Chemical modification of starch

Effect of Fenton reaction parameters on the structure and properties of oxidized wheat starch

Wheat starch was oxidized through a Fenton reaction by hydrogen peroxide and Iron II sulfate as a catalyst at various concentrations and reaction duration. The formation of carbonyl and carboxyl groups confirmed the starch oxidation as determined with Fourier-transform infrared (FTIR) spectroscopy. The degree of oxidation was estimated by carbonyl and carboxyl titration. The various oxidized wheat starches presented considerable variations in their oxidation level as a function of the catalyst concentration and oxidative process duration. The effect of the Fenton reaction parameters on the starch macromolecular chains and microstructure was evaluated by X-ray diffraction and amylose content estimation. Significant depolymerization of the starch macromolecules was observed, mainly in the starch amorphous phase, followed by a degradation of the crystalline phase at a higher oxidation level. SEM observations revealed changes in starch structure, which ranged from minor degradation of the starch granules to a more crosslinked morphology.

Functionalization Methods of Starch and Its Derivatives: From Old Limitations to New Possibilities

It has long been known that starch as a raw material is of strategic importance for meeting primarily the nutritional needs of people around the world. Year by year, the demand not only for traditional but also for functional food based on starch and its derivatives is growing. Problems with the availability of petrochemical raw materials, as well as environmental problems with the recycling of post-production waste, make non-food industries also increasingly interested in this biopolymer. Its supporters will point out countless advantages such as wide availability, renewability, and biodegradability. Opponents, in turn, will argue that they will not balance the problems with its processing and storage and poor functional properties. Hence, the race to find new methods to improve starch properties towards multifunctionality is still ongoing. For these reasons, in the presented review, referring to the structure and physicochemical properties of starch, attempts were made to highlight not only the current limitations in its processing but also new possibilities. Attention was paid to progress in the non-selective and selective functionalization of starch to obtain materials with the greatest application potential in the food (resistant starch, dextrins, and maltodextrins) and/or in the non-food industries (hydrophobic and oxidized starch).

Effect of pH on the Redox and Sorption Properties of Native and Phosphorylated Starches

Starch is a common biopolymer that can be used for removing heavy metal ions from aqueous solutions. A valuable property of starch is its functional diversity, which can be enhanced by chemical modification. Hydroxyl groups enclosed in the starch and formed during hydrolysis act as reducing agents of Cr(VI). The sorption properties of native starch depend mainly on the presence of carboxyl groups formed during redox processes and basic centers created during acid hydrolysis, while the superiority of phosphorylated starch is related to the presence of phosphate groups binding Cr(III) ions. The effectiveness of starch depends on a series of equilibria established in its aqueous suspension and chromate ions solution, where the pH is the driving force for these processes. In this article, a systematic discussion of pH changes being the consequence of chemical reactions unraveling the extraordinary functionalities of starch was given. It also explained the influence of establishing equilibria and chemical modifications of starch on the efficiency of chromium ion removal. This allowed for the development of a comprehensive mechanism for the interaction of Cr(VI) and Cr(III) ions with native and phosphorylated starch.

Preparation and structural properties of starch phosphate modified by alkaline phosphatase

In this study, a method for the synthesis of starch phosphate using the transferase properties of alkaline phosphatase was explored. Maize starch was treated with a pyrophosphate solution containing alkaline phosphatase and catalytic ions under pH 8 at 37 °C. The synthesis of starch phosphate was evaluated and compared with untreated and treated starch controls. The phosphorus content of the samples increased up to 8500% with the catalytic ion concentration, whereas the peak viscosity by up to 41.4% decreased. The crystallinity and enthalpy of the phosphorylated samples were reduced by up to 26.8% and 23.3%, respectively; however, no significant was observed by Fourier-transform infrared spectrometer. The roughness of the starch surface and the distribution of elemental phosphorus were observed by scanning electron microscopy and energy dispersive Spectrometry. X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry results further indicated the grafting of the phosphate radical.

