Waxy Starch Research Articles

Molecular Characterization of a Spontaneous Waxy Starch Mutation in Cassava

ABSTRACTCassava (Manihot esculenta Crantz) starch is traded in international markets more than starch from any other source. The starch industry requires cassava cultivars with novel starch characteristics for commercial exploitation. A natural source of waxy (amylose‐free) cassava starch, clone AM 206‐5, was identified at the International Center for Tropical Agriculture (CIAT). The granule‐bound starch synthase I (GBSSI) gene is related to the waxy starch trait. The objectives of this study were to introgress the waxy starch mutation into Thailand's cassava breeding populations, to analyze the inheritance of waxy starch in cassava, and to develop molecular markers for this trait. AM 206‐5 (wxwx) was crossed with several elite cultivars (WxWx) to transfer the wx allele. Unrelated “F1” (Wxwx) genotypes were crossed among themselves to produce a “F2” segregating population with negligible levels of inbreeding depression. The waxy starch phenotype was recovered in 25.7% of the 11,192 genotypes tested. This result provides further evidence that cassava is a functional diploid and that only one copy of GBSSI is present in cassava. A full‐length genomic DNA sequence of GBSSI was isolated and characterized from C8, a waxy starch “F2” clone derived from AM 206‐5. We exploited these sequence differences to develop two diagnostic single‐nucleotide‐amplified polymorphism (SNAP) markers to differentiate homozygous waxy (wxwx) from the heterozygous (Wxwx) and homozygous (WxWx) nonwaxy genotypes.

Modulation of Starch Digestion for Slow Glucose Release through “Toggling” of Activities of Mucosal α-Glucosidases

Starch digestion involves the breakdown by α-amylase to small linear and branched malto-oligosaccharides, which are in turn hydrolyzed to glucose by the mucosal α-glucosidases, maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI). MGAM and SI are anchored to the small intestinal brush-border epithelial cells, and each contains a catalytic N- and C-terminal subunit. All four subunits have α-1,4-exohydrolytic glucosidase activity, and the SI N-terminal subunit has an additional exo-debranching activity on the α-1,6-linkage. Inhibition of α-amylase and/or α-glucosidases is a strategy for treatment of type 2 diabetes. We illustrate here the concept of "toggling": differential inhibition of subunits to examine more refined control of glucogenesis of the α-amylolyzed starch malto-oligosaccharides with the aim of slow glucose delivery. Recombinant MGAM and SI subunits were individually assayed with α-amylolyzed waxy corn starch, consisting mainly of maltose, maltotriose, and branched α-limit dextrins, as substrate in the presence of four different inhibitors: acarbose and three sulfonium ion compounds. The IC(50) values show that the four α-glucosidase subunits could be differentially inhibited. The results support the prospect of controlling starch digestion rates to induce slow glucose release through the toggling of activities of the mucosal α-glucosidases by selective enzyme inhibition. This approach could also be used to probe associated metabolic diseases.

Physicochemical, morphological, thermal and IR spectral changes in the properties of waxy rice starch modified with vinyl acetate.

Waxy rice starch was modified with vinyl acetate at levels of 4, 6, 8, and 10% with degree of substitution of 0.021, 0.023, 0.032 and 0.056. The modified starches were studied for physicochemical, morphological, thermal and infra red spectral properties. Waxy starch acetates had high water holding capacity and did not sediment. Scanning electron microscopy revealed surface damage of the granules and their fusion. X ray diffractography showed that crystalline peak intensity had increased on acetylation. Differential scanning calorimetry studies showed changes in thermal properties. While gelatinization temperatures of modified starches were higher than the native starch, their transition enthalpies were lower than the native starch. IR spectra of the starch acetates did not show the peak typical for acetyl group. Thus, modification of waxy rice starch with vinyl acetate caused changes in the starch properties. The high water holding capacity of starch acetates can be exploited for specific applications.

