Trends and challenges of starch-based foams for use as food packaging and food container

The effect of agar from the seaweed Gracilaria fisheri on properties of biodegradable starch foam

This work focuses on the potential of agar from the seaweed Gracilaria fisheri to modify the properties of starch foam. The effects of different ratios of glycerol and agar on the properties of starch foams were investigated. All formulations used in this study produced easy-to-handle, smooth, single-use foam trays with no visible cracks. The addition of agar slightly affected the off-white color of the foam but red and yellow color values significantly decreased with increments of agar content. As the agar content was increased, the foam became less dense. A foam produced at a glycerol:agar ratio of 3:7 exhibited the highest values of flexural stress at maximum load (3.23 MPa), modulus (194.46 MPa) and hardness (97.50), and the highest temperature at maximum weight loss (Tmax) (337 °C). Therefore, starch foam modified with agar from Gracilaria fisheri showed suitable physical, mechanical and thermal properties for food packaging, and could possibly be used in the place of expanded polystyrene (EPS) foam.

Biodegradable starch foams reinforced by food-chain side streams

Biodegradable starch foam trays offer an eco-friendly substitute for petroleum-based single-use packaging, notably polystyrene foams. However, they lack flexibility, tensile strength, and water-sensitivity, addressable through lignocellulosic reinforcement. This study aimed to develop biodegradable starch foam trays filled with different food-chain side streams for sustainable alternative packaging. Corncob, soybean straw, cassava peel, araucaria seed hull, yerba mate stalks and yerba mate leaves petiole were collected, dried and ground to <250 μm. The trays were filled with 13 % (w/w) of each food-chain side streams and produced by hot molding. The trays morphology, moisture, water activity (aw), thickness, bulk density, tensile strength, elongation at break, Young's modulus, bending strength, maximum deflection, and sorption isotherms were investigated. Reinforcements slightly increased the foams bulk density, reduced the tensile strength and maximum deflection and while bending strength increased from 0.20 MPa to 1.17-1.80 MPa. The elasticity modulus decreased by adding any filling, that resulted in ductility improvement; however, these packaging have moisture-sensitive material especially for aw higher than 0.52, which drives the use recommendation for dry products storage or shipping/transport. The biodegradable starch foam trays filled with side streams were successfully produced and offer excellent alternative to petroleum-based packaging low-density material with bending strength improved.

Forefront Research of Foaming Strategies on Biodegradable Polymers and Their Composites by Thermal or Melt-Based Processing Technologies: Advances and Perspectives

The last few decades have witnessed significant advances in the development of polymeric-based foam materials. These materials find several practical applications in our daily lives due to their characteristic properties such as low density, thermal insulation, and porosity, which are important in packaging, in building construction, and in biomedical applications, respectively. The first foams with practical applications used polymeric materials of petrochemical origin. However, due to growing environmental concerns, considerable efforts have been made to replace some of these materials with biodegradable polymers. Foam processing has evolved greatly in recent years due to improvements in existing techniques, such as the use of supercritical fluids in extrusion foaming and foam injection moulding, as well as the advent or adaptation of existing techniques to produce foams, as in the case of the combination between additive manufacturing and foam technology. The use of supercritical CO2 is especially advantageous in the production of porous structures for biomedical applications, as CO2 is chemically inert and non-toxic; in addition, it allows for an easy tailoring of the pore structure through processing conditions. Biodegradable polymeric materials, despite their enormous advantages over petroleum-based materials, present some difficulties regarding their potential use in foaming, such as poor melt strength, slow crystallization rate, poor processability, low service temperature, low toughness, and high brittleness, which limits their field of application. Several strategies were developed to improve the melt strength, including the change in monomer composition and the use of chemical modifiers and chain extenders to extend the chain length or create a branched molecular structure, to increase the molecular weight and the viscosity of the polymer. The use of additives or fillers is also commonly used, as fillers can improve crystallization kinetics by acting as crystal-nucleating agents. Alternatively, biodegradable polymers can be blended with other biodegradable polymers to combine certain properties and to counteract certain limitations. This work therefore aims to provide the latest advances regarding the foaming of biodegradable polymers. It covers the main foaming techniques and their advances and reviews the uses of biodegradable polymers in foaming, focusing on the chemical changes of polymers that improve their foaming ability. Finally, the challenges as well as the main opportunities presented reinforce the market potential of the biodegradable polymer foam materials.

