Waxy Maize Starch Granules Research Articles

Supramolecular structure and in vitro digestive properties of plasma-treated corn starches varying in amylose content

The effects of plasma treatment on the multi-scale structure and in vitro digestibility of maize starch with different amylose contents were systematically evaluated. The results demonstrated that all maize starches' molecular weights (MW) decreased when treated with plasma, among which the MW of waxy maize starch displayed the largest reduction. Plasma treatment led to an increase in the thickness of the semi-crystalline lamellae and double helix proportions of waxy and normal maize starches. However, high-amylose maize starch presented a less ordered structure by plasma treatment. Additionally, larger pores and channels were observed on the surface of plasma-treated waxy and normal maize starch granules. Moreover, deposits were displayed on the surface of high-amylose maize starch granules. These changes increased the in vitro digestibility and hydrolysis rate of three starches after plasma treatment. Notably, plasma treatment caused diverse alterations in the structure and functionality of maize starch varying in amylose content, leading to maize starch with better digestibility, therefore being used as an ingredient for functional foods.

Impact of Starch Binding Domain Fusion on Activities and Starch Product Structure of 4-α-Glucanotransferase.

A broad range of enzymes are used to modify starch for various applications. Here, a thermophilic 4-α-glucanotransferase from Thermoproteus uzoniensis (TuαGT) is engineered by N-terminal fusion of the starch binding domains (SBDs) of carbohydrate binding module family 20 (CBM20) to enhance its affinity for granular starch. The SBDs are N-terminal tandem domains (SBDSt1 and SBDSt2) from Solanum tuberosum disproportionating enzyme 2 (StDPE2) and the C-terminal domain (SBDGA) of glucoamylase from Aspergillus niger (AnGA). In silico analysis of CBM20s revealed that SBDGA and copies one and two of GH77 DPE2s belong to well separated clusters in the evolutionary tree; the second copies being more closely related to non-CAZyme CBM20s. The activity of SBD-TuαGT fusions increased 1.2-2.4-fold on amylose and decreased 3-9 fold on maltotriose compared with TuαGT. The fusions showed similar disproportionation activity on gelatinised normal maize starch (NMS). Notably, hydrolytic activity was 1.3-1.7-fold elevated for the fusions leading to a reduced molecule weight and higher α-1,6/α-1,4-linkage ratio of the modified starch. Notably, SBDGA-TuαGT and-SBDSt2-TuαGT showed Kd of 0.7 and 1.5 mg/mL for waxy maize starch (WMS) granules, whereas TuαGT and SBDSt1-TuαGT had 3-5-fold lower affinity. SBDSt2 contributed more than SBDSt1 to activity, substrate binding, and the stability of TuαGT fusions.

Butyl Group Distribution, Intestinal Digestion, and Colonic Fermentation Characteristics of Different Butyrylated Starches.

Despite being a promising butyrate carrier, butyrylated starch remains poorly understood in terms of the correlation between starch structure and fermentation characteristics. Herein, three butyrylated starches derived from different botanical sources were prepared with a similar degree of substitution. Raman microscopy and water contact angle analysis suggested that a relatively large proportion of butyl group substitutions occurred within the interior of butyrylated waxy maize starch (B-WMS) granules. In vitro digestion results showed that branch points provided butyl groups with a specific protection from enzymatic hydrolysis, whereas butyl groups significantly increased the resistant starch content of butyrylated starch. Moreover, the porous morphology with less distributed butyl groups on the granular surface contributed to a faster fermentation rate in B-WMS. The current study reveals the influence of botanical origin on butyl group distribution, which in turn plays a pivotal role in regulating the intestinal digestion and colonic fermentation of butyrylated starch.

