Modification of starch: A review on the application of “green” solvents and controlled functionalization

The relationship between linear chain length distributions of amylopectin and the functional properties of the debranched starch-based films

The relationship between linear chain length distributions and the functional properties of the starch-based films after pullulanase debranching treatment of corn (CS), rice (RS) and wheat (WS) were investigated. The results indicated that the film thickness was negatively correlated with A chains content (r = -0.939) and apparent amylose content (r = -0.926), and was positively correlated with B3 chains content (r = 0.847). The tensile strength of the debranched starch-based films were positively correlated with apparent amylose content (r = 0.813), and the elongation at break were inversely proportional to B3 chains content (r = -0.817). The hydrophobicity of the starch-based films was positively and negatively correlated with the proportions of linear chains with DP 6-12 (r = 0.892) and DP 25-36 (r = -0.863), respectively. On the contrary, no significant correlation was noticed between chain length distribution of amylopectin and transparency and thermal stability.

Synthesis and properties of tetrazole-containing polyelectrolytes based on chitosan, starch, and arabinogalactan

The synthesis of tetrazole-containing derivatives of chitosan, starch, and arabinogalactan was carried out by a sequence of reactions including cyanoethylation of polysaccharides and subsequent azidation of cyanoethyl derivatives. The reaction of cyanoethylation of polysaccharides with acrylonitrile proceeds in the temperature range 40–60°C in the presence of NaOH. The transformation of nitrile groups into tetrazole rings (azidation) of cyanoethylated polysaccharide derivatives was carried out with a mixture of sodium azide with ammonium chloride in DMF at 105°C. The reaction with the participation of derivatives of starch and arabinogalactan is characterized by the degree of conversion of nitrile groups into tetrazole rings, which is close to the maximum. The introduction of unsubstituted tetrazole rings into the structure of polysaccharides of acidic N–H substantially changes some of their properties. Like other carbo- and hetero-chain polymers containing N–H unsubstituted tetrazole rings in the structure, tetrazolated polysaccharides exhibit the properties of acidic polyelectrolytes. Tetrazole-containing derivatives of chitosan exhibit the properties of polyampholytes. The presence of tetrazole rings in the structure of modified polysaccharides allows the reaction with epoxy compounds to yield network polymers capable of limited swelling in aqueous media with the formation of polyelectrolyte hydrogels.

An Insight into the Gelatinization Properties Influencing the Modified Starches Used in Food Industry: A review

Native starch is subjected to various forms of modification to improve its structural, mechanical, and thermal properties for wider applications in the food industry. Physical, chemical, and dual modifications have a substantial effect on the gelatinization properties of starch. Consequently, this review explores and compares the different methods of starch modification applicable in the food industry and their effect on the gelatinization properties such as onset temperature (To), peak gelatinization temperature (Tp), end set temperature (Tc), and gelatinization enthalpy (ΔH), studied using differential scanning calorimetry (DSC). Chemical modifications including acetylation and acid hydrolysis decrease the gelatinization temperature of starch whereas cross-linking and oxidation result in increased gelatinization temperatures. Common physical modifications such as heat moisture treatment and annealing also increase the gelatinization temperature. The gelatinization properties of modified starch can be applied for the improvement of food products such as ready-to-eat, easily heated or frozen food, or food products with longer shelf life.

Cold plasma technologies: Their effect on starch properties and industrial scale-up for starchmodification

Native starches have limited applications in the food industry due to their unreactive and insoluble nature. Cold plasma technology, including plasma-activated water (PAW), has been explored to modify starches to enhance their functional, thermal, molecular, morphological, and physicochemical properties. Atmospheric cold plasma and low-pressure plasma systems have been used to alter starches and have proven successful. This review provides an in-depth analysis of the different cold plasma setups employed for starch modifications. The effect of cold plasma technology application on starch characteristics is summarized. We also discussed the potential of plasma-activated water as a novel alternative for starch modification. This review provides information needed for the industrial scale-up of cold plasma technologies as an eco-friendly method of starch modification.

