Preparation and characterization of cationic corn starch with a high degree of substitution in dioxane-THF-water media

Cationic corn starch derivatives with a high degree of substitution are prepared in alkaline solution or in mixed media of organic solvent and water with different levels of the cationic reagent, 2,3-epoxypropyltrimethylammonium chloride. The starch cationization yield is investigated, and the results indicate that the degree of substitution (DS) of the samples depends on the reaction conditions and reaction media. The maximum DS values are up to 1.37 in 1,4-dioxane alkaline-aqueous solution. Meanwhile, the structures of the cationic starch derivatives are characterized by elemental analyses, FTIR spectroscopy, X-ray diffraction, and ¹³C NMR spectroscopy, as well as by SEM techniques.     

Locations of hypochlorite oxidation in corn starches varying in amylose content

The general oxidation mechanism by hypochlorite on starch has been well studied, but the information on the distribution of the oxidation sites within starch granules is limited. This study investigated the locations where the oxidation occurred within corn starch granules varying in amylose content, including waxy corn starch (WC), common corn starch (CC), and 50% and 70% high-amylose corn starch (AMC). Oxidized corn starches were surface gelatinized by 13 M LiCl at room temperature to different extents (approximately 10%, 20%, 30%, and 40%). The surface-gelatinized remaining granules were separated and studied for structural characteristics including carboxyl content, amylose content, amylopectin chain-length distribution, thermal properties, and swelling properties. Oxidation occurred mostly at the amorphous lamellae. More carboxyl groups were found at the periphery than at the core of starch granules, which was more pronounced in oxidized 70% AMC. More amylose depolymerization from oxidation occurred at the periphery of CC. For WC and CC, amylopectin long chains (>DP 36) were more prone to depolymerization by oxidation. The gelatinization properties as measured by differential scanning calorimetry also supported the changes in amylopectin fine structure from oxidation. Oxidized starches swelled to a greater extent than their unmodified counterparts at all levels of surface removal. This study demonstrates that the locations of oxidation and physicochemical properties of oxidized starches are affected by the molecular arrangement within starch granules.     

Synthesis of oxidized guar gum by dry method and its application in reactive dye printing

The aim of this study was to prepare oxidized guar gum with a simple dry method, basing on guar gum, hydrogen peroxide and a small amount of solvent. To obtain a product with suitable viscosity for reactive dye printing, the effects of various factors such as the amount of oxidant and solvent, reaction temperature and time were studied with respect to the viscosity of reaction products. The product was characterized by Fourier transform infrared spectroscopy, size exclusion chromatography, scanning electron microscopy and differential scanning calorimetry. The hydrated rate of guar gum and oxidized guar gum was estimated through measuring the required time when their solutions (1%, w/v) reached the maximum viscosity. The effects of the salt concentration and pH on viscosity of the resultant product were studied. The mixed paste containing oxidized guar gum and carboxymethyl starch was prepared and its viscosity was determined by the viscometer. The rheological property of the mixed paste was appraised by the printing viscosity index. In addition, the applied effect of mixed paste in reactive dye printing was examined by assessing the fabric stiffness, color yield and sharp edge to the printed image in comparison with sodium alginate. And the results indicated that the mixed paste could partially replace sodium alginate as thickener in reactive dye printing. The study also showed that the method was low cost and eco-friendly and the product would have an extensive application in reactive dye printing.     

Preparation of carbon quantum dots based on starch and their spectral properties

A simple method for the synthesis of water‐soluble carbon quantum dots (CQDs) has been developed based on chemical oxidation of starch. The structures and optical properties of the CQDs were characterized by ultraviolet–visible (UV–Vis) spectroscopy, photoluminescence spectroscopy (PL) and transmission electron microscopy. The CQDs were found to emit bright blue fluorescence and disperse uniformly. The effects of ambient temperature, light and pH on the properties of CQDs were studied. The CQDs exhibited good chemical stability, good photostability and pH sensitivity. Furthermore, the interaction between CQDs and bovine serum albumin (BSA) was investigated. Copyright © 2014 John Wiley & Sons, Ltd.     

