Biofilms based on cassava starch containing extract of yerba mate as antioxidant and plasticizer

Nelumbo nucifera flower extract incorporated alginate/polyvinyl alcohol films as a sustainable pH indicator for active food packaging applications

In recent years, there has been a growing demand for environmentally friendly smart packaging materials. Therefore, in this study, we developed an eco-friendly pH-sensitive indicator film through the solvent casting process, incorporating alginate, polyvinyl alcohol, garlic, and Nelumbo nucifera flower extract. The effect of extract on the chemical and physical properties of the film were extensively studied using various characterization techniques. XRD and FTIR reveal the strong interaction between the polymers and the extract. The incorporation of the extract influenced various parameters such as swelling behavior, water solubility, and moisture content, while also improving the film's thermal stability, biodegradability, as well as its antioxidant and antimicrobial properties. Interestingly, the film exhibited a color change in response to pH change. During shrimp storage, the film showed a visible transition from purple to green, indicating shrimp spoilage. Additionally, the film's ability to detect freshness was confirmed by measuring total volatile basic nitrogen (TVBN). These findings suggest that the PVA/alginate/garlic/Nelumbo nucifera film shows promise as an intelligent packaging material for real-time food monitoring applications.

Effect of apple polyphenols on physicochemical properties of pea starch/pulp cellulose nanofiber composite biodegradable films

A pea starch (PS) and pulp cellulose nanofibers (CNF-P) hybrid matrix biodegradable film was prepared using apple polyphenol (AP) as the active substance. SEM and thermogravimetric analyses showed that apple polyphenols could be uniformly distributed and form hydrogen bonds with the matrix, and the increase in crystallinity improved the thermal stability of the films (the final residue of the films increased from 22.66 % to 31.82 %). The TS and EAB of the films reached their maximum values of 11.14 ± 1.73 MPa and 71.55 ± 8.8 %, respectively, at an AP content of 1.5 %. It should be noted that the antioxidant properties of the films were significantly positively correlated with the AP content, and the DPPH radical scavenging rate of the films reached 73.77 % at an AP content of 4.5 %, which was about 49 times higher than that of the control film. The same trend was observed in the UV-vis spectra. In addition, the total color difference and water solubility of the membranes increased from 4.29 ± 0.29 to 31.86 ± 1.90 and from 20.01 ± 0.97 % to 21.70 ± 1.99 %, respectively, and the biodegradability also showed an upward trend. These findings provide a theoretical basis and data support for the development of multifunctional biodegradable food packaging materials.

Development, characterization and application of starch-based film containing polyphenols of piper betle L. waste in chicken meat storage

The current study aimed to develop a sustainable solution to extend the shelf life of chicken meat by developing starch-based functional film embedded with polyphenolic extract of waste petioles of betel leaf (BLP). The results showed that loading of the extract significantly (p < 0.05) improved flexibility, thickness, water solubility, DPPH radical scavenging activity, and UV light protection ability by enhancing intermolecular interactions among potato starch, guar gum, and the extract. The developed film showed optimum mechanical and water barrier properties at a 4% BLP extract concentration computed through TOPSIS method (A multi-criteria decision-making approach). During the shelf life study, the extract embedded film maintained the quality of chicken meat for up to 12 days at refrigerated temperature. Biodegradation time of the extract-blended films was considerably decreased to 14 days from 28 days for the native film, indicating suitable alternative to non-biodegradable film for storing the raw meat.

Thermoplastic Starch Biocomposite Films Reinforced with Nanocellulose from Agave tequilana Weber var. Azul Bagasse

In this work, cellulose nanocrystals (CNCs), bleached cellulose nanofibers (bCNFs), and unbleached cellulose nanofibers (ubCNFs) isolated by acid hydrolysis from Agave tequilana Weber var. Azul bagasse, an agro-waste from the tequila industry, were used as reinforcements in a thermoplastic starch matrix to obtain environmentally friendly materials that can substitute contaminant polymers. A robust characterization of starting materials and biocomposites was carried out. Biocomposite mechanical, thermal, and antibacterial properties were evaluated, as well as color, crystallinity, morphology, rugosity, lateral texture, electrical conductivity, chemical identity, solubility, and water vapor permeability. Pulp fibers and nanocelluloses were analyzed via SEM, TEM, and AFM. The water vapor permeability (WVP) decreased by up to 20.69% with the presence of CNCs. The solubility decreases with the presence of CNFs and CNCs. The addition of CNCs and CNFs increased the tensile strength and Young's modulus and decreased the elongation at break. Biocomposites prepared with ubCNF showed the best tensile mechanical properties due to a better adhesion with the matrix. Images of bCNF-based biocomposites demonstrated that bCNFs are good reinforcing agents as the fibers were dispersed within the starch film and embedded within the matrix. Roughness increased with CNF content and decreased with CNC content. Films with CNCs did not show bacterial growth for Staphylococcus aureus and Escherichia coli. This study offers a new theoretical basis since it demonstrates that different proportions of bleached or unbleached nanofibers and nanocrystals can improve the properties of starch films.