•

Cold plasma technology could be an effective, sustainable alternative for starch modification.

•

The extent of modification of starches from different botanical sources depends on the type of cold plasma technology used.

•

For mainstream adoption of cold plasma modified starches, research on safety and consumer perception must be conducted.

Reaction Mechanisms Applied to Starch Modification for Biodegradable Plastics: Etherification and Esterification

Although many studies are being actively conducted to develop biodegradable plastic materials, most of these reports focused more on efficiency or performance improvement than on the reaction mechanism. This paper discussed the reaction mechanism applied to starch modification by etherification and esterification, which are the most studied in the field of biodegradable plastics. In the starch-reforming reaction by etherification, the effects of the reaction temperature, pH, solvent, and by-products on the chemical structure and physical properties of biodegradable plastics were discussed. In esterification, the structure of the substituents and the reaction solvents were examined. As a material that can replace plastics, the aim is to help derive new ideas on the design of reaction condition that can expand the use of starch.

New Techniques in Structural Tailoring of Starch Functionality

Inherent characteristics of native starches such as water insolubility, retrogradation and syneresis, and instability in harsh processing conditions (e.g., high temperature and shearing, low pH) limit their industrial applications. As starch properties mainly depend on starch composition and structure, structural tailoring of starch has been important for overcoming functional limitations and expanding starch applications in different fields. In this review, we first introduce the basics of starch structure, properties, and functionalities and then describe the interactions of starch with lipids, polysaccharides, and phenolics. After reviewing genetic, chemical, and enzymatic modifications of starch, we describe current progress in the areas of porous starch and starch-based nanoparticles. New techniques, such as using the CRISPR-Cas9 technique to tailor starch structures and using an emulsion-assisted approach in forming functional starch nanoparticles, are only feasible when they are established based on fundamental knowledge of starch. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Novel cellulose supported 1,2-bis(4-aminophenylthio)ethane Ni(ii) complex (NiII(BAPTE)(NO3)2-Cell) as an efficient nanocatalyst for the synthesis of spirooxindole derivatives

Cellulose was used as a support for immobilizing a Ni(ii) complex of 1,2-bis(4-aminophenylthio)ethane to prepare NiII(BAPTE)(NO3)2-Cell as a new organo-inorganic hybrid nanocatalyst. The properties of the prepared catalyst were studied using various analyses such as FT-IR, XRD, SEM, TGA and EDX. NiII(BAPTE)(NO3)2-Cell was employed as a reusable catalyst for the synthesis of spirooxindole derivatives via a three-component condensation of isatin, malononitrile and reactive methylene compounds. The nanocatalyst can be readily and quickly separated from the reaction mixture and can be reused for at least eight successive reaction cycles without a significant reduction in efficiency. The facile accessibility to the starting materials, use of green solvents and conducting the reactions in eco-friendly and cost-effective conditions have made this protocol a suitable method for preparing spirooxindole derivatives.

Eleocharis dulcis corm: phytochemicals, health benefits, processing and food products

Eleocharis dulcis, an aquatic plant belonging to Cyperaceae family, is indigenous to Asia, and also occurs in tropical Africa and Australia. The edible corm part of E. dulcis is a commonly consumed aquatic vegetable with a planting area of 44.46 × 10³ hm² in China. This work aims to explore the potential of E. dulcis corm for use as a new food source for sufficient nutrients and health benefits by reviewing its nutrients, phytochemicals, functions, processing and food products. Eleocharis dulcis corm contains starches, dietary fibers, non-starch polysaccharides, proteins, amino acids, phenolics, sterols, puchiin, saponins, minerals and vitamins. Among them, phenolics including flavonoids and quinones could be the major bioconstituents that largely contribute to antioxidant, anti-inflammatory, antibacterial, antitumor, hepatoprotective, neuroprotective and hypolipidemic functions. Peel wastes of E. dulcis corm tend to be enriched in phenolics to a much higher extent than the edible pulp. Fresh-cut E. dulcis corm can be consumed as a ready-to-eat food or processed into juice for beverage production, and anti-browning processing is a key to prolonging shelf life. Present food products of E. dulcis corm are centered on various fruit and vegetable beverages, and suffer from single categories and inadequate development. In brief, underutilized E. dulcis corm possesses great potential for use as a new food source for sufficient nutrients and health benefits. © 2021 Society of Chemical Industry.

