Mechanical and structural properties of solution-cast high-amylose maize starch films

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.

The relationship between molecular structure and film-forming properties of thermoplastic starches from different botanical sources

To illustrate the correlations between molecular structures and the film-forming properties of thermoplastic starch from various botanical sources, starches from cereal, tuber and legume were modified by thermoplastic extrusion and the corresponding thermoplastic starch films were prepared including thermoplastic corn starch (TCS), thermoplastic rice starch (TRS), thermoplastic sweet potato starch (TSPS), thermoplastic cassava starch (TCAS) and thermoplastic pea starch (TPES) films. TPES film displayed a higher tensile strength (6.28 MPa) and stronger water resistance, such as lower water solubility (15.70 %), water absorption (42.35 %), and water vapor permeability (0.285 g·mm·h-1·m-2·kPa-1) due to higher contents of amylose and B1 chains. TCAS showed a smoother and more amorphous film due to higher amylopectin content, resulting higher elongation at break and larger opacity. TCS film was the most transparent due to a compacter network and more ordered crystallinity structure, which was suit for the packaging of fresh vegetables and aquatic products, whereas TCAS film was the opaquest, which protected package foods from light such as meat products, etc. The outcome would provide an innovative theory to regulate accurately the functional properties of thermoplastic starch films for different food needs.

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.

Nano-cellulose reinforced starch bio composite films- A review on green composites

Plastic-based food packaging is generating a serious environmental problem by accumulating large amounts of plastic in the surroundings. Ecological and health concerns are driving research efforts for developing biodegradable films. There are few alternatives that could reduce the environmental impact; one of them is to substitute petroleum-based plastic with starch-based film. Starch has remarkable properties, including biodegradability, sustainability, abundancy, and capable of being modified or blended with other polymers. However, low mechanical strength and low water resistance restrict its application in food packaging. Nanocellulose isolated from lignocellulosic fibers has attracted tremendous interest in the field of science due to high crystallinity and mechanical strength, unique morphology along with abundancy, renewability, and biodegradability. Therefore, nano cellulose as a reinforcer proved to be a good option for fabricating biocomposites for food packaging. The current review will give a critical snapshot of the potential application of nanocellulose in food packaging and discuss new challenges and opportunities for starch biocomposites enriched with nano cellulose.

Effect of Alkali Treatment on Structure and Properties of High Amylose Corn Starch Film

Alkali treatment is used for melt extrusion film formation with corn starch, but optimal conditions for this procedure are still unknown. In this study, the changes in properties and structure of high amylose corn starch (70%) films with different concentrations of sodium hydroxide (NaOH), prepared by melting extrusion, were investigated. With increasing sodium hydroxide concentrations, the tensile strength of the high-amylose starch film decreased gradually, while the elongation at break increased. The tensile strength of the high amylose starch (HAS) film with 2% NaOH-treatment was 10.03 MPa and its elongation at break was 40%. A 2% NaOH-treatment promoted the orderly rearrangement of starch molecules and formed an Eh-type crystal structure, which enlarged the spacing of the single helix structure, increased the molecular mobility of the starch, and slowed down the process of recrystallization; a 10% NaOH-treatment oxidized the hydroxyl groups of the high amylose corn starch during extrusion, formed a poly-carbonyl structure, and initiated the degradation and cross-linking of starch molecule chains.

Relevance of Interactions between Starch-based Coatings and Plum Fruit Surfaces: A Physical-Chemical Analysis

In order to extend the shelf life of the fruit, improve appearance, and to keep all nutrition properties of the plum from diminishing, edible coatings comprised of wheat starch and wheat starch-whey protein isolate (in ratio 80/20) were created. Stand-alone films were produced to assess properties which helped to understand the phenomena occurring on the surface level of coated plums. The properties of coatings based on starch are similar to starch coatings containing oil because the natural epicuticular wax layer of plums merges with coating materials. Adding oil doubled the contact angle value and the dispersive component of the surface tension. The workings of adhesion and cohesion, spreading coefficient, water absorption, water content, and solubility in water of the films decreased. Similar processes were observed on the fruits' surface. In appearance, the coating process is similar to polishing the plum surface for removing crystalline wax. The color parameters of coated fruits did not significantly change. Newly formed bonds or interactions established between starch, whey proteins, water, glycerol, and oil are displayed by Fourier transform infrared (FTIR) analysis. This work revealed how the interactions between the epicuticular wax on the fruit's surface and the hydrocolloid-based coatings affect the efficiency of the coatings.

