Water Vapor Permeability Research Articles

Experimental and theoretical studies on antioxidant and antibacterial properties of chitosan-gelatin functional composite films loaded with flavonoids

Chitosan-gelatin-flavonoid functional composite films were prepared with chitosan, gelatin, and three flavonoids (Naringenin, Apigenin, and Luteolin). The effect of three flavonoids on physical, antioxidant, and antibacterial properties of functional composite film was investigated from experimental and Density functional theory (DFT) simulations. The tensile strength, thermal stability, water solubility, water vapor permeability, antioxidant activity, and antibacterial activity of chitosan-gelatin-flavonoid functional composite films were improved with flavonoid (Naringenin, Apigenin, and Luteolin) incorporation. The release behavior of Apigenin from functional composite film was much lower than that of Naringenin or Luteolin. ABTS+ radical scavenging ability values of functional composite films followed: Luteolin (69.53 %) > Naringenin (41.39 %) > Apigenin (36.13 %). The antibacterial activities of functional composite films against Staphylococcus aureus followed: Luteolin (52.03 mm) > Apigenin (49.34 mm) > Naringenin (43.15 mm). The total number, location of hydroxyl groups on ring-B, and the unsaturation degree on pyrone ring of flavonoids influenced antioxidant and antibacterial activities of functional composite films. The minimum bond dissociation enthalpy values of flavonoids followed: Luteolin < Apigenin < Naringenin. The interaction energy of Apigenin-chitobiose was stronger than that of Naringenin or Luteolin. These results will shed light on flavonoid selection for functional composite films of food packaging.

Development of an intelligent packaging material incorporating betacyanin from red beetroot extract into polyvinyl alcohol films

This research aimed to develop an intelligent packaging material by incorporating betacyanin from red beetroot extract into polyvinyl alcohol (PVA) film. Betacyanin was extracted using three solvents (Distilled Water, Ethanol, and Methanol), and films were prepared. The methanolic extract had the highest betacyanin content (416.57µg/100g), while the distilled water extract had the lowest (310.22µg/100g). Incorporating betacyanin increased the film thickness, with methanol-extracted films (MEF) being the thickest (126.36µm). Light transmittance differed significantly, being highest in ethanol-extracted films (EEF) (4.32%) compared to control (3.65%) and MEF (3.82%). Water solubility was highest in the control sample (44.94%), and water vapor permeability was lowest in methanol-extracted films (14.25gmsPa-1 × 10-7), indicating better film quality. MEF had the lowest lightness (L*=31.71), while control films had the highest (L*=38.84). The a* value was lowest for control films (a*=1.97) and highest for methanol-extracted films (a*=6.08). EEF had the highest b* value (b*=6.58±0.95), and control films had the lowest (b*=4.01). All films exhibited low mechanical resistance with tensile strengths ranging from 2.84 to 3.16 MPa. Additionally, these films can detect pH changes, acting as promising colorimetric bioindicators. The study concludes that intelligent films made with methanol-extracted betacyanin are viable for developing pH-responsive packaging for the food industry.

Fabrication and characterization of carvacrol encapsulated gelatin/chitosan composite nanofiber membrane as active packaging material

In this study, carvacrol was effectively encapsulated in gelatin/chitosan composite nanofiber membrane using the electrospinning method with the help of the cationic surfactant cetyltrimethylammonium bromide (CTAB). The effects of CTAB (0.0 %, 1 %, w/w) and bioactive carvacrol (0.0 %, 1.0 %, 3.0 %, 5.0 %, 7.0 %, 10 %, w/w) on the structural, physicomechanical, antibacterial, and antioxidant characteristics of the nanofiber membranes were investigated. The results demonstrated that the antibacterial and antioxidant characteristics of the gelatin/chitosan composite nanofiber membrane (GC) and GC-CAR membrane (with the addition of 1.0 % carvacrol) were unsatisfactory. As carvacrol and CTAB were both added, the elongation at break, antibacterial, and antioxidant properties of the nanofiber membranes significantly improved (p < 0.05), while the water vapor permeability (WVP) significantly decreased (p < 0.05). When the added amount of carvacrol was 5 % (w/w), the nanofiber membrane (GC-CAR5-CTAB) exhibited the best antioxidant and antibacterial performance. Finally, the GC-CAR5-CTAB membrane was applied to the preservation of strawberries and Erjingtiao chilies, and their shelf life was effectively extended. The above results indicate that the nanofiber membrane prepared in this study has great potential for application in food-active packaging.

