Native Corn Starch Granules Research Articles

The effect of reduction on the properties of the regioselectively oxidized starch granules prepared by bromide-free oxidation system

Development of intact oxidized starch granules by regioselective oxidation technology is of interest and provides a new research direction for oxidized starch. In this study, new sodium tetrahydridoborate (NaBH4)-treated oxidized starch (OS-BH4) granules were prepared by a one-pot method, where native corn starch (NS) granules were oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)/sodium hypochlorite (NaClO) system followed by reduction with NaBH4. Oxidized starch (OS) granules without NaBH4 reduction were also prepared to investigate the effect of C6 aldehyde groups remained after TEMPO-mediated oxidation on properties of the granules. When degrees of oxidation were controlled to be not higher than 12%, both the OS and OS-BH4 granules had similar morphology to the NS granules with envelopes. Compared to the OS granules, except for lower pasting temperatures and dextrose equivalents, the OS-BH4 granules had higher molecular weights, degrees of polymerization (DP), peak viscosities, final viscosities, and swelling power. Difference of the properties was considered related to (1) repulsive forces formed between the C6 carboxylate groups, (2) C6 aldehyde groups with lower hydrophilicity than the C6 hydroxyl groups, and (3) some hemiacetal linkages formed between the C6 aldehyde groups and the hydroxyl groups. Furthermore, pregelatinized OS-BH4 granules were preliminarily prepared, which showed good swelling behavior with intact granular morphology in alkaline environment.

Development and characterization of irradiated-corn-starch films

The effect of 60Co gamma ray irradiation on the physicochemical and crystalline properties of native corn starch were investigated. Fourier transform infrared spectroscopy and X-ray diffraction showed that irradiation had a slight effect on the molecular structure of corn starch with crystallinity decreasing with increasing irradiation dose. Particle size analysis showed that 59.1% of native corn starch granules had sizes of ≥8 μm, which decreased to only 24.1% after treatment with an irradiation dose of 40 kGy. Irradiated-corn-starch films were prepared by casting gelatinized irradiated-corn-starch solutions. An increased irradiation dose was found to increase the tensile strength of the resultant films, but caused a significant decrease in water vapor permeability. The irradiated-corn-starch films showed potential for the development of biodegradable starch films with improved properties.

Infusion of catechin into native corn starch granules for drug and nutrient delivery systems

Hydrophilic nutrients, a water insoluble drug, and amino acids were used as infusion materials for analysis w ith HPLC and a micro-plate reader. Only catechin, gallic a cid, and caffeine infused into native corn starch granules. While catechin remained in the native corn starch granule after several washing steps, infused caffeine and gallic acid were washed out. A release study was also performed using pancreatin α-amylase. Infused catechin was successfully released when native corn starch granules were decomposed. Infusion and maintenance of catechin in native corn starch granules were probably due to a unique chemical structure of the benzene-tetrahydropyran group that affected interactions with starch. However, experiments using epicatechin and rutin indicated that the benzenetetrahydropyran group structure may not have been the only reason for infusion of guest materials. The 3 dimensional structure of the benzene-tetrahydropyran group probably also influenced infusion of materials.

Cross-flow microfiltration of fermentation broth containing native corn starch

Cross-flow microfiltration of fermented mash containing native corn starch granules from a simultaneous saccharification and fermentation process, was investigated with respect to the process performance. Influence of transmembrane pressure and cross-flow velocity on normalized permeate flux rate decline and membrane fouling were examined. The microfiltration system was equipped with a tubular ceramic membrane with 0.45μm pore size. A combined pore-blockage–cake-filtration model was successfully used to determine the process performance and identify principal fouling mechanisms. Experimental results revealed that the fouling phenomenon taking place during microfiltration of the fermented mash follows a pattern of initial complete pore blockage and subsequent cake formation. As a result, initial rapid flux decline is followed by gradual flux decline. Fouled membranes were characterized using scanning electron microscopy (SEM). The membrane surface characteristics examined by SEM images evidenced formation of dense deposit on the upper membrane surface. Rinsing the fouled membrane with water followed by investigation of the permeate flux rate indicated occurrence of increased fouling, when microfiltration was carried out at high transmembrane pressure. The highest normalized flux decline was observed for microfiltration operated at the highest transmembrane pressure (1.4bar) and the lowest cross flow velocity (1ms−1). It is recommended to use high cross-flow velocity (4.55ms−1) and low transmembrane pressure (0.35bar) to minimize membrane fouling, triggered by components of the fermented mash.