Proso millet (Panicum miliaceum L.) fermentation for fuel ethanol production

The objective of this research was to determine the conversion efficiency of proso millet to ethanol compared to corn in a bench-scale dry-grind procedure. Seven proso millet cultivars and six advanced breeding lines containing waxy starch were fermented with Saccharomyces cerevisiae and ethanol production was compared with normal corn and “highly fermentable” corn. The highly fermentable corn exhibited the highest fermentation efficiency (97.0±1.4%). Among proso millet lines, those with the highest fermentation efficiencies were: Huntsman (85.9±0.6%), 172-2-9 (90.8±0.2%), 172-2-13 (85.1±2.5%), and 182-4-24 (84.7±2.1). Waxy proso millet lines resulted in higher fermentation efficiencies than the non-waxy proso millet varieties containing normal starch (82.4±5.5% vs. 75.5±7.4%, respectively, p=0.01). Proso millet distiller's dried grains with solubles (DDGS) contained more protein (26.6–33.4%) than the DDGS from corn (17.2–23.4%). These data indicate that proso millet exhibits promise as a feedstock for ethanol production, especially if breeding programs focus on selecting “highly fermentable” lines for advancement.

Rice Starch Diversity: Effects on Structural, Morphological, Thermal, and Physicochemical Properties—A Review

Abstract: Rice starch is one of the major cereal starches with novel functional properties. Significant progress has been made in recent years on the characterization of rice starches separated from different rice cultivars. Studies have revealed that the molecular structure and functional properties are affected by rice germplasm, isolation procedure, climate, agronomic conditions, and grain development. Morphological studies (microscopy and particle size analysis) have reflected significant differences among rice starch granule shapes (polyhedral, irregular) and in granule size (2 to 7 μm). Nonwaxy and long‐grain rice starches show greater variation in granular size than the waxy starches. Rice starch granules are smaller than other cereal starches with amylose contents varying from virtually amylose‐free in waxy to about 35% in nonwaxy and long‐grain rice starches. Amylose content appears to be the major factor controlling almost all physicochemical properties of rice starch due to its influence on pasting, gelatinization, retrogradation, syneresis, and other functional properties. Waxy rice starches have high swelling and solubility parameters, and larger relative crystallinity values than nonwaxy and long‐grain starches. However, nonwaxy rice starches have a higher gelatinization temperature than the waxy and long‐grain starches. The bland taste, nonallergenicity, and smooth, creamy, and spreadable characteristics of rice starch make it unique and valuable in food and pharmaceutical applications. This review provides recent information on the variation in the molecular structure and functional properties of different rice starches.

The Extrapolation Method for Hyper Differential Scanning Calorimetry

In order to eliminate the temperature lag effect and obtain the accurate temperature results from hyper differential scanning calorimetry (Hyper-DSC) operated at high heating rate, an adjustable method, namely “Extrapolation Method”, had been introduced by us in former papers. And in this paper, we wanted to support the accuracy of this method by other instruments. Specifically, the extrapolated glass transition temperatures (Tg, 61.5 °C) of PLA film, which was obtained by Hyper-DSC, was close to the value detected directly by normal DSC (62.0 °C). And the extrapolated Tg of waxy starch film (59.7 °C for 8.7% moisture content, and 57.2 °C for 11.2% moisture content) was close to the values detected by modulated temperature DSC (MT-DSC) (63.6 °C and 56.8 °C correspondingly). Consequently, these experimental results support that the “Extrapolation Method” is a feasible way to eliminate temperature lag effect for Hyper-DSC.

