Water Vapor Permeability Values Research Articles

Development of Polymeric Films Based on Sunflower Seed Proteins and Locust Bean Gum.

Most polymeric food packaging materials are non-biodegradable and derived from petroleum, thus recent studies have focused on evaluating alternative biodegradable materials from renewable sources, with polysaccharides and proteins as the main types of employed biopolymers. Therefore, this study aimed to develop biopolymeric films based on sunflower proteins and galactomannans from locust bean gum. The influence of the galactomannan amount (0.10%, 0.30%, 0.50%, and 0.75% w/v) on the physicochemical, thermal, and mechanical properties of cast sunflower protein-based films was studied. Sunflower proteins gave rise to yellowish, shining, and translucid films. With the incorporation of locust bean gum-derived galactomannans, the films became more brown and opaque, although they still maintained some translucency. Galactomannans significantly changed the proteins' secondary structures, giving rise to films with increased tensile resistance and stretchability. Nevertheless, the increase in the galactomannan amount did not have a significant effect on the film's thermal stability. The protein/galactomannan-based films showed values of water vapor and oxygen permeability that were slightly higher than those of the pristine materials. Overall, blending locust bean gum galactomannans with sunflower proteins was revealed to be a promising strategy to develop naturally colored and translucid films with enhanced mechanical resistance while maintaining flexibility, fitting the desired properties for biodegradable food packaging materials.

The enhancement in antifungal efficacy of konjac glucomannan films with attapulgites immobilized of AgNPs

The objective of this study was to enhance the water barrier properties and antifungal efficacy of KGM film by incorporating (attapulgites-Ag nanoparticles, APTs-AgNPs) composites. The X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), and Energy dispersive X-ray (EDS) analyses indicated that the successful fabrication of APTs-AgNPs composites. Water vapour permeability (WVP), moisture content (MC), water solubility (WS) and water absorption (WA) values decreased by 19.15%, 12.50%, 74.96% and 41.74% respectively, while the water contact angle (WCA) increased by 134.74%. These results demonstrated that the water barrier property of KGM/APTs-AgNPs films was superior to that of pure KGM films. The Rheological properties, fourier transform infrared (FTIR) spectrum, X-ray diffraction (XRD) patterns and Scanning electron microscopy (SEM) images results indicated that hydrogen bonds formed between homogeneous APTs-AgNPs (1.5 wt%) and KGM, which enhanced the water barrier properties of the KGM/APTs-AgNPs films. The KGM/APTs-AgNPs composite films possessed excellent oxygen permeability, Mechanical properties, UV barrier properties, opacity properties and thermostability. Moreover, KGM/APTs-AgNPs films slowly released Ag+ and exhibited long-acting antifungal efficacy against Aspergillus niger, as the inhibition circle diameter was 20.70 ± 0.32 mm for 10 days. Therefore, KGM/APTs-AgNPs films could be a potential alternative to petroleum-based films.

Preserving plum perfection: Buckwheat starch edible coating with xanthan gum and lemongrass essential oil

The research focused on the fabrication of composite coatings using buckwheat starch (BS) and xanthan gum (XG) with incorporation of lemongrass (Cymbopogon citratus) essential oil (LEO) with varying concentration (0.75 %, 1.0 % and 1.25 % (w/v). BS was extracted from buckwheat groats (Fagopyrum esculentum) and its physico-chemical characteristics were determined. BS showed spherical and polygonal morphology and its XRD pattern was similar to starch extracted from other cereal sources. The amount of reducing sugar, starch and amylose content in extracted BS were 0.99 ± 0.33 %, 86.32 ± 0.22 % and 21.02 ± 1.89 % respectively, which indicates that BS is a suitable base material for the formation of edible coatings. XG was mixed with BS in different ratios (1:1, 2:1, 3:1 and 4:1) to optimize the best ratio of combination for composite coatings. The coating with a ratio of 2:1 was very smooth and was chosen for incorporation of LEO and the coatings physical, functional, mechanical, thermal and micro-structural characteristics were examined. The coating S5 with 1.25 % (w/v) concentration of LEO showed the best results with least moisture content (MC), minimum water vapor permeability (WVP) and maximum contact angle value. Moreover, the S5 formulation had the highest antioxidant (73.3 %) ability and maximum antimicrobial efficiency with inhibition zones of 22.09 ± 0.06 mm and 28.65 ± 0.14 mm against S. aureus and E. coli respectively. The coatings were then coated on plum fruit, and various parameters like weight loss, pH, shrinkage and TSS were calculated every 4th day during the 20 days of refrigeration period. The coated plums' ripening pace was delayed by the S5 formulation which improved moisture retention, maintained the plums' TSS value and overall pH. Therefore, composite coatings made up of BS, XG and 1.25 % (w/v) can be used as a cost-effective bio-active coating material for plum preservation under refrigeration conditions.

