Fabrication and physicochemical characterization of HPMC films with commercial plant extract: Influence of light and film composition

Development of pH-freshness smart label based on gellan gum film incorporated with red cabbage anthocyanins extract and its application in postharvest mushroom

Novel colorimetric films based on gellan gum (GG) containing red cabbage anthocyanins extract (RCAE) were prepared as pH-freshness smart labels for real-time visual detection of mushroom freshness. The GG/RCAE films had excellent pH and ammonia sensitivity. The GG/RCAE-0.2-0.3 films had the highest sensitivity to acetic acid. The SEM micrographs, AFM images, FT-IR and XRD spectra demonstrated that RCAE were successfully combined into the film-forming substrate. The incorporation of RCAE resulted in the increase of thermal stability, opacity and surface hydrophobicity of films. Meanwhile, the GG/RCAE-0.2 film exhibited stronger tensile strength and excellent color stability at 4℃. The color changes of GG/RCAE-0.2 film were visually easier to distinguish during the storage of mushroom. The results showed the GG/RCAE films could be used as pH-freshness smart labels to detect the freshness of fruits and vegetables.

Electrical and mechanical properties of self-supported hydroxypropyl methylcellulose-polyaniline conducting films

The purpose of this work was to develop a simple method to produce self-supported films composed of hydroxypropyl methylcellulose (HPMC) and polyaniline (PANI) by the direct mixture of aqueous dispersions of both polymers with subsequent drying. The addition of HPMC, a cellulose derivative with an excellent film-forming capacity, was fundamental to overcoming the poor processability of PANI, which impairs its use in many technological applications. All films showed conductivity in the order of 10^-2 to 10^-3 S cm^-1, which is in the range for metals or semiconductors. The typical electroactivity of PANI was also maintained in the hybrid films. The thermal stability and the mechanical properties of the pristine PANI were also improved with the addition of HPMC. Cellulose-containing conducting polymers can be considered a material of the future, with possible applications in several areas, such as smart wallpapers, e-papers, and sensors.

Incorporating Portulaca oleracea extract endows the chitosan-starch film with antioxidant capacity for chilled meat preservation

This study aimed to investigate the application potential of Portulaca oleracea extract (POE) in active packaging for the preservation of chilled meat. First, the antioxidant capacity and active ingredients of POE were systematically studied. The results demonstrated that POE has excellent antioxidant capacity and contains abundant antioxidant compounds. Subsequently, antioxidant-active packaging films based on chitosan and starch containing different concentrations of POE (CS/POE films) were successfully developed. The main physicochemical and mechanical properties of the CS/POE films were characterized and evaluated. The CS/POE films exhibited remarkable antioxidant activity and can significantly reduce lipid oxidation in meat. Compared with polyethylene film, the CS/POE films-treated meats had better preservation effects and longer shelf-life. These findings suggested that CS/POE film has the potential to become a good alternative to conventional plastics in food packaging. In conclusion, Portulaca oleracea extract is an excellent natural antioxidant with great potential in active packaging for chilled meat preservation.

Colorimetric and antioxidant films based on biodegradable polymers and black nightshade (Solanum nigrum L.) extract for visually monitoring Cyclina sinensis freshness

In this study, colorimetric and antioxidant films were developed by using cassava starch (CS), κ-carrageenan (KC) and black nightshade fruit anthocyanins (BNA), and their physical and functional properties were investigated. We found BNA presented significant color changes in different pH solutions. And incorporation of BNA significantly increased the tensile strength, water vapor permeability, UV-vis light barrier property, pH-sensitivity and antioxidant activity of CS-KC film. Results of structural characterization indicated that H-bonds were formed between CS, KC and BNA in films and the film compactness was significantly improved by BNA incorporation. Results of the rheological property assay showed the films had high apparent viscosity with an obvious shear-thinning behavior. When applied to monitoring the quality change of Cyclina sinensis, CS-KC-BNA films exhibited significant color changes with the degradation process of C. sinensis qualities. Our results suggested CS-KC-BNA films could be utilized in smart packaging in food industry.

