Amylose Chain Length Research Articles

Fine structure of starch biomacromolecules and digestibility: The regulative role of amylose and amylopectin in the digestive hydrolysis of starch in rice

The digestibility of starch in staple foods has rarely been examined at the bio-macromolecular level. This study addresses this by investigating the fine structures of amylose and amylopectin to understand their roles in starch digestibility in cooked white rice. Using the static INFOGEST protocol and oral processing by human volunteers, we assessed the starch digestion characteristics of 13 rice varieties, with amylose and amylopectin chain length distribution being analyzed using size-exclusion chromatography and high-performance anion exchange chromatography, respectively. Kinetic modelling revealed that chewed white rice follows a typical parallel digestion pattern, with rapidly (SF) and slowly digestible starch (SS) being digested simultaneously at distinctly different rates. Amylose content (AC) and amylose weight were significantly and positively correlated with the digestion rate and extent of SS, whereas the digestion rate and extent of SF were closely linked to amylopectin, particularly its short and intermediate chains (degree of polymerization 13–36). Compared to low-amylose rice (AC < 25 %), high-amylose rice exhibited significantly higher SS but with a lower digestion rate, attributed to its higher AC with shorter chains and fewer short to intermediate Ap branches. These findings provide insights into starch structure-digestibility relationships, aiding the development of rice varieties with slower digestion rates.

Effects of amylose and amylopectin fine structure on the thermal, mechanical and hydrophobic properties of starch films

The fine structures of pumpkin, potato, wheat, cassava, and pea starches were determined, followed by an evaluation of how these structures affected the properties of starch films. The structures significantly influenced film properties. Starches with larger molecular weights exhibited greater thermal stability. The tensile strength of starch film was negatively associated with the amylose chain length (r = −0.88, p < 0.05). The chain length distributions of amylose and amylopectin affected the mechanical properties of starch films by influencing structure ordering, supported by the positive correlation between the double helix content and the tensile strength (r = 0.95, p < 0.05). The amylopectin B1, B2, and B3 chains increased film mechanical strength. Conversely, amylopectin A-chains reduced the mechanical strength. The water contact angle was negatively correlated with the B3 chain proportion (r = −0.93, p < 0.05). The pumpkin starch exhibited the highest tensile strength (14.29 MPa), while the wheat starch film showed the highest water contact angle (112°). This study offers valuable insights into the structure-function relationships of starch films, thereby facilitating the acquisition of starch films with enhanced strength and stability through screening or designing starch structures. Consequently, this will expand the application of starch films as packaging materials in various food products.

Investigation of the link between first-order kinetic models of the in vitro digestion of native starches and the accompanying changes in their crystallinity and structure

Starch is the main source of dietary energy for humans. In order to understand the mechanisms governing native starch in vitro digestion, digestion data for six starches [wheat, maize, (waxy) maize, rice, potato and pea] of different botanical sources were fitted with the most common first-order kinetic models, i.e. the single, sequential, parallel and combined models. Parallel and combined models provided the most accurate fits and showed that all starches studied except potato starch followed a biphasic in vitro digestion pattern. The biological relevance of the kinetic parameters was explored by determining changes in crystallinity and molecular structure of the undigested starch residues during in vitro digestion. While the crystallinity of the undigested potato starch residues did not change substantially, a respectively small and large decrease in their amylose content and chain length during in vitro digestion was observed, indicating that amylose was digested slightly preferentially over amylopectin in native starch. However, the molecular structure of the starch residues changed too slowly and/or only to an insufficient extent to relate it to the kinetic parameters of the digested fractions predicted by the models. Such parameters thus need to be interpreted with caution, as their biological relevance still needs to be proven.

Structure and functional properties of starches from Xiaozhan rice: Effects of varieties and growing regions

This study aimed to understand structure and functionality of starches from different Xiaozhan rice varieties grown in the same region and from the same variety grown in different regions. The amylose content varied from 15.6% to 23.2% among all rice starches, and the proportions of A, B1, B2, and B3 chains of amylopectin were in the range of 28.4%–38.1%, 46.2%–51.4%, 8.0%–13.4%, and 2.5%–12.0%, respectively. Significant differences were noted in swelling power, gelatinization, pasting, gel textural properties and in vitro enzymic digestibility of rice starches from different varieties grown at the same region and from the same variety grown in different regions. Correlation analysis results showed that amylose content and chain length distribution of amylopectin were the major determinants for the functional properties and amylolysis of starches, respectively. This study suggests that the quality of Xiaozhan rice related to starch properties was affected by the rice varieties and growing regions. The results obtained in this study are of importance for optimizing breeding strategies to produce better rice varieties.

