Light Barrier Research Articles

Novel bioactive films integrated with Pickering emulsion of ginger essential oil for food packaging application

Biocomposite films based on carboxymethyl cellulose (CMC)/polyvinyl alcohol (PVOH) added ginger essential oil (GEO) via Pickering emulsion (PE) method were fabricated and applied for preservation of bread. The films were assessed for their physicochemical, morphological, mechanical, thermal, antioxidant, and microbial properties. SEM imaging indicated encapsulation of GEO spherical droplets into PE. The films exhibited lower tensile strength, higher elongation at break, and thickness after adition of GEO PE. ATR/FT-IR spectroscopy demonstrated the formation of some interaction between polymer matrix and GEO PE. Packaging of bread slices with GEO integrated biocomposite films extended the shelf life of bread from 4 to 30 days. Remarkably, the GEO-loaded CMC/PVOH films showed excellent UV and light barrier properties, high antioxidant and antimicrobial activities, which make them suitable for food packaging application.

Active caseinate/guar gum films incorporated with gallic acid: Physicochemical properties and release kinetics

Composite active films based on sodium caseinate/guar gum were prepared by the incorporation of gallic acid at different concentrations to investigate its effect on the structure, physicochemical properties, and the release kinetics from the film. The incorporation of gallic acid imparted changes in the FT-IR spectra. Water vapor permeability (WVP) of films decreased up to 21% after the incorporation of gallic acid in the film. The gallic acid released from the films GAI* 60 μg.ml−1 , GAII* 250 μg.ml−1 and GAIII* 650 μg.ml−1 was 67%, 32% and 30% respectively. Similarly, the diffusion coefficient was also affected by an increase in the concentration and was: 8.10 × 10 −12 m 2 s −1 , 6.23 × 10 −12 m 2 s −1 , and 4.5 × 10 −12 m 2 s −1 for GAI, GAII and GAIII films respectively. Molecular docking suggested the potential inactivation of oxidative enzymes due to binding of gallic acid near their active sites. Therefore, gallic acid releasing films maybe considered as an active food packaging for fruits and vegetables (F&V). • Physicochemical properties of caseinate films were modified by the incorporation of gallic acid. • Permeability and light barrier properties of the films were significantly affected by the incorporation of gallic acid. • A maximum of 67% of gallic acid was released from the film with lowest gallic acid concentration. • The DPPH antioxidant activity of food simulant solutions ranged between ∼40 and 80%. • Oxidative enzyme inactivation by using phenolic compounds is a new concept in food packaging domain.

Effect of purple sugarcane peel extracts on properties of films based on lemon peel waste pectin and the application in the visible detection of food freshness

In this work, the effect of purple sugarcane (Saccharum officinarum) peel anthocyanin extracts (PSPAEs) on the physical and functional properties of films based on lemon peel waste pectin (LPP) was investigated for the first time. PSPAEs have great compatibility with LPP matrix, and the LPP/PSPAEs composite film demonstrated a higher ultraviolet light barrier capacity. The incorporation of PSPAEs significantly improved the physical properties of LPP films confirmed by the enhanced mechanical properties and thermal stability, which might be associated with the more compact structure observed by scanning electron microscope images and possible intermolecular interaction such as hydrogen bond interactions between film components demonstrated via Fourier transform infrared spectra and X-ray diffraction analysis. Furthermore, PSPAEs imparted excellent functional properties on LPP films, including antioxidant properties and sensitive color response to the pH alternation and ammonia atmosphere, which favored the possible application in monitoring food freshness. Herein, LPP/PSPAEs films were employed to detect the freshness of shrimp and beef, and a visually discernible color change could be observed as the food turned from fresh to stale. In addition, the LPP/PSPAEs composite films displayed great biodegradability in the soil. The results showed that could impart excellent properties on LPP films, and LPP/PSPAEs composite film is a promising biodegradable film that can be used for intelligent detection of food freshness.