Polysaccharide/mesoporous silica nanoparticle-based drug delivery systems: A review

Mesoporous silica nanoparticles (MSNs) have been well-researched in the design and fabrication of advanced drug delivery systems (DDSs) due to their advantages such as good biocompatibility, large specific surface area and pore volume for drug loading, easily surface modification, adjusted size and good thermal/chemical stability. For MSN-based DDSs, gate materials are also necessary. And natural polysaccharides, one kind of the most abundant natural resource, have been widely applied as the "gatekeepers" in MSN-based DDSs. Polysaccharides are cheap and rich in sources with good biocompatibility, and some of them have important biological functions. In this review article, polysaccharides including chitosan, hyaluronic acid, sodium alginate and dextran, et al. are briefly introduced. And the preparation processes and properties such as controlled drug release, cancer targeting and disease diagnosis of functional polysaccharide/MSN-based DDSs are discussed.

Development of Starch-Based Materials Using Current Modification Techniques and Their Applications: A Review

Starch is one of the most common biodegradable polymers found in nature, and it is widely utilized in the food and beverage, bioplastic industry, paper industry, textile, and biofuel industries. Starch has received significant attention due to its environmental benignity, easy fabrication, relative abundance, non-toxicity, and biodegradability. However, native starch cannot be directly used due to its poor thermo-mechanical properties and higher water absorptivity. Therefore, native starch needs to be modified before its use. Major starch modification techniques include genetic, enzymatic, physical, and chemical. Among those, chemical modification techniques are widely employed in industries. This review presents comprehensive coverage of chemical starch modification techniques and genetic, enzymatic, and physical methods developed over the past few years. In addition, the current applications of chemically modified starch in the fields of packaging, adhesives, pharmaceuticals, agriculture, superabsorbent and wastewater treatment have also been discussed.

Improvements in thermal and mechanical properties of composites based on thermoplastic starch and Kraft Lignin

Thermoplastic starch (TPS) is a widely studied biopolymer as an alternative to the use of conventional polymers. In this sense, the incorporation of fillers or reinforcements coming preferably from other substances of natural origin, can be an alternative to try to improve some mechanical and thermal properties of starch polymers. Thus, Kraft Lignin (KL), can be an excellent filler to be incorporated, since it presents mechanical and thermal properties and reduces the cost and weight of the final compounds. TPS films were prepared by casting using dimethyl sulfoxide (DMSO) as solvent and additives with 2, 4 and 8% KL. Characterization of TPS films and compositions with KL were carried out by Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TGA), Dynamic Thermomechanical Analysis (DMTA), tensile testing and contact angle. Samples were also analyzed for biodegradation and for the ability to remove contaminants in water, Metil Orange (MO), by Ultraviolet-Visible Spectroscopy (UV-Vis). The FT-IR spectra of the films showed bands typical of functional groups derived from starch and lignin, with the intensity of these bands varying among the samples studied. Micrographs revealed slightly different morphologies among the films, but all showed irregular shapes with structures that appeared as plots. Increasing the percentage of KL led to an increase in contact angle values, showing a more hydrophobic behavior. In the TGA analysis, it was possible to observe a change in the main degradation event of the films for lower temperatures, especially of TPS - 4 and 8% KL compared to the TPS film. Films with KL had the peak of maximum degradation shifted to temperatures below the starch film, where the decrease in intensity of the main peak in the TPS - 4% KL and TPS - 8% KL samples demonstrates that there was less mass loss in the event. There was also in the percentage of residue as the addition of KL was increased The DMTA analyses allowed for the conclusion that presence of KL in TPS film allowed for an increase in its energy storage property, and that the loss modulus followed a decreasing order of storage modulus values to TPS - 8% KL from TPS. For the tensile strength property only TPS - 4% KL has significant improvement, and the elongation at break showed an increase for TPS - 4 and 8% KL compared to TPS. Samples showed a continuous and progressive biodegradation process, being completely biodegraded within 10 days. The monitoring of the ability to remove contaminants from water by UV-Vis, also showed promising results of compounds for this application. The best results were obtained, in most tests, for the TPS- 4% KL films.