Synthesis, characteristics, and applications of modified starch nanoparticles: A review

Nowadays, starch nanoparticles (SNPs) are drawing attention to the scientific community due to their versatility and wide range of applications. Although several works have extensively addressed the SNP production routes, not much is discussed about the SNPs modification techniques, as well as the use of modified SNPs in typical and unconventional applications. Here, we focused on the SNP modification strategies and characteristics and performance of the resulting products, as well as their practical applications, while pointing out the main limitations and recommendations. We aim to guide researchers by identifying the next steps in this emerging line of research. SNPs esterification and oxidation are preferred chemical modifications, which result in changes in the functional groups. Moreover, additional polymers are incorporated into the SNP surface through copolymer grafting. Physical modification of starch has demonstrated similar changes in the functional groups without the need for toxic chemicals. Modified SNPs rendered differentiated properties, such as size, shape, crystallinity, hydrophobicity, and Zeta-potential. For multiple applications, tailoring the aforementioned properties is key to the performance of nanoparticle-based systems. However, the number of studies focusing on emerging applications is fairly limited, while their applications as drug delivery systems lack in vivo studies. The main challenges and prospects were discussed.

Sulfur functionality-modified starches: Review of synthesis strategies, properties, and applications

Starch is the second most abundant naturally-occurring polymer after cellulose that possess superior physicochemical and biological features with numerous practical applications ranging from industrial to biomedical. Despite, native starch suffer from some drawbacks, including difficult processability, low shear and thermal stability, weak mechanical properties, and tendency to easily retrograde and undergo syneresis. Therefore, modification of native starch is necessary for circumvent the above-mentioned problems and expanding application ranges. This natural polymer can be modified using chemical, physical, enzymatic, and genetic engineering strategies. Amongst, chemical approaches have received more attention owing to enhancing physicochemical and biological features that lead to higher performance than those of the other strategies. In this context, incorporation of sulfur functionality-containing groups (sulfonation and sulfation) can be considered as an efficient approach due to significant enhancement in physiochemical properties, including zeta potential (move to negative values), molecular weight, processiability (e.g., solubility and meltability), and rheology. Furthermore, this strategy can modified some biological features, such as hemocompatibility, protein sorption, biostability, adhesion and proliferation of numerous cells, antithrombogenicity, antiinflammatory, antiviral, antimicrobial, antioxidant, antifungal, anticoagulant and antifouling properties. Accordingly, this review highlight's the synthesis strategies, physiochemical and biological properties, as well as applications of sulfur functionality-modified starches in numerous practical fields.

Analysis of the Heterogeneities of First and Second Order of Cellulose Derivatives: A Complex Challenge

The complexity of the substituent distribution in polysaccharide derivatives is discussed and defined. The challenges regarding analytical characterization that results from various interrelated categories of distributions, including molecular weight, chemical composition, and microstructure, are outlined. Due to these convoluted levels of complexity, results should always be interpreted with carefulness. Various analytical approaches which have been applied to starch and cellulose derivatives are recapped, including enzymatic, mass spectrometric, and chromatographic methods. The relation of heterogeneities of first and second order among and along the polysaccharide chains is addressed. Finally, examples of own analytical work on cellulose ethers are presented, including the MS analysis of methyl cellulose (MC) blends and fractionation studies of fully esterified MC, especially its 4-methoxybenzoates by gradient HPLC on normal phase. Preparative fractionation according to the degree of substitution (DS) allows follow-up analysis in order to get more detailed information on the substituent distribution in such sub-fractions.

Starch-capped sulphur nanoparticles synthesised from bulk powder sulphur and their anti-phytopathogenic activity against Clavibacter sepedonicus

Water-soluble, stable nanoparticles of elemental sulphur with a size of 9-52 nm have been synthesised using the stabilising potential of starch. Sulphide anions were used as sulphur precursors that were generated earlier from the bulk powder sulphur in the base-reduction system NaOH-N2 H4 ·H2 O followed by their oxidation with molecular oxygen to element sulphur atoms. Using a set of modern spectral and microscopic methods (XRD, optical spectroscopy, DLS, TEM), the phase state, elemental composition of the nanocomposites and their nanomorphological characteristics have been investigated. It was found that nanocomposites are formed as sulphur particles with the shape which is nearly spherical dispersed in the polysaccharide starch matrix with a pronounced tendency to cluster into ring formations. Water solubility and stability of the obtained nanoparticles is ensured by sorption of starch macromolecules on the surface of sulphur nanoparticles, with the thickness of the stabilising shell in a range of 10-171 nm. In vitro experiments were carried out to study the anti-microbial activity of the obtained sulphur nanocomposite (1.6% S) using the propidium iodide fluorescent dye staining method and the diffusion method. It showed that the water solution of the starch-capped sulphur nanoparticles at the concentration of 6.25 µg/ml had a pronounced anti-phytopathogenic activity against the potato ring rot pathogen Clavibacter michiganensis subsp. sepedonicus.