Antibacterial poly(butylene succinate-co-terephthalate)/titanium dioxide/copper oxide nanocomposites films for food packaging applications

Titanium dioxide (TiO2)/copper oxide (CuO) nanoparticles (NPs) were synthesized by co-precipitation method. The photocatalytic activities of TiO2 were enhanced by the incorporation of CuO. The poly(butylene succinate-co-terephthalate) (PBST)-based nanocomposite (PTC) films were prepared via solvent casting method. Mechanical properties, UV-Vis light barrier, water vapor permeability (WVP), antibacterial properties, and preservation properties of composite films were evaluated. When the content of TiO2/CuO NPs was 3 %, the best overall properties of the film were obtained. The tensile strength and elongation at break reached maximum values of 35.6 ± 0.4 MPa and 590.7 ± 5.3 %, respectively. Meanwhile, the WVP values and UV-Vis transmittance of PTC-3 film decreased. The inhibition rates were close to 90 % against Staphylococcus aureus and Escherichia coli. Moreover, the PTC-3 film could extend the shelf life of cherry tomato after conducting preservation experiments for 18 days. Prepared PTC films had potential for food packaging.

Functional chitosan/zein films with Rosa roxburghii Tratt leaves extracts prepared by natural deep eutectic solvents

In this study, the bioactive extract of Rosa roxburghii Tratt (RRT) leaves was incorporated into a chitosan/zein matrix to produce a food packaging film with higher antioxidant and antimicrobial activities. The natural deep eutectic solvent (NADES) was taken as the extraction solvent and green plasticizer to prepare the film matrix. The physical and structural properties of chitosan/zein films with different concentrations of RRT leaves extracts were characterized by infrared spectroscopy analysis, thermogravimetric analysis, X-ray diffraction and scanning electron microscope. The incorporation of RRT leaves extract significantly improved the mechanical properties, light barrier properties and water vapor permeability of the chitosan/zein films. Moreover, the films containing RRT leaves extract had better antioxidant activities and antibacterial activities, with the highest DPPH and ABTS radical scavenging activities of 88.17 % and 86.84 %, respectively, and also effectively inhibited the growth of microorganisms and extended the shelf life of blueberries and cherry tomatoes.

Fish gelatin/chitosan blend films incorporated with betel (Piper betle L.) leaf ethanolic extracts: Characteristics, antioxidant and antimicrobial properties

Mechanical, barrier, and thermal properties of biodegradable films prepared using different gelatin/chitosan blends without and with betel leaf ethanolic extract (BLEE) at 1 and 2% were investigated. Incorporation of BLEE enhanced elasticity and heat-seal ability of the films. However, the seal ability was diminished with increasing chitosan proportion (p < 0.05). Ultraviolet and visible light barrier abilities along with water vapor permeability were improved (p < 0.05) for films containing 2% BLEE. Swelling and water solubility of the films were lessened with augmenting BLEE concentrations (p < 0.05). Antioxidant and antibacterial activities were upsurged as BLEE levels incorporated increased. SEM images of selected films showed smooth homogenous surface and cross-section in film sample devoid of BLEE, while those incorporated with BLEE had slightly rough surface and cross-section. FT-IR spectra revealed differences in peaks and patterns between films without and with BLEE. Addition of BLEE enhanced thermal stability of film. Thus, gelatin/chitosan films containing BLEE could serve as active packaging with satisfactory properties.

MAX: a simple, affordable, and rapid tissue clearing reagent for 3D imaging of wide variety of biological specimens

Transparency of biological specimens is crucial to obtaining detailed 3-dimensional images and understanding the structure and function of biological specimens. This transparency or tissue clearing can be achieved by adjusting the refractive index (RI) with embedding media and removing light barriers such as lipids, inorganic deposits, and pigments. Many currently available protocols consist of multiple steps to achieve sufficient transparency, making the process complex and time-consuming. Thus, in this study, we tailored the recipe for RI adjustment media named MAX based on the recently reported MACS protocol to achieve a single-step procedure, especially for ECM-rich tissues. This was achieved by the improvement of the tissue penetrability of the RI-matching reagent by combining MXDA with sucrose or iodixanol. While this was sufficient for the 3D imaging in many applications, MAX can also be combined with modular processes for de-lipidation, de-coloration, and de-calcification to further maximize the transparency depending on the special features of the tissues. Our approach provides an easy alternative for tissue clearing and 3D imaging.