Investigation of polypropylene yarns containing silver nanoparticles: Fiber characteristics, yarn properties, and fabric performance analysis

AbstractThis study focuses on the development of antimicrobial technical textiles using silver‐infused polypropylene fibers to meet the escalating demand for enhanced protection against pathogens in medical settings. Various polypropylene‐based fibers with different silver concentrations and cross‐sections were produced through spinning experiments, resulting in six distinct fiber types. Comprehensive analyses, including differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X‐Ray diffraction (XRD), were conducted to evaluate thermal and structural properties. Physical strength and morphological characteristics were examined to determine optimal compositions. Subsequently, selected fibers were spun into yarns and knitted to create textile surfaces. Evaluation encompassed physical attributes, color, morphology, water vapor permeability, and antimicrobial efficacy against Gram‐negative bacteria, particularly E.coli. The results demonstrated over 99% antibacterial activity across all samples, highlighting their potential utility in medical textiles and other applications. Additionally, the study revealed that the water vapor permeability values were higher in fabric samples without silver nanoparticle additives, with a negligible decrease observed in samples with higher silver nanoparticle concentrations. The antibacterial activity was found to increase with higher silver concentrations in trilobal cross‐section samples. Round cross‐section samples exhibited higher antibacterial activity at the same silver concentration. These findings provide valuable insights for future antibacterial‐based fiber production studies and literature.

Effect of Soybean Oil on the Improvement of the Functionality of Edible Membrane-Type Food Packaging Films Based on Caseinate-Carboxymethyl Chitosan Compositions.

Edible film biopolymers are gaining attention to tackle problems of plastic waste and food safety to alleviate environmental problems associated with plastic products in food packaging. In this study, caseinate-carboxymethyl chitosan (CA-CMCH) composite films were made with the incorporation of soybean oil (SO) using a casting technique. The influence of different soybean oil concentrations at 0, 0.5, and 1% (w/w) on physical, mechanical, barrier, and surface characteristics of films composed of caseinate-carboxymethyl chitosan (CA-CMCH) was evaluated. The brightest film (L* value of 95.95 ± 0.30) was obtained with the edible film made from the control group of samples with sodium caseinate (NaCA-100; 100% NaCA). The results also indicated that samples with 1% SO in NaCA-75 and CaCA-75 had lower water vapor permeability (WVP), while those with NaCA-50 and CaCA-50 showed higher values of WVP. For mechanical properties, this study found that incorporating soybean oil into the caseinate-carboxymethyl (CA-CMCH) composite films led to an enhancement of both tensile strength and elongation at break. The morphological structures, determined using SEM, of control and composite films showed compact and homogenous surfaces. Overall, the addition of soybean oil contributed to the improvement of the functional properties of the edible films, offering potential solutions to the environmental issues associated with plastic packaging and enhancing the safety and performance of food packaging.

Comfort Properties and Antimicrobial Activity of Cotton and Nylon/PU Knits Treated with Microcapsules Containing Sea Buckthorn Oil

This study was performed to investigate comfort properties and antimicrobial activity of cotton and nylon knits treated with microcapsules containing sea buckthorn fruit oil reported as having antimicrobial efficacy depending on concentration of microcapsules and treatment types. Chitosan-arabic gum microcapsules containing sea buckthorn fruit oil were prepared and they were treated on cotton and nylon/PU knit respectively by an experimental design of 2 different treatment types (bath immersion method and screen printing method) Χ 5 different concentration levels of microcapsules (20, 30, 40, 50, and 60% on the weight of fabric). As comfort properties, stiffness, water-vapor permeability, and air permeability were measured objectively. Antimicrobial activity was evaluated by calculating the percentage reduction of the bacterium. As results, stiffness values of the treated knits were slightly higher than those of untreated ones, which was thought not to affect touch in wear. The values of water-vapor permeability and air permeability of both cotton and nylon after the treatment were not significantly decreased. These results means that microcapsules loaded on the knits might not worsen their wear comfort. As for antimicrobial activity, more than 90% of bacterial reduction rates against S. Aureus were shown in cotton jersey by screen printing even after repeated laundry while those was found in nylon/PU tricot by bath immersion. From these results, it was concluded that chitosan-arabic gum microcapsule containing sea buckthorn fruit oil could be utilized for textiles to provide antimicrobial activity.

