swelling power, viscoelastic properties, and gel firmness. Debranched starches revealed a trimodal amylopectin distribution of three fractions: FIII (DP 12), FII (DP 24.31), and FI (DP 63) and FIII (DP 12), FII (DP 24.69), and FI (DP 67) for the low and high gelatinization starch groups, respectively. The higher proportion of FI long chain entanglement with amylose chain lengths to form longer helical structures was confirmed in the high gelatinization starch group, which developed "true" gels with better shear resistance, frequency independence, and higher gel firmness. Significant amounts of resistant starch fractions revealed the potential for application of these genotype starches in diverse foods.

Amylose–lipid complexation: a new fractionation method

Amylose fractions of different peak Degree of Polymerisation (DP) (DP20, DP60, DP400, DP950) were complexed with docosanoic acid (C22) and glyceryl monostearate (GMS) at 60 and 90 °C. Complexation yields, relative crystallinities, dissociation temperatures and enthalpies increased with amylose chain lengths (DP20–DP60–DP400). Relative crystallinities and thermal stabilities of the DP950-complexes were slightly lower than those of the other amylose fractions, probably due to increased conformational disorders, resulting in crystal defaults. Molecular weight distributions of the complexes revealed that, irrespective to the complexation temperature, the critical DP for complex formation and precipitation was 35 and 40 for complexes with GMS and C22, respectively, corresponding to the length needed to accommodate two GMS- or C22-molecules within an amylose helix. Complexation of dextrins with a well-chosen lipid, allows to separate starch derived dextrins with a predictable critical chain length as border. Dextrins, of sufficient DP will complex and precipitate, while the shorter dextrins will remain in solution.

Changes in Retrogradation Properties of Rice Starches with Amylose Content and Molecular Properties

ABSTRACTThe increases in storage modulus (G′), retrogradation enthalpy change (ΔH) and ΔH‐related Avrami kinetic parameters of gelatinized rice starch dispersions at 25% (w/w) were investigated with respect to storage period, amylose content (AC), and molecular properties. Three high‐AC and five low‐AC rice cultivars were compared for understanding the multiple influences of AC and molecular properties involved. After refining the results of correlation analysis, the G′ of just‐cooled samples changed positively, mainly with AC and additionally with the average chain length of amylose (CLAM) and the weight ratio of extra‐long plus long chains to short chains of amylopectin (AP) (rAPchain). The developed ΔH on short‐term storage (10 days) elevated with increasing AC and CLAM and decreasing degree of polymerization of AP (DPAP), but after long‐term aging for one to three months with increasing rAPchain, especially for the low‐AC cultivars examined. Greater Avrami rate constants for retrogradation could be attributed to the combination of a lower DPAP and rAPchain or AP chain length and a greater CLAM. The polynomials using these critical factors to describe the retrogradation parameters were elucidated and could account for 85–99.6% of data deviations.