Central composite design optimization of active and physical properties of food packaging films based on chitosan/gelatin/pomegranate peel extract

Chitosan and gelatin-based materials containing pomegranate peel extract were prepared for potential application as food packaging materials. An optimized composition of 0.8% chitosan, 0.2% gelatin and 1 mg g-1 of extract was chosen with the aid of a central composite design, presenting low viscosity (8.36 ± 0.20 Pa s) and solubility (26.00 ± 5.50%), as well as an expressive inhibition halo against Botrytis cinerea (6.17 ± 0.36 mm). The interaction between the polymeric matrix and the extract was confirmed by spectroscopic and morphological analysis. Rheologically, the optimized formulation was more resistant to deformation and shear (activation energy increased by almost 5 kJ mol-1) than the formulation without the extract. The use of pomegranate peel extract changed the film color, reduced its solubility (by more than 5%), increased mechanical resistance (tensile strength increased by 15 mPa), and improved light barrier properties by 30%. The extract also imparted antioxidant activity to the film, which was able to inhibit 20% of DPPH (2,2-diphenyl-1-picrylhydrazyl) radical at 38 mg mL-1. The optimized composition also showed inhibitory bacterial properties (31.2 and 125 µg mL-1) against S. aureus and S. enteritidis, respectively. Thus, the optimized film exhibited interesting characteristics for food packaging applications, many of them brought by the use of pomegranate peel extract, which highlights the valuable contribution of this agro-industrial waste to the properties of the polymeric films.

Preparation, characterization, and application of edible antibacterial three-layer films based on gelatin–chitosan–corn starch–incorporated nisin

Edible antibacterial three-layer films based on gelatin–chitosan/nisin–corn starch (GEL-CS/N-COS) were developed by layer-by-layer method. The microstructure and intermolecular interaction of the three-layer film was analyzed by SEM, ATR/FTIR, and XRD. Layer-by-layer technology enhanced the ultraviolet–visible light barrier property and elongation at break. In addition, the water solubility was reduced. Nisin was added into the three-layer film to further enhance its thermal stability and antibacterial activity. Importantly, GEL–CS–COS system exhibited good controlled release behavior of nisin. Cherry tomatoes were stored in GEL-CS/N-COS film packaging, and the effect on the shelf life of cherry tomatoes was evaluated. The results show that weight loss and total bacterial count were reduced, and higher firmness and better color were observed during storage for 22 days. These results suggest that developed three-layer film loaded with nisin is a potential antibacterial and edible material for food packaging applications.

Development of a Multifunctional Edible Coating and Its Preservation Effect on Sturgeon (Acipenser baeri♀× Acipenser schrenckii♂) Fillets during Refrigerated Storage at 4 °C.

Although many coatings and films can improve the quality and shelf life of fish fillets during refrigerated storage, a more multifunctional coating material is needed. In this study, an edible alginate/protein-based coating solution was prepared by incorporating antimicrobial agents. The coating properties were characterized and its effects on the quality and shelf life of sturgeon fillets during refrigeration (4 °C) were investigated. Compared with sodium alginate coating (2% sodium alginate + antibacterial agents, H), the composite coatings (2% sodium alginate + antibacterial agents + 1:15 or 1:10 protein solution, HP-15 and HP-10) exhibited a more stable structure and better light, gas, and water barrier properties, and showed better quality-preservation effects on sturgeon fillets. The composite coatings treatments, especially HP-10 composite coating, exhibited significant (p &lt; 0.05) effects in inhibiting microbial growth, maintaining sensory quality, reducing the production of total volatile basic nitrogen (TVB-N), decreasing nucleotide breakdown, and delaying the lipid oxidation and protein degradation in fillets. These findings confirm that the composite coatings can be used as a multifunctional coating material for freshness preservation of sturgeon fillets to improve quality and extend shelf life.