Eco-friendly nanocomposite biofilm based on sage seed gum/gelatin/TiO2: Fabrication and characterization.

In the current study, the sage seed gum/gelatin-TiO2 (SG/Ge-TiO2) nanocomposite films were prepared. Their physical, mechanical, chemical, barrier, surface, structural, and microbial characteristics are determined as a function of different ratios of sage seed gum (SG) to gelatin (1 to 2, 2 to 1 and 1 to 1) and different concentrations of TiO2 nanoparticles (0, 2, 4% based on biopolymer (w/v)). The results indicated increases in the tensile strength, elongation at break, thickness, brightness (L*), whiteness index (WI), and contact angle, as gelatin content and concentration of TiO2 nanoparticles increase. In addition, the increases of TiO2 nanoparticles and the increased content of SG lead to an increase in the surface roughness of the films. As the gelatin content and the concentration of TiO2 nanoparticles increased, the barrier characteristics against water vapor, oxygen, and light increased, so that the water vapor, oxygen, and light permeability in the SG 1-Ge 2-4% film decreased by 66.93%, 80.89%, and 47.43%, respectively, compared to the SG 2 Ge 1-0% film. According to the results of structural and thermal investigation, the crystallinity degree in the films increased as the gelatin content and the concentration of TiO2 nanoparticles increased, resulting in the enhanced thermal stability of the film. The addition of TiO2 nanoparticles brought about antimicrobial characteristics in the film, with no significant effect on the antioxidant activity and total phenol content (p>0.05). The results indicated that SG-Ge-TiO2 bionanocomposite films (especially SG 1-Ge 2-4%) can be considered a suitable option for active food packaging as well as medical applications (e.g. active wound adhesive) due to its favorable characteristics.

Date seed extract encapsulated-MCM-41 incorporated sodium alginate/starch biocomposite films for food packaging application

In this study, we developed active bio-composite films using a sodium alginate/starch (1,1) matrix incorporating date seed extract encapsulated mesoporous silica (DSE@MCM-41) up to 7.5 wt%. Incorporating DSE@MCM-41 significantly improved the films' properties, enhancing antioxidant efficacy and UV-blocking capabilities. Notably, the films exhibited a 29.5 % increase in tensile strength, a 34.81 % decrease in water absorption, and a reduction in water vapor permeability to 1.76 × 10−8 g m−1.h−1.pa−1 at 5 wt% DSE@MCM-41 concentration. These enhancements, coupled with sustained DSE release, effectively extended the shelf life of black grapes by up to 16 days. These results demonstrate the potential of DSE@MCM-41-incorporated bio-composite films to improve food preservation and extend shelf life, making them suitable candidates for advanced food packaging systems.

Improvement of the properties of essential oil-starch film with whey protein isolated fibril and sodium caseinate

Essential oil-starch films are important bioactive films, but their properties are not good enough and need improved. In this work, sodium caseinate (CAS) was utilized to improve the distribution and release of Cinnamon essential oils (CEO), and whey protein isolate fibril (WPIF) of different loadings (0 %, 4 %, 8 % and 12 %, w/w) in starch basis was added to enhance the mechanical properties of starch films. Physical, mechanical, thermal, structural, antibacterial properties, and essential oil release in the films were investigated. CAS-CEO nanoemulsion (190.7±9.4 nm) promoted the compatibility between starch and WPIF. The addition of CAS-CEO nanoemulsion and WPIF synergistically enhanced the tensile strength, stiffness, crystallinity and antibacterial effects, reduced the water vapor permeability of films, and especially delayed the release of essential oil from the films. The starch film composited with CAS-CEO nanoemulsion and appropriate loading of WPIF (8 %) significantly improved the film properties, but the addition of 12 % WPIF disrupted the properties, which might be attributed to the excessive aggregation of WPIF. The work provided useful information for improving the properties of CEO films via adding the emulsifier of CAS and the texture booster of WPIF, which could help to improve the film properties containing oil-soluble bioactive agents.