Impacts of Acid Treatment on the Characteristics of Native Corn Starch Granules

Native corn starches were acid-treated at 53 °C for hours in HCl aqueous solution. The peak temperature (Tp) and heat of gelatinization (ΔHgel) before and after treatments were determined. The average particle size, TG and viscosity were measured. The results showed that the viscosity of corn starch decreased from 630mPa to 4.6mPa after acid treatment for 6h. The average particle size decreased and ΔHgel decreased obviously after acid modification.

Synthesis of aliphatic amidediol and used as a novel mixed plasticizer for thermoplastic starch

In this paper, aliphatic amidediol was synthesized and mixed with glycerol used as a plasticizer for preparing thermoplastic starch (AGPTPS). The yield of aliphatic amidediol was 91%. FT-IR expressed that the mixture of aliphatic amidediol and glycerol formed stronger and stable hydrogen bond with starch molecules compared to the native cornstarch. By scanning electron microscope (SEM) native cornstarch granules were proved to transfer to a homogeneous continuous system. After being stored for a period time at room temperature, the mechanical properties of AGPTPS were also studied. As a mixed plasticizer, aliphatic amidediol and glycerol would be practical to extend TPS application scopes.

Study on the properties of ethylenebisformamide plasticized corn starch (EPTPS) with various original water contents of corn starch

EPTPSs were prepared based on various original water contents of corn starch (10%, 13%, 16% and 19%). The structure and mechanical performance of resulting TPSs were studied in detail. The hydrogen bond between plasticizer and starch was detected by FT-IR. By scanning electron microscope (SEM), native corn starch granules were proved to transfer to a continuous phase. The crystallinity and retrogradation of EPTPSs were studied by X-ray diffraction (XRD). The effect of water on the mechanical properties of EPTPSs was also tested. The effect of moisture content on the glass–rubber transition temperature ( T g) was studied using dynamic thermal mechanical analysis (DMTA). It revealed that T g of EPTPS decreased with increasing moisture content.

Study on the properties of ethylenebisformamide and sorbitol plasticized corn starch (ESPTPS)

A mixed plasticizer (ethylenebisformamide and sorbitol) was used to the preparation of thermoplastic starch (TPS). And the other three TPSs were prepared as a contradistinction, including glycerol plasticized starch (GPTPS), ethylenebisformamide plasticized starch (EPTPS), and sorbitol plasticized starch (SPTPS). FT-IR expressed that the microcosmic chemical environments of the group in all these TPSs mentioned above shifted to lower frequency compared with the native corn starch, which indicated that, the strong and stable hydrogen bond had been formed between plasticizers and starch. By scanning electron microscope (SEM) native corn starch granules were proved to transfer to a continuous phase. After being stored for 2 weeks at ambient atmosphere, the mechanical properties of these TPSs were investigated and a comprehensive tensile stress and elongation at break of ESPTPS was obtained better than that of EPTPS, SPTPS, and GPTPS. X-ray diffraction (XRD) showed that the typical A-style crystallinity in the native corn starch has been destructed. On the other hand, water resistance of ESPTPS was better than the conventional GPTPS. ESPTPSs proved to be having good thermal stability by thermogravimetric analysis (TGA), and the decomposition temperature was increased with the increase of the sorbitol content. T g (detected by dynamic thermal mechanical analysis (DTMA)) of ESPTPSs was lower than that of EPTPS and SPTPS.

The Effects of Citric Acid on the Properties of Thermoplastic Starch Plasticized by Glycerol

The effects of citric acid on the properties of glycerol-plasticized thermoplastic starch (GPTPS) were studied. In the presence of citric acid and glycerol, native cornstarch granules are transferred to a continuous phase as shown by scanning electron microscopy (SEM). As shown by thermogravimetric analysis (TGA), the improvement in thermal stability confirms that the adhesion between citric acid, glycerol, water and starch in TPS was enhanced with the addition of citric acid. It was proven by Fourier transform infrared (FTIR) spectroscopy that citric acid can form stronger hydrogen-bond interactions with starch than glycerol. Both FTIR spectroscopy and X-ray diffractometry of citric acid-modified GPTPS (CATPS) revealed that citric acid can effectively inhibit starch re-crystallization (i.e. retrogradation), because of the strong hydrogen-bond interaction between citric acid and starch. Rheology studies revealed that citric acid can obviously decrease the shear viscosity and improve the fluidity of TPS. Citric acid can also improve the elongation of GPTPS and ameliorate the water resistance of GPTPS at high relative humidities, but decreased the tensile stress.