Flexible cellulose nanofibers/MXene composite films for UV-shielding packaging

Cellulose nanofibers (CNF) based films are promising packaging materials, but the lack of special functions (especially UV-shielding property) usually restrict their further applications. In this work, MXene was incorporated into the CNF film by a direct solvent volatilization induced film forming method to study its UV-shielding property for the first time, which avoided the using of a vacuum filtration equipment. The composite films containing glycerin could be folded repeatedly without breaking, showing good flexibility. The structure and properties of MXene/CNF composite films (CMF) were characterized systematically. The results showed that MXene distributed uniformly in the CNF film matrix and there was strong hydrogen bonding interaction between CNF and MXene. The tensile strength and Young's modulus of the composite films could reach 117.5 MPa and 2.23 GPa, which was 54.1 % and 59.2 % higher than those of pure CNF film, respectively. With the increase of MXene content, both the UVA and UVB shielding percentages increased significantly from 17.2 % and 25.5 % to 100.0 %, showing excellent UV-shielding property. Moreover, CMF exhibited a low oxygen permeability (OP) value of 0.39 cc μm d−1 m−2 kPa−1, a low water vapor permeability (WVP) value of 5.13 × 10−11 g−1s−1Pa−1 and a high antibacterial rate against E. coli (94.1 % at 24 h), showing potential application in the packaging field.

Water vapour permeability of inorganic construction materials

Water vapour permeability (WVP) data on brick, stone, plaster and cement-based materials from some seventy publications are reviewed and assessed. Almost all sources use standard cup-test methods or close variants. Comparisons of WVP values from different sources on similar materials confirm that reproducibility between different laboratories is poor. Some deficiencies of cup-test methods are discussed, including uncertainties arising from the use of saturated-salt humidistats and desiccants. There is evidence that the water vapour resistance factor decreases as volume-fraction porosity increases, and data support a simple porosity–tortuosity relation. Data also show that the resistance factor decreases with increasing mean relative humidity across the test specimen, with the wet-cup value consistently lower than the dry-cup values for a given material. The contribution of liquid film flow to mass transfer is discussed. It is shown how film thickness and film-flow permeability may be estimated from the water-vapour sorption isotherm; and a related regression equation is developed It is concluded that available data are inadequate to establish the fundamental physics of WVP; vapour-only permeability data for engineering purposes should be obtained in dry-cup tests at low humidity; and research studies should aim to integrate the WVP into the framework of unsaturated flow theory.

Thermal Comfort Properties of 100% Cashmere Knitted Fabrics

The purpose of this research is to investigate the effects of knitting type (plain, rib, purl), knitting tightness (three different loop lengths), and plied-yarn (single-ply, two-ply and three-ply) on the thermal comfort properties of cashmere knitted fabrics. Thermal comfort properties of the sample fabrics were measured using Alambeta, Permetest, Textest 3300. Subsequently, the results were statistically evaluated with SPSS program. The findings of this research revealed that the knitting type, knitting tightness and plied-yarn usage significantly affect certain thermal comfort properties of cashmere knitted fabrics. Specifically, the plain knitted fabric exhibits the lowest thermal resistance value and the highest relative water vapor permeability value. The loose knitted fabric demonstrates the highest air permeability, while the fabric knitted with single-ply yarn has the lowest thermal conductivity and thermal resistance values, as well as the highest relative water vapor permeability and air permeability values.

Intelligent double-layer films based on gellan gum/mica nanosheets/anthocyanin/konjac glucomannan/carrageenan for food real-time freshness monitoring

In this work, double-layer intelligent films were designed and synthesized based on Broussonetia papyrifera fruit anthocyanin (BPFA), mica nanosheets (MN), konjac glucomannan (KG), carrageenan (CA) and gellan gum (GG) using layer-by-layer casting strategy for real-time and in situ food freshness monitoring. The KG/CA/BPFA layer served as the indicator layer, while the GG/MN layer acted as the protective outer layer. It was observed that the water vapor permeability value of the GG-MN/KG-CA-BPFA double-layer film was reduced by 4.7 times, and the tensile strength was increased by 4.1 times compared with the GG film, which could be related to the reinforcing effect and proper barrier property of MN. Notably, the double-layer film blocked most of UV-light and oxygen, and its water contact angle reached 102.4° ± 1.18°. In particular, the films showed favorable visually detectable colorimetric responses to different pH buffer solutions and volatile ammonia. More importantly, visual assessment using shrimps as test specimens demonstrated distinct color alteration from red to blue-grey on spoilage. The color change of the film was also highly correlated with TVB-N (R2 = 0.964) and pH (R2 = 0.999). In conclusion, the newly designed double-layer film exhibited excellent performance, which guides an innovative approach for advanced food-packing material development.