Facile synthesis and antibacterial performance of novel biofilms based on bacterial cellulose from jackfruit rags, incorporating polyvinyl alcohol, Ag nanoparticles, and Eclipta prostrata extract

The advancements of antibacterial biofilms have received much attention in biomedical, wound healing, and food packaging. Here, we developed a novel bacterial cellulose (BC) through Acetobacter xylinum strains using jackfruit rags as a carbon source, under different fermentation conditions. The highest BC production of 5.668 g L–1 of dried weight BC was obtained from the medium with 1: 2 (w v–1) of jackfruit rags/water ratio, 4.5 initial pH and 9 days of incubation. Further bacterial cellulose was incorporated into mixture of polyvinyl alcohol (PVA), biogenic silver nanoparticles (AgNPs) and Eclipta prostrata extract (EPE) to develop antimicrobial films. The micromorphology, mechanical, and functionality of BC/PVA/AgNPs/EPE biofilms were compared with those of BC/PVA, BC/PVA/EPE, BC/PVA/AgNPs film precursors. The results showed that mechanical strength of BC/PVA/AgNPs/EPE biofilms increased, while their water vapor permeability significantly decreased. Fourier transform infrared and scanning electron microscopy revealed excellent compatibility between AgNPs, EPE and the BC/PVA matrix. The BC/PVA/AgNPs/EPE biofilm had strong antibacterial performance against Escherichia coli and Staphylococcus aureus, as the average zone of inhibitions were 18.5 ± 0.33 mm and 21.0 ± 0.3 mm, respectively. These outcomes suggest that the BC/PVA/AgNPs/EPE biofilm can be a good candidate for antibacterial food packaging.

Interactions, structures, and functions of pomegranate peel reinforced starch film

This work aimed to exploit the effects of pomegranate peel (PP) addition (10 %) and homogenization process (0–12,000 rpm) on the film-forming behavior and interactions of starch film to improve its microstructures and properties. Microrheology results showed that the viscosity of the film suspension was reduced by homogenization, and the amylopectin aggregation was restricted by PP particles under film formation. This helped improve the accessibility of starch and PP, increasing the hydrogen bond energy in the composites from 18.12 to 19.35 kJ/mol and promoting the ester bonds as confirmed by the FTIR results. As a result, the starch film reinforced by PP and homogenization showed a uniform and compact microstructure with reduced water activity, increased UV-blocking capacity (from 67.46 % to 90.11 %), enhanced mechanical resistance, and reduced water vapor permeability (from 4.70 to 2.21 × 10−10·g·m−1·s−1·Pa−1). Additionally, the starch film with 10 % PP also presented superior antimicrobial properties and antioxidant activity with rates of over 86 %, providing an effective strawberry preservation function.

Influence of copper ion cross-linked CMC-PVA film on cell viability and cell proliferation study

In this study, films composed of carboxymethyl cellulose and polyvinyl alcohol were fabricated using the solution casting method. Citric acid (4 %) was employed as a cross-linking agent, while glycerol (3 %) as a plasticizer. Cupric chloride (CuCl2·2H2O) was used for cross-linking at concentrations 0.5 %, 1 %, and 3 % over different times. The cross-linking with copper ions led to a noticeable reduction in elasticity, with the breaking strain ranging from 17.9 %–52.9 %. The ion hydration phenomenon increased the contact angle and swelling ratio. Fourier-transform infrared (FTIR) spectroscopy confirmed esterification reactions and copper ion cross-linking with sodium carboxymethyl cellulose (Na-CMC). The films showed antibacterial activity against Staphylococcus aureus and Escherichia coli. The ion-released mechanism followed was the non-Fickian super case-II type. The concentration and duration of cross-linking significantly influenced cell viability and proliferation. FE-SEM analysis revealed that effective concentrations of CuCl2.2H2O were 0.5 % and 1 %, and cross-linking times were 5–15 min, facilitating cell attachment and proliferation. Films are non-adhesive with water vapor permeation 800–900 g/m2/day. These results indicate the potential use of the films in treating second-degree burn wounds with low to medium exudate levels. This study provides valuable insights into the development of copper-infused materials for advanced wound healing applications.

