Research advances in chemical modifications of starch for hydrophobicity and its applications: A review

Dielectric barrier discharge plasma: A green method to change structure of potato starch and improve physicochemical properties of potato starch films

The effects of dielectric barrier discharge (DBD) plasma treatment on the physicochemical properties of potato starch and its films were studied. The results showed that the plasma species caused etching lead to small cracks and pores in potato starch particles and that oxidation, de-polymerization, and crosslinking were the main mechanisms underlying the effects of DBD plasma treatment. As the treatment time extended, starch hydrolysis, turbidity, syneresis, and gelatinization temperatures increased first and then decreased, whereas the solubility, swelling power, and water absorption significantly increased (P < 0.05). There was a decrease in the retrogradation tendency of the starch gels. The surfaces of the DBD plasma-modified potato starch-based films were relatively flat. After a 9-min treatment, the films exhibited the lowest water vapor permeability and highest tensile strength. In conclusion, the use of DBD plasma is a simple and green method to enhance the properties of potato starch and its film.

One-Pot Synthesis of Amphiphilic Biopolymers from Oxidized Alginate and Self-Assembly as a Carrier for Sustained Release of Hydrophobic Drugs

In this paper, we developed an organic solvent-free, eco-friendly, simple and efficient one-pot approach for the preparation of amphiphilic conjugates (Ugi-OSAOcT) by grafting octylamine (OCA) to oxidized sodium alginate (OSA). The optimum reaction parameters that were obtained based on the degree of substitution (DS) of Ugi-OSAOcT were a reaction time of 12 h, a reaction temperature of 25 °C and a molar ratio of 1:2.4:3:3.3 (OSA:OCA:HAc:TOSMIC), respectively. The chemical structure and composition were characterized by Fourier transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance (¹H NMR), X-ray diffraction (XRD), thermogravimetry analyser (TGA), gel permeation chromatography (GPC) and elemental analysis (EA). It was found that the Ugi-OSAOcT conjugates with a CMC value in the range of 0.30–0.085 mg/mL could self-assemble into stable and spherical micelles with a particle size of 135.7 ± 2.4–196.5 ± 3.8 nm and negative surface potentials of −32.8 ± 0.4–−38.2 ± 0.8 mV. Furthermore, ibuprofen (IBU), which served as a model poorly water-soluble drug, was successfully incorporated into the Ugi-OSAOcT micelles by dialysis method. The drug loading capacity (%DL) and encapsulation efficiency (%EE) of the IBU-loaded Ugi-OSAOcT micelles (IBU/Ugi-OSAOcT = 3:10) reached as much as 10.9 ± 0.4–14.6 ± 0.3% and 40.8 ± 1.6–57.2 ± 1.3%, respectively. The in vitro release study demonstrated that the IBU-loaded micelles had a sustained and pH-responsive drug release behavior. In addition, the DS of the hydrophobic segment on an OSA backbone was demonstrated to have an important effect on IBU loading and drug release behavior. Finally, the in vitro cytotoxicity assay demonstrated that the Ugi-OSAOcT conjugates exhibited no significant cytotoxicity against RAW 264.7 cells up to 1000 µg/mL. Therefore, the amphiphilic Ugi-OSAOcT conjugates synthesized by the green method exhibited great potential to load hydrophobic drugs, acting as a promising nanocarrier capable of responding to pH for sustained release of hydrophobic drugs.

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.

Anchor and bridge functions of APTES layer on interface between hydrophilic starch films and hydrophobic soyabean oil coating

One of the well-recognized weaknesses of starch-based materials is their sensitivity to moisture, which limits their expanding applications. Natural materials, soyabean oils have been used as a coating for starch film, but the poor interface between hydrophilic starch and hydrophobic soyabean oil needs to be improved. In this work, (3-Aminopropyl) triethoxysilane (APTES) was used to reinforce the bonding between starch matrix and the coating of bio-based acrylated epoxidized soyabean oil (AESO). Study results show that APTES interacted effectively with both starch films via hydrogen bonding, and chemical bonds with AESO through the Michael addition reaction. Pull adhesion and cross-cutting tests demonstrated that the interfacial adhesion was significantly improved after treating their surface with APTES. The interfacial adhesion strength increased over 4 times after treating with 1.6 wt% APTES. The starch films treated with APTES and AESO coating were intact after soaking in water for more than 2 h.