Antioxidant packaging films developed by in-situ cross-linking chitosan with dialdehyde starch-catechin conjugates

In this study, four dialdehyde starch-catechin (DAS-catechin) conjugates were prepared by conjugating (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG) with dialdehyde starch. Then, DAS-catechin conjugates were used as antioxidant and cross-linking agents to produce chitosan (CS) based antioxidant packaging films. The functionality of CS/DAS-catechin conjugate films was determined. Results showed four DAS-catechin conjugates formed Schiff-base linkages and hydrogen bond interactions with CS, resulting in improved film uniformity. Compared with plain CS film, CS/DAS-catechin conjugate films owned higher UV–vis light, water vapor and oxygen barrier ability, lower swelling degree, and stronger tensile strength, thermal stability and antioxidant activity. The cross-linking between CS and DAS-catechin conjugates delayed the biodegradable process of CS film. CS/DAS-catechin conjugate films showed good performance on inhibiting sunflower seed oil oxidation. Notably, CS/DAS-ECG conjugate film had the highest oxygen barrier, mechanical and antioxidant performances among four CS/DAS-catechin conjugate films. Therefore, CS/DAS-ECG conjugate film is an antioxidant packaging candidate for edible oil.

Double-Layered Films Based on Furcellaran, Chitosan, and Gelatin Hydrolysates Enriched with AgNPs in Yerba Mate Extract, Montmorillonite, and Curcumin with Rosemary Essential Oil.

Double-layered active films based on furcellaran (1st layer—FUR), chitosan, and gelatin hydrolysates (2nd layer—CHIT+HGEL) were successfully prepared. Bioactive ingredients were added to the 1st film layer: AgNPs, which were synthesized in situ with yerba mate extract; montmorillonite clay (MMT); and different loads of ethanolic curcumin (CUR) extract enriched with rosemary essential oil (REO). SEM images confirmed the presence of AgNPs with a size distribution of 94.96 ± 3.33 nm throughout the films, and AFM and SEM photos indicated that the higher substance concentrations had rougher and more porous film microstructures. However, the water vapor transmission rate was reduced only at the lowest load of this ingredient. Despite the tensile strength of the films having decreased, the incorporation of the compounds showed a tendency towards reducing the modulus of elasticity, resulting in a lower stiffness of the composites. The addition of CUR and AgNPs improved the UV light barrier properties of the materials. The presented films showed quick reactions to changes in the pH value (from orange to red along with an increase in pH from 2 to 10), which indicates their potential use as indicators for monitoring the freshness of food products. Composite No. 2 showed the highest antimicrobial potential, while none of the presented films showed an antifungal effect. Finally, the antioxidant activities of the films increased dramatically at higher AgNP and CUR loads, suggesting an outstanding potential for active food packaging applications.

Enhancing the physicochemical and functional properties of gelatin/graphene oxide/cinnamon bark oil nanocomposite packaging films using ferulic acid

Protein such as fish gelatin (FG) is widely used as a raw material to develop biodegradable packaging. However, its mechanical and water vapour barrier properties are still inferior as compared to synthetic polymers. Thus, in this research, a reinforcing nanofiller which is graphene oxide (GO, 2% w/w based on FG) and a crosslinking process using ferulic acid (FA) were incorporated to produce gelatin-graphene oxide/ferulic acid (gel-GO/FA) films with enhanced properties. Different concentrations of FA (0%, 0.5%, 1.0%, 2.0%, 3.0%, and 4.0% w/w) were used and the resulting films were analyzed. Cinnamon bark oil (CEO, 5% w/w based on FG) was incorporated to enhance the antioxidant activities of the films. The incorporation of FA resulted in a denser film microstructure and increased tortuosity, as shown by scanning electron microscopy (SEM) as well as the decreased (p < 0.05) water vapour permeability of the films. The antioxidant activities of the films improved significantly (p < 0.05) with FA concentration, with the highest values of DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging activity, ABTS (2,2-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid) scavenging activity, and total phenolic content of 97.41%, 98.67%, and 79.50 mg GAE/ g, respectively. In this study, the optimal concentration of the FA is 1% as the films showed the highest (p < 0.05) Young’s modulus and tensile strength. In addition, 1% FA was sufficient to result in a significant (p < 0.05) decrease of the ultraviolet (UV) light transmittance (wavelength= 200. 280, and 400 nm) and opacity. This research reveals that crosslinking gel-GO films with FA can improve the mechanical, water vapour and light barrier, thermal stability, as well as functional properties, potentially broadening their applications as food packaging.

