Thermoplastic starch nanocomposites: sources, production and applications - a review

Sustainable, cytocompatible and flexible electronics on potato starch-based films

Environmental concerns and climate protection are gaining increasing emphasis nowadays. A growing number of industries and scientific fields are involved in this trend. Sustainable electronics is an emerging research strand. Environmentally friendly and biodegradable or biobased raw materials can be used for the development of green flexible electronic devices, which may serve to reduce the pollution generated by plastics and electronics waste. In this work, we present cytocompatible, electrically conductive structures of nanocarbon water-soluble composites based on starch films. To accomplish this goal, potato starch-based films with glycerol as a plasticiser were developed along with a water-soluble vehicle for nanocarbon-based electroconductive pastes specifically dedicated to screen printing technology. Films were characterized by optical microscopy, scanning electron microscopy (SEM) mechanical properties and surface free energy.

Antioxidant Edible Films Derived from Belitung Taro Tubers (Xanthosoma sagittifolium) Incorporated with Moringa Leaf Extract (Moringa oleifera)

Edible films are thin films frequently manufactured using natural bioresources and are employed in food packaging to safeguard food quality. This research prepared edible films from renewable biomass consisting of Belitung taro tuber starch (Xanthosoma sagittifolium) and incorporated sorbitol as a plasticizer, carboxymethyl cellulose as a reinforcing agent, and moringa leaf extract (Moringa oleifera) as an antioxidant. The physicochemical characteristics of the resulting edible films were examined. The most favorable treatment was identified in an edible film containing 3% (v/v based on the total volume of 100 mL) of moringa leaf extract. This exhibited a tensile strength of 6.86 N/mm2, percent elongation of 73.71%, elasticity of 9.37×10-3 kgf/mm2, water absorption of 349.03%, solubility of 93.18%, and water vapor transmission speed of 3.18 g/h m2. Its shelf life was five days at ambient temperature. The edible film was found to have 135.074 ppm of half maximal inhibitory concentration (IC50) based on the antioxidant analysis of inhibition concentration (IC50) value measurements, and was classified as having moderate antioxidant activity. Additionally, the biodegradability assessment revealed that the edible films degraded within 14 days. Based on this data, it can be deduced that adding moringa leaf extract enhances the physicochemical and functional characteristics of the film. These edible films can be used as substitutes for nonrenewable and nonbiodegradable packaging materials.

Non-Traditional Starches, Their Properties, and Applications

This review paper focuses on the recent advancements in the large-scale and laboratory-scale isolation, modification, and characterization of novel starches from accessible botanical sources and food wastes. When creating a new starch product, one should consider the different physicochemical changes that may occur. These changes include the course of gelatinization, the formation of starch-lipids and starch-protein complexes, and the origin of resistant starch (RS). This paper informs about the properties of individual starches, including their chemical structure, the size and crystallinity of starch granules, their thermal and pasting properties, their swelling power, and their digestibility; in particular, small starch granules showed unique properties. They can be utilized as fat substitutes in frozen desserts or mayonnaises, in custard due to their smooth texture, in non-food applications in biodegradable plastics, or as adsorbents. The low onset temperature of gelatinization (detected by DSC in acorn starch) is associated with the costs of the industrial processes in terms of energy and time. Starch plays a crucial role in the food industry as a thickening agent. Starches obtained from ulluco, winter squash, bean, pumpkin, quinoa, and sweet potato demonstrate a high peak viscosity (PV), while waxy rice and ginger starches have a low PV. The other analytical methods in the paper include laser diffraction, X-ray diffraction, FTIR, Raman, and NMR spectroscopies. Native, "clean-label" starches from new sources could replace chemically modified starches due to their properties being similar to common commercially modified ones. Human populations, especially in developed countries, suffer from obesity and civilization diseases, a reduction in which would be possible with the help of low-digestible starches. Starch with a high RS content was discovered in gelatinized lily (>50%) and unripe plantains (>25%), while cooked lily starch retained low levels of rapidly digestible starch (20%). Starch from gorgon nut processed at high temperatures has a high proportion of slowly digestible starch. Therefore, one can include these types of starches in a nutritious diet. Interesting industrial materials based on non-traditional starches include biodegradable composites, edible films, and nanomaterials.

Characterization of Thermoplastic Starch Plasticized with Ternary Urea-Polyols Deep Eutectic Solvent with Two Selected Fillers: Microcrystalline Cellulose and Montmorillonite

The aim of the study was to prepare and characterize composite materials based on thermoplastic starch (TPS)/deep eutectic solvent (DES). Potato starch was plasticized with ternary DES: urea:glycerol:sorbitol and modified with the selected fillers: microcrystalline cellulose and sodium montmorillonite. Films were prepared via twin-screw extrusion and thermocompression of the extrudates. Then, the physicochemical properties of the TPS films were examined. The ternary DES effectively plasticized the polysaccharide leading to a highly amorphous structure of the TPS (confirmed via mechanical tests, DMTA and XRD analyses). An investigation of the behavior in water (swelling and dissolution degree) and water vapor transmission rate of the films was determined. The introduction of the two types of fillers resulted in higher tensile strength and better barrier properties of the composite TPS films. However, montmorillonite addition exhibited a higher impact than microcrystalline cellulose. Moreover, a cone calorimetry analysis of the TPS materials revealed that they showed better fire-retardant properties than TPS plasticized with a conventional plasticizer (glycerol).

Effective Aging Inhibition of the Thermoplastic Corn Starch Films through the Use of Green Hybrid Filler

Recently, hybrid fillers have been widely used to improve the properties of biopolymers. The synergistic effects of the hybrid fillers can have a positive impact on biopolymers, including thermoplastic corn starch film (TPCS). In this communication, we highlight the effectiveness of hybrid fillers in inhibiting the aging process of TPCS. The TPCS, thermoplastic corn starch composite films (TPCS-C), and hybrid thermoplastic corn starch composite film (TPCS-HC) were stored for 3 months to study the effect of hybrid filler on the starch retrogradation. TPCS-C and TPCS-HC were prepared by casting method with 5 wt% of fillers: nanocellulose (NC) and bentonite (BT). The alteration of the mechanical properties, aging behavior, and crystalline structure of the films were analyzed through the tensile test, Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and water absorption analysis. The obtained data were correlated to each other to analyze the retrogradation of the TPCS, which is the main factor that contributes to the aging process of the biopolymer. Results signify that incorporating the hybrid filler (NC + BT) in the TPCS/4BT1NC films has effectively prevented retrogradation of the starch molecules after being stored for 3 months. On the contrary, the virgin TPCS film showed the highest degree of retrogradation resulting in a significant decrement in the film’s flexibility. These findings proved the capability of the green hybrid filler in inhibiting the aging of the TPCS.