Poly(lactic acid) (PLA) and polyhydroxyalkanoates (PHAs), green alternatives to petroleum-based plastics: a review

In spite of the fact that petroleum-based plastics are convenient in terms of fulfilling the performance requirements of many applications, they contribute significantly to a number of ecological and environmental problems. Recently, the public awareness of the negative effects of petroleum-based plastics on the environment has increased. The present utilization of natural resources cannot be sustained forever. Furthermore, oil is often subjected to price fluctuations and will eventually be depleted. The increase in the level of carbon dioxide due to the combustion of fossil fuel is causing global warming. Concerns about preservation of natural resources and climate change are considered worldwide motivations for academic and industrial researchers to reduce the consumption and dependence on fossil fuel. Therefore, bio-based polymers are moving towards becoming the favorable option to be utilized in polymer manufacturing, food packaging, and medical applications. This paper represents an overview of the feasibility of both Poly Lactic Acid (PLA) and polyhydroxyalkanoates (PHAs) as alternative materials that can replace petroleum-based polymers in a wide range of industrial applications. Physical, thermal, rheological, and mechanical properties of both polymers as well as their permeability and migration properties have been reviewed. Moreover, PLA's recyclability, sustainability, and environmental assessment have been also discussed. Finally, applications in which both polymers can replace petroleum-based plastics have been explored and provided.

Review of the Most Important Methods of Improving the Processing Properties of Starch toward Non-Food Applications

Starch is the second most abundantly available natural polymer in the world, after cellulose. If we add its biodegradability and non-toxicity to the natural environment, it becomes a raw material very attractive for the food and non-food industries. However, in the latter case, mainly due to the high hydrophilicity of starch, it is necessary to carry out many more or less complex operations and processes. One of the fastest growing industries in the last decade is the processing of biodegradable materials for packaging purposes. This is mainly due to awareness of producers and consumers about the dangers of unlimited production and the use of non-degradable petroleum polymers. Therefore, in the present review, an attempt was made to show the possibilities and limitations of using starch as a packaging material. The most important physicochemical features of this biopolymer are discussed, and special attention is paid to more or less environmentally friendly methods of improving its processing properties.

Preparation and Optimization of Water-Soluble Cationic Sago Starch with a High Degree of Substitution Using Response Surface Methodology

Modification and characterizations of cationic sago starch with 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHPTAC) prepared via etherification reaction was reported in this study. The optimization of cationic sago starch modification was performed by utilizing the combination of response surface methodology and central composite design (RSM/CCD). The effect of each variable and the interaction between the three variables, the concentration of CHPTAC, concentration of the catalyst NaOH, and the reaction times on the degree of substitution (DS) of the product were investigated and modeled. Moderate conditions were employed and a water-soluble cationic sago starch with high DS value was obtained. Based on RSM, the highest DS = 1.195 was obtained at optimum conditions: 0.615 mol of CHPTAC concentration (CHPTAC/SS = 5), 30% w/v NaOH, and 5 h reaction time, at 60 °C reaction temperature. Furthermore, the cationic sago starch was characterized using Fourier transform infrared spectroscopy, FTIR, X-ray diffraction, XRD, and field emission scanning electron microscopy, FESEM.

Investigation of the Adsorption Behavior of Jet-Cooked Cationic Starches on Pulp Fibers

The optimization of the thermal treatment of cationic starch in the paper industry offers the opportunity to reduce the energy consumption of this process. Four different industrially relevant cationic starches, varying in source, cationization method and degree of substitution were treated by a steam-jet cooking procedure, comparable to industrially employed starch cooking processes. The influence of the starch properties and cooking parameters on the adsorption behavior of the starches on cellulosic pulp was investigated. The adsorbed amount was affected by the cooking temperature and the type of starch. For some starch grades, a cooking temperature of 115 °C can be employed to achieve sufficient starch retention on the pulp fibers. The energy consumption could further be reduced by cooking at higher starch concentrations without loss of adsorption efficiency.