Preparation and Characterization of High Amylose Corn Starch⁻Microcrystalline Cellulose Aerogel with High Absorption

Microcrystalline cellulose (MCC) aerogels were synthesized, blendingwith high amylose corn starch of different contents based on a NaOH–urea solution, and following by vacuum freeze-drying technology. The microstructure of the aerogel was observed by scanning electron microscopy (SEM) as an interconnected, porous three-dimensional structure, while X-ray diffractogram (XRD) measurements showed that the crystalline form was converted from cellulose I to cellulose II during dissolution and regeneration. Thermogravimetric analysis (TGA) showed that the content of starch had little effect on the thermal stability of the aerogel, whereas the content of starch had great influences on absorption and viscoelastic properties. When the ratio of starch was 10% and 15%, the prepared aerogels presented a low density and abundant pores, which endowed the aerogels, not only with the highest absorption ratio of pump oil and linseed oil (10.63 and 11.44 g/g, respectively), but also with better dynamic viscoelastic properties.

Modification of functional properties of pullulan-whey protein bionanocomposite films with nanoclay

In this study, biodegradable nanocomposite film composed of pullulan - whey protein isolate (WPI) - montmorillonite (MMT) were developed and characterized as a function of incorporating various amounts of MMT nanoparticles (0, 1, 3 and 5 % wt). Results showed that the water-vapor permeability, moisture content, moisture absorption and water solubility decreased when the nano-MMT content was increased. Tensile strength improved and elongation at break simultaneously decreased with increasing MMT content. The glass transition temperature (Tg(and melting-point temperature (Tm) increased with increasing nano-MMT content. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis revealed uniform distribution of MMT into the polymer matrix. Atomic force microscopy (AFM) showed enhancement of films' roughness with increasing MMT content.

Composite materials derived from biodegradable starch polymer and Atriplex halimus fibers

Biocomposites from starch and cellulose fibers have gained renewed interest as environmentally friendly materials and as biodegradable renewable resources for a sustainable development. In this study, natural fibers were extracted from a Mediterranean saltbush (Atriplex halimus) plant found abundantly in North Africa. The composites were prepared by a solution casting method from corn starch using 0–15 wt.% of micro-cellulose fibers as a filler. The structure of the composites was investigated by Fourier transform infrared spectroscopy. The physical properties of the composites were determined by mechanical tensile tests, thermogravimetric analysis and water absorption. The results showed that higher fiber content raised the elastic modulus by 92% and the temperature of degradation by up to 355°C. Optical microscopy revealed a good adhesion between the matrix and the fibers owing to their chemical similarities. Water uptake measurements showed that the composites had a much better water resistance and a more hydrophobic character than pure thermoplastic starch films. Biodegradability tests confirmed that the prepared composites are an environmentally safe material suited for different applications.

Thermoplastic starch processing and characteristics-a review

Canola Council of Canada, Winnipeg, Manitoba, Canada The rising costs of nonrenewable feedstocks and environmental concerns with their industrial usage have encouraged the study and development of renewable products, including thermoplastic starch (TPS). Starch is an abundant, plant-based biodegradable material with interesting physicochemical characteristics that can be exploited, and this has received attention for development of TPS products. Starch exhibits usable thermoplastic properties when plasticizers, elevated temperatures, and shear are present. The choice of plasticizer has an effect on TPS, even when these have similar plasticization principles. Most TPS have glass transition temperature, Tg, in the range of approximately -75 to 10°C. Glassy transition of TPS is detected by differential scanning calorimeter (DSC) and thermodynamic analyzer (DMA), although DMA has been found to be more sensitive and effective. TPS has low tensile properties, typically below 6 MPa in tensile strength (TS). The addition of synthetic polymers, nanoclay, and fiber can improve TS and water-resistance ability. The moisture sorption behavior of TPS is described in GAB and BET models, from which monolayer moisture content and specific area are derived. Current studies on surface tension, gas permeability, crystallinity, and so on of the TPS are also reviewed.

Mechanical properties of a high amylose content corn starch based film, gelatinized at low temperature

In the present study, a better knowledge of the influence of plasticizer content, storage relative humidity and film thickness on the mechanical properties of high amylose corn starch based films gelatinized at low temperature, is presented. The mechanical properties, tensile strength and percentage of elongation at break of high amylose corn starch films plasticized with glycerol were evaluated using tension tests. The films exhibited an increase in elongation and a decrease in tensile strength with increasing plasticizer concentration. When the glycerol level was high, some fissures were detected in the dry films, possible due to phase separation (starch-glycerol) phenomena. Film crystallinity is related to the reorganization capacity of the polymer chain, and thus the relative film crystallinity should increase with plasticizer content (glycerol and water). The mechanical properties were found to be strongly dependent on the water content due to the hydrophilic nature of starch films. The influence of moisture sorption on tensile strength was similar to that of plasticization with glycerol. The relationship between polymer chain mobility and water content explained this behavior. Elongation suffered a different effect and maximum values were reached at 45% relative humidity. The final drop in elongation was due to a softening of the structure at high relative humidity. The thicker the film the longer the drying time required, leading to greater relative crystallinity due to the corresponding increase in the possibility for chain reorganization. As a consequence, linear increases in tensile strength and elongation were observed with film thickness over the whole range studied (30 to 100 µm).