Effect of silver nanoparticles in polyethylene packaging on physicochemical, microbiological, and textural properties of oil cake.

This study investigated silver nanoparticle (SNP)/titanium dioxide polyethylene films as chemical preservative substitutes to increase the shelf life of oil cake. The research examined three types of packaging films: standard low-density polyethylene (LDPE), LDPE with 3% SNP, and LDPE with 5% SNP, and assessed their impact on oil cake shelf life. Analysis of packaging films included scanning and transmission electron microscopy (SEM and TEM), and Fourier-transform infrared spectroscopy. The study evaluated the effects of SNP on chemical and microbial stability on oil cakes in different storage days (1st, 15th, 30th, and 37th days) at 25 °C. Parameters such as moisture content, water vapor permeability, water activity, peroxide, fat acidity, texture, and microorganisms were studied. The results demonstrated that SNP-containing films can extend the shelf life of oil cake up to 37 days, marked by a significant decrease in microbial growth, particularly mold, compared to conventional packaging films. Notably, films with 5% SNP concentrations exhibited the highest efficacy in preserving the quality of the oil cake. Higher concentrations of SNP led to an increased reduction in microbial load and enhanced mold control while maintaining favorable quality assessment indices throughout the storage period from day 1 to day 30. Remarkably, oil cake packaged with a 5% SNP polymer film displayed the most promising outcomes, extending shelf life up to 30 days at 25 °C.

Beet Root Peel Extract as a Natural Cost‐Effective pH Indicator and Food Preservative in Edible Film: Shelf Life Improvement of Cold‐Stored Trout Fillet

ABSTRACTIn this study, chitosan (C)‐polyvinyl alcohol (P) edible film containing bio‐fabricated nanosilver particles (nAg) (as antimicrobial agent) and beetroot peel extract (BRPE) (as antioxidant agent and pH indicator) was used as spoilage indicator in cold‐stored rainbow trout fillets. DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) radical scavenging activity (43.02%), reducing power (2.87), and total phenolic content (360.50 mg GAE/g) of ethanolic BRPE were higher than aqueous extract. Silver nanoparticles were biosynthesized using silver nitrate reduction by chitosan, confirmed by UV–Visible spectroscopy, optical and scanning electron microscope images, and X‐ray diffraction analysis. The highest tensile strength (4.20 MPa) and elongation at break (118%) belonged to the CP‐BRPE film, and the lowest water vapor permeability (2.45 10−5 g/s/m/P) was related to the CP‐nAg film. Also, the lowest total viable count (6.17 log CFU/g), psychrotrophic bacteria (6.27 log CFU/g), Enterobacteriaceae (4.9 log CFU/g), pH (5.66), total volatile basic‐nitrogen (TVB‐N) (22.1 mg/100 g of fish), and thiobarbituric acid reactive substances (TBARS) (0.705 mg MDA/kg of fish) values of the packaged trout fillets were significantly (p ≤ 0.05) observed in CP‐BRPE‐gnAg treatment among the other treatments at the end of the storage period, and CP‐gnAg, CP‐BRPE, and CP treatments were in the next ranks, respectively. Colorimetric analysis of the used films showed that the films containing BRPE depicted color spectra of red to yellow at the same time as the spoilage symptoms initiated in the packaged fillets. It is concluded that BRPE not only increased the preservative effects of chitosan‐polyvinyl alcohol film containing green silver nanoparticles but also can be considered as a natural cost‐effective spoilage indicator of the rainbow trout fillets during cold storage time.

