Peppermint oil-infused polylactic acid films: A novel approach for antimicrobial and biodegradable food packaging

Extensive research is currently dedicated to creating biodegradable packaging materials that match the qualities of traditional synthetic packaging materials. Among these options, polylactic acid (PLA) is noteworthy. PLA is a renewable-source-derived thermoplastic polymer with excellent barrier properties, mechanical strength, and a strong safety profile. To enhance food product shelf life, active packaging materials, incorporating functional ingredients like antimicrobials, have gained prominence. Peppermint essential oil is one such active ingredient, offering potential improvements in preserving food freshness and safety. This study's objective is to craft antimicrobial, biodegradable food packaging materials by blending peppermint oil into PLA films. Various peppermint oil concentrations (1.25%, 1.875%, and 2.5% w/v) were blended with PLA to assess their impact on opacity, water vapor permeability (WVP), mechanical and thermal properties, and antimicrobial characteristics. Higher peppermint oil concentrations increased opacity, making them advantageous for light-sensitive food items. These films reduced WVP without affecting PLA's thermal stability. Antimicrobial effectiveness was evaluated against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), showing inhibition with 1.875% and 2.5% w/v peppermint oil concentrations. Compared to control, PLA films with peppermint oil extended the shelf life of packaged chicken breast meats from 3 to 8 days. As a result, incorporating peppermint oil into PLA films presents a promising solution for advanced antimicrobial and biodegradable food packaging. Highlights: The incorporation of peppermint oil resulted in higher opacity values. Peppermint incorporated PLA films showed antimicrobial activity. Peppermint oil addition decreased water vapor permeability of PLA films. Peppermint oil added PLA films increased the shelf life of chicken meat up to 8 days

Development of simultaneous antioxidant and visual pH-sensing films based on guar gum loaded with Aronia melanocarpa extract

Anthocyanins have attracted increasing attention for different packaging systems due to having functional features such as biocompatibility, antioxidative activity, visible colour response at varying pH values. In this study, the extract of Aronia melanocarpa as anthocyanins source was incorporated into guar gum films to take advantage of both antioxidant and pH responsive attributes. Aronia addition did not affect the thermal stability of guar gum films. Radical scavenging activity of the films (%) was measured by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay, and aronia added films exhibited very strong antioxidant activity (up to 85%). The colour of aronia solution varied from pink to brown with pH ranging from 1 to 13. Similarly, when the films were immersed in buffer solutions at different pH values, the visual colour varied from pink to brownish yellow. ΔE values of GR_AR_3 (guar gum films having the highest aronia concentration) ranged between 23.31 and 40.62 at pH 1–13. This result proved colour change of the films can be even detected by untrained consumers. Furthermore, the films were found to be very sensitive to ammonia vapour. Aronia incorporated guar gum films could be suggested as both antioxidant films to prevent foods oxidation from oxidation and promising intelligent films to monitor the deterioration of foods

Zero-field nuclear magnetic resonance of chemically exchanging systems.

Zero- to ultralow-field (ZULF) nuclear magnetic resonance (NMR) is an emerging tool for precision chemical analysis. In this work, we study dynamic processes and investigate the influence of chemical exchange on ZULF NMR J-spectra. We develop a computational approach that allows quantitative calculation of J-spectra in the presence of chemical exchange and apply it to study aqueous solutions of [15N]ammonium (15N[Formula: see text]) as a model system. We show that pH-dependent chemical exchange substantially affects the J-spectra and, in some cases, can lead to degradation and complete disappearance of the spectral features. To demonstrate potential applications of ZULF NMR for chemistry and biomedicine, we show a ZULF NMR spectrum of [2-13C]pyruvic acid hyperpolarized via dissolution dynamic nuclear polarization (dDNP). We foresee applications of affordable and scalable ZULF NMR coupled with hyperpolarization to study chemical exchange phenomena in vivo and in situations where high-field NMR detection is not possible to implement

Fabrication of gallic acid loaded Hydroxypropyl methylcellulose nanofibers by electrospinning technique as active packaging material