Molecular structure in relation to swelling, gelatinization, and rheological properties of lotus seed starch

Relationships between molecular structure and physicochemical properties of starch remain to be better defined. This research was a follow-up of previous studies aiming to fill this gap using lotus seed starch (LS) (a novel C-type starch source) as a model system. By means of correlation analysis, the effects of molecular structure on physicochemical properties of LS were revealed. Content and chain length of amylose affected mainly rheological properties of LS. Short and long B-chains differently affected the short-range ordered structure of starch granules, thermal properties, and the transmittance of starch paste. In addition to the influences of amylose and amylopectin internal structure, several “novel” relationships related to the effects of amylopectin external structure were found in the LS-based model system. For instance, the molar amount of clustered A-chains (Aclustered) in lotus seed amylopectin was significantly related to the short-range molecular order in the granules. Moreover, the importance of Aclustered-chains was reflected by their influences on various properties of LS upon gelatinization and retrogradation. Successive influences of the molar amount of Aclustered-chains on starch properties during pasting were revealed. This study highlighted the importance of amylopectin external structure in addition to the under-studied amylopectin internal structure in affecting starch physicochemical properties.

Physicochemical properties of starch in sodium chloride solutions and sucrose solutions: Importance of starch structure.

The influences of sodium chloride (NaCl)/sucrose on starch properties as affected by starch structural characteristics are little understood. In this study, the effects were observed in relation to the chain length distribution (from size exclusion chromatography) and granular packing (inferred through morphological observation and determination of swelling factor and paste transmittance) of starches. Adding NaCl/sucrose dramatically delayed the gelatinization of starch that had a high ratio of short-to-long amylopectin chains and had loose granular packing. The effects of NaCl on the viscoelasticity of gelatinizing starch were related to the flexibility of amylopectin internal structure. Effects of NaCl/sucrose on starch retrogradation varied with starch structure, co-solute concentration, and analytical method. The co-solute-induced changes in retrogradation were highly associated with amylose chain length distribution. Sucrose strengthened the weak network formed by short amylose chains, while the effect was not significant on amylose chains that were capable of forming strong networks.

Slow starch hydrolysis of non-glutinous rice flour and potato starch heated with taxifolin: contribution of proteins to the former and longer amylose to the latter

Taxifolin (dihydroquercetin), which has various pharmacological functions, is contained in edible plants. Some taxifolin-containing foodstuffs such as adzuki bean and sorghum seeds are cooked by themselves and with other starch-containing ingredients. In this study, non-glutinous rice flour (joshin-ko) and potato starch were heated with taxifolin. The heating resulted in the slowdown of pancreatin-induced hydrolysis of suspendable starch in joshin-ko and soluble starch in potato starch. The products of taxifolin formed by the heating such as quercetin were combined with starch during the heating and/or retrogradation, which was converted into the suspendable starch in joshin-ko and the soluble starch in the potato. Taking the difference in protein content and amylose chain length between joshin-ko and potato starch into account, the slowdown is discussed to be due to the binding of the reaction products of taxifolin to proteins in suspendable starch in joshin-ko and to soluble amylose in potato starch.

Effect of alkyl chain length and amylose/amylopectin ratio on the structure and digestibility of starch-alkylresorcinols inclusion complexes