Resistant glutarate starch from adlay: Preparation and properties

Reaction conditions were optimized to increase the content of resistant starch in adlay starch using esterification with glutaric acid, and the physicochemical properties of the prepared glutarate starches were investigated. Different amounts of glutaric acid (0.1–0.5 g/g starch, dry weight basis) were reacted with adlay starch at various temperatures (70–130 °C) and reaction times (3–9 h). The resistant starch levels increased with increased glutaric acid content, reaction temperature, and reaction time. The color difference was mainly affected by reaction time. The highest resistant starch content (RS 66%) was obtained using conditions of 0.4 g glutaric acid/g starch, 115 °C, and 7.5 h, with a color difference of 10.24. After digestion with α-amylase and amyloglucosidase, the water-soluble fraction of glutarate starch had more oligosaccharides than high-amylose maize starch (RS 43%). FT-IR and solid-state NMR detected carbonyl groups in the glutarate starch, indicating the formation of cross-linkages through esterification. The granular structure of the glutarate starches was not destroyed and they retained birefringence. After heating with an excess of water, the granules kept their shape but lost their birefringence. The glutarate starches had low solubility in both cold and hot water, and the resistant starch contents were unchanged after heating due to the restriction of swelling by cross-linking. The glutarate starches had a similar chain-length distribution to raw starch, indicating that acid hydrolysis took place at branching points in the amorphous region. Furthermore, the glutarate starches possessed a weaker crystalline region, more diverse double helical chains, and lower enthalpy than raw starch.     

Structural characteristics and physicochemical properties of oxidized corn starches varying in amylose content

The effects of amylose content on the extent of oxidation and the distribution of carboxyl groups in hypochlorite-oxidized corn starches were investigated. Corn starches including waxy corn starch (WC), common corn starch (CC), and 50% and 70% high-amylose corn starches (AMC) were oxidized with NaOCl at three concentrations (0.8%, 2%, and 5%). Carboxyl and carbonyl content of oxidized starches increased with increasing NaOCl concentration. High-AMC (70%) had slightly higher carboxyl and carbonyl contents at 0.8% NaOCl, whereas WC had significantly higher carboxyl and carbonyl contents at 2% and 5% NaOCl levels. Carbohydrate profiles by high-performance size-exclusion chromatography indicate that amylose was more susceptible to depolymerization than amylopectin. Degradation of amylopectin long chains (DP >24) was more pronounced in WC and CC than in AMCs. The crystalline lamellae of WC started to degrade at 2% NaOCl, but those of the other corn starches remained intact even at 5% NaOCl level according to X-ray crystallinity. By using anion-exchange chromatography for separation and size-exclusion chromatography for characterization, carboxyl groups were found to be more concentrated on amylopectin than on amylose, particularly in AMCs. Oxidation decreased gelatinization temperature and enthalpy with WC showing the most decrease and 70% AMC showing the least. The gelatinization enthalpy of 50% AMC decreased significantly faster than those of CC and 70% AMC after 0.8% oxidation. Retrogradation of amylopectin slightly increased after oxidation with increasing oxidation level. The peak viscosities of oxidized WC and CC were higher than those of their native counterparts at 0.8% NaOCl, but this increase was not observed in AMCs. The setback viscosities of 2% NaOCl-oxidized 50% and 70% AMCs were much higher than those of the unmodified counterparts. The extent of oxidation and physicochemical properties of oxidized starches varied greatly with the amylase:amylopectin ratio of corn starches. Amylose was suggested to play an important role in controlling the oxidation efficiency.     

Effects of extrusion and glycerol content on properties of oxidized and acetylated corn starch-based films

Oxidized and acetylated corn starch-based films were prepared by casting with glycerol as a plasticizer. The present study investigated the effects of extrusion prior to film-making and glycerol content on the properties of starch films. The films with extrusion exhibited lower tensile strength, higher elongation at break, higher water vapor permeability and higher oil permeability than those without extrusion. Extrusion reduced heat sealability of the films. With the increase of glycerol content, the films became more flexible with higher elongation at break and lower tensile strength. Water vapor permeability, oil permeability and the range between the onset temperature and the melt peak temperature rose as glycerol content increased. The thermograms indicated that plasticizers and biopolymers were compatible. These results suggested that extrusion did no good to starch films while glycerol content had apparent effect on the mechanical and barrier properties of the films.     