The objective of this study was to encapsulate gallic acid in Hydroxypropyl methylcellulose (HPMC)/poly-ethylene oxide (PEO) blend nanofiber by using electrospinning and examine the usage of nanofibers as active packaging materials. Gallic acid loaded nanofibers showed homogenous morphology. Gallic acid was loaded into nanofibers efficiently and nanofibers showed strong antioxidant activity. As the gallic acid amount increased, the TGA curves had shifted one stage to two stage degradation and degradation temperature (T-d) of gallic acid decreased from 275 degrees C to 250 degrees C due to the crystalline structure change. Interaction between gallic acid and HPMC/PEO nanofiber demonstrated that gallic acid successfully embedded into the nanofibers. Gallic acid loaded nanofibers decreased the oxidation of walnut during storage. Overall, electrospinning technique was proved to be an efficient method to encapsulate bioactive compounds and gallic acid loaded nanofibers showed promissory results that can be suggested as great potential to active packaging material

Effects of Microwave-Infrared Combination Drying on Quality of Eggplants

The objective of this study was to investigate the effects of hot-air drying and microwave-infrared combination drying on drying characteristics and quality parameters of eggplants. Eggplant slices were dried by using microwave-infrared combination oven at different microwave powers (30, 40, and 50 %) and different infrared (IR) powers (10, 20, and 30 %). Hot-air drying was performed in a tray dryer at 50 A degrees C with an air velocity of 1.5 m/s. As quality parameters, color, rehydration ratio, shrinkage, microstructure, and pore size distribution of dried eggplants were chosen. Microwave-IR combination provided significantly shorter drying time than hot-air drying. Osmotic dehydration also reduced drying time in microwave-IR combination oven. Effective diffusivity of moisture in hot-air drying (5.070 x 10(-10) m(2)/s) was found to be lower than that observed in microwave-IR drying (7.100 x 10(-9)-1.445 x 10(-8) m(2)/s). Higher microwave and IR powers increased but osmotic pretreatment decreased effective diffusivity. Decrease in IR power and osmotic dehydration treatment increased L* but decreased a* values of dried eggplants. Microwave-IR-dried eggplants had more porous structure than hot-air-dried ones. Therefore, these eggplants had lower shrinkage and higher rehydration ratio than hot-air-dried ones. Osmotically dehydrated eggplants had higher shrinkage and lower rehydration ratio than untreated ones

Enhancing oxidative stability of walnuts by using gallic acid loaded lentil flour based electrospun nanofibers as active packaging material

The objective of this study was to enhance oxidative stability of walnuts present in active packages produced by electrospinning technology. Gallic acid was encapsulated into lentil flour/polyethylene oxide (PEO) nanofibers. To promote the solubility of lentil proteins, pH of solutions was adjusted to pH 1 and pH 10 which were far away from isoelectric point of lentil proteins. While acidic solutions had lower viscosity values than alkaline solutions, their electrical conductivity values were significantly higher. When the scanning electron microscopy (SEM) images were examined, it should be noted that alkaline nanofibers showed homogenous structure. Although gallic acid was not so stable at alkaline conditions, gallic acid loaded nanofibers prepared at alkaline pH still showed antioxidant activity after electrospinning. The physical and thermal properties of encapsulated gallic acid and nanofibers were examined by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and differential scanning calorimeter (DSC) analyses. FTIR results indicated the effect of pH on chemical properties of nanofibers and the interaction between gallic acid and lentil flour-based nanofibers. Gallic acid addition reduced onset temperature and thermal stability. Therefore, it could be taken as evidence of incorporation of gallic acid. Disappearance of enthalpic peak related to melting of crystalline structure of gallic acid in DSC thermal curves confirmed successful encapsulation of gallic acid. Fabricated gallic acid loaded nanofibers were used to pack walnuts and the reduction in oxidation of walnuts with lower peroxide, p-anisidine and Totox values was observed. This would make these packaging materials substantially preferable for packing of foods being highly susceptible to oxidation

Nanostructured poly(lactic acid)/soy protein/HPMC films by electrospinning for potential applications in food industry