Thermoplastic starch/polyvinyl alcohol blends modification by citric acid-glycerol polyesters

Thermoplastic starch/polyvinyl alcohol (TPS/PVA) films have limitations for being used in long-term applications due to starch retrogradation. This leads to plasticizer migration, especially when low molecular weight plasticizers such as glycerol, are used. In this work, we employed mixtures of oligomers based on glycerol citrates with higher molecular weight than glycerol as plasticizers for potato-based TPS/PVA blends obtained by melt-mixing. This constitutes an alternative to reduce plasticizer migration while keeping high swelling degree, and to provide high mechanical performance. The novelty lies in the usage of these oligomers by melt-mixing technique, aspect not deeply explored previously and that represents the first step towards industrial scalability. Prior to the blending process, oligomers mixtures were prepared with different molar ratios of citric acid (0-40 mol%) and added them. This minimizes the undesirable hydrolysis effect of free carboxylic groups on starch chains. The results demonstrated that the migration of plasticizers in TPS/PVA blends decreased by up to 70 % when the citric acid content increased. This reduction was attributed to the higher molecular weight (the majority in the range 764-2060 Da) and the 3D structure of the oligomers compared to using raw glycerol. Furthermore, the films exhibited a 150 % increase in Young's modulus and tensile strength without a reduction in elongation at break, while maintaining a high gel content, due to a moderate crosslinking.

Evolution of the free volume during water desorption in thermoplastic starch/citric acid films: In situ positron annihilation studies

The effect of citric acid (CA) concentration and water content on the free hole volume of thermoplastic cassava starch films (TPS) was studied. To this aim, continuous in situ positron annihilation lifetime spectroscopy measurements were performed at fixed moisture content and during water desorption. The results show that the increase in CA concentration leads to wider free hole volume distributions with lower mean values. During water desorption, the mean values and width of such distributions systematically decrease with the exposure time, and the evolution of the hole volumes was well-described using the Kohlrausch-Williams-Watts function. The water vapour permeability was significantly higher in films incorporating 5 % (w/w) of CA, in line with the more open network of this material that was revealed in the hole volumes distribution. The Young's modulus of all the developed films increased significantly after partial water desorption, which was attributed to the plasticizer loss reflected in a decrease in the mean hole volume value (between 4 % and 13 %). This work evidences that the control and report of the relative humidity are essential when testing TPS-based films, as their nanostructures are strongly dependent on external conditions.

Study of the Plasticization Effect of 1-Ethyl-3-methylimidazolium Acetate in TPS/PVA Biodegradable Blends Produced by Melt-Mixing

The first step towards the production and marketing of bioplastics based on renewable and sustainable materials is to know their behavior at a semi-industrial scale. For this reason, in this work, the properties of thermoplastic starch (TPS)/polyvinyl alcohol (PVA) films plasticized by a green solvent, as the 1-ethyl-3-methylimidazolium acetate ([Emim⁺][Ac^-]) ionic liquid, produced by melt-mixing were studied. These blends were prepared with a different content of [Emim⁺][Ac^-] (27.5-42.5 %wt.) as a unique plasticizer. According to the results, this ionic liquid is an excellent plasticizer due to the transformation of the crystalline structure of the starch to an amorphous state, the increase in flexibility, and the drop in T_g, as the [Emim⁺][Ac^-] amount increases. These findings show that the properties of these biomaterials could be modified in the function of [Emim⁺][Ac^-] content in the formulations of TPS, depending on their final use, thus becoming a functional alternative to conventional polymers.