Hydrogen peroxide increases the activities of soxRS regulon enzymes and the levels of oxidized proteins and lipids in Escherichia coli

The effects of hydrogen peroxide treatments on Escherichia coli KS400 and AB1157 cells were assessed by monitoring the accumulation of oxidative damage products, carbonyl proteins and thiobarbituric acid-reactive substances (TBARS), as well as the activities of selected antioxidant enzymes. H(2)O(2) treatment stimulated increases in both TBARS and carbonyl protein levels in dose- and time-dependent manners in KS400 cells. The accumulation of TBARS was much more variable with H(2)O(2) treatment; TBARS content was significantly increased in response to 5 microM H(2)O(2), whereas a significant increase in carbonyl protein content occurred at 100 microM H(2)O(2). Similarly, treatment with 20 microM hydrogen peroxide for different lengths of time resulted in peak TBARS accumulation by 20 min, whereas carbonyl protein levels were significantly elevated only after 60 min. In AB1157 cells, treatment with 20 microM hydrogen peroxide for 20 min led to strong increases in both carbonyl protein and TBARS levels. This treatment also triggered increased activities of enzymes of the oxyR regulon (catalase, peroxidase, and glutathione reductase) in both strains. In the AB1157 strain, H(2)O(2) exposure also increased the activities of two enzymes of the soxRS regulon (superoxide dismutase and glucose-6-phosphate dehydrogenase) by 50-60%. The data show differential variability of lipids versus proteins to oxidative damage induced by H(2)O(2,) as well as strain-specific differences in the accumulation of damage products and the responses by antioxidant enzymes to H(2)O(2) stress.     

Gel formation in mixtures of high amylopectin potato starch and potato starch

The effects of starch granules on the rheological behaviour of gels of native potato and high amylopectin potato (HAPP) starches have been studied with small deformation oscillatory rheometry. The influence of granule remnants on the rheological properties of samples treated at 90 °C was evident when compared with samples treated at 140 °C, where no granule remnants were found. The presence of amylose in native potato starch gave to stronger network formation since potato starch gave higher moduli values than HAPP, after both 90 and 140 °C treatments. In addition, amylose may have strengthened the network of HAPP because higher moduli values were obtained when native potato starch was added to the system. The moduli values of the mixtures also increased with increasing polysaccharide concentration in the system, which is due to an increment in the polysaccharide chain contacts and entanglements. Finally, it was found that a mixture of commercial amylose from potato starch and HAPP resulted in lower values of G′ compared to native potato starch. This indicates that the source of amylose is important for the properties in a blend with native amylopectin.     

Effects of acid hydrolysis and defatting on crystallinity and pasting properties of freeze-thawed high amylose corn starch

Paste of defatted and/or mildly acid-hydrolyzed high amylose corn starch was freeze-thawed, and then the starch was isolated by vacuum drying for the analysis in crystallization and pasting properties. X-ray diffraction pattern and differential scanning calorimetric analysis showed that the crystallinity of the freeze-thawed starch was increased as the degree of hydrolysis increased. The diffraction pattern revealed B- and V-crystals with patterns with diffraction peaks at 17, 20, and 23–25° (2θ), which were developed by amylose recrystallization during the freeze-thawing. The crystal melting enthalpies, for dual endothermic transitions above 100 °C, which resulted from the melting of amylose–lipids complex and amylose double helices were raised by the treatment. The isolated and dried starch formed a paste by aqueous heating under the ambient pressure, and its paste viscogram exhibited substantially higher resistance to shear-thinning, and rapid setback upon cooling. Acid hydrolysis, however, reduced overall paste viscosity, possibly due to the increased crystallinity. Enzyme-resistant starch content in the acid hydrolyzed starch was increased by the freeze-thawing, but not by acid hydrolysis. It was slightly increased by defatting.     

Preparation and properties of starch acetate fibers for potential tissue engineering applications

This article reports the development of fibers from starch acetates that have mechanical properties and water stability better than most polysaccharide‐based biomaterials and protein fibers used in tissue engineering. In this research, starch acetates with three different degrees of substitution (DS) have been used to develop fibers for potential use as tissue engineering scaffolds. Varying the DS of starch acetate will provide fibers with different mechanical properties, hydrophilicity, and degradation behavior. Fibers made from DS 2.3 and 2.8 starch acetates have mechanical properties and water stability required for tissue engineering applications. The starch acetate fibers support the adhesion of fibroblasts demonstrating that the fibers would be suitable for tissue engineering and other medical applications. Biotechnol. Bioeng. 2009;103: 1016–1022. © 2009 Wiley Periodicals, Inc.     