Development of active and intelligent pH food packaging composite films incorporated with litchi shell extract as an indicator

The anthocyanin-rich litchi shell extract (LE) was mixed with the matrix to prepare active/intelligent food packaging composite films. The microstructure and properties of composite films were characterized. The results showed that the composite films incorporated with LE had texture-oriented layered, compact, uniform cross-sections. The composite films with LE showed different degrees of red. The composite films had similar water vapor transmission rates (1.62-1.65 × 10^-12 g·cm/cm²·Pa·s). However, gelatin/chitosan/polyvinyl alcohol/litchi shell extract (Gel/Csa/PVA/LE) film had better UV blocking rates (0-20 %), the best tensile strength (18.6 MPa) and elongation at break (116%). When the composite films monitored for fish freshness at 4 °C (10 d) and 25 °C (3 d), the Gel/Csa/PVA/LE film had the pH sensitivity to show an obvious color change at 25 °C, 1th day. The results suggested that the Gel/Csa/PVA/LE film could be applied to intelligent food packaging film to indicate the freshness of fish.

A novel edible packaging film based on chitosan incorporated with persimmon peel extract for the postharvest preservation of banana

This study aimed to develop a novel edible packaging film for the postharvest preservation of banana based on chitosan (CS) and persimmon peel extract (PPE). Scanning electron microscopy (SEM) analysis showed PPE was evenly distributed in the CS matrix and Fourier transform infrared (FT-IR) spectroscopy analysis showed CS and PPE interacted to form hydrogen bonds, demonstrating good compatibility. Simultaneously, the addition of PPE also significantly improved CS film's physical properties and antioxidant activity. Among them, the CS film containing 10% PPE (CS-PPE 10) showed the optimal mechanical properties, water vapor barrier properties and oxygen barrier properties. The CS film containing 15% PPE (CS-PPE 15) exhibited the best thermal stability, UV-Vis barrier properties and antioxidant activity. In the experiment of banana preservation, CS-PPE 10 film obtained optimal performance on decreasing senescence spots, weight loss, fruit softening, cell wall degradation, inhibiting the activities of polyphenol oxidase and cell wall degrading enzymes and maintaining the content of total soluble sugar and ascorbic acid during the storage period. Consequently, CS-PPE 10 film was expected to be a novel edible packaging material to maintain banana quality and prolong shelf life.

Fabrication and characterization of a pH-sensitive intelligent film incorporating dragon fruit skin extract

A novel intelligent pH-sensing indicator based on gelatin film and anthocyanin extracted from dragon fruit skin (Hylocereus polyrhizus) (DFSE) as a natural dye was developed to monitor food freshness by the casting method. Anthocyanin content of DFSE was 15.66 ± 1.59 mg/L. Dragon fruit bovine gelatin films were characterized by Fourier transform infrared spectroscopy (FTIR) and observed by a scanning electron microscope (SEM). Moisture content, mechanical properties, water solubility, water vapor permeability (WVP), light transmittance, color, and pH-sensing evaluations were evaluated for potential application. FTIR spectroscopy revealed that the extracted anthocyanin could interact with the other film components through hydrogen bonds. When the extract was added, films showed a smooth and clear surface as observed by SEM. The addition of anthocyanin increased the moisture content, thickness, and water solubility of the films, but decreased the WVP and light transmittance of films. Also, the incorporation of 15% v/v DFSE decreased the tensile strength from 17.04 to 12.91 MPa, increasing the elongation at break from 91.19% to 107.86%. The films showed higher ΔE with increasing DFSE content, which indicated that the film had good color variability. A significant difference in the color of the films was observed with exposure to different pH buffer solutions. The findings demonstrated that gelatin film incorporated with DFSE could be used as a visual indicator of pH variations to monitor the freshness of foods during storage time.