Recent Developments in Cassava (Manihot esculenta) Based Biocomposites and Their Potential Industrial Applications: A Comprehensive Review

The rapid use of petroleum resources coupled with increased awareness of global environmental problems associated with the use of petroleum-based plastics is a major driving force in the acceptance of natural fibers and biopolymers as green materials. Because of their environmentally friendly and sustainable nature, natural fibers and biopolymers have gained significant attention from scientists and industries. Cassava (Manihot esculenta) is a plant that has various purposes for use. It is the primary source of food in many countries and is also used in the production of biocomposites, biopolymers, and biofibers. Starch from cassava can be plasticized, reinforced with fibers, or blended with other polymers to strengthen their properties. Besides that, it is currently used as a raw material for bioethanol and renewable energy production. This comprehensive review paper explains the latest developments in bioethanol compounds from cassava and gives a detailed report on macro and nano-sized cassava fibers and starch, and their fabrication as blend polymers, biocomposites, and hybrid composites. The review also highlights the potential utilization of cassava fibers and biopolymers for industrial applications such as food, bioenergy, packaging, automotive, and others.

Preparation and characterization of polyvinyl alcohol-piperic acid composite film for potential food packaging applications

Piperic acid, a natural product-based derivative, has been used with polyvinyl alcohol for the first time to form polymer composite films for its suitable modification in physicochemical and antimicrobial properties. Initially, piperic acid was synthesized from piperine, a natural alkaloid extracted from black pepper (Piper nigrum). The solvent casting method was used for the synthesis of PVA-piperic acid composite films. The films were characterized by various spectral and microscopic techniques like UV-visible spectroscopy, FT-IR, SEM, XRD, and TGA. The antibacterial activity was shown by these polymer composites of piperic acid against Gram-positive Staphylococcus aureus (S. aureus-ATCC8738P) and Gram-negative Escherichia coli (E. coli-ATCC8739) was worthwhile. The antifungal activity of the composite films was evaluated by the food poisoning technique. Percentage mycelial growth inhibition was found maximum against Fusarium solani than Aspergillus and Penicillium. The water vapour and oxygen barrier properties are enhanced with the incorporation of increased content of piperic acid. Also, enhancement in the tensile strength of PVA/PA composite film was observed, while elongation at break shows decreased trend with the addition of piperic acid. The surface properties of polymer composite films were determined by contact angle measurements. Contact angle shows a considerable increase in these films when compared to virgin PVA film. It was increased by 56.1° in 15 mL composite film containing a higher concentration of piperic acid than virgin PVA.

Characterisation and Antibacterial Properties of Novel Biodegradable Films Based on Alginate and Roselle (Hibiscus sabdariffa L.) Extract

Composite films were prepared with alginate and roselle extract (HE) at different concentrations (1%, 3%, and 5% w/v) via solvent casting technique and analyzed in terms of physical, mechanical, and antibacterial properties. The incorporation of HE into alginate films resulted in rough and heterogeneous surface characteristics with increasing concentrations of HE. The thickness and water vapor permeability of alginate-HE composite films were significantly higher (p < 0.05) compared to pure alginate films. Moreover, water content, solubility, swelling, tensile strength, and elongation at break value of the composite films decreased (p < 0.05) with increasing concentrations of the extract. FTIR spectra revealed shifts and intensity variations in the composite films and the formation of new peaks suggesting a possible interaction between alginate and HE. Alginate-HE films exhibited good antibacterial activity against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacteria. The antibacterial effect of the films, more pronounced against Gram-positive bacteria, increased with higher amounts of HE. The resulting films may be utilised as new biodegradable, antibacterial films in the food packaging industry to prolong shelf life and preserve food safety.

Graphical Abstract

Supplementary Information

The online version of this article (10.1007/s12649-022-01710-3) contains supplementary material, which is available to authorized users.

Degradable photo-crosslinked starch-based films with excellent shape memory property

With the increasingly serious plastic pollution, people's demand for the multi-functional biodegradable plastics is becoming more and more urgent. Inspired by the crosslinked shape memory polymers, the crosslinked starch films were synthesized by inducing the decomposition of benzophenone into free radical and depriving hydrogen on starch macromolecules under UV irradiation, in order to gain a high shape memory performance. The results showed that a three-dimensional crosslinking network between starch macromolecule chains was formed. Compared with the uncrosslinked starch films, the photo-crosslinked films not only had higher mechanical property (tensile strength increased by 154%), but also had better water resistance (water contact angle from 60° to 87°) due to the reduction of free hydroxyl groups. In addition, the stable covalent bonds serving as netpoints endow photo-crosslinked films with great improvement in shape memory property, with nearly 180° bending recovery. More importantly, the maximum shape memory fixity ratio (R_f) and shape memory recovery ratio (R_r) under stretch deformation were 96.5% and 99.8%, respectively. And the R_f and R_r could reach 94.6% and 79.8% even at higher strain. In all, the excellent shape memory performance and good degradability crosslinked starch films, which have great potential application in disposable heat-shrinkable packaging materials.