Understanding the multi-scale structure and digestibility of different waxy maize starches

This work concerns different cultivars of waxy maize starch (WMS), from which a significant correlation between the multi-scale structure and the digestibility has been identified. WMSs show a typical A-type crystalline polymorph. The surface porosity of WMS granules facilitates their digestibility. In contrast, the in vitro digestion results indicate that the resistant starch (RS) content increased with higher contents of amylose, single helices, and surface short-range ordered structures. Resistant starch (RS) was found to be made up of single helices and perfect crystallites formed by the fraction of chains with a degree of polymerization (DP) between 13 and 24. Slowly digestible starch (SDS) consists of single helices. Rapidly digestible starch (RDS) is mainly composed of disordered molecular chains in the amorphous regions of starch. This work reveals the relationship between the multiscale structure and digestibility of different WMSs and can provide guidance for the application of WMSs in food or non-food fields.

Estimation of individual starch granule swelling under hydro-thermal treatment

Abstract We propose an automatic algorithm to analyse the swelling kinetics of individual particles floating in a diluted suspension. Our approach is illustrated with a case study in which a diluted aqueous suspension of starch granules are submitted to various heating treatments. The evolution of modified waxy maize starch granules placed on a temperature-controlled stage was tracked using time-lapse light microscopy (one image per second). We relied on an automatic algorithm, developed for the present study, to estimate morphological and kinetic parameters for a large number of granules. Observations showed that above a given temperature, starch granules will evolve towards an equilibrium size. Due to variability of swelling kinetic, individual behaviour was different from the global one. These results suggest that modelling works should take into account the size heterogeneity and kinetic variability of starch granules.

Effect of hydrocolloids on waxy maize starch and its distarch phosphates

Native and cross-linked waxy maize starch (WMS) were heated in water or one of 9 hydrocolloid (HC) solutions. Results indicated that HC affected pasting of the starch and that the various HC interacted to different degrees with native WMS granules (controlling their swelling and disintegration). After comparing the results to those for normal maize starch (NMS), it was concluded that most HC acted on both WMS and NMS, only in different ways and to different degrees, and that the presence or absence of amylose was probably involved in creating the differences, but that might not be the entire reason. Results also indicated that native WMS, less cross-linked WMS, and more cross-linked WMS each behaved in a distinct way when a HC was added and that most HC effected an increase in granule strengthening with cross-linked NMS being strengthened more than cross-linked WMS. A hypothesis for the effects of HC on granule swelling and pasting is presented. It is also acknowledged that attributes imparted by the HC itself may impact paste rheology.

Distribution of octenylsuccinate substituents within a single granule of modified waxy maize starch determined by Raman microspectroscopy

Octenylsuccinic anhydride (OSA)-modified starches were prepared in granular form from waxy maize starch at two levels (3% and 9%, based on the weight of starch) of OSA reagent. The distribution of OS groups at five positions within a single starch granule was determined by Raman microspectroscopy. OSA-modified starch had one additional peak at 1670 cm−1, indicative of the carbonyl group in OS group bound to starch molecules. For each Raman spectrum obtained at a given position on a starch granule, the ratio of the band areas of carbonyl (1679 cm−1) to starch (2910 cm−1) was calculated. The highest level of OS groups was found on the granular surface. However, the level of OS groups in the center of granules also was high and nearly equal to that on the surface. The regions between the surface and the hilum of the waxy maize starch granules had reduced OS substitution.

Characterization of non-solvent precipitated starch using asymmetrical flow field-flow fractionation coupled with multiple detectors

Non-solvent precipitated starch (non-SPS) is a novel component for starch-based emulsions. Herein, three non-SPS materials were prepared using ethanol as a precipitant of waxy maize starch granules (WMs). The WMs were either untreated (SP) or pre-treated via acid-hydrolysis (AHSP). In addition, SP was modified using n-octenyl succinic anhydride (OSA), yielding OSASP. This study aimed to investigate the influence of the non-SPS preparation method on the size, molar mass (M), and apparent density (ρapp) of the materials when subjected to different dissolution/dispersion procedures using asymmetrical flow field-flow fractionation (AF4). The results showed that the molar mass, size, and apparent density depended on the type of non-SPS with a decrease in Mw (1.8–9.4 g/mol) and rrms (60–148 nm) upon re-dispersion in different media in the order: SP > OSASP > AHSP. Moreover, different types of non-SPS materials displayed different conformational properties and were stable in aqueous solution at room temperature in the investigated time (24 h).