Monitoring the infection process of Rhizopus stolonifer on strawberry fruit during storage using films based on chitosan/polyvinyl alcohol/polyvinylpyrrolidone and plant extracts

Different formulations based on nanoparticles of chitosan-plant extracts were evaluated to detect the infection process from the earliest stage of the fungus Rhizopus stolonifer on strawberry fruit during storage. Chitosan/polyvinyl alcohol (Ch/PVA) and chitosan/polyvinylpyrrolidone (Ch/PVP) films enriched with nanoparticles (NPs) of chitosan blended with plant extracts were prepared. They were placed inside a plastic package containing inoculated fruits and stored at 25 °C for 72 h. The thickness values of the films were in the range of 0.10 to 0.25 mm. All samples showed a maximum absorbance peak of about 300-320 nm; however, the Ch/PVP films enriched with NPs of chitosan and 10% of radish extract had an evident decrease in the optical absorbance as the fungal infection progressed. Additionally, as observed by scanning electron microscopy, the cross-section and surface morphology of films were not modified during storage, and the growth of R. stolonifer was evident after 48 h. Therefore, the Ch/PVP films enriched with chitosan NPs blended with 10% radish extract could be a reliable indicator of this fungus's growth.

Effect of different ionic liquids acting as plasticizers on the multi-scale structures and physical properties of hydroxypropyl methylcellulose/monosodium phosphate photophobic film

Different ionic liquid (IL)s were added to hydroxypropyl methylcellulose /monosodium phosphate (HPMC/MSP) photophobic film to improve its ductility, and their effects on its multi-scale structures and physical properties were studied. After adding these ILs, smoothness of the fractal structure, tensile strength, modulus of the film did not change obviously, while the crystallinity, the number of holes, and elongation increased, the hole size and T_g decreased. Compared to films with other ILs, the film with 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF₄) showed the largest elongation and crystallinity, the smallest hole size, the least holes, and highest whiteness. The film with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) showed the largest water content and the lowest T_g. The increased elongation proved that all these ILs could improve the ductility of the film, among which, [EMIM]BF₄ had the strongest plasticizing effect.

Effect of various additives on the properties of the films and coatings derived from hydroxypropyl methylcellulose-A review

Edible films and coating materials are commonly used as appropriate packaging materials to extend the shelf life of fresh food. Due to all their properties, edible film and coating materials have been received much attention. They are biodegradable, edible, and good barrier against environmental parameters; thereby, they could carry and deliver food additives protecting food quality. Hydroxypropyl methylcellulose (HPMC), a cellulose derivatives, can act as an excellent film-forming agent for coating food produces. The aim of this study was to provide an overview of the HPMC properties and investigate the effects of various additives on its film-forming properties, such as rheological behavior, water vapor, and gas permeability, as well as mechanical, optical, antioxidant, and antimicrobial properties, with a focus on the recent progress and outputs, which has been recently published. Hydroxypropyl methylcellulose is prone to be commonly used as an advanced film-forming and coating materials for the sake of well miscibility with a wide range of organic and inorganic materials. However, this polymer requires further improvements regarding moisture susceptibility and thermal properties.

Influence of solution properties and pH on the fabrication of electrospun lentil flour/HPMC blend nanofibers

Electrospinning is a method used in fiber production in which an electric force is applied to create jets of charged polymer solutions. The objective of this study was to obtain homogeneous nanofibers from lentil flour and hydroxypropyl methylcellulose (HPMC) blend by using electrospinning method. Distilled water was used as solvent. The effects of pH (7, 10 and 12), lentil flour concentration (1% and 2% (w/v)) and HPMC concentration (0.25%, 0.5% and 1% (w/v)) on solution properties and fiber morphology were investigated. When the pH was increased, the viscosity of the solutions containing 1% and 2% lentil flour decreased. Increasing the pH values caused an increase in the electrical conductivity. At pH value of 7, homogeneous nanofibers could not be obtained whereas fibers were perfectly homogeneous at alkaline pH values. Nanofiber diameter decreased with increase in pH when 2% lentil flour was used. On the other hand, diameter of fibers did not show any significant change with pH for 1% lentil flour. When the lentil flour concentration was increased, viscosity and fiber diameter increased at pH10. When HPMC concentration was increased, both viscosity and fiber diameter increased but electrical conductivity did not show any significant change. Average fiber diameters ranged between 198±4 and 254±5nm for solutions prepared with different lentil flour and HPMC concentrations at different pH values.