Starch can form inclusion complexes with various phenolic compounds. The structure of phenolic compound and the amylose/amylopectin ratio of starch affect their complexing ability and functional properties. In this study, 5-heptadecylresorcinol (ARs-17) and 5-heneicosylresorcinol (ARs-21) were screened and the influences of amylose content on the formation and physicochemical properties of starch-alkylresorcinols (ARs) inclusion complexes were evaluated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). The digestion curves and logarithm-of-slope (LOS) plots were obtained by in vitro digestion experiments. The results demonstrated that waxy maize starch (WMS) was not able to form inclusion complexes with ARs-17 or ARs-21, however, the possibility of ARs adsorption on amylopectin existed. For normal maize starch (MS), it could only form inclusion complex with ARs-21, and there was uncomplexed ARs in the inclusion complex due to its lower proportion of amylose. High amylose starches (G50 and G80) formed VII-type inclusion complexes with both ARs-17 and ARs-21, especially a small amount of VI-type inclusion complexes was present in ARs-21 inclusion complexes. Meanwhile, the crystallinity, thermal stability, and anti-digestive properties of starch-ARs inclusion complexes increased with the increment of ARs alkyl chain length and amylose content. This study suggested that high amylose starch facilitated stable delivery of ARs, which could improve the bioaccessibility of ARs. • The higher content of amylose and longer alkyl chain length facilitated complexation. • High amylose starch formed both VI and VII inclusion complexes with ARs-21. • In case of insufficient amylose, ARs were likely to adsorb on amylopectin. • The reduced digestion was due to the ordered structure or ARs inhibition on enzymes.

Effects of amylose and amylopectin molecular structures on rheological, thermal and textural properties of soft cake batters

The rheological, thermal and textural properties of batter are critical for the eating and processing quality of soft cake products. Wheat starch molecular structures play an important role on these properties. However, the underlying mechanisms are not well understood. In this study, fluorophore-assisted carbohydrate electrophoresis and size-exclusion chromatography were used to measure amylopectin and amylose chain-length distribution. The obtained data were fitted with two different biosynthesis-based models, resulting in few biologically-meaningful parameters. For cake batter, the rheological, thermal and textural properties were measured by rheometer, differential scanning calorimetry and texture analyser. The length of amylose intermediate to long chains and amylopectin long chains was significantly positively correlated with the viscoelasticity of cake batter. The length of long amylose chains showed a negative correlation with the frequency value of crossover point between G′ and G″ curves. Moreover, different combinations of long amylopectin and intermediate-long amylose chains contributed to the formation of multi-endothermic gelatinization peaks. From flour-water system to flour-lipid-protein system, the main factors determining rheological and thermal properties changed from short amylopectin to long amylopectin and intermediate-long amylose chains. This study provides the first associations between starch molecular fine structure and functional properties of cake batter, which could help food industry breed and select suitable wheat varieties for improved batter quality. • The functional properties of flour-lipid cake batter were investigated in this study. • Long AP & medium and long AM chains are positively correlated with viscoelasticity. • Decrease of long AM chain length increases crossover point x value of rheology curves. • Cake batter shows two endothermic peaks in gelatinization curves. • Chain length distribution of AM is the determining factor for flour-lipid batter.

Rice noodle quality is structurally driven by the synergistic effect between amylose chain length and amylopectin unit-chain ratio

Chewiness, slipperiness, and rapid rehydration are satisfactory qualities for rice noodles. These qualities are dependent on rice starch structure. However, the synergistic effect of fine structure of amylose (AM) and amylopectin (AP) on rice noodle quality remains unclear. In this work, six rice varieties, three from early indica and three from late indica, with similar amylose content for each pair were analyzed to assess the synergistic effects between AM and AP fine structures. The results showed that the combination of amylose long-chains and a low amylopectin unit-chain (APC) ratio favored the maintenance of relatively intact starch granules, resulting in a higher die expansion ratio and improvement of the mechanical properties of rice noodles (Hardness varied from 403 g to 1627 g). Meanwhile, higher die expansion was associated with a larger rehydration ratio. These results suggest that the synergistic effect between AM and AP fine structures significantly affects rice noodles' quality.

Differences in Eating Quality Attributes between Japonica Rice from the Northeast Region and Semiglutinous Japonica Rice from the Yangtze River Delta of China.