Comprehensive enhancement of flame retardant starch/cellulose/diatomite composite foams via metal-organic coordination

In recent years, considerable attention has been given to the utilization of biomass for producing bio-based foams, such as starch-based foams. Despite their renewability and widespread availability, these foams still present certain drawbacks regarding their poor mechanical properties and flammability. To tackle these concerns, a metal ion cross-linking strategy was employed by incorporating calcium ions (Ca2+) solution into foamed starch/cellulose slurry. Followed by ambient drying, starch/cellulose composite foam was successfully fabricated with a remarkable enhancement in various properties. Specifically, compared to the control sample, the compressive strength and modulus increased by 26.2 % and 123.0 %, respectively. Additionally, the Ca2+ cross-linked starch/cellulose composite foam exhibited excellent heat resistance, water stability, and flame retardancy. The limiting oxygen index (LOI) reached 52 %, with a vertical combustion rating of V-0. Along with the addition of 2 phr diatomite, it demonstrated a significant enhancement on flame retardancy with a LOI of 65 %, although the apparent density of the composite foam was not low enough. This study indicated a green and simple method to obtain starch-based composite foams with enhanced comprehensive properties including thermal, water stability, mechanical, and flame retardancy, expanding their potential applications in areas such as building materials and rigid packaging.

Effects of different proportions of erythritol and mannitol on the physicochemical properties of corn starch films prepared via the flow elongation method

In this study, corn films based on corn starch were fabricated through the casting method, and various plasticizers (namely, erythritol and d-mannitol) were incorporated. The study delved into the gelatinization and physicochemical characteristics of these corn starch-based films. Additionally, the impact of different ratios of plasticizers on reductive gelatinization was assessed using RVA analysis. The investigation also encompassed the effects of varying plasticizer ratios on starch granule expansion, amylose dissolution, and amylopectin melting. Interestingly, as the proportion of d-mannitol increased, there were gradual increases in film thickness, water content, and water contact angle, alongside decreases in water vapor permeability, crystallinity, and water solubility of the corn starch-based films. In essence, this research provides a fundamental basis for potential industrial applications of corn starch-based films.

Effect of Operational Variables on Supercritical Foaming of Caffeic Acid-Loaded Poly(lactic acid)/Poly(butylene adipate-co-terephthalate) Blends for the Development of Sustainable Materials

Expanded polystyrene will account for 5.3% of total global plastic production in 2021 and is widely used for food packaging due to its excellent moisture resistance and thermal insulation. However, some of these packages are often used only once before being discarded, generating large amounts of environmentally harmful plastic waste. A very attractive alternative to the conventional methods used for polymer processing is the use of supercritical carbon dioxide (scCO2) since it has mass-transfer properties adapted to the foam morphology, generating different path lengths for the diffusion of active compounds within its structure and can dissolve a wide range of organic molecules under supercritical conditions. The objective of this research was to evaluate the effect of operational variables on the process of caffeic acid (CA) impregnation and subsequent foaming of polylactic acid (PLA) as well as two PLA/poly(butylene-co-terephthalate-adipate) (PBAT) blends using scCO2. The results showed an increase in the degree of crystallinity of the CA-impregnated samples due to the nucleation effect of the active compound. On the other hand, SEM micrographs of both films and foams showed significant differences due to the presence of PBAT and its low miscibility with PLA. Finally, the results obtained in this work contribute to the knowledge of the important parameters to consider for the implementation of the impregnation and foaming process of PLA and PLA/PBAT blends with potential use in food packaging.