Distribution of octenylsuccinic groups in modified waxy maize starch: An analysis at granular level

This study aimed to report the distribution of octenylsuccinic (OS) groups in waxy maize starch granules. A series of octenylsuccinic anhydride (OSA) substituted starch with degree of substitution (DS) ranging from 0.018 to 0.068 were prepared. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed an integrated granular structure of OSA starch were maintained, and the crystal regions, likewise, were not modified. Fourier transform infrared spectroscopy (FTIR) results suggested that OS groups could be grafted on surface of starch granules. However, Confocal 2D Raman microscopy confirmed that OS groups are located unevenly throughout the starch granule, with an increased intensity in the center. A refined lamellar model was proposed, which indicated that OS groups occurred on each layer of amorphous regions, and further modified the center of the cavity, probably due to the OSA reagent accessibility to hilum by the presence of a large number of channels in each granule.

Measurement and characterization of external oil in the fried waxy maize starch granules using ATR-FTIR and XRD

Concerns regarding increased dietary oil uptake have prompted efforts to investigate the oil absorption and distribution in fried starchy foods. In the present study, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, together with a chloroform–methanol method, was used to analyze the external and internal oil contents in fried starchy samples. The micromorphology of fried starchy samples was further investigated using scanning electron microscope (SEM), polarized light microscope (PLM) and confocal laser scanning microscopy (CLSM). The results indicated that large amounts of oil were absorbed in or within waxy maize starch, but the majority of oil was located near the surface layer of the starch granules. After defatting, the internal oil was thoroughly removed, while a small amount of external oil remained. As evidenced by the changes of the crystalline characteristics with the help of X-ray diffraction (XRD), the interaction between starch and lipids on the surface was confirmed to form V-type complex compounds during frying at high moisture.

Disruption and molecule degradation of waxy maize starch granules during high pressure homogenization process

The mechanism underlying the fragmentation of waxy maize starch (WMS) granules during high-pressure homogenization (HPH) was studied and the results were interpreted in terms of granular and molecular aspects. The diameter of disrupted starch granules decreased exponentially with increasing HPH pressure, but decreased linearly with increasing of HPH cycles. Scanning electron microscopy revealed a cone-like inside-out disruption pattern through the channels that resulted in separation of blocklets fragments or starch fragments. The Mw of amylopectin was reduced by ∼half following treatment at 150MPa with two cycles, or at 100MPa for eight cycles, and the decrease was in accordance with the disruption of starch granules. This indicated that amylopectin was “protected” by blocklets, and the disruption of WMS granules mainly occurred close to the linkage among blocklets. Increasing the HPH pressure appeared to be more effective for breaking starch granules than increasing the number of HPH cycles.

Morphological characteristics and physicochemical properties of the coproducts from wet milling of waxy maize starch

The aim of this work was to evaluate the morphological characteristics and physicochemical properties of coproducts obtained in wet milling of waxy maize starch (WMS). Coproduct A was obtained from the sieving process and was characterized by its high content of dietary fiber and starch (44 and 37 g 100 g−1, respectively), and the coproduct B was obtained from the flotation and decantation of the aqueous part and showed high contents of proteins and lipids (16 and 32 g 100 g−1, respectively). Micrographs showed higher content of WMS and dietary fiber in coproduct A. Both the coproducts showed a diffraction pattern of X-ray type A with higher definition of peaks in coproduct A. There was not significant difference between the gelatinization temperatures of coproducts A and B (73.47 and 73.90 °C, respectively), since the WMS granules did not degrade during extraction steps of WMS. Coproduct A showed higher waxy maize starch content retained during the wet processing, with Tp 73.47 °C, ΔH 47.34 J g−1 and relative crystallinity 67.10%. Principal component analysis showed both the morphological and physicochemical behaviors were important in the discrimination of coproducts from wet milling of waxy maize. Coproduct A can be used as raw material in the preparation of bakery products due to the high fiber content and higher WMS content. On the other hand, coproduct B did not show viscosity but showed higher content of lipid and protein; then, it is indicated to be used as a supplement of lipids and proteins in preparations of food products.