The fabrication of a novel film based on polycaprolactone incorporated with chitosan and rutin: potential as an antibacterial carrier for rainbow trout packaging

ABSTRACT

Rutin and chitosan could be utilized in the food industry owing to their antioxidant and antibacterial properties. This study was carried out to fabricate novel films using polycaprolactone (PCL-sole), PCL and chitosan (PCL-CS), PCL and rutin (PCL-R), and PCL, chitosan, and rutin (PCL-CS-R) through electros pinning method. Physical properties, in vitro antibacterial and antioxidant properties of the films, and their antibacterial activity on rainbow trout were further investigated. The PCL-CS, PCL-R, and PCL-CS-R had smaller fiber diameter and film thickness and lower viscosity while they showed higher surface tension, water contact angle, and conductivity and better antibacterial and antioxidant properties compared with PCL-sole film (P < 0.05). The PCL-CS-R film respectively decreased 17.45%, 19.27%, and 18.39% more populations of L. monocytogenes, S. aureus, and E. coli compared to PCL-sole film in the fish samples. Therefore, the PCL-CS-R film can be potentially used in active packaging because of its antioxidant and antibacterial activities.

GRAPHIC ABSTRACT

Nopal cladode as a novel reinforcing and antioxidant agent for starch-based films: A comparison with lignin and propolis extract

The potential use of nopal cladode flour (NC) as reinforcing/bioactive agent in cassava starch-based films was evaluated and compared with the use of propolis extract or lignin, which are commonly used for these purposes. Cassava starch-based films containing untreated NC (S-NC), NC treated at pH 12 (S-NC12), aqueous propolis extract at two different concentrations (SP1 or SP2), or lignin (S-L) were produced by the casting technique; glycerol was used as plasticizer. NC12 and NC affected the mechanical properties of the cassava starch-based film similarly as compared to propolis extract and lignin. Moreover, NC and NC12 had different performance as reinforcing and antioxidant agent in cassava starch-based film. Thus, S-NC12 film was more elongable (28.5 ± 6.5%), more hydrophobic (contact angle: 70.8° ± 0.1), less permeable to water vapor (0.8 ± 0.0 × 10^-10 g·m^-1·s^-1·Pa^-1) and had better antioxidant activity by ABTS^•+ (44.70 ± 0.3 μM Trolox·g^-1 of film) than the S-NC film. SEM and TGA analysis of films showed that NC12 was better incorporated into the cassava starch matrix than NC, lignin and propolis extract. Overall, nopal cladode flour has potential use in the production of active biodegradable packaging for the food preservation with high oxidation rate.

Coffee silverskin and starch-rich potato washing slurries as raw materials for elastic, antioxidant, and UV-protective biobased films

Food processing wastes together with the perishable foodstuff loss promote environmental and societal concerns. Food byproducts can have value as a source of functional molecules for developing active packaging without food waste, under a circular economy. Nevertheless, the often-associated extraction/chemical processes compromise the sustainability of food byproducts reusability. In this work, coffee silverskin (CS) and starch, recovered from coffee roasting and potato industries, respectively, were together gelatinized to form in-situ films. Targeting to fit with the food application requirements, it is important to understand the influence of crude CS amount (1%, 5%, and 10% w/w of dry starch weight) on potato starch-based film properties. CS conferred a brownish coloration to the films, maintaining their transparency. The films colour intensity, antioxidant activity, and water tolerance were directly related with the CS dosage. Moreover, as high the CS amount, higher the elasticity, stretchability, and UV radiation absorption of the pristine films. These data emphasized that CS molecules extracted during gelatinization prevented the starch-starch hydrogen bonding and conferred functional and barrier properties. Overall, adding crude CS during potato starch gelatinization revealed to be an efficient strategy to tune the performance of potato starch-based films, opening an opportunity for valorising coffee roasting and potato byproducts.