Differences of Nano-Structure between Waxy and Normal Starch

This paper focused on the differences of nano-structure between waxy wheat starch (WWS), normal wheat starch (NWS), waxy maize starch (WMS), and normal maize starch (NMS). Observed by Atomic Force Microscope (AFM), it found that the nano-structure of waxy starch was composed by nano-particles and nano-chains. The nano-particles, which should be the remained crystalline region after the collapse of granules, were wrapped by nano-chains, which should be the dissociated amylose/amylopectin chains in amorphous region. But the nano-structure of normal starch was a little difference, namely only nano-particles could be observed. These distinctions changed the viscosity of starch pasting. That is to way, the viscosity of waxy starch pasting was higher than those of normal starch. The reasons for this should come from the interaction between nano-structure. Specifically, the interaction between particles was weaker than it between particles and chains. Therefore, the viscosity of waxy starch was higher than it of normal starch

Influence of amylose content on cooking time and textural properties of white salted noodles

White salted noodles were prepared from reconstituted flours of various amylose content to determine the effects of amylose content on noodle dough properties and texture of noodles cooked for optimum cooking time. With decrease of amylose content from 26.5 to 3. 0%, optimum water absorption of noodle dough increased from 39 to 49% and cooking time of noodles decreased from 16 to 7 min. Hardness of cooked noodles prepared from reconstituted flour consistently decreased with increase in proportion of waxy starch. Noodles less than 12.4% amylose content exhibited higher springiness and cohesiveness than noodles greater than 17.1% amylose content. Cohesiveness and springiness of noodles prepared with partial waxy starches, of which amylose content ranged from 16. 6 to 22. 7%, were comparable to those of noodles prepared from <12. 4% amylose content. Amylose content of starch was significantly correlated with hardness, springiness, and cohesiveness of cooked noodles prepared from reconstituted flours.

Amylopectin structure of heat–moisture treated starches

AbstractThe effects of heat–moisture treatment (HMT; moisture content of 25%, at 100°C for 24 h) on starch chain distribution and unit chain distribution of amylopectin in normal rice, waxy rice, normal corn, waxy corn, normal potato, and waxy potato starches were investigated. After HMT, starch chain distribution (amylose and amylopectin responses) of waxy corn and potato starches were identical to those of untreated starches, whereas the chromatographic response of waxy rice starch showed a slight decrease, but with a slight increase in peak tailing. This result indicated that HMT had no (or very limited) effect on the degradation of amylopectins. Analysis of unit chain distribution of amylopectins revealed that waxy characteristics affected the molecular structure of amylopectin in untreated starches, i.e., the CL of normal‐type starches was greater than that of waxy‐type starches. After HMT, the CL and unit chain distribution of all starches were no different than those of untreated starches. The results implied that changes in the physico‐chemical properties of HMT starches would be due to other phenomena rather than the degradation of amylopectin molecular structure. However, the thermal degradation of amylopectin molecules of waxy starches could occur by HMT at higher treatment temperatures (120 and 140°C).

Study on melting and crystallization of short-linear chains from debranched waxy starches by in situ synchrotron wide-angle X-ray diffraction

In situ melting and crystallization of short-linear α-1,4-glucan (short-chain amylose, or SCA) from debranched waxy starches were investigated by synchrotron wide-angle X-ray diffraction. Amorphous SCA was prepared by dissolving completely debranched waxy starches in alkaline solution and neutralized by hydrochloric acid. When hydrated with 50% water at 25°C, all amorphous SCA crystallized immediately and gave a B-type structure. The SCA from debranched waxy potato starch had a longer average chain length and a higher melting temperature but relatively lower crystallinity upon hydration; it was not completely melted at 100°C and retained its original B-type structure during rapid cooling. In contrast, the SCA from debranched waxy wheat and waxy maize starches had a large portion of low molecular weight fractions, a higher crystallinity upon hydration, and a lower melting temperature. These differences suggest that amylopectin short chains crystallized more readily but their crystals were weaker than those of long chains. After the B-type crystals of hydrated SCA from waxy wheat and waxy maize starches melted, they reformed into the A-type polymorph upon rapid cooling. The thermal properties showed that the A-type polymorph of debranched waxy wheat and waxy maize starches had a higher melting temperature than their B-type structure.