Camelina sativa Oilseed Cake as a Potential Source of Biopolymer Films: A Chemometric Approach to Synthesis, Characterization, and Optimization

In this work, the possibility of obtaining biopolymer films from Camelina sativa oilseed cake (CSoC) at different parameters of the synthesis process was investigated. The pH (values 8, 10, and 12), the temperature (60, 80, and 100 °C), and the concentration of the cake in the film-forming suspension (3, 4, and 5%) were varied. The films obtained were characterized by studying the mechanical, barrier, physico-chemical, structural, and biological properties (antioxidant and antimicrobial). The results showed moderate mechanical properties, indicating the application of these biopolymer materials as coatings. Low values of water vapor permeability (5.1–12.26 g/m2h) and very low transmission in the UV range (less than 2%) indicate good barrier properties. FTIR analysis confirmed the films’ composite structures: peaks related to proteins, polysaccharides, lipids, and cellulose were detected. The biological activity of the obtained CSoC films was pronounced so that they could be used for active packaging. All films have high antioxidant activity, which is more pronounced in samples synthesized at pH 8. The films possess antibacterial properties against S. aureus, while some had an inhibitory effect on S. typhimurium. Standard score analysis showed that the film sample synthetized at pH = 10, temperature = 100 °C, and concentration = 5% had optimal investigated properties.

Uticaj etarskih ulja na osobine biopolimernih filmova na bazi divljeg lana (Camelina sativa L.)

The aim of this work was the activation of biopolymer material based on wild flax cake (Camelina Sativa) with eucalyptus and rosemary essential oils added in different concentrations (0.5%, 1% and 2%). The wild flax cake, left over after the cold pressing of the oil, was used to obtain biopolymer films. To obtain active packaging, essential oils were added to this biopolymer material and the influence of the addition of essential oils on the physico-chemical, mechanical, barrier and biological properties of biopolymer films based on wild flax cake was examined. The obtained results showed the most significant influence on water vapor permeability. The control sample had a water vapor permeability value of 5.43 g/m 2 h, while in the sample with 2% added eucalyptus essential oil, this value was 3.14 g/m 2 h. Antioxidant activity was also confirmed in the control sample without added essential oils (60.10%), but with the addition of 2% eucalyptus essential oil, this value increased to 78.54%. Eucalyptus essential oil proved to be more effective than rosemary oil on the investigated properties of the films. The addition of essential oils to biopolymer films broadens the spectrum of functional properties, including the improvement of mechanical, barrier and biological properties.

Characterization of biodegradable films based on guar gum and calcium caseinate incorporated with clary sage oil: Rheological, physicochemical, antioxidant, and antimicrobial properties

Clary sage essential oil (CSEO) has been reported for its wide food and pharmaceutical applications. This work aimed to produce biodegradable active guar gum-calcium caseinate (GG-CC) based film incorporated with CSEO and to evaluate its physico-chemical, antioxidant, and antibacterial properties. Solvent casting technique was used to prepare the composite films containing CSEO at 0.1, 0.15, and 0.2% (v/v). The chemical, rheological, morphology, mechanical, thermal, optical, crystalline, biodegradable, water barrier, antioxidant and antimicrobial potential of the samples were assessed by various analytical methods. Rheological findings of filmogenic solution revealed that the viscosity of filmogenic solutions (GCEO2–GCEO4) increased with an increase in the concentration of the CSEO. CSEO addition in GG-CC film exhibited a homogenous structure with low crystallinity, transparency, water vapor permeability, moisture content, and tensile strength values, whereas a rise in elongation at break, thickness, and thermal stability was observed. Fourier transforms infrared (FTIR) results suggested the interaction between CSEO and GG-CC-CSEO films also exhibited satisfactory antioxidant activity against DPPH and ABTS free radicals and higher antimicrobial effect against the Gram-negative bacteria (Pseudomonas aeruginosa). This work revealed that CSEO has the potential to be used as an active ingredient in the development of films for food packaging applications.