Transparent, flexible, and multifunctional starch-based double-network hydrogels as high-performance wearable electronics

To meet the increasing demands of sustainability and eco-friendliness, biopolymer-based hydrogels combining flexibility and ionic conductivity have drawn great attention for green and wearable sensors. However, the preparation of transparent, flexible, durable, and highly sensitive biopolymer hydrogel-based sensors for strain/pressure and humidity sensing remains a challenge. Herein, a facile one-step strategy is proposed to fabricate transparent, highly flexible, and multifunctional starch/polyacrylamide double-network hydrogels based on natural renewable starch. The resultant hydrogels exhibit fast self-adhesive ability and present high flexibility attributing to the double network consisting of cross-linked starch and polyacrylamide. Then the hydrogels can be assembled as transparent, self-adhesive, flexible, highly sensitive, and multifunctional strain/pressure and humidity sensors for accurate healthcare monitoring. The hydrogel-based sensor shows ultrahigh sensitivity to humidity (35-97% relative humidity). The multifunctionality and biological advantages of starch-based hydrogels offer potential applications in next-generation green and wearable electronics.

Trend of Modification by Autoclave at Low Pressure and by Natural Fermentation in Sweet Potato and Cassava Starches

Sweet potatoes (Ipomoea batatas L.) and cassava (Manihot esculenta C.) are part of the largest food crops in many countries. They have good nutritional value because, in addition to containing vitamins, minerals, carotenoids, and anthocyanins in varied contents, due to the existence of various colors of their pulps, they have starch as their major constituent. As such, they are considered valuable raw materials for the food factory. The starch granules have distinct morphologies and properties, related to the type of cultivar, planting conditions, storage, and processing, which in turn can affect the quality of the final products to which they have been added. The use of native starches in the food industry has limitations, which can be improved by modifications. Physical methods, as they are associated with green technology, and do not pollute the environment, have demonstrated great potential for this purpose. Both modifications—by autoclave at low pressure and natural fermentation—have shown potential in modifying these starches.

Green and clean modification of cassava starch - effects on composition, structure, properties and digestibility

There is a growing need for clean and green labeling of food products among consumers globally. Therefore, development of green modified starches, to boost functionality, palatability and health benefits while reducing the negative processing impacts on the environment and reinforcing consumer safety is in high demand. Starch modification started in mid-1500s due to the inherent limitations of native starch restricting its commercial applications, with chemical modification being most common. However, with the recent push for "chemical-free" labeling, methods of physical and enzymatic modification have gained immense popularity. These methods have been successfully used in numerous studies to alter the composition, structure, functionality and digestibility of starch and in this review, studies reported on green modification of cassava starch, one of the most common utilized starches, within the last ten years have been critically reviewed. Recent research has introduced starch as an abundant, natural substrate for producing resistant starches through biophysical technologies that act as dietary fiber in the human body. It is evident that different techniques and processing parameters result in varying degrees of modification impacting the techno-functionality and digestibility of the resultant starch. This can be exploited by researchers and industrialists in order to customize starch functionality in accordance with application.

Does polysaccharide quaternization improve biological activity?