Multiscale Structure of Starches Grafted with Hydrophobic Groups: A New Analytical Strategy

Starch, an abundant and low-cost plant-based glucopolymer, has great potential to replace carbon-based polymers in various materials. In order to optimize its functional properties for bioplastics applications chemical groups need to be introduced on the free hydroxyl groups in a controlled manner, so an understanding of the resulting structure-properties relationships is therefore essential. The purpose of this work was to study the multiscale structure of highly-acetylated (degree of substitution, 0.4 < DS ≤ 3) and etherified starches by using an original combination of experimental strategies and methodologies. The molecular structure and substituents repartition were investigated by developing new sample preparation strategies for specific analysis including Asymmetrical Flow Field Flow Fractionation associated with Multiangle Laser Light Scattering, Nuclear Magnetic Resonance (NMR), Raman and Time of Flight Secondary Ion Mass spectroscopies. Molar mass decrease and specific ways of chain breakage due to modification were pointed out and are correlated to the amylose content. The amorphous structuration was revealed by solid-state NMR. This original broad analytical approach allowed for the first time a large characterization of highly-acetylated starches insoluble in aqueous solvents. This strategy, then applied to characterize etherified starches, opens the way to correlate the structure to the properties of such insoluble starch-based materials.

Mechanical and Thermal Properties of Self-Assembled Kaolin-Doped Starch-Based Environment-Friendly Nanocomposite Films

Environment-friendly advanced materials are promising candidates for the engineering of nanoscience and nanotechnology. Here, starch–kaolin self-assembled nanocomposite films were prepared using potato starch and an indigenous layered material, kaolin. The films consist of kaolin and the matrix, which were prepared by the disruption and plasticization of starch granules with water and glycerol. Self-assembled nanocomposite films with 0%, 5%, 10%, 15%, and 20% w/w of kaolin were fabricated by casting and evaporating the mixture from homogeneous aqueous suspension at 95 °C. The thickness of the film—about 200 μm—was controlled by a predesigned glass frame. The resulting films were conditioned before testing, and the effect of accelerated aging in a moist atmosphere was investigated. The films were characterized using attenuated total reflection infrared (ATR-IR) spectroscopy for the interaction of moieties via function groups, X-ray diffraction (XRD) for crystallinity change, universal testing machine (UTM) for tensile strength Young’s modulus and elongation at break investigation. The thermal stability of the films using thermogravimetric analysis (TGA) and the effect of temperature on contraction behaviors using thermal mechanical analysis (TMA) were carried out. The distribution of kaolin into the matrix and morphology of the self-assembled nanocomposite films were observed from scanning electron microscopy (SEM) images. Developed nanocomposite materials from an indigenous source would play a vital role in the field of food packaging industries in Bangladesh.

Cationic starches in paper-based applications-A review on analytical methods

This review focuses on cationic starches with a low degree of substitution (<0.06) which are mainly used for production of paper-based products. After a brief introduction on starch in general, cationization pathways and importance of cationic starches in paper production, this review emphasizes on the analytical challenges from different perspectives. These include the different length scales of starches when in solution: the macromolecular level, their assembly into nm aggregates and finally hydrocolloids with hundreds of nanometers of diameter. We give an overview on the current state of the art on the analysis of such challenging samples and aim at providing a guideline for obtaining and presenting reliable analytical data.

Flame Retardancy of Wood Fiber Materials Using Phosphorus-Modified Wheat Starch

Biopolymer-based flame retardants (FR) are a promising approach to ensure adequate protection against fire while minimizing health and environmental risks. Only a few, however, are suitable for industrial purposes because of their poor flame retardancy, complex synthesis pathway, expensive cleaning procedures, and inappropriate application properties. In the present work, wheat starch was modified using a common phosphate/urea reaction system and tested as flame retardant additive for wood fibers. The results indicate that starch derivatives from phosphate/urea systems can reach fire protection efficiencies similar to those of commercial flame retardants currently used in the wood fiber industry. The functionalization leads to the incorporation of fire protective phosphates (up to 38 wt.%) and nitrogen groups (up to 8.3 wt.%). The lowest levels of burning in fire tests were measured with soluble additives at a phosphate content of 3.5 wt.%. Smoldering effects could be significantly reduced compared to unmodified wood fibers. The industrial processing of a starch-based flame retardant on wood insulating materials exhibits the fundamental applicability of flame retardants. These results demonstrate that starch modified from phosphate/urea-systems is a serious alternative to traditional flame retardants.