Adaptive speed and separation monitoring based on switching of safety zones for effective human robot collaboration

• Design of dynamically switched safety zones which are used to monitor human presence • Implementation of safety architecture using safety sensors, safety PLC and robot's controller • Use the status of the safety zones to adapt robot behaviour based on the signals received • Ensure safe co-existence and collaboration of human operators with industrial robots This paper presents the design and deployment of a system that enables the safe cooperation and interaction of human operators with industrial robots. Dynamically switched safety zones are used to monitor human presence and respectively adapt robot behavior, namely speed and movement status. An overhead safety camera system is used to identify moving objects within each zone and produce warning and stop signals which are used to regulate the behavior of the robot, slowing it down and stopping it respectively. Based on the real time position reporting of the robot, continuous switching between zone configurations is achieved. This leads to a more efficient speed and separation monitoring process, as defined by ISO/TS 15066, EN-ISO 10218-1 and EN ISO 10218-2, compared to a fixed fence solution. Unlike the case of virtual fences which are currently implemented using light barriers, this approach allows humans to use more workspace from the robot while ensuring separation. The control architecture design and the implementation of the system on a pilot cell inspired from the automotive industry are presented in this paper, as well..

Physical, mechanical and antioxidant properties of chicken skin gelatin films incorporated with virgin coconut oil

This study aimed to determine the physical, mechanical, and antioxidant properties of chicken skin gelatin films incorporated with virgin coconut oil (VCO). Prepared chicken skin gelatin films at different VCO concentrations (0–30%) were characterized for their physical (water vapor permeability and light transmission), mechanical (tensile strength, elongation at break), and antioxidant (DPPH scavenging activity and total phenolic content) properties. The tensile strength and elongation at the film's break showed a decreasing and increasing trend with the increase of VCO concentration. The water vapor permeability of films showed no significant difference as the added oil concentration increased. In addition, the films with VCO added showed a good light barrier with a lower light transmission value at a high oil concentration. The incorporation of oil in gelatin films decreases the glass transition temperature (Tg) with the increasing amount of oil. Furthermore, the film's microstructure became rougher and more discontinuous with the addition of oil percentage. The increasing VCO concentration also enhanced the intensity of the Amide A, Amide I, Amide II, and Amide III functional groups. DPPH scavenging activity and total phenolic content in films also increased with VCO concentration. Thus, these results revealed that VCO could be incorporated with gelatin film to make active film packaging or edible film packaging for some food applications for protein-rich food, such as meat or edible packaging for primary packaging.

Development of a pH-sensitive film based on collagen/chitosan/ZnO nanoparticles and mulberry extract for pork freshness monitoring

pH-sensitive films based on collagen, chitosan, ZnO-nanoparticles and mulberry extract (CC/ZnO/ME) were developed to monitor pork freshness. Fourier transform infrared analysis revealed that collagen, chitosan, ZnO-nanoparticles and ME interacted via hydrogen bonds. The UV–vis light barrier ability of CC/ZnO/ME film was gradually enhanced as increasing ME content from 0.5 to 2.0 % wt. Compared with CC film, the mechanical strength and DPPH radical free scavenging rate of the CC/ZnO/ME film had increased by 13.84 MPa and 58.74 %, respectively. CC/ZnO/ME1 and CC/ZnO/ME2 films exhibited better pH-sensitivity than CC/ZnO/ME3 film, with color visibly changing from red to blue/green in different buffer solutions (pH 3–12). When monitoring the freshness of pork stored at 4℃, the color of CC/ZnO/ME2 film changed from deep purple to blue when TVB-N content exceeded the maximum permissible limit (15 mg/100 g) on 6th day.