Pectin Edible Films Filled with Ilex paraguariensis Concentrate Extract and Its Characterization

Ilex paraguariensis (IP) extract was added to prepare edible films using a central rotational composite design (CCRD) 22 with IP extract and sorbitol concentrations as variables. The IP extract was characterized by color parameters, total phenolic content, caffeine, flavonoids, and chlorophyll content, and antioxidant activity and the edible films were assessed for the same analysis and thickness, water vapor permeability (WVP), solubility in water, fluorescence, photodegradation and UV/Vis light barrier, FT-IR, thermogravimetry, and differential exploratory colorimetry. Sorbitol increased thickness and WVP, while the extract influenced the concentration of phenolic compounds in the films. The optimum concentrations of extract and sorbitol were 10% and 15%, respectively. Films presented thermal resistance (until 230 °C) and an excellent barrier to UV light. Furthermore, these films could carry compounds originally in IP, showing good functional properties concerning the water vapor barrier (showing a great variation scale due to the possibility to increase sorbitol or not, between 3.33 and 5.27 g mm/m2 day KPa). The films showed great potential to replace conventional primary packaging, and if consumed with food, as a bullet paper, they can add nutritional value to the packaged product.

The Effect of Kappa Carrageenan Composition on the Characteristics of Chitosan-Kappa Carrageenan Hydrogel Film

Chitosan-Kappa Carrageenan (Chit-KC) hydrogel films have been made using a casting method with different compositions. This research aimed to investigate the effects of different compositions on the chemical, physical, and mechanical characteristics of the Chit-KC hydrogel films. The compositions of the kappa carrageenan in the Chit-KC films were 0%, 16.67%, 33.33%, 50.0%, and 100.0%. The films were characterized using FTIR, SEM, DTA-TGA, and XRD instruments to analyze their functional groups, morphology, thermal properties, and crystallinity. They were also tested for their solubility, swelling, water vapor permeability (WVP), and mechanical characteristics. The results revealed that the addition of kappa-carrageenan induced the formation of a polyelectrolyte complex. The polyelectrolyte complex caused an increase in swelling, crystallinity, and WVP values and a decrease in solubility, tensile strength, elongation, and elasticity. It also caused the formation of film layers and granules on the surface of the hydrogel film. The IR spectra exhibited that the Chit-KC hydrogel films contained O-H, C-H, C=O, S=O, C-O, and C-O-C groups. The DTA-TGA test results revealed that the film began decomposing at around 200°C and re-decomposing at 300°C.

Preparation and Characterization of Lithraea molleoides Gum Flour and Its Blend Films

Lithraea molleoides fruit gum (LMFG) is a valuable product obtained from the total hydrolysis of the fruit. The hydrolysis process involves three methods: thermal (LMFGT), alkaline (LMFGB), and acid (LMFGA). Through these methods, the aim is to break bonds and de-esterify polysaccharides, resulting in increased solubility and decreased molecular weight. The resulting hydrolysates are then combined with pectins in a 1:2 ratio to form films. In this study, the focus is on utilizing the hydrolysates of Lithraea molleoides gums for film applications, with an evaluation of their structural and physicochemical characteristics. The films produced exhibit excellent mechanical properties and low water vapor permeability, as well as exceptional thermal stability. These properties make them highly suitable for industrial films in pharmaceutical and food applications. This research highlights the potential of LMFG-based films as a viable solution for various industrial needs due to their outstanding performance across multiple parameters.

Characteristics of whey protein concentrate/egg white protein composite film modified by transglutaminase and its application on cherry tomatoes.

In order to obtain food packaging film with better performance, whey protein concentrate (WPC) and egg white protein (EWP) were used as film-forming substrates, and its film properties weremodified by transglutaminase (TG). Then the effect of TG on the mechanical, physical, barrier, and microstructural properties of the WPC/EWP composite biodegradable film was investigated, and its preliminary application potential was explored. Compared toWPC and EWP films, WPC/EWP composite film had higher transmittance, tensile strength (TS), and thermal stability. Fluorescence results showed that the film experienced fluorescence quenching after TG treatment. Fourier transform infrared and x-ray diffraction results showed that WPC and EWP had good compatibility in the biodegradable film, the hydrogen bond interaction of film was increased due to TG, resulting in an increase in TS. Meanwhile, the water vapor permeability and contact angle of WPC/EWP film treated with TG at 5U/g protein increased by 28% and 76.1%, respectively. Besides, the WPC/EWP biodegradable film modified by TG (TG-W/E) was applied as a coating film on cherry tomatoes, effectively reducing the weight loss rate during storage from 14.2% to 10.8%. Furthermore, indexes, such as solid content, spoilage rate, hardness, pH, and lycopene, showed that the film had a good preservation effect on cherry tomatoes. To conclude, the appropriate addition of TG has a positive effect on the film properties of the WPC/EWP biodegradable film, which is beneficial to the development and utilization of protein-based film. WPC/EWP biodegradable film modified by TG has a great application prospect in extending the shelf life of fruit and vegetable.

