Improved material properties of solution-cast starch films: Effect of varying amylopectin structure and amylose content of starch from genetically modified potatoes

The application of starch-based edible film in food preservation: a comprehensive review

Using renewable resources for food packaging not only helps reduce our dependence on fossil fuels but also minimizes the environmental impact associated with traditional plastics. Starch has been a hot topic in the field of current research because of its low cost, wide source and good film forming property. However, a comprehensive review in this field is still lacking. Starch-based films offer a promising alternative for sustainable packaging in the food industry. The present paper covers various aspects such as raw material sources, modification methods, and film formation mechanisms. Understanding the physicochemical properties and potential commercial applications is crucial for bridging the gap between research and practical implementation. Finally, the application of starch-based films in the food industry is discussed in detail. Different modifications of starch can improve the mechanical and barrier properties of the films. The addition of active substances to starch-based films can endow them with more functions. Therefore, these factors should be better investigated and optimized in future studies to improve the physicochemical properties and functionality of starch-based films. In summary, this review provides comprehensive information and the latest research progress of starch-based films in the food industry.

Correlation between chain structures of corn starch and properties of its film prepared at different degrees of disorganization

This study investigated the relationship between the chain structure of corn starch and the properties of corn starch-based films formed with starch pastes with different degrees of disorganization (70, 80, and 90 °C). The degree of gelatinization, chain length distribution, amylose content, and molecular weight of the corn starch were determined by the water absorption index, ion chromatography, spectrophotometry, and gel chromatography, respectively. The thickness, surface roughness, solubility, water content, water vapor permeability, mechanical properties, and maximum thermal degradation rate of corn starch-based films formed with starch pastes with different degrees of disorganization were evaluated. The moisture content, thickness and surface roughness of films formed with the starch pastes decreased. At the same time, the solubility, elongation at break, water vapor permeability, and molecular weight distribution increased with increasing heat treatment temperature. The maximum thermal degradation rate and tensile strength of the corn starch-based films formed with the starch pastes decreased with increasing heat treatment temperature. The gradual decrease in the amylose content of corn starch-based films formed with starch paste with increasing heat treatment temperature led to a change in the performance of the corn starch-based films.

Recent Advances in Starch-Based Blends and Composites for Bioplastics Applications

Environmental pollution by synthetic polymers is a global problem and investigating substitutes for synthetic polymers is a major research area. Starch can be used in formulating bioplastic materials, mainly as blends or composites with other polymers. The major drawbacks of using starch in such applications are water sensitivity and poor mechanical properties. Attempts have been made to improve the mechanical properties of starch-based blends and composites, by e.g., starch modification or plasticization, matrix reinforcement, and polymer blending. Polymer blending can bring synergetic benefits to blends and composites, but necessary precautions must be taken to ensure the compatibility of hydrophobic polymers and hydrophilic starch. Genetic engineering offers new possibilities to modify starch inplanta in a manner favorable for bioplastics applications, while the incorporation of antibacterial and/or antioxidant agents into starch-based food packaging materials brings additional advantages. In conclusion, starch is a promising material for bioplastic production, with great potential for further improvements. This review summarizes the recent advances in starch-based blends and composites and highlights the potential strategies for overcoming the major drawbacks of using starch in bioplastics applications.

Enzymatic synthesis of wet-resistant lignosulfonate-starch adhesives

This work describes a new method for improving the properties, mainly the wet-resistance, of starch-based adhesives using enzymatically polymerized lignosulfonates. A correlation of viscosity with molecular weight was found, allowing simple control of enzymatic polymerization of lignosulfonates. Incorporation of lignosulfonates polymerized from 29 kDa to > 4500 kDa using laccase led to a considerable increase in wet-resistance (from 15 to 20 min for the laminating glue and from 150 to 1200 min for the bag glue) while not affecting (for the laminating glue) or even improving the bonding time (from 80 to 60 s for the bag glue). Finally, the effect of active laccase in the final adhesive was investigated by enzymatic inactivation using NaN₃ before formulation of the glue, as well as by extra laccase addition. In conclusion, this study shows that enzymatically polymerized lignosulfonate is a robust strategy for improving wet resistance of starch-based adhesives.