Differences in cooked rice and starch and protein physicochemical properties of three japonica rice were compared systematically. Cultivars of japonica rice, Daohuaxiang2, from Northeast China (NR) and two semiglutinous japonica rice (SGJR), Nangeng46 and Nangeng2728, from the Yangtze River Delta (YRD) were investigated. Both Daohuaxiang2 and Nangeng46 achieved high taste values, but there were great differences in starch and protein physicochemical properties. Daohuaxiang2 showed higher apparent amylose content (AAC), lower protein content (PC), and longer amylopectin (especially fb2 and fb3) and amylose chain lengths, resulting in thicker starch lamellae and larger starch granule size. Its cooked rice absorbed more water and expanded to larger sizes. All of these differences created a more compact gel network and harder but more elastic cooked rice for Daohuaxiang2. Nangeng46 produced a lower AAC, a higher PC, shorter amylopectin and amylose chain lengths, thinner starch lamellae, and smaller starch granule sizes, creating a looser gel network and softer cooked rice. The two SGJR, Nangeng46 and Nangeng2728, had similar low AACs but great differences in taste values. The better-tasting Nangeng46 had a lower PC (especially glutelin content) and higher proportion of amylopectin fa chains, which likely reduced the hardness, improved the appearance, and increased the adhesiveness of its cooked rice. Overall, both types of japonica rice from the NR and YRD could potentially have good eating qualities where Nangeng46’s cooked rice was comparable to that of Daohuaxiang2 because of its lower AC. Moreover, its lower PC and higher proportion of amylopectin fa chains likely improved its eating quality over the inferior-tasting SGJR, Nangeng2728. This research lays a foundation for the improvement of the taste of japonica rice in rice breeding.

Chemical components and chain-length distributions affecting quinoa starch digestibility and gel viscoelasticity after germination treatment.

A germination treatment was explored in this study as a green strategy to reduce the in vitro starch digestibility of cooked quinoa. The alterations of chemical compositions, starch chain-length distributions (CLDs) and rheological characteristics of quinoa flours after the germination treatment were characterized. Results showed that a significant alteration of amylose CLDs and the starch digestibility was observed for cooked quinoa flours after different germination times. By fitting starch digestograms to the logarithm of slop (LOS) plot and the combination of parallel and sequential kinetics model (CPS), two starch digestible fractions with distinct rate constants were identified. Pearson correlation analysis further found that the observed starch digestive characteristics could be largely explained by the alterations of amylose CLDs caused by the germination treatment. More specifically, the rapidly digestible starch fraction mainly consisted of amorphous amylopectin molecules and amylose intermolecular crystallites. On the other hand, the slowly digestible starch fraction was largely formed by intramolecular interactions among amylose short chains (degree of polymerization (DP) < 500). These results suggest that germination may be a promising way to develop cereal products with slower starch digestibility.

The molecular structure of starch from different Musa genotypes: Higher branching density of amylose chains seems to promote enzyme-resistant structures

Starch from bananas/plantains, belonging to the genus Musa spp, is gaining prominence given its great potential as a healthy food ingredient made from an inexpensive raw material. Recent works highlight the outstanding potential of Musa starch to develop enzyme-resistant structures upon retrogradation. However, despite the wide variety of Musa cultivars (due to both natural mutation and breeding selection), there is no comparative investigation of the starch molecular structure from the most commonly cultivated Musa genotypes. In this work, the starch from six Musa cultivars harvested during the same growing season from the same parcel, was purified and analyzed for amylose ratio, amylose chain length distribution, and amylopectin unit and internal chain length distribution. Results showed significant differences between the fine structure of all Musa amylopectin molecules, which were structurally categorized as type 4 (consisting of a high number of B3-chains, few BS- and Bfp-chains, and low S:L and BS:BL ratios). Moreover, the different Musa starches exhibited dramatic differences in amylose ratio (17.7–27.6%), amylose branching degree (as evidenced by differences in the population of short chains of approximately 260 glucose units, GU) and a shorter average length (approximately 1000 GU) of the population of long amylose unit chains. Remarkably, these differences in amylose structure resulted in the cultivar Manzano (Musa AAB, silk subgroup) to possess a dramatically lower extension of in vitro starch digestion (C90 = 4.70%) than the rest of the cultivars (C90 = 17–18%) after full gelatinization and retrogradation for 7 days.