Yerba Mate Extract in Microfibrillated Cellulose and Corn Starch Films as a Potential Wound Healing Bandage

Microfibrillated cellulose films have been gathering considerable attention due to their high mechanical properties and cheap cost. Additionally, it is possible to include compounds within the fibrillated structure in order to confer desirable properties. Ilex paraguariensis A. St.-Hil, yerba mate leaf extract has been reported to possess a high quantity of caffeoylquinic acids that may be beneficial for other applications instead of its conventional use as a hot beverage. Therefore, we investigate the effect of blending yerba mate extract during and after defibrillation of Eucalyptus sp. bleached kraft paper by ultrafine grinding. Blending the extract during defibrillation increased the mechanical and thermal properties, besides being able to use the whole extract. Afterwards, this material was also investigated with high content loadings of starch and glycerine. The results present that yerba mate extract increases film resistance, and the defibrillated cellulose is able to protect the bioactive compounds from the extract. Additionally, the films present antibacterial activity against two known pathogens S. aureus and E. coli, with high antioxidant activity and increased cell proliferation. This was attributed to the bioactive compounds that presented faster in vitro wound healing, suggesting that microfibrillated cellulose (MFC) films containing extract of yerba mate can be a potential alternative as wound healing bandages.

Methods of Incorporating Plant-Derived Bioactive Compounds into Films Made with Agro-Based Polymers for Application as Food Packaging: A Brief Review

Plastic, usually derived from non-renewable sources, is among the most used materials in food packaging. Despite its barrier properties, plastic packaging has a recycling rate below the ideal and its accumulation in the environment leads to environmental issues. One of the solutions approached to minimize this impact is the development of food packaging materials made from polymers from renewable sources that, in addition to being biodegradable, can also be edible. Different biopolymers from agricultural renewable sources such as gelatin, whey protein, starch, chitosan, alginate and pectin, among other, have been analyzed for the development of biodegradable films. Moreover, these films can serve as vehicles for transporting bioactive compounds, extending their applicability as bioactive, edible, compostable and biodegradable films. Biopolymer films incorporated with plant-derived bioactive compounds have become an interesting area of research. The interaction between environment-friendly biopolymers and bioactive compounds improves functionality. In addition to interfering with thermal, mechanical and barrier properties of films, depending on the properties of the bioactive compounds, new characteristics are attributed to films, such as antimicrobial and antioxidant properties, color and innovative flavors. This review compiles information on agro-based biopolymers and plant-derived bioactive compounds used in the production of bioactive films. Particular emphasis has been given to the methods used for incorporating bioactive compounds from plant-derived into films and their influence on the functional properties of biopolymer films. Some limitations to be overcome for future advances are also briefly summarized. This review will benefit future prospects for exploring innovative methods of incorporating plant-derived bioactive compounds into films made from agricultural polymers.

Development and evaluation of edible films based on cassava starch, whey protein, and bees wax

Films and edible coatings based on biopolymers have been developed as a packaging, which can be obtained from biodegradable materials and have properties similar to common plastics. These edible materials have many applications in the food industry, preventing mass transfer between the product and the surrounding environment. The objective of this study was to develop and evaluate the physicochemical and mechanical properties of edible films based on cassava starch (CS), whey protein (WP), and beeswax (BW). Response surface methodology has been used and the experiments were carried out based on face-centred composite design. On the other hand, three CS-based controls were formulated to evaluate the effect of the inclusion of WP and BW. The optimization of multiple responses established the optimal formulation: CS (3.17 %), WP (1.30 %), BW (0.50 %), presenting the following response variables: tensile stress (1.92 MPa), elongation (40.4 %), Young's modulus (42.1 MPa), water vapor permeability 1.79 × 10^-11 (g mm/s cm² Pa), swelling capacity (300.3 %), thickness (0.128 mm), moisture content (6.74 %), and colour: lightness (89.9), chromaticity a∗ (-1.8), chromaticity b∗ (7.7), saturation (9.9), tone (101.1°), and yellowness index (17.7). The selection and evaluation of this optimal formulation are essential because it is the material that shows the best possible mechanical and physicochemical properties using the studied components. The results, especially its good mechanical properties and low permeability to water vapour, would allow its application as a coating for fruits, vegetables, among others, effectively delaying its weight loss due to dehydration.