The natural polysaccharides, due to their structural diversity, commonly present very distinct solubility and physical chemical properties and additionally have intrinsic biological activities that, gene-rally, reveal themselves in a light way. The chemical modification of the molecular structure can improve these parameters. In this review, original articles that approached the quaternization of polysaccharides for purposes of biological application were selected, without limitation of year of publication, in the databases Scopus, Web of Science and PubMed. The results obtained from the bibliographic survey indicate that the increase in positive charges caused by quaternization improves the interaction between modified polysaccharides and structures that have negative charges on their surface, such as the cell wall of microorganisms and some cells in the human body, such as the DNA. This greater interaction is reflected as an increase in the biological activity of all polysaccharides broached in this study. Another important data obtained was the fact that the chemical changes did not affect or irrelevantly affect the toxicity of almost all of the polysaccharides that were quaternized. Therefore, polysaccharide quaternization is a safe and effective way to obtain improvements in the biological behavior of these macromolecules.

Impact of thermo-sonication on quality indices of starch-based sauces

In this study, ultrasonication, a physical, relatively cheap, and environmentally benign technology, was investigated to characterize its effect on functional properties of rice starch and rice starch-based sauces. Temperature-assisted ultrasound treatment improved the granular swelling power, fat and water absorption capacities, and thermal properties of rice starch, signifying its suitability in the formulation of starch-based sauces. Rheological characterization of the formulated sauces revealed a shear-thinning flow behavior, well described by the Ostwald de Waele model, while viscoelastic properties showed the existence of a weak gel. Results indicated that ultrasonication significantly enhanced the pseudoplastic behavior of starch-based sauces. Additionally, textural analysis showed that textural attributes (stickiness, stringiness, and work of adhesion) were also improved with ultrasonication. Moreover, enhanced freeze/thaw stability was also achieved with ultrasound-treated starch-based sauces. Overall, the results from this study show that ultrasound-treated starches can be used in the formulation of sauces and potentially other food products, which meets the requirements for clean label and minimally processed foods.

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.

A one pot one step combined radical and ring-opening route for the dual functionalization of starch in aqueous medium

Starch based materials are attractive bio-based alternative to fully synthetic polymers. Native starch has however limited thermoprocessability and properties and must be modified. In order to improve the properties of starch-graft-poly(butyl-acrylate-co-styrene) copolymers via a process as green as possible, we report herein a new method for the dual functionalization of the polysaccharide via a one pot one step reaction in aqueous medium combining free radical polymerizations and ring-opening chemistry. Poly(butyl acrylate) or poly(butyl acrylate-co-styrene) (ca. 60 000 g/mol) and oligo(ε-caprolactone) were grafted on starch with a grafting percentage up to 75 %. The copolymers show two glass transition temperatures: one around 55-60 °C related to starch and a second attributed to the grafted vinyl polymers, from -46 °C to 20 °C depending on butyl acrylate/styrene ratio. The resulting dual functionalized materials exhibit excellent mechanical properties, with elongation at break in the range 20-210 %, while single functionalized starch shows less than 5 %.

Deep eutectic solvents based on urea, polyols and sugars for starch treatment

Deep eutectic solvents (DES) based on urea (U), polyols (glycerol -G, sorbitol - S) and monosugars (glucose - Glu, fructose - Fru) were obtained, thermally characterized and used for potato starch treatment: dissolution and plasticization. The polysaccharide was dissolved in U/glycerol mixtures forming transparent, non-retrograded gels. The dissolution process was confirmed by microscopic observations and DSC analysis. Plasticizing efficiency of DES in thermoplasticized starch (TPS) via compression molding was investigated using mechanical tests, DMTA, XRD, TGA and FTIR analysis. Although all studied DES were able to plasticize starch effectively, the most flexible films were with urea/glycerol mixture: the highest elongation at break exceed 200%. XRD analysis confirmed high amorphization of starch with the urea-based DES after thermocompression. Moreover, introduction of urea as DES inhibited its recrystallization in the polysaccharide matrix.

