Properties and characterization of biodegradable films obtained from different starch sources

Substituting corn starch with wolf's fruit and butterfly lily starches in thermopressed films: Physicochemical, mechanical, and biodegradation properties

The industrial use of corn starch competes with food supplies, encouraging the investigation of native starches as an alternative for its partial replacement. This study aimed to analyze the effects of replacing corn starch (CS) with wolf's fruit (WFS) and butterfly lily (BLS) starches on the physicochemical, mechanical, and biodegradation properties of starch-based films. Plasticized (with glycerin and citric acid) and unplasticized films were prepared with a microwave (10 s) and by thermopressing (1.5 t/120 °C/2 min) and were analyzed for amylose, scanning electron microscopy, X-ray diffraction, and paste properties. Furthermore, the biodegradability of films was tested in two soils over 42 days. Our results show that BLS is not a suitable raw material to replace corn starch. WFS with 27.5 % apparent amylose content and granule size of 12.5 μm produced films with thickness, permeability, tensile strength, and elongation of ~110 μm, ~4.8 g (m.s.Pa)-1, ~2.5 MPa, and ~2.9 %, respectively, similar to CS. The biodegradability of WFS film showed greater resistance (≤61.4 %), increasing with the addition of plasticizers (89-93 % for WFS302) or partial replacement of CS (73-91 % for CSWFS303). These findings indicate that WFS can partially or fully replace CS in thermopressed films.

Synthesis of a Bioactive Nitric Oxide-Releasing Polymer from S-Nitrosated Starch

The incorporation of nitric oxide (NO) into polymeric matrices minimizes degradation and facilitates controlled release. This optimization increases the field of application of NO, in dressings, food protective films, and implant devices, among others. This work presents an economical and easy way to manufacture bioactive nitric oxide-releasing polymer (BioNOR-P) and evaluates its bactericidal and antioxidant activity (AA), mechanical behavior, cytotoxicity, and genotoxicity, seeking future use in different applications. The BioNOR-P film was obtained by a casting method, forming a homogeneous, transparent film with good mechanical properties. The release of NO in an aqueous medium showed the film's ability to release NO slowly, at a rate of 0.58 nmol/g-1 min-1. Furthermore, the noncytotoxicity and antioxidant activity observed by NO release from BioNOR-P, as well as the ability to inhibit bacterial growth, may aid in the development of a NO-released polymer with different areas of application.

Plant Cadmium Toxicity and Biomarkers Are Differentially Modulated by Degradable and Nondegradable Microplastics in Soil

The impact of microplastics (MPs) as emerging pollutants on plant heavy metal toxicity has been extensively reported in vegetable-soil systems over recent years. However, little attention has been given to cultivar variations between degradable and non-degradable MPs. This study investigated the effects of degradable polylactic acid (PLA) and nondegradable polypropylene (PP) MPs on plant growth and biomarker (malonaldehyde (MDA) and antioxidant enzymes) performance in Cd-contaminated arable soil. The results show that both types of MPs significantly impacted plant biomass and biomarker contents across all three Cd levels. The degree of impact was significantly sensitive to both the type and dose of MPs, as they reduced the soil pH and cation exchange capacity (CEC) while increasing soil dissolved organic carbon (DOC), microbial biomass carbon, and nitrogen. PP exhibited greater root growth inhibition and phytotoxicity at higher doses of 1% and 5% compared to PLA. Specifically, the highest MDA contents were 1.44 and 2.20 mmol mg-1 protein for shoots and roots, respectively, in the 5% PLA treatment under a 10.1 mg kg-1 Cd level, which were 1.22 and 1.18 times higher than those in corresponding treatments of 5% PP. Overall, PLA had less significant effects on plant phytotoxicity, Cd availability, and soil properties compared to PP. Regression pathway analysis indicated that MPs increased shoot Cd uptake by altering both soil physical-chemical and microbial characteristics. Among the soil variables, pH, CEC, and Cd bioavailability were found to play vital roles. Yet, no single variable acts alone in the mechanism for plant Cd uptake. PLAs are suggested to replace conventional non-biodegradable plastics to control environmental MP pollution, particularly in agricultural systems with higher Cd contamination. However, the long-term effects of the by-products generated during the biodegradation process require further investigation.

Sodium Trimetaphosphate Crosslinked Starch Films Reinforced with Montmorillonite

Synthetic polymers are the main food packaging material, although they are nonbiodegradable and their recycling process is expensive. A biodegradable, eco-friendly material, with high availability and low cost, such as starch, is a promising solution for the production of films for food packaging. To enhance starch film mechanical and barrier properties, nanoclays have been incorporated within the film matrix. Crosslinking is a well-established method to modify starch properties, but it has not been investigated in combination with nanoclay addition. In the present study, films were developed with starch that was crosslinked through the addition of 5, 15, and 40% wt. sodium trimetaphosphate (STMP) based on dry starch weight. To investigate the interaction between crosslinking and nanoclay addition, montmorillonite (MMT) was added at a 10.5% wt. concentration based on dry starch weight. Experimental data revealed a synergistic effect between STMP crosslinking and MMT addition regarding film thickness, elongation at break, color properties, and opacity. Regarding barrier properties, MMT addition negated the effect of STMP crosslinking, while, in the case of moisture content, it did not alter the effect of STMP crosslinking. Finally, in the case of tensile strength, a synergistic effect followed by a negative interaction was observed. In conclusion, the addition of MMT can potentially enhance, alongside crosslinking, some properties of the films, while other properties are not affected any more than just by crosslinking.

Comparison of Physical and Thermal Properties of Mulching Films Made of Different Polymeric Materials

The development of polymer materials causes their huge expansion into various areas of everyday life, as well as plant and animal production. Their chemical resistance, good physical properties, and ease of processing result in an increasing use of this group of materials. Outdoor plant production both in open plantations and greenhouses requires various types of materials supporting the vegetation process as well as protecting against pests and weeds. A large group here are various types of materials used for covers of field crops, the main role of which is to prevent uncontrolled and excessive growth of weeds and thus reduce the use of herbicides as plant protection products. Cover films also have other important functions, such as reducing direct water evaporation, better moisture retention around the root system, increasing soil temperature (faster vegetation), etc. However, as always, the problem of introducing new material into agriculture production and the difficulty of its disposal arises. In recent times, farmers' interest in various forms of mulch to protect crops and increase yields has grown significantly. In the publication, the authors attempted to analyze selected commercial properties, but also mulch produced on a laboratory scale, based on biodegradable and petroleum-derived materials.

Edible film of native jicama starch, agarwood Aetoxylon Bouya essential oil and calcium propionate: Processing, mechanical, thermal properties and structure

The objective of this study was to determine the properties of natural jicama starch and edible film made from the starch. The film was prepared by adding agarwood aetoxylon bouya essential oil and calcium propionate to investigate its properties as an edible coating for fruit or vegetables. The microstructure of the edible film was observed using scanning electron microscopy. The three main materials mostly had significant effects (P < 0.05) on the properties of the sample films, and starch film incorporating essential oil‑calcium propionate showed optimum properties as an edible coating material because it had the highest elongation of 10.81%, the lowest stiffness with a Young's modulus of about 2.53 MPa, the lowest of water vapor transmission rate and permeability of 0.117 g h^-1 m^-2 and 3.092 g mm h^-1 m^-2 kPa^-1, respectively, and the lowest weight loss of 75.30%. It was also found that the microstructure of starch-essential oil‑calcium propionate film had a homogeneous surface and the presence of essential oil droplets was not visible.