Functional properties of pregelatinized and cross-linked cassava starch obtained by extrusion with sodium trimetaphosphate

Cassava starch was cross-linked with sodium trimetaphosphate (STMP) on a Cerealtec single-screw extruder at different extrusion temperatures and concentrations of STMP and NaOH. The effect of variables on functional properties of the products was analysed by the response–surface methodology. The degree of substitution (DS) was influenced by NaOH and phosphorus level, and increased when their concentration increased. Extrusion temperature affected water absorption, cold viscosity and gel characteristics. The introduction of phosphate groups by cross-linking, with maximum DS of 1.5×10⁻⁴, increased the gel strength, water absorption index, resistance to high temperature and shear, and decreased gel cohesiveness, starch clarity and water solubility index. The products had different DS and degree of gelatinization and thus can be applied in several kinds of foods.     

Determination of the DS and substituent distribution of cationic alkyl polyglycosides and cationic starch ethers by GLC after dealkylation with morpholine

The total DS and substituent distribution of starch and alkyl polyglycosides functionalised as O-(2-hydroxy-3-trimethylammonium)propyl ethers were determined by GLC. To achieve volatile analytes, the samples were submitted to methanolysis, N-demethylation and O-trimethylsilylation. Alternatively hydrolysis, reduction with NaBH(4) and subsequent O-acetylation were performed, but suffered from intramolecular acetal formation of 2-O-substituted residues, preventing reduction. Morpholine as nucleophile was superior to thiophenolate with regard to quantitative dealkylation and side product formation. The ratio of un-, mono-, di-, tri-, and tetrasubstituted compounds was determined. The total DS values calculated from these mole fractions were in good agreement with those obtained from elemental analysis or NMR from standards. Regioselectivity of the cationisation reaction was determined after methanolysis, permethylation and Hofmann elimination by GLC.     

Starch derivatives of high degree of functionalization. 1. Effective, homogeneous synthesis of p-toluenesulfonyl (tosyl) starch with a new functionalization pattern

Pure p-toluenesulfonyl (tosyl) starch with an insignificant formation of chlorodeoxy groups was prepared by reacting starch dissolved in the solvent system N,N-dimethyl acetamide in combination with LiCl. Interestingly, the viscosity of the starch dissolved in the solvent system increases with the increasing amount of LiCl. The tosyl starch samples obtained were characterized by means of elemental analysis, FITR and ¹³C NMR spectroscopy. The degree of substitution (DS_Tos) of the products can be controlled in range from 0.4 to 2.0 by adjusting the molar ratio of tosyl chloride per anhydroglucose unit up to 6.0 mol/mol. The tosyl starch samples are readily soluble in various organic solvents. As revealed by means of ¹³C NMR analysis as well as by analysis of the corresponding 6-iodo-6-deoxy derivatives, a faster tosylation at position 2 than at positions 6 and 3 takes place. The thermal stability of tosyl starch increases with increasing DS_Tos and degradation starts at 166°C for the sample of DS_Tos of 0.61. The remaining OH groups of tosyl starch are reactive and can be additionally modified by acetylation reactions.     

Comparison of methods to determine the degree of gelatinisation for both high and low starch concentrations

A general procedure was developed to measure the degree of gelatinisation in samples over a broad concentration range. Measurements based on birefringence, DSC (Differential scanning calorimetry), X-ray and amylose–iodine complex formation were used. If a 10 w/w % wheat starch–water mixture was used, each method resulted in approximately the same degree of gelatinisation vs. temperature curve. In case the gelatinisation of a 60 w/w % wheat starch–water mixture was followed as a function of the temperature, each method resulted in a different degree of gelatinisation vs. temperature curve. DSC and X-ray measurements are preferred, because they can be used to determine when the final stage of the gelatinisation process has been completed. Birefringence and amylose–iodine complex formation measurements are suitable alternatives if DSC and X-ray equipment is not available, but will lead to different results. The differences between the methods can be explained by considering the phenomena that take place during the gelatinisation at limiting water conditions.

Based on the experimental data obtained with DSC and X-ray measurements, the gelatinisation of 10 w/w % and 60 w/w % wheat starch–water mixtures started at the same temperature (approximately 50 °C). However, complete gelatinisation was reached at different temperatures (approximately 75 °C and 115 °C for, respectively, 10 w/w % and 60 w/w % wheat starch–water mixtures) according to the experimental DSC and X-ray data. These results are in accordance with independent DSC measurements that were carried out.