The Use of Phosphonates to Inhibit Salt Crystallization: A Laboratory Study for the Sustainable Conservation of Mural Paintings in the Hypogea Context

This research is focused on the laboratory study of salt crystallization inhibitor products as new materials for conservation treatments which can be applied to mortars and painted plasters; as is well known, salt crystallization is one of the most frequent causes of decay processes on decorated architectural surfaces in a wide range of environments. Specifically, the study targets the field of the preventive conservation of mural paintings within rupestrian heritage sites. For the first time, systematic investigations were performed on mock-ups made of plaster painted with two different pigments: yellow ochre and carbon black. Two types of phosphonate inhibitors, PBTC (2-phosphonobutane-1,2,4-tricarboxylic acid) and ATMP (aminotris (methylene phosphonic acid)), were chosen and applied at two different concentrations. Given the limited literature available, and the presence of pigments potentially sensitive to treatment with salt inhibitors, preliminary tests were required. Their effects on the chromatic features of the pigments were evaluated visually and using colorimetry. The changes in the behaviour of water circulation in the mortar resulting from the treatments were evaluated through water vapour permeability and absorption tests. Accelerated crystallization experiments were carried out to assess how inhibitors could influence the growth of salts and the resulting material damage. The latter was carried out by employing sodium sulphate and calcium sulphate solutions, quantifying the damage to the specimens through material loss in weight and the percentage of painted surface loss. Based on the overall results, the product with the best performance was identified was ATMP 0.1% (by volume) in deionized water. The obtained results show that salt inhibitor treatments are promising for in situ application and could represent an innovative approach to promote the sustainable conservation of mural painting, particularly those located in hypogeal contexts, where the salt supply cannot be removed and slowing the growth of salts and/or changing their crystalline habitus may be effective in limiting their damage.

The potential of helichrysum italicum essential oil-infused alginate coatings and film for prolonging the shelf-life of cherry tomatoes

This study aimed to develop edible coatings and films using sodium alginate (1 % Alg) and varying concentrations of Helichrysum italicum essential oil (HIEO) (0.3 % and 0.5 %) for cherry tomato preservation. The treatments consisted of Alg, Alg/0.3 % HIEO, and Alg/0.5 % HIEO. The physico-chemical, mechanical, water vapor permeability, optical, thermal, and antifungal properties of these coatings and films were examined. Scanning electron microscopy and Fourier transform infrared spectroscopy analyses showed that the addition of HIEO resulted in a heterogeneous morphology and slight chemical structural changes in the Alg film. The Alg/0.5 % HIEO films exhibited improved water vapor permeability, antioxidant capacity, ultraviolet light barrier properties, elongation at break, and thermal stability. Additionally, 0.5 % HIEO significantly reduced the mycelial growth of Botrytis cinerea (in vitro), making Alg/0.5 % HIEO the optimal coating. Cherry tomatoes coated with Alg/0.5 % HIEO and stored at 25 °C and 60 % relative humidity for 18 d showed reduced weight loss (5.22 ± 1.45 %) and preserved firmness (6.43 N). This coating also inhibited the Rhizopus stolonifer lesion diameter by 61.36 % (in vivo). In conclusion, Alg/0.5 % HIEO coatings are promising sustainable active packaging solutions for cherry tomato storage applications.

Enhancing Strawberry Freshness: Multifunction Sustainable Films Utilizing Two Types of Modified Carbon Nanotubes for Photothermal Food Packaging.