Polycaprolactone nanofiber coated with chitosan and Gamma oryzanol functionalized as a novel wound dressing for healing infected wounds

This study was conducted to design and evaluate a wound dressing based on a polycaprolactone (PCL) nanofiber coated with gamma oryzanol (GO) and chitosan (CS) in mice model. All the dressings were prepared by electrospinning method, and their morphology and physical properties were investigated. The mice were divided into five groups and treated with I) PCL-sole (PCL), III) PCL-mupirocin (PCL-M), IV) PCL-GO, IV) PCL-CS, and V) PCL-CS-GO. Wound area, total bacterial count, histopathological parameters, and expressions of IL-1β, TNF-α, IL-10, MMP-9, EGF, and VEGF were assessed. The fibers were randomly distributed in PCL group, but loading CS and GO increased the complexity and placing on the dressings. PCLs loaded with GO and CS showed lower viscosity, surface tension, and fiber diameter and higher conductivity and water contact angle compared to unloaded PCLs (P < 0.05). The treatment with PCLs loaded with mupirocin, CS, and GO significantly reduced wound area and total bacterial count (P < 0.05). Loading PCLs with mupirocin, CS, and GO decreased the expressions of IL-1β, TNF-α, MMP-9, but increased the expressions of IL-10 and VEGF compared to the unloaded PCL group (P < 0.05). The most optimal responses to wound healing and physical parameters belonged to the PCL-CS-GO group.

Effect of yerba mate extract on the performance of starch films obtained by extrusion and compression molding as active and smart packaging

Native or hydrolyzed starch and yerba mate extract (10 wt.% or 20 wt.%) films prepared by extrusion and compression molding were investigated. Native starch material (TPNS) exhibited lower water vapor permeability and higher Young's Modulus (E) compared to hydrolyzed starch matrix (TPHS) but decreases in strain at break (ε_b) and toughness (T). The incorporation of 10 wt.% of extract in TPNS led to greater E and ε_b and it resulted the most hydrophobic material. Conversely, TPHS with 20 wt.% of additive resulted the film with the highest ε_b and T, indicating a plasticizing effect of the extract in this concentration and system. All materials disintegrated after 10 weeks of burial, contributing to waste reduction. Biofilms containing yerba mate extract showed antioxidant activity and color changes in different pH, indicating their promising role as active and smart packaging for food, in accordance with the new trends for biodegradable and functional packaging.

Physical, Barrier, Mechanical, and Biodegradability Properties of Modified Starch Films with Nut By-Products Extracts

Starch-based films with phenolic extracts could replace the use of petroleum-based plastics. In this study, octenyl succinate starch (OSS) films with pecan nutshell extract (PSE) or hazelnut skin extract (HSE) were prepared. The water resistance, as well as the optical, physical, mechanical, and biodegradable properties of these films, were investigated. The PSE and HSE improved the water resistance (decreasing the solubility to 17% and increasing the contact angle to 96.80°) and UV-light barrier properties of the films. For PSE and HSE, as their concentrations increased, the film rigidity decreased since these extracts acted as plasticizers. Micrographs obtained by scanning electron microscopy (SEM) depicted a homogeneous surface as a result of extracts dispersion through the polymeric matrix and the interactions between the phenolic compounds (PC) of the extracts and the OSS. The phenolic extracts from nut by-products and octenyl succinic anhydride (OSA) starch could be used to develop films to replace the conventional plastics.

Conservação pós-colheita de pêssegos com aplicação de revestimentos aditivados de extrato de erva-mate

Resumo O objetivo do presente estudo foi verificar o potencial da aplicação de revestimentos à base de fécula de mandioca (F), aditivados de extrato (E) de erva-mate (Ilex paraguariensis St. Hill), na conservação pós-colheita de pêssegos. Foram utilizados frutos cv. Della Nona e os tratamentos aplicados foram: frutos sem revestimento (Testemunha), frutos com revestimentos à base de fécula de mandioca aditivados de extrato de erva-mate nas concentrações de 0 g L-1 (F+0%E), 5 g L-1 (F+5%E), 10 g L-1 (F+10%E) e 15 g L-1 (F+15%E). Os frutos foram armazenados por 10 dias a 1 °C, com 95% de umidade relativa (UR). Para avaliação da qualidade pós-colheita dos frutos, foram realizadas análises físico-químicas, incluindo sólidos solúveis, acidez titulável, perda de massa e firmeza. Para avaliação do efeito in vitro dos revestimentos no crescimento do fungo Monilinia fructicola, agente causal da podridão parda, avaliou-se a germinação de conídios e a área abaixo da curva de crescimento micelial. Para avaliação do controle da podridão parda in vivo, determinou-se incidência (%) e índice de infecção, e as enzimas peroxidase e polifenoloxidase. Observou-se que o uso de revestimentos reduziu a perda de massa dos frutos em 50%, aumentou o teor de sólidos solúveis e intensificou a coloração vermelha dos frutos, tornando-os mais atraentes ao consumidor. Além disso, houve aumento da atividade da enzima peroxidase em frutos revestidos e o tratamento com aditivo de 15% de extrato de erva-mate inibiu o desenvolvimento de podridão parda nos pêssegos.