Dissolution of unmodified waxy starch in ionic liquid and solution rheological properties

Dissolution of waxy corn starch in 1-ethyl-3-methylimidazolium acetate (EMIMAc) was qualitatively studied and compared with gelatinisation process in water. The rheological properties of starch–EMIMAc solutions were investigated in dilute and semi-dilute regions, from 0.1 to 10wt% over temperature range from 20°C to 100°C. The values of zero shear viscosity were obtained by applying Carreau–Yasuda model to shear-thinning flow curves and plotted vs. polymer concentration. Power law exponents in viscosity-concentration dependence in semi-dilute region were compared with the ones reported previously for microcrystalline cellulose. Intrinsic viscosity was obtained as a function of temperature and compared with the one of microcrystalline cellulose; starch was found to be much less temperature sensitive than cellulose. Amylopectin overlap concentration in EMIMAc was compared with the one in water and 0.5M NaOH–water. Based on these comparisons it was suggested that starch conformation in EMIMAc is similar to the one in water (compact ellipsoid). The activation energy was calculated for starch–EMIMAc solutions and demonstrated to obey power-law concentration dependence.

Visualisation of Cornstarches Granule with Different Amylose/Amylopectin Contents: A Combined CLSM and SEM Approach

The morphologies and microstructures of cornstarches with different amylose/amylopectin ratios (waxy: 0/100; maize: 23/77; Gelose 50: 50/50; Gelose 80: 80/20) were studied by a combined SEM and confocal laser scanning microscope (CLSM). CLSM allowed the visualization of cross-sections of starch granules without the need for sectioning techniques that lead to destruction of the microstructure of sample. The influence of the amylose/amylopectin ratio on the internal structures and morphologies was able to be revealed by this choice of techniques. It was found that the granules of the high-amylopectin starches were more regular in shape than those of the high-amylose starches, but the surfaces of the high-amylose starches were smoother than those of the high-amylopectin starches. The high-amylose starches (G50 and G80) were brighter than that of low-amylopectin starches (waxy and maize) under confocal laser light, and the average fluorescence intensity sequence of the granules was G80&gt;G50&gt;maize&gt;waxy. Waxy and maize starches show clearly cavities and channels while G50 and G80 present bright core.

Evaluation of the Functional Properties of Promising Dioscorea trifida L. Waxy Starches for Food Innovation

Few natural waxy starches are offered to the industry demand. Therefore, the morphological, physical, and chemical characteristics of “Mapuey” waxy starch were assessed. Amylose contents of starches isolated from Dioscorea trifida L. (“Mapuey”) landraces cultivated in the Amazons of Venezuela were lower (&lt;8.1%) than commercial Mapuey starch (&gt;8.7%). DSC onset gelatinization temperatures varied from 71.1 to 73.2°C. All starches exhibited B-type patterns, with degrees of crystallinity varying from 28% to 33%. The highest crystallinity was found for the starches exhibiting the highest amylose content. At 90°C, solubility and swelling power varied from 2.3 to 4.3% and 20.9 to 32.8%, respectively. Gel clarity was variable from 20.8 to 62.1%. A 5% starch suspension induced a high RVA peak viscosity between 1667 and 2037 cP. This natural waxy yam resource is a promising ingredient for food industry.

Structural and physicochemical properties of starch gels prepared from partially modified starches using Thermus aquaticus 4-α-glucanotransferase

Abstract The modified starch gels prepared from partial enzyme treatments (1, 3, and 6 U/g starch; 2-h incubation) of the corn and rice starch pastes using Thermus aquaticus 4-α-glucanotransferase (TAαGT) were investigated for their molecular characteristics, microstructures, and physicochemical properties. Unlike the native and partially modified normal starches, the native and partially modified waxy starches could not form gels strong enough for textural analysis after 24 h for gel setting. Features of the partially modified normal starches were the specific apparent amylose contents and maximum iodine absorption wavelength ( λ max , ∼567 nm), as well as the tri-modal molecular weight profiles and flatter side-chain distributions. Also, the partially modified normal starch gels possessed fractured surfaces with discontinuous crystalline fibrous assembly that differed from the native starch gels’ porous continuous network, which resulted in more brittle, rigid, and resilient gels compared with the native gels.