Recent trends in the application of modified starch in the adsorption of heavy metals from water: A review

The presence of polyfunctional ligands on the bio-macromolecules acts as an efficient adsorbent for heavy metal ions. Starch is one of the most abundant, easily available and cheap biopolymer of plant origin. However, native starch exhibits significantly low adsorption capacity due to the absence of some essential functional groups like carboxyl, amino or ester groups and is thus modified using various reaction routes like grafting, cross-linking, esterification, oxidation and irradiation for addition of functional groups to increase its adsorption capacity. The present review provides a comprehensive discussion on the above mentioned modification schemes of starch over the last 10-15 years highlighting their preparation methods, physico-chemical characteristics along with their adsorption capacities and mechanisms of heavy metal ions from water.

Micellar Drug Delivery Systems Based on Natural Biopolymers

The broad diversity of structures and the presence of numerous functional groups available for chemical modifications represent an enormous advantage for the development of safe, non-toxic, and cost-effective micellar drug delivery systems (DDS) based on natural biopolymers, such as polysaccharides, proteins, and peptides. Different drug-loading methods are used for the preparation of these micellar systems, but it appeared that dialysis is generally recommended, as it avoids the formation of large micellar aggregates. Moreover, the preparation method has an important influence on micellar size, morphology, and drug loading efficiency. The small size allows the passive accumulation of these micellar systems via the permeability and retention effect. Natural biopolymer-based micellar DDS are high-value biomaterials characterized by good compatibility, biodegradability, long blood circulation time, non-toxicity, non-immunogenicity, and high drug loading, and they are biodegraded to non-toxic products that are easily assimilated by the human body. Even if some recent studies reported better antitumoral effects for the micellar DDS based on polysaccharides than for commercial formulations, their clinical use is not yet generalized. This review is focused on the studies from the last decade concerning the preparation as well as the colloidal and biological characterization of micellar DDS based on natural biopolymers.

Effect of ionic liquid 1-buyl-3-methylimidazolium halide on the structure and tensile property of PBS/corn starch blends

As a promising biodegradable resin, poly (butylene succinate) (PBS) is often blended with starch to reduce the cost. In this paper, 1-buyl-3-methylimidazolium halide pre-plasticized corn starch (CS) was blended with PBS to prepare PBS/corn starch blend material modified by ionic liquid (PBS/CS-IL). Ionic liquid (IL) acted as plasticizer and compatibilizer, and the effects of 1-butyl-3-methylimidazolium halide with different halogen anion on PBS/Starch blends were explored. The effects of IL on the structure and tensile property of PBS/Starch blends were evaluated by FTIR, SEM, DSC, TGA and XRD, respectively. Test results showed that the addition of IL significantly reduced the crystallinity of PBS/Starch blends, and the size of starch particles in the PBS matrix was also effectively reduced. IL also acted as a compatibilizer of starch and PBS, and induced the morphology of the blends to change from "sea-island" structure to homogeneous phase. The results of the tensile test showed that compared with the PBS/Starch blend without IL, the elongation at break of PBS/CS-IL increased from 22% to 93%. This study provided a simple and feasible method for the preparation of low-cost PBS bio-composite materials, and provided theoretical support for future industrial production.

The Importance of Ionic Liquids in the Modification of Starch and Processing of Starch-Based Materials

The main applications of ionic liquids in chemistry and material research on one of the most important natural polymers—starch—are presented in this review. A brief characterization of ionic liquids and the advantages and disadvantages of using them in the modification and processing of polysaccharides is presented. The latest reports on the use of various ionic liquids as solvents or co-solvents; as media for synthesizing starch derivatives in oxidation, etherification, esterification, and transesterification, with particular emphasis on biocatalyzed reactions; and as plasticizers or compatibilizers in the processing of starch-based polymers have been investigated. The current trends, possibilities, and limitations of using this type of compound for the production of functional starch-based materials are presented.