Theoretical Insights into Three Types of Oxidized Starch-Based Adhesives: Chemical Stability, Water Resistance, and Shearing Viscosity from a Molecular Viewpoint

To better understand the origin and difference associated with chemical stability, water resistance, and shearing viscosity of three types of different oxidized modified starch-based adhesives, a detailed theoretical investigation from a molecular viewpoint has been performed using the AM1 semiempirical level and the DFT-B3LYP level, respectively. As a result, our findings suggest that, by Mulliken population analysis (MPA), frontier orbital analysis, and electrostatic potential (EP) analysis based on B3LYP/6-31G calculations, the chemical stability, water resistance, and shearing viscosity of the oxidized modified starch-based adhesives are uniformly improved and corresponding difference for each property presents an identical order: the oxidized grafted cross-linked starch-based adhesive > the oxidized grafted starch-based adhesive > the oxidized starch-based adhesive, which is well consistent with experimental results.

Esterification of potato starch by a biocatalysed reaction in an ionic liquid

In this study, potato starch was esterified with oleic acid, using 1-butyl-3-methylimidazolium chloride as a reaction medium and an immobilised lipase from Thermomyces lanuginosus as a catalyst. The degree of substitution (DS) of the products was determined by the volumetric method; and the best esterified product (with the highest DS) was determined by an elemental analysis. The effect of the reaction parameters on the DS, such as the time and the temperature, were also studied. The product with the highest DS (0.22) was found in the reaction carried out at 60 °C for 4h. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) analyses confirmed the esterification of the potato starch. Furthermore, the results of X-ray diffraction (XRD) and a scanning electron microscopy (SEM) revealed that the crystallinity and the morphology of the native potato starch was slightly changed during its partial gelatinisation in the ionic liquid, and was completely destroyed as a result of the formation of the esters. The thermal stability of the starch oleate decreased, when compared to the unmodified starch, as was indicated by a thermal gravimetric analysis (TGA).

Chemical Modifications of Starch: Microwave Effect

This paper presents basic methods of starch chemical modification, the effect of microwave radiation on the modification process, and the physicochemical properties of starch. It has been shown that the modifications contribute to improvement of the material performance and likewise to significant improvement of its mechanical properties. As a result, more and more extensive use of starch is possible in various industries. In addition, methods of oxidized starch and starch esters preparation are discussed. Properties of microwave radiation and its impact on starch (with particular regard to modifications described in literature) are characterized.

Recent progress in chemical modification of starch and its applications

Starch has received much attention as a promising natural material both in biomedical fields and waste water treatment due to its unique biological and adsorptive properties.

Thermoresponsive xylan hydrogels via copper-catalyzed azide-alkyne cycloaddition

In the present work, hydrogels of birch wood xylan and thermoresponsive poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEG-PPG-PEG) were prepared using copper catalyzed alkyne-azide cycloaddition (CuAAC) in aqueous reaction conditions. First, reactive azide groups were introduced on the backbone of xylan by etherification of 1-azido-2,3-epoxypropane in alkaline water/isopropanol-mixture at ambient temperature, providing degree of substitution (DS) values up to 0.28. On the second step, the azide groups were reacted with propargyl bifunctional PEG-PPG-PEG utilizing CuAAC, leading to formation of crosslinked hydrogels. The novel xylan derivatives were characterized with liquid and solid state nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA). The temperature controlled swelling behavior of the developed hydrogels was evaluated in the range of 7-70 °C by water absorption and compressive stress-strain measurements, which showed a reduction in water content and change in stiffness with increasing temperature. The morphology of the hydrogels at different temperatures was studied by scanning electron microscopy (SEM), which showed a reduction in pore size with increasing temperature.