Electroconductive starch/multi-walled carbon nanotube films plasticized by 1-ethyl-3-methylimidazolium acetate

Starch/multi-walled carbon nanotube (MWCNT) films were prepared by casting using an ionic liquid (1-ethyl-3-methylimidazolium acetate, [emim⁺][Ac^-]) as plasticizer for the first time. The effect of the MWCNT content (0.25-5 wt.%, with respect to the sum of starch and plasticizer mass) on thermal, mechanical and electroconductive behavior of the films was studied. Films containing 0.5 wt.% MWCNT showed increases of 327 % in maximum tensile strength, 2484 % in Young's modulus and 82 % in elongation at break. The significant improvements are explained by the good MWCNT dispersion in the matrix and by the effect of [emim⁺][Ac^-] as an efficient plasticizer, which leads to higher extensibility. The MWCNT/[emim⁺][Ac^-] combination have a synergistic effect on film electrical conductivity, increasing a 130% (3 wt.% MWCNT). These films, easily prepared by a "green" process, have potential applications in the packaging industry but also in the field of lithium batteries, fuel cells and dye-sensitized solar cells.

Influence of Starch Composition and Molecular Weight on Physicochemical Properties of Biodegradable Films

Thermoplastic starch (TPS) films are considered one of the most promising alternatives for replacing synthetic polymers in the packaging field due to the starch biodegradability, low cost, and abundant availability. However, starch granule composition, expressed in terms of amylose content and phosphate monoesters, and molecular weight of starch clearly affects some film properties. In this contribution, biodegradable TPS films made from potato, corn, wheat, and rice starch were prepared using the casting technique. The effect of the grain structure of each starch on microstructure, transparency, hydration properties, crystallinity, and mechanical properties of the films, was evaluated. Potato starch films were the most transparent and corn starch films the most opaque. All the films had homogeneous internal structures—highly amorphous and with no pores, both of which point to a good starch gelatinization process. The maximum tensile strength (4.48–8.14 MPa), elongation at break (35.41–100.34%), and Young’s modulus (116.42–294.98 MPa) of the TPS films were clearly influenced by the amylose content, molecular weight, and crystallinity of the film. In this respect, wheat and corn starch films, are the most resistant and least stretchable, while rice starch films are the most extensible but least resistant. These findings show that all the studied starches can be considered suitable for manufacturing resistant and flexible films with similar properties to those of synthetic low-density polyethylene (LDPE), by a simple and environmentally-friendly process.

Comparative study on properties of starch films obtained from potato, corn and wheat using 1-ethyl-3-methylimidazolium acetate as plasticizer

Starch films are gaining attention as substitutes of synthetic polymers due to their biodegradability and low cost. Some ionic liquids have been postulated as alternatives to glycerol, one of the best starch plasticizers, due to their great capacity to form hydrogen bonds with starch and hence great ability of preventing starch retrogradation and increasing film stability. In this work, [emim⁺][Ac^-]-plasticized starch films were prepared from potato, corn and wheat starch. The effect of starch molecular structure in terms of granular composition (amylose and phosphate monoester contents) and molecular weight (M_w) on film properties was evaluated. Potato starch films were the most amorphous because of the higher M_w and phosphate monoester content of potato starch, both contributing to a lower rearrangement of the starch chains making the crystallization process difficult. In contrast, corn and wheat starches lead to more crystalline films because of their lower M_w, which may imply higher mobility and crystal growth rate, and lower phosphate monoester content. This more crystalline structure could be the responsible of their better mechanical properties. [emim⁺][Ac^-] can be considered suitable for manufacturing starch films showing corn and wheat starch films similar properties to synthetic low-density polyethylene, but involving a simple and environmentally-friendly process.

Influence of oxidized starch on physicomechanical, thermal properties, and atomic force micrographs of cassava starch bioplastic film

Oxidized starch was produced and its effect on starch-based bioplastic film has been evaluated. The produced oxidized starch was coarse, brownish with 15.68% carbonyl content, insoluble in cold water and has a positive influence on bioplastic films. The film thickness increased with increase in the amount of added oxidized starch from 0.21% (film_O) to 0.23% (film_6O). The film moisture content dropped from 7.93% (film_O) to 5.36% (film_6O), likewise the film water solubility decreased from 13.48% (film_O) to 5.75% (film_6O). Addition of oxidized starch led to longer biodegradability and enduring water absorption kinetics. The mechanical property was improved by the addition of oxidized starch. The derivative thermogravimetry analysis indicates five degradation stages for all the bioplastic films, while films surface roughness was shown by AFM. The research has revealed that oxidized starch can be used to improve the physicomechanical properties of starch based bioplastic film.