Evaluation of the barrier and antimicrobial properties of biodegradable films based on potato waste starch containing natural additives

This study investigates the antimicrobial and water vapor barrier properties of biodegradable films made from potato (Solanum tuberosum) waste starch and the natural additives glycerol, propolis, and montmorillonite ("chaco"). Films were produced using the casting method, and their physical, antimicrobial, and barrier properties were analyzed. Film compositions were established using an experimental design of mixtures. The water vapor permeability values ranged from 0.44 × 10−10 to 8.55 × 10−10 g/(m·s·Pa). The permeation energy was lower than that of polyvinyl chloride and polypropylene films but higher than that of cellophane films. The solubility values ranged from 58 to 66%, and the tensile modulus ranged from 2.15 to 5.15 MPa. The largest inhibition halo diameter obtained for Staphylococcus aureus was 17 mm. The developed packages completely biodegrade within 30 days under composting conditions at ambient temperatures. These findings suggest the potential application of these biodegradable packages for fresh products such as fruits and vegetables.

Agro-Industrial Protein Waste and Co-Products Valorization for the Development of Bioplastics: Thermoprocessing and Characterization of Feather Keratin/Gliadin Blends.

Biopolymers based on plant and animal proteins are interesting alternatives in the development of films with future prospects as food packaging. Considering that in recent years there has been an increasing interest in the valorization of agro-industrial residues and by-products and that the blending of polymers can lead to materials with improved properties, in this work, keratin-rich feather fibers and gliadins were blended at different ratios in order to develop sustainable and biodegradable films. Control gliadin G100, feather F100 films, and their blends at 3:1 (G75F25), 2:2 (G50F50), and 1:3 (G25F75) ratios were successfully developed through thermoprocessing. The physical properties were differentiated as a function of the concentration of both polymeric matrices. Although gliadins showed higher hydrophilicity as confirmed by their highest swelling degree, films with high gliadin ratios exhibited lower water vapor permeability values at low and medium relative humidities. On the other hand, the feather fiber-based films displayed the highest Young's modulus values and provided an oxygen barrier to the blends, principally at the highest relative humidity. In conclusion, the blend of these protein-based polymers at different ratio resulted in interesting composites whose physical properties could be adjusted.

Chitosan-based edible film incorporated with wampee (Clausena lansium) seed essential oil: Preparation, characterization and biological activities

Chitosan (Ch)-based edible composite films were prepared by incorporating blending wampee seed essential oil (WSEO) into a Ch matrix, using the incorporation ratio as a variable. The physical, mechanical properties, structure morphology and rheological properties were determined using tensile strength (TS), elongation at break (EB), water vapor permeability (WVP) tests together with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) observations and apparent viscosity and shear rate. In addition, the antimicrobial, antioxidant activities were investigated by the DPPH & ABTS radicals scavenging and inhibition zone assays, respectively. Compared with Ch, the incorporation of WSEO significantly decreased (P < 0.05) the TS, EB, and WVP values, especially when the WSEO ratio reached 1.0 % or higher. Meanwhile, the films exhibited greatly improved visible light barrier performance after WSEO incorporation. Both FTIR spectroscopy and SEM observations reflected the crosslinking between WSEO and Ch. Meanwhile, the composite films demonstrated smaller particle size and weaker rheological viscosities, which enhanced the antimicrobial and antioxidant capabilities when compared with those of Ch. Therefore, this study suggested that WSEO incorporated with Ch is an effective ingredient for the preparation of edible films with enhanced physicochemical and biological properties.

Study of the Physical, Chemical, and Structural Properties of Low- and High-Methoxyl Pectin-Based Film Matrices Including Sunflower Waxes.

The development of bio-based materials remains one of the most important alternatives to plastic materials. Although research in this field is growing, reporting various materials and methodologies, it is still necessary to increase exploration. The aim of this work was to expand and complement previous research on the preparation and characterization of high- and low-methoxyl pectin films obtained by casting, with the addition of commercial and recovered sunflower waxes. The results showed that the addition of sunflower waxes to the pectin matrix generated some discontinuity in the aggregate, increasing the thickness and roughness of the film. However, due to their hydrophobic nature, the waxes contributed to lower vapor transmission rate values of the films. On the other hand, the low-methoxyl pectin films had a more crystalline structure, which could help to diminish water vapor permeability values, mechanical resistance and rigidity, and improve their elongation. Regarding chemical characteristics, most of the raw materials' chemical groups were found in the resulting films, and the presence of C-H bending due to pectin gelation was observed. Finally, the compatibility and contribution of pectin and sunflower waxes to the production of the films were demonstrated, as well as the possibility of using materials from industrial waste in food packaging applications.