Effect of Starch and Paperboard Reinforcing Structures on Insulative Fiber Foam Composites

Single-use plastic foams are used extensively as interior packaging to insulate and protect items during shipment but have come under increasing scrutiny due to the volume sent to landfills and their negative impact on the environment. Insulative compression molded cellulose fiber foams could be a viable alternative, but they do not have the mechanical strength of plastic foams. To address this issue, a novel approach was used that combined the insulative properties of cellulose fiber foams, a binder (starch), and three different reinforcing paperboard elements (angular, cylindrical, and grid) to make low-density foam composites with excellent mechanical strength. Compression molded foams and composites had a consistent thickness and a smooth, flat finish. Respirometry tests showed the fiber foams mineralized in the range of 37 to 49% over a 46 d testing period. All of the samples had relatively low density (Dd) and thermal conductivity (TC). The Dd of samples ranged from 33.1 to 64.9 kg/m3, and TC ranged from 0.039 to 0.049 W/mk. The addition of starch to the fiber foam (FF+S) and composites not only increased Dd, drying time (Td), and TC by an average of 18%, 55%, and 5.5%, respectively, but also dramatically increased the mechanical strength. The FF+S foam and paperboard composites had 240% and 350% higher average flexural strength (σfM) and modulus (Ef), respectively, than the FF-S composites. The FF-S grid composite and all the FF+S foam and composite samples had equal or higher σfM than EPS foam. Additionally, FF+S foam and paperboard composites had 187% and 354% higher average compression strength (CS) and modulus (Ec), respectively, than the FF-S foam and composites. All the paperboard composites for both FF+S and FF-S samples had comparable or higher CS, but only the FF+S cylinder and grid samples had greater toughness (Ωc) than EPS foam. Fiber foams and foam composites are compatible with existing paper recycling streams and show promise as a biodegradable, insulative alternative to EPS foam internal packaging.

Microplastic pollution in urban stormwater inlet sediments influenced by land use type of runoff drainage area

Since the urban stormwater inlet (USI) acts as a link in the migration of microplastics (MPs) in stormwater, sufficient information on MPs in USI sediments is very important for understanding urban diffuse microplastic pollution. In this study, the abundance and characteristics of MPs in the USI sediments of Ma'anshan City, China, were analyzed based on urban land use type. MPs were prevalent in the USI sediments, with the average abundances of 536.77 ± 313.92 items·kg-1 for commercial areas, 505.64 ± 400.82 items·kg-1 for campuses, 694.71 ± 219.95 items·kg-1 for industrial areas, 526.41 ± 152.34 items·kg-1 for residential areas, and 1107.75 ± 422.10 items·kg-1 for main roads, indicating a high microplastic pollution in the USI sediments from main roads. The microplastic polymers were mainly polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), and polystyrene (PS), accounting for 46.75 %-100.00 %, with PP MPs being the most abundant. Fiber MPs had the highest proportion in USI sediments from both campuses (35.30 %) and industrial areas (38.19 %), while film MPs were the most abundant for both commercial areas (39.91 %) and residential areas (35.65 %). The average proportions of fiber (27.29 %), fragment (29.18 %), and film (28.68 %) were almost equal for main roads, unlike other land use types. Except for campuses, transparent MPs were the most common for all land use types, with average proportions of 29.60 %-42.70 %. The proportions of MPs with sizes of <1000 μm were 72.54 % for commercial areas, 77.11 % for campuses, 76.05 % for industrial areas, 70.76 % for residential areas, and 74.29 % for main roads, respectively, with a consistent result with previous study that the MPs of <1000 μm are the predominant in the environment. This study enriches the knowledge of microplastic pollution in USI sediments and will benefit the mitigation of diffuse microplastic pollution.