Effect of heat-moisture treatment under mildly acidic condition on fragmentation of waxy maize starch granules into nanoparticles

Waxy maize starch was modified by a heat-moisture treatment (HMT) under acidic conditions followed by homogenization to create starch nanoparticles. Waxy maize starch was heated at 130 °C for 3, 5, or 8 h under mildly acidic conditions (0.00, 0.10, or 0.15 N sulfuric acid solution) and homogenized for up to 60 min. The crystalline, molecular, and granular structures of starch were effectively changed without severe loss of starch substance (less than 25%) by the HMT under acidic conditions. The HMT under acidic conditions enhanced short-range order of starch granules based on the results of FT-IR but decreased the proportion of amylopectin long chains. The data suggest that the amorphous region of the starch granule was readily hydrolyzed by the acidic condition during the HMT. Moreover, homogenization after the HMT (0.15 N for 8 h) induced fragmentation of starch granules into nano-sized particles with diameters less than 40 nm.

Processing of edible films based on nanoreinforced gelatinized starch

Fully biobased edible films were prepared using native potato starch plasticized with glycerol and further reinforced with catechin (Cat) and starch nanocrystals (SNC) obtained by acidic hydrolysis from waxy maize starch granules. The thermal stability of starch nanocrystals obtained at different pH was studied, resulting on a decreasing in thermal stability at higher pH values. The X-ray diffraction patterns of the plasticized reinforced materials display complete destructuration of starch by solvent casting process. Plasticized films showed lower onset degradation temperatures than non-plasticized starch film. The reduction of the inter- and intra-molecular bonds interaction within the polymer matrix due to glycerol presence leads to a decrease of the thermal stability of the whole system. On the other hand, Cat and SNC produced an increase on the thermal stability of the bionanocomposites delaying the beginning of the thermal decomposition of starch/glycerol systems of about 20 °C. The mechanical performance was also improved in the ternary bionanocomposite edible films. All the edible films were fully disintegrated in compost conditions suggesting their possible applications as biodegradable edible films for packaging.

Molecular rearrangement of waxy and normal maize starch granules during in vitro digestion

The objective of the present study is to understand the changes in starch structures during digestion and the structures contributing to slow digestion properties. The molecular, crystalline, and granular structures of native waxy maize, normal maize, high-amylose maize, and normal potato starch granules were monitored using SEC, XRD, DSC, and SEM. The amylose and amylopectin molecules of all four starches were hydrolyzed to smaller dextrins, with some having linear molecular structure. Neither the A- nor B-type crystallinity was resistant to enzyme hydrolysis. Starch crystallites with melting temperature above 120°C appeared in waxy and normal maize starches after digestion, suggesting that the linear dextrins retrograded into thermally stable crystalline structure. These crystallites were also observed for high-amylose maize starch before and after digestion, contributing to its low enzyme digestibility. On the contrary, the enzyme-resistant granular structure of native normal potato starch was responsible for its low susceptibility to enzyme hydrolysis.

Amaranth protein films reinforced with maize starch nanocrystals

The effect of the addition of starch nanocrystals – prepared from waxy and normal maize starch granules – to amaranth protein formulations on the physicochemical and structural properties of the resulting nanocomposite films was studied. All nanocomposites films were homogeneous, translucent and had similar thickness and optical properties than the neat protein film due to the good dispersion of the nanoreinforcements in the protein matrix and the good chemical affinity between both components. Nevertheless, the presence of nanocrystals affected differently the way in which protein matrix stabilized, according to the origin of the reinforcement: mainly by disulfide bonds for waxy maize nanocrystals and by hydrogen bonds for normal maize nanocrystals. This induced a different reinforcing effect for amaranth protein films, being more significant for normal maize nanocrystals that however presented a lower crystallinity. Moreover, nanocomposite films presented improved water vapor permeability (WVP), water uptake (WU), surface hydrophobicity and mechanical behavior than proteins films and also a delay in their weight loss in soil.

Extrusion of polysaccharide nanocrystal reinforced polymer nanocomposites through compatibilization with poly(ethylene oxide).