The relationship between the expression pattern of starch biosynthesis enzymes and molecular structure of high amylose maize starch

Two high amylose (HAM) inbred lines with apparent amylose contents of 55 % and 62 %, respectively, were selected to explore the relationship between molecular structure and gene expression of starch-synthase involved enzymes. GPC analysis of debranched starches showed that the HAM starches (HAMSs) had shorter amylose chains and longer amylopectin chains than normal maize starch (NMS). FACE analysis showed that these HAMSs had a higher content of amylopectin chains of DP > 21. Quantitative Real-Time PCR analysis showed that the HAM lines had specifically low expression of the starch branching enzyme IIb (SBEIIb), and the starch synthase IIIa (SSIIIa) homologue, and high expression of the isoamylase 2 (ISA2), potentially suppressing the generation of amylopectin molecules through deficient branching and excessive debranching process, thereby increasing the relative amylose content. A high expression of GBSS1 was potentially associated with increased short amylose chain lengths in HAMSs.

Theoretical Modeling of Electronic Structures of Polyiodide Species Included in α-Cyclodextrin.

The molecular mechanism of blue color formation in an iodine-starch reaction is studied by employing the iodine-α-cyclodextrin (α-CD) complex as a practical model system that resembles the structural properties of the blue amylose-iodine complex. To this end, we construct, using the quantum chemistry method, a molecular model of the complex (I5-/Li+/2α-CD) that consists of one I5-, two molecules of α-CD, and a lithium cation, and this model is employed as a basic unit in constructing the structural models of polyiodide ions (I5-)n. The initial structure in the geometry optimization is adopted from the α-CD-iodine complex structure obtained from the X-ray crystallography study. The structural models of (I5-)n are built by adding the basic unit n times along the crystal axis and by optimizing the structure using quantum mechanics/molecular mechanics (QM (iodine)/MM (α-CD)) calculations. The electronic absorption spectra of the resulting model structures are calculated by time-dependent density functional theory (TD-DFT). We find that I5- acts as a basic unit of coloration in the visible region. The visible color originates from the electronic transition within the I5- molecule, and any charge transfer between the I5- ion and either of α-CD or a coexisting counter cation is not involved. We also reveal that the electronic transitions of (I5-)n are delocalized, which accounts for the well-known observation that the color of the iodine-starch reaction becomes bluish with an increase in the chain length of amylose. Furthermore, the preresonance Raman spectra calculated from the model suggest that the vibrational motions are localized in the I5- subunit dominantly. A comparison between an experimental absorption spectrum feature of the α-CD-iodine complex and the calculated ones of (I5-)n ions with various n values suggests that (I5-)4 polyiodide ions tend to be populated dominantly in the α-CD-iodine complex under aqueous conditions.

Amylolysis as a tool to control amylose chain length and to tailor gel formation during potato-based crisp making

Potato flakes (PFs) are used for producing potato-based crisps. Their cold-water swelling starch instantly binds water during dough mixing. The dough is then sheeted and deep-fried. We here used α-amylase from Bacillus subtilis (BSuA) and Bacillus stearothermophilus (BStA) to unravel the role of PF amylose (AM) during crisp production. Treating PFs with BSuA [30.0 EU/g PF dry matter (dm), 10 min, 40 °C] increased the extractable starch (E-S) content from 8.6 to 42.7% of PF dm but the degree of polymerization (DP) of the E-S chains was lower than 150. Although time domain proton nuclear magnetic resonance (TD 1H NMR) analysis showed that these enzymatically released starch chains with DP lower than 150 readily crystallize during dough making, they are not able to contribute to formation of strong gels. In contrast, amylolysis of PF starch by BStA (30.0 EU/g PF dm, 10 min, 40 °C) only slightly impacted the E-S content (11.0% of PF dm) but increased the level of relatively short extractable amylose (E-AM) chains [(DP between 150 and 1500 (E-AM150-1500)] by 35%. Incubation (10 min, 60 °C) of 7.8% of the PF dm in the dough recipe with the same BStA dosage prior to dough making showed that E-AM150-1500 chains increase the extent of AM crystallization during dough making (as evidenced by TD 1H NMR analysis) and thereby strengthen the starchy gel network. As a consequence, expansion of the food matrix during deep-frying was hampered, which increased product hardness and reduced oil uptake by 10% and 8%, respectively. This study is the first to show that the level of AM chains of intermediate length is crucial for the texture of potato-based food matrices.