Currently, antimicrobial films with stable and efficient antibacterial activities are receiving considerable attention in the food packaging industry. Herein, a chemically/physically linked konjac glucomannan-sodium alginate (KGM-SA)@carbon nanotubes (CNTs)/Fe3+ composite film with outstanding resistance to ultraviolet radiation, oxidation, and bacteria, as well as excellent photothermal effects and mechanical properties, was successfully prepared using a solvent flow method. Tannic acid-modified carboxyl-functionalized CNTs (TCCNTs), l-cysteine-modified carboxyl-functionalized CNTs (LCCNTs), and Fe3+ were incorporated into the prepared film. The film structure of KGM-SA@CNTs/Fe3+ was characterized using various methods, confirming the formation of a dual-cross-linked network through metal-coordination bonds and hydrogen bonding. This unique structure endowed the film with excellent water vapor permeability (3.58 g mm/m2 day kPa), water resistance (water contact angle = 93.66°), and thermal stability. Further, the film exhibited outstanding photothermal conversion efficiency and stability under near-infrared irradiation (300 mW/cm2) as well as excellent bactericidal properties against Staphylococcus aureus and Escherichia coli, achieving a bacterial inhibition rate of >99%. In a strawberry preservation experiment, the KGM-SA@CNTs/Fe3+ composite film exhibited remarkable preservation effects, extending the shelf life of strawberries by 4-6 d. Thus, this photothermal antibacterial film offers a new approach for the application of CNTs in food packaging.

New Materials from the Integral Milk Kefir Grain Biomass and the Purified Kefiran: The Role of Glycerol Content on the Film’s Properties

Microbial exopolymers are gaining attention as sources for the development of biodegradable materials. Milk kefir, a fermented dairy product produced by a symbiotic community of microorganisms, generates milk kefir grains as a by-product, consisting of the polysaccharide kefiran and proteins. This study develops two materials, one from whole milk kefir grains and another from purified kefiran. Film-forming dispersions were subjected to ultrasonic homogenisation and thermal treatment, yielding homogeneous dispersions. Kefiran dispersion exhibited lower pseudoplastic behaviour and higher viscous consistency, with minimal effects from glycerol. Both films exhibited continuous and homogeneous microstructures, with kefiran films being transparent and milk kefir films displaying a yellowish tint. Analysis revealed that milk kefir films comprised approximately 30% proteins and 70% kefiran. Kefiran films demonstrated stronger interpolymeric interactions, as evidenced using thermogravimetric and mechanical tests. Glycerol increased hydration while decreasing thermal stability, glass transition temperature, elastic modulus, and tensile strength in both films. However, in kefiran films, elongation at the break and water vapour permeability decreased at low glycerol content, followed by an increase at higher plasticiser contents. This suggests an unusual interaction between glycerol and kefiran in the absence of proteins. These findings underscore differences between materials derived from the whole by-product and purified kefiran, offering insights into their potential applications.

Development of polyvinyl alcohol/carboxymethylcellulose-based bio-packaging film with citric acid crosslinking and clove essential oil encapsulated chitosan nanoparticle pickering emulsion

This study developed polyvinyl alcohol (PVA)/carboxymethylcellulose (CMC)-based films, using citric acid (CA) as a non-toxic crosslinking agent, to enhance the shelf life of water-soluble packaging films. Clove essential oil (CEO)-loaded chitosan nanoparticles (CSNPs) were prepared via Pickering emulsion and incorporated into PVA/CMC/CA composite films. The encapsulation of CEO was confirmed by FTIR and optical microscopy. Thermal properties were analyzed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), revealing improved thermal stability and a decrease in glass transition temperature (Tg) upon crosslinking. The formation of ester bonds was confirmed by ATR-FTIR and 13CNMR. Water contact angle (WCA) measurements showed a decrease in hydrophilicity, enhancing the barrier properties of the films. SEM images demonstrated good dispersion of CSNP/CEO within the matrix, improving mechanical and barrier properties. The films exhibited a 30 % reduction in water vapor permeability and water solubility. Controlled release studies indicated that the composite films sustained CEO release, extending the shelf life of cherry tomatoes. Thus, these PVA/CMC/CA-CSNP/CEO composite films offer strong potential for food preservation applications.