Polysaccharide nanocrystals with a rodlike shape but with different dimensions and specific surface area were prepared from cotton and capim dourado cellulose, and with a plateletlike morphology from waxy maize starch granules. The rheological behavior of aqueous solutions of poly(ethylene oxide) (PEO) with different molecular weights when adding these nanoparticles was investigated evidencing specific interactions between PEO chains and nanocrystals. Because PEO also bears hydrophobic moieties, it was employed as a compatibilizing agent for the melt processing of polymer nanocomposites. The freeze-dried mixtures were used to prepare nanocomposite materials with a low density polyethylene matrix by extrusion. The thermal and mechanical behavior of ensuing nanocomposites was studied.

Structural changes from native waxy maize starch granules to cold-water-soluble pyrodextrin during thermal treatment.

The structural changes occurring during the thermal conversion of insoluble native waxy maize starch granules to cold-water-soluble pyrodextrin under acidic conditions have been investigated by multiple techniques, including synchrotron small-angle X-ray scattering (SAXS), wide-angle X-ray scattering, differential scanning calorimetry, and gel permeation chromatography. In a mixture of water/glycerol (20/80, w/w), the SAXS characteristic peak at ca. 0.6 nm(-1) decreased in intensity as pyrodextrin solubility increased. The peak disappeared as pyrodextrin solubility reached 100%. Starch crystal size, its associated melting enthalpy, and pyrodextrin molecular size decreased as solubility increased. Although starch structure changed during thermal conversion, the pyrodextrins appeared identical to the native starch when observed in glycerol under a normal and polarized light microscope. It is proposed that the starch backbone is hydrolyzed by acid in the amorphous region and the crystalline region with starch molecules being hydrolyzed into small molecular fractions but persisting in a radial arrangement.

Analysis of a preferential action of α-amylase from B. licheniformis towards amorphous regions of waxy maize starch

Waxy maize starch was subjected to α-amylase (Bacillus licheniformis) hydrolysis in buffered medium to determine the evolution of reaction in quantitative terms and also in terms of the morphology and crystallinity of the partially hydrolyzed starch granules. Gathered data allowed studying the pattern of action of this α-amylase over waxy maize starch granules, with particular focus on a preferential hydrolysis of the amorphous regions of starch. Results showed that waxy maize starch hydrolysis followed a two-stage kinetic profile with an initial stage characterized by high reaction rate, followed by a slower second stage. The change of hydrolysis rate occurred at approximately 6h of reaction, a time for which X-ray diffraction data quantitatively analyzed by three different techniques showed a maximum of crystallinity in partially hydrolyzed granules. Scanning electron microscopy images illustrated the action of α-amylases which implied the exoerosion of the granules surface, the entry of α-amylases into the granules through radial channels, their endoerosion towards the granule exterior, and their fragmentation. Fragmentation of waxy maize starch granules revealed internal layered structures of starch which were interpreted as hydrolyzed/non-hydrolyzed growth rings. Under the conditions chosen, kinetic, electron microscopy and X-ray data all gave evidence of a preferential action of α-amylase from Bacillus licheniformis towards the less ordered regions of waxy maize starch. Results showed that, provided the proper hydrolysis time is chosen, starch granules with increased crystallinity can be obtained by a pure enzymatic treatment.

Pickering emulsions stabilized by native starch granules

The surface properties of native starch, namely rice, waxy maize, wheat and potato starch were characterized by contact angle measurement, zeta-potential, and then the emulsifying ability of these native starch granules was investigated by using liquid paraffin as oil phase and starch granules as sole emulsifier. It was found that emulsions could be prepared by using rice, waxy maize and wheat starch granules as emulsifier, but not potato starch, which had no emulsifying ability even when the concentration of starch granules as high as 15wt% relative to water phase. Rice starch was the best emulsifier among these native starches. The emulsion stabilized by rice granules proved to be stable to coalescence for several months when the starch concentration was above 3wt% relative to water phase. With the increasing of the rice starch concentration, the sizes of droplets decreased and the stability of emulsions enhanced. The salt and pH values had no significant influence on the packing structure of native starch granules at interface.