As an alternative to oil based materials, there is a demand for easily degradable packaging materials. With this regard, the objective of this study is to produce bilayer nanofiber sheets composed of Poly (lactic acid) (PLA) and soy protein, hydroxypropyl methylcellulose (HPMC) and combination of them by using electrospinning. In addition, it was aimed to analyze morphological, optical, thermal properties of films and investigate permeability characteristics. Homogenous nanofibers were successfully collected onto PLA sheets. The solution containing HPMC had the highest viscosity and the lowest electrical conductivity values. Therefore, HPMC based nanofibers had the highest the average diameter values. Combining nanofibers with PLA sheets decreased transparency as compared to the transparency of neat PLA, it also did not improve permeability values. When the thermal properties of PLA/nanofibers were examined it was observed that while PLA sheet showed one stage degradation, bilayer films had two stage degradation. Soy protein containing nanofibers showed higher thermal stability. The FTIR spectrum of PLA/nanofiber sheets displayed the chemical characteristics of both PLA and nanofibers. PLA/nanofiber sheets obtained by electrospinning can be suggested in packaging of light sensitive foods

Characterization of curcumin incorporated guar gum/orange oil antimicrobial emulsion films.

Edible films are manufactured from natural, renewable, nontoxic, and biodegradable polymers and are safe alternatives to plastic food packaging. Despite ongoing research, biopolymer-based edible films still are not at a quality to ensure total commercial replacement of synthetic packaging materials. The study aims to compare the effectiveness of some novel methods employed to improve edible film properties. These include dispersion of orange oil (1% & 2% v/v) and/or curcumin into guar gum (GG), glycerol and lecithin-based edible films that are further reinforced with Sodium trimetaphosphate (STMP) crosslinking with the aim enhancing films physical properties. The films were characterized by measurement of film thickness, density, moisture content, water dissolvability, FTIR Spectroscopy, opacity, water vapor permeability, tensile properties, and antimicrobial activity. Orange oil and curcumin preserved their antimicrobial activity inside the films, which bestowed the films with an active packaging function. Control GG films had acceptable tensile and barrier properties that were further improved. All other film properties, such as opacity, dissolvability, and moisture content, that should be designed for specific application, were successfully modified with the methods used. Our results confirm successful application of STMP crosslinking, emulsion film formation, and active agent addition to edible films in manufacturing GG films for packaging

Citric acid cross-linked curcumin/chitosan/chickpea flour film: An active packaging for chicken breast storage

Since there has been an increasing interest in natural, non-toxic, and biodegradable food packages instead of plastic ones, scientists put great effort into eliminating the potential drawbacks of these biodegradable films. In this study, citric acid (CA) was utilized as a crosslinker for the films produced by chitosan (CS), chickpea flour (CF), and active agent curcumin (CUR) by a solvent casting technique. CA was introduced into the film for-mulations at different concentrations (0, 0.5%, 1%, 1.5% w/v), and the influence on the functional film char-acteristics were extensively analyzed.Increasing CA concentration in formulation caused a reduction in water vapor permeability (WVP) of the films such that the film with the highest CA concentration (1.5-CUR/CF/CS) was 62.6% more resistant to water vapor than film without CA (0-CUR/CF/CS). When CA concentration in the film formulation was increased, elongation at break (EAB) value increased from 1.64% +/- 0.13%, to 11.1%+/- 1.21% whereas tensile strength (TS) value decreased from 7.83 +/- 0.08 MPa to 3.58 +/- 0.20 MPa. Contrary to expectations, antioxidant activity of the films decreased with increasing CA concentration. X-Ray Diffraction (XRD) patterns of the films proved the amorphous nature and inhibitory characteristic of CA against retrogradation. In addition to all these, CA concentration significantly influenced Thermogravimetric analysis (TGA) pattern of the films with the increasing number of degradation stages. Besides the cross-linker characteristic of CA, it also extensively enhanced the antibacterial characteristic of the films. Films formulated with 1.5% (w/v) CA (1.5-CUR/CF/CS) showed antibacterial effect against both Escherichia coli (E.coli) (ATCC 11229) and Staphylococcus aureus (S.aureus) (ATCC 43300). Finally, chicken breast packed with 1.5-CUR/CF/CS films remained below unacceptable microbial threshold limits even at the end of the 9th-day of storage compared to samples packaged with the film with no antibacterial activity