The Flory equation was adapted to provide a quantitative explanation for the curves describing the degree of starch gelatinisation as a function of the starch–water ratio and the temperature. The gelatinisation curves that were obtained with the model are in good agreement with the experimentally determined curves. The parameters , ΔH_u and χ₁₂ that resulted in the lowest sum of the squared residuals are 291 ± 63 °C, 29.2 ± 3.9 kJ/mol and 0.53 ± 0.05 (95% confidence interval). These values agree with other values reported in literature.     

Development of formulae for estimating amylose content and resistant starch content based on the pasting properties measured by RVA of Japonica polished rice and starch

We searched for the easy and simple method to measure the novel indicators which reflect not only AAC, but also (RS) based on pasting properties using RVA. Novel indexes such as SB/Con and Max/Fin (Maximum viscosity/Minimum viscosity) ratios had a very high correlation with proportion of intermediate and long chains of amylopectin; Fb₁₊₂₊₃ (DP ≧ 13). In Japonica polished rice, estimation formulae for AAC and RS content were developed using novel indexes based on pasting properties by RVA, and these equations showed determination coefficients of 0.89 and 0.80 for calibration and 0.71 and 0.75 for validation test. We developed the estimation formulae for AAC and RS content for Japonica starch samples. These equations showed determination coefficients of 0.86 and 1.00 for calibration and 0.76 and 0.83 for validation test, which showed that these equations can be applied to the unknown rice samples.     

Enzymatic modification of cassava starch by bacterial lipase

Enzymatic modification of starch using long chain fatty acid makes it thermoplastic suitable for a myriad of industrial applications. An industrial lipase preparation produced by Burkholderia cepacia (lipase PS) was used for modification of cassava starch with two acyl donors, lauric acid and palmitic acid. Reactions performed with palmitic acid by liquid-state and microwave esterification gave a degree of substitution (DS) of 62.08% (DS 1.45) and 42.06% (DS 0.98), respectively. Thermogravimetric analysis showed that onset of decomposition is at a higher temperature (above 600°C) for modified starch than the unmodified starch (280°C). Modified starch showed reduction in α-amylase digestibility compared to native starch (76.5–18%). Swelling power lowered for modified starch as esterification renders starch more hydrophobic, making it suitable for biomedical applications as materials for bone fixation and replacements, carriers for controlled release of drugs and bioactive agents. Thus enzymatic esterification is ecofriendly.     

HNO3/H3PO4–NANO2 mediated oxidation of cellulose — preparation and characterization of bioabsorbable oxidized celluloses in high yields and with different levels of oxidation

The reaction of cellulose with a mixture of HNO₃/H₃PO₄–NaNO₂ (2:1:1.4, v/v/%w) at room temperature for different time intervals has been investigated to produce oxidized cellulose (OC), a biocompatible and bioresorbable polymer. The results revealed an increase in carboxyl content of OC with increasing reaction time, corresponding to about 8.0, 13.4, 17.4 and 18.4% carboxyl content after 12, 24, 36, and 48 h, respectively. The yield of OC ranged between 75 and 81%. The use of different ratios of HNO₃ and H₃PO₄, (11:1, 4:1, 2:1, 1:1, 1:2, and 1:4; v/v), in the reaction had no significant effect on the carboxyl content and yield of the OC products. All products, as produced, were low crystallinity (27–35%) fibrous materials. The length of fibers decreased with increasing reaction time. After ball milling for 24 h, the length of fibers further decreased and products converted into a fine powder consisting of small fibers and aggregated non-fibrous particles. The degrees of polymerization (DP) of the OC products produced after 12, 24, and 48 h of reaction duration were 81, 63, and 53, respectively. After ball milling for 24 h, the corresponding values changed to 57, 51 and 46. However, no significant change in the crystallinity of the products was noted after ball milling. The TGA results showed the OC products to be less thermally stable than cellulose. The degradation temperature appears to decrease with increasing carboxyl content. In conclusion, the results show that the low crystallinity OC products can be successfully prepared in high yields and with different levels of carboxyl content from cellulose by treatment with a mixture of HNO₃/H₃PO₄–NaNO₂.