Effect of Glue Spreads on the Structural Properties of Laminated Veneer Lumber from Spindleless Rotary Veneers Recovered from Short Rotation Hevea Plantation Logs

Unproductive young rubber trees (15 years old) with smaller diameters (15 to 18 cm) compared to conventional rubber logs, harvested at the age of 25 years old, were selected for the production of laminated panels. Spindleless rotary veneer peeling was applied to logs from short-rotation rubber forest plantations to produce veneers for structural purposes. This raises questions about the utilization of these small-diameter logs with respect to its effect on the quality of veneer and laminated panels produced. This study examines the effect of the glue spread rates on the physical and mechanical properties of rubberwood laminated veneer lumber (LVL). Analysis of variance shows that the application of a 280 g/m² glue spread rate significantly improved the density, water absorption and dimensional stability of rubberwood LVL. The mechanical properties of rubberwood LVL produced with a 200 g/m² glue spread rate met the minimum requirement for the 2.1E-3100F stress class; 91.05 MPa for the modulus of rupture in the flatwise direction and 50.23 MPa for compressive strength parallel to the longitudinal axis. The modulus of elasticity in the flatwise direction of 11,189.55 MPa reached the minimum requirement for the 1.5E-2250F stress class.

Starch phosphate carbamate hydrogel based slow-release urea formulation with good water retentivity

In this work, a novel starch phosphate carbamate hydrogel (SPC-Hydrogel) and its corresponding urea hydrogel (SPCU-Hydrogel) slow-release fertilizer (SRF) were prepared by one-step free radical copolymerization of SPC and acrylamide (AM) without and with urea addition. A series of characterization measurements including FTIR, XRD, EDS, XPS are utilized to confirm the successful formation of the SPC-Hydrogel. The SEM shows SPC-Hydrogel has a porous three-dimensional network architecture. Furthermore, SPC-Hydrogel matrix exhibits superior water absorbency achieving 80.2 g/g than that (70.5 g/g) of the native starch hydrogel (NS-Hydrogel) and desirable water retention capacity in soil with a weight loss of only 48% for 13 days. Compared with pure urea and NS based urea hydrogel (NSU-Hydrogel), the SPCU-Hydrogel releases 50.3% for 15 h, achieving an almost complete release more than 25 h in aqueous phase. While only 46.6% of urea is released in 20 days which extends about 30 days in soil column assays. The maize seedlings growth assays also present an intuitive evaluation on the prominent soil water holding and plant growth promotion role of SPCU-Hydrogel. In conclusion, the present work has demonstrated a novel strategy via preparing biomass hydrogel SRF to enhance the utilization effectiveness of fertilizer and retain soil humidity.

Starch biosynthesis in cereal endosperms: An updated review over the last decade

Starch is a vital energy source for living organisms and is a key raw material and additive in the food and non-food industries. Starch has received continuous attention in multiple research fields. The endosperm of cereals (e.g., rice, corn, wheat, and barley) is the most important site for the synthesis of storage starch. Around 2010, several excellent reviews summarized key progress in various fields of starch research, serving as important references for subsequent research. In the past 10 years, many achievements have been made in the study of starch synthesis and regulation in cereals. The present review provides an update on research progress in starch synthesis of cereal endosperms over the past decade, focusing on new enzymes and non-enzymatic proteins involved in starch synthesis, regulatory networks of starch synthesis, and the use of elite alleles of starch synthesis-related genes in cereal breeding programs. We also provide perspectives on future research directions that will further our understanding of cereal starch biosynthesis and regulation to support the rational design of ideal quality grain.

Lignin reinforced, water resistant, and biodegradable cassava starch/PBAT sandwich composite pieces

Following the stipulation to replace nondegradable plastics with biodegradable materials in China, cost-effective and water-resistant packaging materials have become increasingly necessary. In this work, lignin reinforced thermoplastic cassava starch (TPS) pieces were prepared by filling glycerol and lignin powder into starch via a melt blending process and then being pressed into thin pieces. A mechanical properties test showed that following the addition of 3 wt% lignin, the tensile strength of the TPS piece was improved to 16.15 MPa from 3.71 MPa of the original TPS piece. The porous structures of the lignin powder tie the TPS macromolecular chains, induce higher crystallization, and thus provide higher tensile strength and lower elongation at break. After sandwiching two pieces of poly (butylene adipateco-terephthalate) (PBAT)/peanut shell powder composite thin film to each side of the TPS piece, the PBAT/TPS/PBAT sandwich gains excellent water resistance properties. However, as soon as the sandwich piece is cut into smaller ones, they absorb water quickly, implying such pieces can be biodegraded rapidly. These characteristics make it especially suitable for use in the preparation of cabinet waste bags, which are generally stirred into organic fertilizer with the cabinet waste. Slow degradation may negatively affect soil health and farm production.