Antimicrobial and controlled release properties of nanocomposite film containing thymol and carvacrol loaded UiO-66-NH2 for active food packaging

In this work, Zirconium-based metal–organic frameworks (MOFs), UiO-66-NH2, were designed as loading carriers for thymol and carvacrol and added into chitosan to construct antimicrobial packaging films. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA) were applied to characterize the films. Besides, we analyzed the physical properties, mechanical performance, hydrophobicity, release behavior, and antimicrobial capacity of the films. It can be clearly seen that the addition of thymol and carvacrol loaded MOFs into chitosan film significantly improved the thermal stability, light barrier properties, tensile strength, and hydrophobicity. Importantly, UiO-66-NH2 restrained the release rate of thymol and carvacrol compared with pure chitosan film, which endowed efficient antimicrobial capacity against E. coli, S. aureus, and P. citrinum to chitosan films. Overall, the strategy conceived here can be a superior candidate to develop a premium antimicrobial material for active food packaging, which has potential application prospects.

PH-responsive chitosan-based film containing oregano essential oil and black rice bran anthocyanin for preserving pork and monitoring freshness

This study developed an intelligent and antibacterial packaging film using a chitosan matrix embedding oregano essential oil (OEO) and black rice bran anthocyanin (BRBA). Herein, OEO and BRBA were immobilized into the chitosan matrix through noncovalent bonds and uniformly distributed in the films. The chitosan–OEO–BRBAⅡ film exhibited excellent mechanical, antibacterial, antioxidant, and UV–vis light barrier properties, and sensitive and rapid response to pH/NH3. Furthermore, fresh pork was coated with the film for monitoring the freshness and preservation efficiency at 4 °C for 12 days. The film effectively improved the quality indices of pork, including the sensory index, total viable counts, pH, TVB-N value, and color of pork during the storage at 4 °C. The film reduced the abundance of spoilage bacteria related to stress tolerance, pathogenicity, and biofilm formation in the pork. Their odorous volatiles appeared later and were less than those in the untreated group.

A new water-soluble lignin incorporation enhanced the barrier performance of liquid mulching film

In modern agriculture, the eco-friendly liquid mulching film is a promising alternative to traditional plastic mulching films but challenged by its limited barrier performance. In this work, a facile cyanoethylation technique route was proposed to produce water-soluble lignin from industrial waste lignin, which was further used as a biomimetic bonding adhesive and functional additive to cellulose nanowhisker (CNW) to form the building block of liquid mulching film. It was shown that at low degree of cyanoethylation, the water-solubility was improved through disrupting the strong hydrogen bonding of lignin, while remaining its UV light barrier and antioxidant activity. The well designed liquid mulching film fabricated with cyanoethyl lignin (CEL) coated CNW (CEL@CNW) building block and polyvinyl alcohol (PVA) matrix showed excellent UV barrier (reached ∼ 0 % transmittance at 200 nm with 10 wt% of CEL@CNW) and oxygen barrier ability (oxygen transmission rate reached ∼ 0.12 cm3 m−2 d−1 kPa−1 with 5 wt% of CEL@CNW), which could be used for the protection of photo-sensitive avermectin pesticide against photo-degradation. The real application potential of the fabricated PVA/ CEL@CNW liquid mulching film was verified through the good soil water resistance property and the facilitation of corn seed germination and seedling growth. It was proposed that the CEL incorporation mediated the layered structure of liquid mulching film thus significantly enhancing its overall barrier performance. This work provided a new strategy to valorize industrial waste lignin through water-soluble lignin pursuing, while tailoring a technique platform for the fabrication and application of liquid mulching film toward a more sustainable agriculture.

Novel physical treatments (Pulsed light and cold plasma) improve the quality of postharvest apricots after long-distance simulated transportation

Biological control of postharvest transportation by non-thermal treatment is considered a promising physical preservation technology. This study investigated how apricot quality (before simulation of transport vibrations) increased using intense pulsed light (IPL) and dielectric barrier discharge plasma (DBD) techniques. The results showed that DBD and IPL treatments reduced damage to apricot fruit after vibration and inhibited microbial growth on the surface of apricot fruit. By increasing the content of non-enzymatic antioxidants (total phenols, total flavonoids, ABTS, and DPPH radical scavenging activity) and antioxidant enzyme activity (SOD, PPO, POD, and CAT), the antioxidant capacity of apricot fruit was increased, cell structure damage was reduced, and water migration and erosion were inhibited as well. In summary, DBD and IPL treatments inhibited adverse physiological changes in apricot fruit subjected to vibration and mechanical damage, maintained their sensory and nutritional quality, and extended their shelf life.