Pomegranate peel polyphenols as an antioxidant additive for the development and characterization of a new active pectin edible film

AbstractNatural origin products are an appealing substitute for nonbiodegradable materials in the production of new materials to improve the packaging properties and to extend the shelf life quality of foods. The objective of this study was to formulate, elaborate, select, partially characterize, and evaluate the biological properties of an edible film based on pectin, candelilla wax, and glycerol, added with pomegranate peel polyphenols (PPP). An exploratory design 2k Box Hunter and Hunter was made, followed by a Box‐Behnken design 3k to evaluate the properties of water vapor permeability (WVP) of the film, resulting in the film with 0.75% w/v of pectin, 0.2% w/v of candelilla wax, 0.05% v/v of glycerol and 0.02% w/v of PPP with one of the lowest values of WVP (1.78E−10 g/m.s.Pa). After characterization, this treatment showed good structural and optical properties and low humidity values compared to a control film. PPP showed the inhibitory capacity for DPPH (61.2%) and ABTS (48.5%) radicals and reducing activity with the reduction of ferric ion (FRAP) reaching a value of 1676.5 mg TE/g PPP.

Potential effect of citrate nanocellulose on barrier, sorption, thermal and mechanical properties of chitosan/Arabic gum packaging film

Currently, the necessity to diminish environmental pollution caused by petroleum-based packaging plastics has encouraged interest in creating renewable and biodegradable packaging polymers. The objective of this study is the development of a green nanocomposite constructed from citrate cellulose nanospheres (CNC) that have been embedded in (CH/AG) Chitosan/Arabic gum (CNC@CH/AG) to meet the mechanical requirements. Citrate CNC was prepared using a citric acid/HCl acid mixture and it is investigated by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscopy (TEM), Zeta potential, and degree of substitution. CNC@CH/AG film was investigated by FTIR, XRD, scanning electron microscope (SEM), wettability, mechanical, barrier, water vapor sorption, and thermal characteristics. CNC@CH/AG film displayed declining in water vapor permeability. The lowest water vapor permeability (WVP) value was 0.044 ± 23 × 10−3 g. mm. kPa−1. h−1. m−2 compared with control (CH/AG) was 0.129 ± 81 × 10−3 up to 3 mg CNC. For sorption properties, the CNC@CH/AG nanocomposite films are consistent with the GAB model, Smith, Henderson, and Peleg models. In comparison to CH/AG, the addition of CNC enhances all of the nanocomposites' tensile strength and Young's modulus by nearly two and three times, respectively, with a decrease in elongation percentage. The addition of CNC renders CNC@CH/AG nanocomposite films more thermally stable and the total activation energy of CNC@CH/AG nanocomposite film (−94.97 J/mol) is more than three times that CH/AG film (−34.04 J/mole).

The highly stable indicator film incorporating roselle anthocyanin co-pigmented with oxalic acid: Preparation, characterization and freshness monitoring application

A novel stable PVA/HPMC/roselle anthocyanin (RAE) indicator film co-pigmented with oxalic acid (OA) was prepared, its properties, application effects and stability enhancement mechanism were investigated correspondingly. The structural characterization revealed that more stable network was formed due to the co-pigmentation facilitated generation of molecular interactions. Meanwhile, the co-pigmentation improved film mechanical and hydrophobic properties compared to both PVA/HPMC/RAE newly prepared (PHRN) or stored (PHRS) film, expressing as higher tensile strength values (12.25% and 14.44% higher than PHRN and PHRS), lower water solubility (7.22% and 10.09% lower than PHRN and PHRS) and water vapor permeability values (33.20% and 21.05% lower than PHRN and PHRS) of PVA/HPMC/RAE/OA newly prepared (PHON) or stored (PHOS) film. Compared with the PHRS film, the PHOS film still presented more distinguishable color variations when being applied to monitor shrimp freshness, owing to the stabilization behaviors of co-pigmentation in anthocyanin conformation. Hence, the co-pigmentation was an effective strategy to enhance film stability, physical and pH-responsive properties after long term storage, leading to better film monitoring effects when applied in real-time freshness monitoring.