Physicochemical, Antioxidant and Antimicrobial Properties of Electrospun Poly(ε-caprolactone) Films Containing a Solid Dispersion of Sage (Salvia officinalis L.) Extract

In this study, novel active films made of poly(ε-caprolactone) (PCL) containing a solid dispersion of sage extract (SE) were developed by means of the electrospinning technique and subsequent annealing treatment. Initially, the antioxidant and antimicrobial potential of SE was confirmed. Thereafter, the effect of SE incorporation at different loading contents (5%, 10%, and 20%) on the physicochemical and functional properties of the films was evaluated. The films were characterized in terms of morphology, transparency, water contact angle, thermal stability, tensile properties, water vapor, and aroma barrier performances, as well as antioxidant and antimicrobial activities. Thin, hydrophobic films with good contact transparency were produced by annealing of the ultrathin electrospun fibers. Interestingly, the effect of SE addition on tensile properties and thermal stability of the films was negligible. In general, the water vapor and aroma permeability of the PCL-based films increased by adding SE to the polymer. Nevertheless, a strong 2,2-diphenyl-1-picrylhydrazyl (DPPH^·) free radical scavenging ability, and a strong activity against foodborne pathogens Staphylococcus aureus and Escherichia coli were achieved by SE incorporation into PCL matrix. Overall, the obtained results suggest great potential of the here-developed PCL-based films containing SE in active food packaging applications with the role of preventing oxidation processes and microbial growth.

Development of an antioxidative packaging film based on khorasan wheat starch containing moringa leaf extract

The aim of this study was to develop and characterize the properties of khorasan wheat starch (KWS) films containing moringa leaf extract (MLE) as an antioxidative packaging material. KWS was isolated from khorasan wheat and used as a film base material. Different amounts (0, 0.4, 0.7, and 1.0%, w/v) of MLE were added to the KWS film-forming solution and the film properties were examined. Tensile strength of the KWS films decreased and elongation at break increased with increasing MLE content. In addition, the KWS films containing MLE possessed good antioxidative activities and ultraviolet light blocking ability. In particular, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging abilities of the KWS films with 1.0% MLE were 59.45% and 37.89%, respectively. Moreover, KWS films containing 1.0% MLE were biodegradable within 30 days. These findings indicate that the developed KWS films containing MLE can be applied as a biodegradable packaging material with antioxidative activity.

Development and characterization of edible films based on eggplant flour and corn starch

In this study, biodegradable and edible films based on eggplant flour (EF) and corn starch (CS) were prepared using casting method at proportion of 0-100, 25-75, 50-50, 75-25 and 100-0%, w/w. The mechanical, barrier, physical, and biodegradability properties were evaluated. Tensile strength, elongation at break, Young's modulus, thickness, density and L^⁎ parameter of pure starch films were higher than those of other films. Solubility, water vapor permeability (WVP), moisture content and swelling index of films were augmented with the substitution of CS by EF. Color measurement of the edible films indicated that increasing the proportion of EF increased a^⁎, b^⁎ and opacity values. The highest amount of water sorption was obtained for pure EF films. Moreover, the incorporation of EF accelerated films biodegradability compared to ones with only starch. In general, EF is a promising material for the formulation of edible and biodegradable films with adequate physical properties for food applications by direct contact.

Development and preparation of active starch films carrying tea polyphenol

Starch films incorporated with tea polyphenol (TP) were developed to produce active food packaging. The effect of the incorporation of TP with different content on the structure, physicochemical properties, antioxidant activity and antimicrobial activity of the starch films was systematically evaluated. Results showed that TP was well dispersed in the starch matrix, which induced a slight influence on the surface and barrier properties of the films. TP addition led to an important improvement in antioxidant capability, as well as inhibition efficiency against the microorganisms of S. aureus and E. coli. However, a decrease in mechanical properties of films was observed. Moreover, a new automatic counting method which combined the computer vision and machine learning algorithm was developed to identify and count the colonies, and the method performed much faster without subjective uncertainty.