Comparative study of the structure and mechanical properties of starch aerogels fabricated from air-classified and isolated pulse starches

Significant amounts of starch and protein are generated as co-products during fractionation of pulse seeds. While pulse proteins (PP) have garnered a lot of interest in numerous applications, little attention is shown to pulse starch (PS). The creation of novel materials such as bioplastics could revolutionize the use of pulse starches. In this study, we investigated the prospects of air-classified and isolated pea, lentil, and faba bean starches as a precursor for fabricating pulse starch bioaerogels (PSBs) via freeze-drying technique. The results evidenced ultra-low densities (<0.1 m2/g), mesopore sizes (2-50 μm), high porosities (∼99 %), low surface areas (SBET = ∼4-18 m2/g) for all the aerogels. The adsorption isotherm showed typical Type II and III profiles, while the thermogravimetric analysis showed more weight loss (74.39-78.12 %) in aerogels mostly developed from isolated starches. Microstructural studies showed a unique distribution of pores within the developed aerogels. FTIR and XPS studies confirmed the presence of an amide (I, II, III) at different absorption bands range (∼1600-1200 cm-1) and functional groups (carboxylic group and the amide group), respectively. All the PSBs became stiffer with a corresponding increase in load, and a reversible deformation in the linear region was identified at <5 % strain. Comparatively, saturated PSBs from air-classified starch at a relative humidity of 95 % showed a drastic reduction in their compressive moduli (CM), while PSBs from isolated starch experienced markedly high CM. Moisture saturation was achieved at 72 h for all the samples. This study provides crucial information that could spark a keen interest in the use of non-conventional starch for the creation of novel and sustainable biobased products with expanded applications.

Production and characterization of starch-lignin based materials: A review

In their pristine state, starch and lignin are abundant and inexpensive natural polymers frequently considered green alternatives to oil-based and synthetic polymers. Despite their availability and owing to their physicochemical properties; starch and lignin are not often utilized in their pristine forms for high-performance applications. Generally, chemical and physical modifications transform them into starch- and lignin-based materials with broadened properties and functionality. In the last decade, the combination of starch and lignin for producing reinforced materials has gained significant attention. The reinforcing of starch matrices with lignin has received primary focus because of the enhanced water sensitivity, UV protection, and mechanical and thermal resistance that lignin introduces to starch-based materials. This review paper aims to assess starch-lignin materials' production and characterization technologies, highlighting their physicochemical properties, outcomes, challenges, and opportunities. First, this paper describes the current status, sources, and chemical modifications of lignin and starch. Next, the discussion is oriented toward starch-lignin materials and their production approaches, such as blends, composites, plasticized/crosslinked films, and coupled polymers. Special attention is given to the characterization methods of starch-lignin materials, focusing on their advantages, disadvantages, and expected outcomes. Finally, the challenges, opportunities, and future perspectives in developing starch-lignin materials, such as adhesives, coatings, films, and controlled delivery systems, are discussed.

Synergistic enhancement of modified sericite on rheological and foaming properties of poly (lactic acid)

Due to low melt strength and slow crystallization rate, poly (lactic acid) (PLA) foam materials are still not satisfactory. In order to improve the foaming performance of PLA, sericite (GA) was selected as the filler and modified by 3-Aminopropyltriethoxysilane (KH-550). Through melt blending with PLA, azodicarbonamide (ADC) foaming agent was selected for molding foaming, and PLA/GA composite foam was prepared. The addition of GA not only acts as a nucleating agent to improve the crystallization performance of the blend, but also improves its complex viscosity and storage modulus, and enhances its melt strength, so that the compressive strength and impact strength of the prepared composite foam are increased by 265.5 % and 224.0 %, respectively. Compared with PE foam, PLA/GA composite foam showed excellent thermal insulation performance through thermal infrared imaging test. Based on its mechanical and thermal insulation properties, this sample provides new materials for the field of wall insulation and foam packaging. This study provides an effective way to improve the melt strength and workability of PLA.