Effect of structural characteristics of modified waxy corn starches on rheological properties, film‐forming solutions, and on water vapor permeability, solubility, and opacity of films

AbstractWaxy corn starch (amylopectin) and three of its chemical derivatives: acetylated cross‐linked (ACLS), oxidized (OS), and octenyl‐succinylated (OSA), were used together with additives such as Tween 80, sorbitol, and beeswax suspension or safflower oil to test their effect on film‐forming solutions (FFS) and films. The objectives of this study were the starch structure characterization, and its correlation with rheological properties of FFS and solubility, opacity, and water vapor permeability (WVP) of the produced films. Analysis of starch structure, rheological characterization, and films micrographs revealed that the starches contained predominantly low MW amylopectin molecules and film properties depended on their ability to reorganize. Additionally, the interaction among groups introduced in modified starches or with additive molecules can hinder or promote starch reorganization, resulting in films with increased or reduced WVP, solubility and transparency properties. Films were obtained by casting and showed a thickness less than 41 µm. Films prepared with OS and beeswax exhibited the best reorganizing capacity of FFS, resulting in less soluble (30.0 ± 1.6%), highly transparent (23.2 ± 3.3 UA × nm) and less permeable films (0.485 ± 0.016 g · mm · m−2 · h−1 · kPa−1). On the other hand, ACLS showed an opposite trend which was attributed to a more open film structure. These results contribute to understand the molecular interactions of waxy starch molecules in FFS which may be useful to design tailored coatings.

Effects of amylose/amylopectin ratio on starch-based superabsorbent polymers

Abstract Biodegradable superabsorbent polymers (SAPs) were prepared by grafting acrylamide onto starches then crosslinking with N,N′-methylene-bisacrylamide. This work focused on the effects of the amylose/amylopectin ratio of starches from the same source (corn) on the grafting reactions and performance of the resultant starch-based SAPs. To characterise each SAP, the acrylamide groups grafted onto the starch were detected by FTIR; grafting ratio and grafting efficiency were evaluated by a gravimetric method; and graft position and the length of the grafted segment were investigated by NMR. The relationships between the microstructures of the starches, and the graft reactions and performance of the SAPs were studied based on the amylose content in the starches. It was found that under the same reaction conditions, the grafting ratio and efficiency increased with increasing amylose content, which corresponds with water absorption ratio. NMR results indicated that the acrylamide group mainly grafted onto C6, and that the length of the grafted segment decreased with increasing amylopectin content in general, and in particular for waxy starch. The high molecular weight and branched structure of amylopectin reduced the mobility of the polymer chains and increased viscosity, which could explain the graft reactions and performance of the starch-based SAPs.

Quantification of total iodine in intact granular starches of different botanical origin exposed to iodine vapor at various water activities

Iodine has been used as an effective tool for studying both the structure and composition of dispersed starch and starch granules. In addition to being employed to assess relative amylose contents for starch samples, it has been used to look at the molecular mobility of the glucose polymers within intact starch granules based on exposure to iodine vapor equilibrated at different water activities. Starches of different botanical origin including corn, high amylose corn, waxy corn, potato, waxy potato, tapioca, wheat, rice, waxy rice, chick pea and mung bean were equilibrated to 0.33, 0.75, 0.97 water activities, exposed to iodine vapor and then absorbance spectra and LAB color were determined. In addition, a new iodine quantification method sensitive to <0.1% iodine (w/w) was employed to measure bound iodine within intact granular starch. Amylose content, particle size distribution of granules, and the density of the starch were also determined to explore whether high levels of long linear glucose chains and the surface area-to-volume ratio were important factors relating to the granular iodine binding. Results showed, in all cases, starches complexed more iodine as water content increased and waxy starches bound less iodine than their normal starch counterparts. However, much more bound iodine could be measured chemically with waxy starches than was expected based on colorimetric determination. Surface area appeared to be a factor as smaller rice and waxy rice starch granules complexed more iodine, while the larger potato and waxy potato granules complexed less than would be expected based on measured amylose contents. Corn, high amylose corn, and wheat, known to have starch granules with extensive surface pores, bound higher levels of iodine suggesting pores and channels may be an important factor giving iodine vapor greater access to bind within the granules. Exposing iodine vapor to moisture-equilibrated native starches is an effective tool to explore starch granule architecture.