Effect of Egg-Coating Material Properties by Blending Cassava Starch with Methyl Celluloses and Waxes on Egg Quality

An egg-coating material was developed to extend the shelf-life and freshness of eggs by blending cassava starch (CS) with gelling agents and waxes. The effects of the properties of this egg coating on egg quality were investigated. Hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose (CMC), beeswax, and paraffin wax were used. CS blended with low-molecular-weight paraffin (Paraffin(L)) and CMC coating material displayed a tensile strength of 4 MPa, 34% elongation at break, 0.0039 g day⁻¹ m⁻² water vapor permeability, and a water contact angle of 89° at 3 min. Eggs coated with CS/CMC/Paraffin(L) solutions had a Haugh unit value of 72 (AA grade) and exhibited a weight loss of 2.4% in 4 weeks. CMC improved the compatibility of CS and Paraffin(L). This improvement and the hydrophobicity of Paraffin(L) provided suitable mechanical and water-resistance properties to the coating material that helped to maintain the quality of the coated AA-grade eggs with low weight loss for 4 weeks.

Comparative study on physicochemical properties of starch films prepared from five sweet potato (Ipomoea batatas) cultivars

Five different sweet potato (Ipomoea batatas) cultivars (Daeyumi, Gogeonmi, Sincheonmi [SCM], Singeonmi, and Sinyulmi [SYM]) were used to extract sweet potato starch (SPS) for developing starch-based films. After the chemical composition and amylose contents of all SPSs were evaluated, the morphological, moisture, mechanical, and barrier properties of the SPS-based films were investigated. As one of the film characteristics, the X-ray diffractograms revealed that the SCM-based film with the highest amylose content (26.34%) had the highest relative crystallinity (24.31%). The SCM-based film also showed higher tensile strength (3.05-fold) and elastic modulus (2.38-fold) than the SYM-based film with the lowest amylose content (21.84%). The water vapor and oxygen permeabilities of the SPS-based films were negatively correlated with the amylose content. Thus, the SCM-based film was less permeable for water vapor (3.16-fold) and oxygen (1.81-fold) than the SYM-based film. These results demonstrated that the sweet potato cultivar, especially the amylose content, plays a significant role in determining the physicochemical properties of the SPS-based films.

Amylose starch with no detectable branching developed through DNA-free CRISPR-Cas9 mediated mutagenesis of two starch branching enzymes in potato

DNA-free genome editing was used to induce mutations in one or two branching enzyme genes (Sbe) in tetraploid potato to develop starch with an increased amylose ratio and elongated amylopectin chains. By using ribonucleoprotein (RNP) transfection of potato protoplasts, a mutation frequency up to 72% was achieved. The large variation of mutations was grouped as follows: Group 1 lines with all alleles of Sbe1 mutated, Group 2 lines with all alleles of Sbe1 as well as two to three alleles of Sbe2 mutated and Group 3 lines having all alleles of both genes mutated. Starch from lines in Group 3 was found to be essentially free of amylopectin with no detectable branching and a chain length (CL) distribution where not only the major amylopectin fraction but also the shortest amylose chains were lost. Surprisingly, the starch still formed granules in a low-ordered crystalline structure. Starch from lines of Group 2 had an increased CL with a higher proportion of intermediate-sized chains, an altered granule phenotype but a crystalline structure in the granules similar to wild-type starch. Minor changes in CL could also be detected for the Group 1 starches when studied at a higher resolution.

Hierarchical Structure and Thermal Property of Starch-Based Nanocomposites with Different Amylose/Amylopectin Ratio

Starch-based materials with reinforced properties were considered as one of the most promising materials to replace the petro-based packaging products, and actually, the molecular structures of starch usually determined the structures and properties of end-used starchy products. Here, starch-based nanocomposites were fabricated by starch esters derived from native starches with different amylose contents and organically modified montmorillonite (OMMT). The fractured surface under scanning electron microscopy (SEM) exhibited wrinkles formed by macromolecular aggregation owing to the interaction competition between the plasticizer and nanofiller with the starch ester. The more intense interaction within amylopectin-rich films promoted the formation of much randomly exfoliation of OMMT observed by Transmission electron microscopy (TEM). As the amylose content increased, the interaction between the starch ester and the nanofiller was weakened, leading to the dispersion morphology of an ordered arrangement and partly intercalated structures in the dimension of 12.92 to 19.77 nm. Meanwhile, such interaction also affected both the inner ordered structure integrity of starch ester and the layer structure consistency of nanofiller according to X-ray diffraction results. Further, the stronger interaction between amylopectin and the nanofiller endowed higher thermal stability to the amylopectin-rich starch-based nanocomposites. In short, these results are beneficial for the application of starch-based nanocomposites in the food packaging industry by regulating the interaction between starch and nanofillers.