Dynamic Modulation of SO2 Atmosphere for Enhanced Fresh-Keeping of Grapes Using a Novel Starch-Based Biodegradable Foam Packaging

To improve the fresh-keeping of highly perishable fruits with high commercial value, a novel starch-based foam packaging material was developed in this study. The foam incorporated the antiseptic ingredient Na₂S₂O₅, which chemically interacted with environmental moisture to release SO₂ as an antifungal agent. Scanning electron microscopy (SEM), moisture absorption and mechanical measurements were used to characterize the unique sandwich-like inner structure of the foam which allowed for the modulable release of SO₂. The starch-based foam exhibited sufficient resilience (~100%) to provide ideal cushioning to prevent physical damage to fresh fruits during transportation. When 25 g/m² of Na₂S₂O₅ was applied, the foam stably released over 100 ppm SO₂ and demonstrated satisfactory antifungal performance (inhibition over 60%) in terms of maintaining the appearance and nutritional values (such as soluble solids 14 vs. 11%, total acidity 0.45 vs. 0.30%, and Vitamin C 3.4 vs. 2.5 mg/100 g) of fresh grapes during a 21 day storage period. Additionally, the residual SO₂ (14 mg/kg) also meets the safety limits (<30 mg/kg). These research findings suggest great potential for the utilization of this novel foam in the food industry.

Evaluating how avocado residue addition affects the properties of cassava starch-based foam trays

Avocado seed (AS) is an interesting residue for biopackaging because it has high starch content (41 %). We have prepared composite foam trays based on cassava starch containing different AS concentrations (0, 5, 10 and 15 % w/w) by thermopressing. Composite foam trays with AS were colorful because this residue contains phenolic compounds. The composite foam trays 10AS and 15AS were thicker (2.1-2.3 mm) and denser (0.8-0.9 g/cm³), but less porous (25.6-35.2 %) than cassava starch foam (Control). High AS concentrations yielded composite foam tray less puncture resistant (~40.4 N) and less flexible (0.7-0.9 %), but with tensile strength values (2.1 MPa) almost similar to the Control. The composite foam trays were less hydrophilic and more water resistant than control due to the presence of protein, lipid, and fibers and starch with more amylose content in AS. High AS concentration in composite foam tray decreases the temperature of thermal decomposition peak corresponding to starch. At temperatures >320 °C the foam trays with AS were more resistant to the thermal degradation due to the presence of fibers in AS. High AS concentrations delayed the degradation time of the composite foam trays by 15 days.

Effect of the addition of fique bagasse microparticles in obtaining a biobased material based on cassava starch

The indiscriminate accumulation of plastic waste has prompted research that leads to obtaining biobased materials. The research aim was to evaluate the effect of incorporating fique bagasse microparticles (FBM) in a cassava starch-based foamed material. First, the FBM extraction conditions were established by acid hydrolysis, for which the effect of acid concentration (5, 10 and 15% H₂SO₄), temperature (70, 80 and 90 °C) and extraction time (3, 5 and 7 h) on particle size, functional groups, color, and thermal properties was evaluated. The addition of FBM to the foamed material was then carried out. To do this, a completely randomized design with five treatments (0, 0.5, 0.75, 1.0 and 1.25% FBM) was evaluated. The response variables were the apparent density, expansion and spring index, compressibility, water absorption, thermal properties and FTIR. The results showed that the acid concentration, temperature and time had an effect on the morphological, chemical and thermal properties of FBM, with 10%, 70 °C and 7 h being the conditions that allowed obtaining the smallest particle size (61.69 ± 12.88 μm²). Moreover, the FBM concentration had a significant effect on the physical and mechanical properties of the foam, unleashing the treatment properties of 0.75%. This indicates that FBM have potential for use in obtaining biobased materials.