Study on the mechanism of ultrasound-accelerated enzymatic hydrolysis of starch: Analysis of ultrasound effect on different objects

Enzymatic hydrolysis of starch is an important process in the food industry. In the present work, ultrasound was introduced in glucoamylase pretreatment, starch pretreatment and mixed reaction system treatment to enhance starch hydrolysis efficiency. These different processes were studied to explore the mechanism of ultrasound in promoting enzymatic reactions. The hydrolysis degree of starch was determined via measuring the reducing sugar yield. Ultrasound caused enzyme inactivation under high temperatures, high ultrasonic power and long-time treatment, especially at high temperatures exceeding 65 °C. Ultrasound pretreatment of starch before enzymolysis led to the furtherance of starch hydrolysis degree. Meanwhile, sonicating the mixed enzymatic reaction system below 65 °C promoted starch hydrolysis significantly, inducing more than five- fold growth in the degree of starch hydrolysis as much as the ultrasound pretreatment caused. Molecular weights analysis conducted by the MALLS system reflected the enormous damage of starch molecules caused by ultrasound. The amylose contents and chain length distributions of samples were separately analyzed by iodine binding method and size exclusion chromatography. The results of the two experiments illustrate that ultrasound could promote the enzymatic hydrolysis of amylopectin, which is harder for glucoamylase to hydrolyze compared to amylose.

Study on crystalline, gelatinization and rheological properties of japonica rice flour as affected by starch fine structure

Although many researches have investigated the effects of starch characteristics on its functional properties to evaluate rice quality, few studies were carried out the correlations between starch molecular structure and rice processing properties. In this study, eight varieties of japonica rice with similar content of protein and lipid and less variant content of amylose (12.12–18.19%) were elaborately selected. The result showed that crystalline and pasting parameters were mainly reliant on the differences in chain length distribution of amylopectin. Amylose content and chain length distribution, especially for average exterior chain length (ECL) and interior chain length (ICL) and their entanglement, showed significant correlation on rheological parameters. Swelling power of rice flour showed negative correlation with amylose content. Furthermore, in temperature-reduction process when the temperature is lower gelatinization temperature of amylopectin, the variation of loss modulus was affected by amylopectin. In addition, the PCA plot clearly revealed the interrelationship of all parameters.

Insights into structure-function relationships of starch from foxtail millet cultivars grown in China

Structure-function relationships of starch isolated from eight cultivars of foxtail millets grown in China were investigated. The starch granules were polygonal with diameters between 5 μm and 10 μm. The amylose content ranged from 16.8% to 26.8%, and the relative crystallinity and the full width at half maximum (FWHM) of the Raman band at 480 cm−1 varying between 33.2% and 36.4% and 15.72 to 15.91, respectively. There were only small differences in amylopectin chain length distribution of the eight foxtail millet starches. Significant differences were noted in swelling power, gelatinization, pasting, gel textural properties of starches, but not in vitro enzymic digestibility. Correlation analysis results showed that amylose content and chain length distribution of amylopectin were more important determinants of functional properties of starch than the structural order of the starch granules.

Intermediate length amylose increases the crumb hardness of rice flour gluten-free breads

Consumers of Gluten Free Bread (GFB) seek soft, cohesive and resilient crumbs. However, the combined effect of amylose (AM) content and chain length, as opposed to only AM content, on crumb hardness have not been studied, neither the synergies of multiple starch molecular features (i.e., amylopectin, AP, and AM fine structures) are understood. In this work, kernels from 5 different rice varieties (Basmati, Thai, Waxy, Sushi and Bomba) were milled after tempering to result in rice flours with less than 8% starch damage varying in AM and AP fine structure, as measured by HPSEC. Dynamic rheology of rice flour gels revealed that Basmati flour exhibited a six-fold higher propensity to form internal Physical Junction Zones (PJZ), those that contribute to the food mechanical properties, than the rest of the starches. Frequency and temperature sweeps revealed AM-AM and AM-AP interactions, respectively, as the internal PJZ. Since Basmati and Bomba exhibited similar AM content and AP fine structure, the intermediate length amylose (699 DP) of Basmati is proved to be the responsible for a greater amount of AM-AM and AM-AP internal PJZ. Interestingly, GFB crumbs made with Bomba flour were 20% softer than those made with Basmati flour. For the first time, AM length is suggested to be a crucial parameter to attain breads with softer and more cohesive crumbs. In fact, results provide strong evidence that the AM length could play a major role than its content in the texture of GFBs crumbs.