Starch chemical modifications applied to drug delivery systems: From fundamentals to FDA-approved raw materials

Starch derivatives are versatile compounds that are widely used in the pharmaceutical industry. This article reviews the advances in the research on hydrophilic and hydrophobic starch derivatives used to develop drug delivery systems over the last ten years, specifically microparticles, nanoparticles, nanocrystals, hydrogels, and scaffolds using these materials. The fundamentals of drug delivery systems, regulatory aspects, and chemical modifications are also discussed, along with the synthesis of starch derivatives via oxidation, etherification, acid hydrolysis, esterification, and cross-linking. The chemical modification of starch as a means to overcome the challenges in obtaining solid dosage forms is also reviewed. In particular, dialdehyde starches are potential derivatives for direct drug attachment; carboxymethyl starches are used for drug encapsulation and release, giving rise to pH-sensitive devices through electrostatic interactions; and starch nanocrystals have high potential as hydrogel fillers to improve mechanical properties and control drug release through hydrophilic interactions. Starch esterification with alginate and acidic drugs could be very useful for site-specific, controlled release. Starch cross-linking with other biopolymers such as xanthan gum is promising for obtaining novel polyelectrolyte hydrogels with improved functional properties. Surface modification of starch nanoparticles by cross-linking and esterification reactions is a potential approach to obtain novel, smart solid dosages.

Essential oils as additives in active starch-based food packaging films: A review

The production of sustainable food packaging from renewable sources represents a prominent alternative to the use of petrochemical-based plastics. For example, starch remains one of the more closely studied replacement options due to its broad availability, low cost and significant advances in improving properties. In this context, essential oils as additives fulfil a key role in the manufacture of renewable active packaging with superior performances. In this review, a comprehensive summary of the impact of adding essential oils to the starch-based films is provided. After a brief introduction to the fundamental concepts related to starch and essential oils, details on the most recent advances in obtaining active starch-based films are presented. Subsequently, the effects of essential oils addition on the structure-property relationships (from physicochemical to antimicrobial ones) are thoroughly addressed. Finally, applications and challenges to the widespread use of essential oils are critically discussed.

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.

Starch/tea polyphenols nanofibrous films for food packaging application: From facile construction to enhance mechanical, antioxidant and hydrophobic properties

Starch based food packaging has been receiving increasing attention. However, the inherent poor properties of starch restrict its practical applications in the versatile material science field. In this study, a fast, simple, and environmentally friendly route to construct polyfunctional starch/tea polyphenols nanofibrous films (STNFs) by one-step temperature-assisted electrospinning was developed. The effects of introduction of tea polyphenols (TP) on the mechanical and antioxidant activity of STNFs were comprehensively investigated. Results of ABTS·+ free radical scavenging assay showed that the antioxidant activity of STNFs was endowed by addition of TP with optimum mechanical properties confirmed by tensile test. More interestingly, the hydrophobicity of STNFs was improved dramatically with increasing cross-linking time as indicated by water contact angle (WCA) measurement showing no effect on the antioxidant activity of the films. The results of this work offer a major step forward to promote functional starch-based materials for sustainable application in food packaging.

An overview on plasticized biodegradable corn starch-based films: the physicochemical properties and gelatinization process

With increasing awareness of environmental protection, petroleum-based raw materials are continuously decreasing, which in turn necessitated the development of eco-friendly sustainable biomaterials, as alternative strategy. Starch could be an ideal substitute. Corn starch has been used as a renewable material for development of biodegradable packaging, owing to great varieties, low cost, large-scale industrial production, and good films forming properties. Unfortunately, its poor mechanical and barrier properties have limited the application of starch-based films. Thence, plasticizers were added to overcome the aforementioned pitfalls and improve the films elongation, distribution, flexibility, elasticity, and rigidity. Addition of plasticizers can change the continuity and therefore would enhance the properties of corn starch-based films. While plasticization can improve the tensile strength and percent elongation, it can reduce the water resistance in prepared films. Herein, we focused on changes of starch granules during gelatinization process, types of biodegradable films, as well as the types of modified starch with plasticizers. Furthermore, the influence of plasticizers on corn starch-based films and the physicochemical properties of various types of corn starch-based films were also addressed.

CaCO3 blowing agent mixing method for biomass composites improved buffer packaging performance

Biodegradable composites with an open-cell structure were developed to replace petroleum-based buffer packaging materials. To overcome the problem of uneven and insufficient foam in the composites, CaCO3 was used as a nucleating agent to prepare porous composites. At 5 wt% CaCO3, more uniform and dense composite cells with better cushioning performance were obtained. A further increase in the CaCO3 content caused the density of the cells and the cushioning properties of the composites to decrease. The addition of CaCO3 improved the thermal stability and water barrier properties. The moisture absorption was reduced by 15%. X-ray diffraction analysis indicated that the addition of CaCO3 destroyed the crystalline structure of the starch and produced a new crystalline peak, resulting in a significant reduction in the crystallinity. The decrease in the crystallinity of the starch resulted in the formation of a homogeneous slurry that produced a uniform foam in the composites.