Altered Tuber Yield in Genetically Modified High-Amylose and Oil Potato Lines Is Associated With Changed Whole-Plant Nitrogen Economy

Breeding for improved crop quality traits can affect non-target traits related to growth and resource use, and these effects may vary in different cultivation conditions (e. g., greenhouse vs. field). The objectives of this study are to investigate the growth and whole-plant nitrogen (N) economy of two genetically modified (GM) potato lines compared to their non-GM parental varieties and when grown in different cultivation conditions. A high-amylose GM potato line and its parent were grown under field and greenhouse conditions for one growing season in Sweden; and a GM oil potato line and its parent were grown in greenhouse conditions only. Tuber yield, above ground biomass, N uptake efficiency and other plant N economy traits were assessed. In both cultivation conditions, the GM lines produced between 1.5 and two times more tubers as compared with their parents. In the greenhouse, fresh tuber yield and N uptake efficiency were unaffected by the genetic modifications, but the GM-lines produced less tuber biomass per plant-internal N compared to their parents. In the field, the fresh tuber yield was 40% greater in the high-amylose line as compared with its parent; the greater fresh tuber yield in the high-amylose GM line was accomplished by higher water allocation to the harvested tubers, and associated with increased N recovery from soil (+20%), N uptake efficiency (+53%), tuber N content (+20%), and N accumulation (+120%) compared with the non-GM parent. The cultivation conditions influenced the yield and N economy. For example, the final fresh above-ground plant biomass and N pool were considerably higher in the greenhouse conditions, whilst the tuber yield was higher in the field conditions. In conclusion, the genetic modification inducing high accumulation of amylose in potato tubers affected several non-target traits related to plant N economy, and increased the plant N uptake and accumulation efficiency of the field-grown plants. Due to strongly increased plant N accumulation compared to the parental variety, the cultivation of the high-amylose line is expected to require higher N fertilization rates. However, starch productivity per unit land area or soil N still is expected to be higher in the high-amylose line.

Mechanical and barrier properties of maize starch-gelatin composite films: effects of amylose content

BACKGROUND

In order to obtain new reinforcing bio-fillers to improve the physicochemical properties of gelatin-based films, three types of maize starch, waxy maize starch (Ap), normal starch (Ns) and high-amylose starch (Al), were incorporated into gelatin film and the resulting film properties were investigated, focusing on the impact of amylose content.

RESULTS

The thickness, opacity and roughness of gelatin film increased depending on the amylose content along with the starch concentration. The effects of the three starches on the mechanical properties of gelatin film were governed by amylose content, starch concentration as well as environmental relative humidity (RH). At 75% RH, the presence of Al and Ns in the gelatin matrix increased the film strength but decreased its elongation, while Ap exhibited an inverse effect. Starch addition decreased the oxygen permeability of the film, with the lowest value at 20% Al and Ns. All starches, notably at 30% content, led to a decrease in the water vapor permeability of the film at 90% RH, especially Ns starch. Furthermore, the starches improved the thermal stability of the film to some extent. Fourier transform infrared spectra indicated that some weak intermolecular interactions such as hydrogen bonding occurred between gelatin and starch. Moreover, a high degree of B-type crystallinity of starch was characterized in Gel-Al film by X-ray diffraction.

CONCLUSION

Tailoring the properties of gelatin film by the incorporation of different types of maize starch provides the potential to extend its applications in edible food packaging. © 2017 Society of Chemical Industry.

Flexible starch-polyurethane films: Physiochemical characteristics and hydrophobicity

Starch-polyurethane (PU) composite films with improved mechanical and hydrophobic properties were developed in this work. A simple and effective microwave-aided starch gelatinisation instrument was used to prepare glycerol plasticized high amylose starch (HAGS) material. Polyethylene glycol-isocyanate (PEG-iso) linker was prepared by reacting PEG 1000 with hexamethylene diisocyanate (HMDI). PEG-iso linker was then grafted into HAGS forming three dimensional urethane networks (PEG-PU). HAGS-PEG-PU composite blends were prepared and dried at ambient temperature to obtain HAGS-PEG-PU films. The mechanical properties and hydrophobicity (as contact angle, CA) of the HAGS-PEG-PU films were measured and analysed. Fourier transform infrared spectroscopy showed good grafting of PEG-iso into starch structure. Increase of PEG-iso concentration up to 20% (w/w) improved the molecular mixing and interpenetration between the starch and PEG-PU. The HAGS-PEG-PU films had improved hydrophobicity as indicated by CA values ranging from 51 to 110°and very high flexibility as evidenced from elongation at break (ε_B) values from 17 to 1000%. The HAGS-PEG-PU film formulation containing 20% (w/w) PEG-iso provided the best flexibility (ε_B>1000%) and hydrophobicity (CA>110°).