Study on physicochemical characteristics of waxy potato starch in comparison with other waxy starches

AbstractThe physicochemical properties of wx potato, wx corn, and wx rice starches were examined and compared. wx potato starch displayed the B‐type XRD pattern, whereas wx rice and wx corn displayed the A‐type. Shapes of wx potato starch were oval or slightly round, wx corn and wx rice starch granules were polygonal. AM contents of the three starches were between 1.0 and 1.5%. Rapid viscosity analyzer data showed initial pasting temperatures of wx potato, wx corn, and wx rice starches as 69.6, 75.4, and 76.8°C, respectively, peak viscosity, breakdown, and setback of wx potato starch were 2114, 1084, and 4 mPa s. Using DSC, onset temperature of gelatinization of wx potato starch was 5.5–7.2°C higher than those of wx rice and wx corn starches. The thermal enthalpies of the starches studied in our laboratory were in the range of 0.2268–1.9900 J/g with decreasing order of wx potato &gt; wx corn &gt; wx rice starch.

Water effect on the interaction between amylose and amylopectin during retrogradation

Possible interactions between amylose (AM) and amylopectin (AP) during a temperature cycled retrogradation (4/30°C 1 day at each temperature, 2 days) in aqueous pastes/gels of corn starch and reconstituted mixtures of AM and AP (1:3 weight ratio) were examined at different water levels (60–90%). With the pastes containing 90% water, no AP crystallization was observed under a differential scanning calorimeter in waxy starch or the starches containing AM. With 80% water, AP crystallization was not observed in waxy starch but it was found in the starches containing AM. With 70% water, AP crystallization was facilitated by the presence of AM. With 60% water, however, AP crystallization was found not to be affected by AM presence. It was evident that the presence of AM (25%) affected AP crystallization during retrogradation but only when the water content in starch pastes/gels was proper (70–80% in this study).

Effects of Pearling, Grinding Conditions, and Roller Mill Flow on the Yield and Composition of Milled Products from Hull‐less Barley

ABSTRACTTwo hull‐less barley cultivars, one with waxy starch and the other with high‐amylose starch, were roller‐milled unpearled and after 15% pearling. Flows of varying length, with diverse roll settings and roll surfaces were used to determine effects on the yield, composition, and properties of milled products. Similar trends were noted for the two cultivars. When using a short flow comprising four break passages and a sizing passage, power consumption during grinding was reduced by 10% when roll flute orientation was changed from dull‐to‐dull (D/D) to sharp‐to‐sharp (S/S). Flute orientation had minimal effects on the yield and brightness of flour, but SS grinding gave a higher yield of a fiber‐rich fraction (FRF). FRF yield and composition are of particular interest because FRF has potential as a functional food ingredient due to elevated levels of β‐glucans (BG) and arabinoxylans (AX). When using smooth frosted rolls (SM) for the sizing passage, power consumption increased by several times over using fluted sizing rolls with little advantage for either yield or BG content of FRF. FRF starch damage increased when smooth sizing rolls were used, and water swelling, a measure of water hydration capacity, also increased. Setting break and sizing rolls sharp‐to‐sharp significantly lowered the mean particle size of the FRF fraction, accompanied by moderate declines in FRF BG and AX contents. FRF yield decreased ≤50% when milling flow was lengthened to three sizing passages with intermediate impact passages, with only a moderate accompanying increase in FRF fiber content, regardless of roll conditions. Pearling 15% before milling reduced the yield of FRF by ≈30% while moderately reducing flour yield. Flour brightness was improved by pearling. When barley was pearled, FRF contained higher amounts of BG, but lower amounts of AX, phenolics, ash, and protein.