Formamide as the plasticizer for thermoplastic starch

AbstractAs a novel plasticizer, formamide was tested in thermoplastic starch (TPS), in which native cornstarch granules were proved to transfer to a continuous phase by scanning electron microscope (SEM) and the hydrogen bond interaction between plasticizer and starch was proved by Fourier transform infrared (FTIR) spectroscopy. Mechanical tests showed that tensile strength and Young's modulus of formamide‐plasticized TPS (FPTPS) were lower than glycerol‐plasticized TPS (GPTPS) and elongation at break and energy break were higher. The effect of formamide and glycerol on the retrogradation of TPS was studied using X‐ray diffractometry. Formamide could effectively restrain the starch retrogradation at three different relative humidity (RH) environments, because it could form the more stable hydrogen bonds with the starch hydroxy group than glycerol. From these results, we found that the elongation at break, energy break, and the retrogradation of TPS were ameliorated by formamide. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1769–1773, 2004

Studies on the morphological and rheological properties of granular cold water soluble corn and potato starches

Granulated cold water soluble (GCWS) starches were prepared from corn starch and starches separated from four potato cultivars using alcoholic-alkaline method. The morphological, thermal and rheological properties of GCWS corn and potato starches were studied. The amylose content of the GCWS starches from corn and potato starches were significantly lower as compared to their counterparts native starches. GCWS potato starches showed higher cold water solubility than GCWS corn starch. Cold water solubility of GCWS starches prepared from different potato cultivars also differed significantly. Native potato starch granules were larger in size (15–45μm), smooth, oval and irregular or cuboidal shaped while native corn starch granules were smaller in size (5–18μm), less smooth, rounded and angular shaped. Both corn and potato starches were distorted and indented during conversion to GCWS starches, however, this effect was more pronounced in potato starches than corn starch. The extent of distortion in GCWS starches differed significantly in starches prepared from different potato cultivars. The potato cultivars having starch with large sized granules showed more granular distortion as compared in those having small sized granules during GCWS starch production. Native corn starch showed higher transition temperatures and lower enthalpy of gelatinization (ΔHgel) than native potato starches. GCWS corn and potato starches did not show any gelatinization endotherm during heating between 20 and 100°C. The rheological properties such as G′, G″, η′ and Tanδ of GCWS corn and potato starches also showed significant variation, when subjected to frequency sweep testing. GCWS potato starches showed higher G′, G″, η′ and lower Tanδ than GCWS corn starch. The G′, G″, η′ of the GCWS starches from both corn and potato increased and Tanδ decreased with the increase in temperature. The turbidity of GCWS and native corn and potato starches increased during storage at 4°C, however, the increase was less pronounced in GCWS starches.

Internal structure of the starch granule revealed by AFM

Atomic force microscopy images of sectioned native corn starch granules show evidence of the well-known radial organisation of the starch macromolecules, with the less-ordered hilum region near to the centre. Native granules show blocks 400–500 nm in size that span the growth rings. Lintnerised starch granules, where a mild acid hydrolysis has been used to remove the amorphous and less crystalline parts of the granule, clearly show smaller ‘blocklets’ within the rings approximately 10–30 nm in size. This level of organisation within the growth rings corresponds to the blocklet or superhelix structures that have been proposed in the literature for the association or clustering of amylopectin helices. Mechanical property imaging techniques have provided enhanced contrast to view this morphology, and shown the deformability of the starch structure under contact mode imaging conditions.

Structural and Chemical Properties of Native Corn Starch Granules

AbstractNative corn starch granules were fractionated according to size and apparent density. Individual fractions were characterized by high performance size exclusion chromatography, differential scanning calorimetry, X‐ray diffraction, scanning electron microscopy and enzymatic susceptibility. Native starch granules were not homogeneous; they showed differences in solubility, enzymatic susceptibility and crystallinity. The small, less dense granules were more crystalline than the more abundant larger and denser granules. Neither the degree of solubility of each starch fraction in methyl sulfoxide (DMSO), nor its enzymatic susceptibility, was correlated with fraction crystallinity. Starch granules with different sizes or apparent densities had inherent variations in their crystallinity, which influences granule functional properties. The helical nature of amylose and amylopectin may also contribute to the functional complexity and variability observed in the population of normal starch granules.