Intelligent pH indicator film composed of agar/potato starch and anthocyanin extracts from purple sweet potato

Advanced technologies in biodegradable packaging using intelligent sensing to fight food waste

The limitation of conventional packaging in demonstrating accurate and real-time food expiration dates leads to food waste and foodborne diseases. Real-time food quality monitoring via intelligent packaging could be an effective solution to reduce food waste and foodborne illnesses. This review focuses on recent technological advances incorporated into food packaging for monitoring food spoilage, with a major focus on paper-based sensors and their combination with smartphone. This review paper offers a comprehensive exploration of advanced macromolecular technologies in biodegradable packaging, a general overview of paper-based probes and their incorporation into food packaging coupled with intelligent sensing mechanisms for monitoring food freshness. Given the escalating global concerns surrounding food waste, our manuscript serves as a pivotal resource, consolidating current research findings and highlighting the transformative potential of these innovative packaging solutions. We also highlight the current intelligent paper-based food freshness sensors and their various advantages and limitations. Examples of implementation of paper-based sensors/probes for food storage and their accuracy are presented. Finally, we examined how intelligent packaging can be an alternative to reduce food waste. Several technologies discussed here have good potential to be used in food packaging for real-time food monitoring, especially when combined with smartphone diagnosis.

Multifunctional Sensors Made with Conductive Microframework and Biomass Hydrogel for Detecting Packaging Pressure and Food Freshness

Food packaging detection devices have attracted attention to optimize storage situations and reduce food spoilage. However, low-cost and highly sensitive multifunctional sensors for detecting both food freshness and packaging pressure are still lacking. In this study, a multifunctional sensor was developed consisting of a MXene coated alcohol-soluble polyurethane fiber network (MXene/APU) and composite biohydrogel films made of konjac glucomannan, chitosan, and blueberry anthocyanin (KCB). Based on the pressure sensitivity of MXene/APU and the color changes of KCB in response to pH values, the sensor can detect internal package bulging, external squeezing, and food deterioration. The pressure sensor shows a sensitivity of 1.16 kPa-1, a response time of 200 ms, a wide strain range of 1092%, and stability over multiple loops. The pressure sensor could detect human motion and identify surface morphologies. The excellent sensor performance was attributed to the porous structure and large specific surface area of microfiber networks, conductivity of MXene nanosheets, and protective effect of KCB films coated on the conductive membrane. Besides, the microfluidic blow-spinning method used to prepare microfiber networks showed the advantages of low energy consumption and high production efficiency. Based on the color changes of blueberry anthocyanin loaded in KCB films in response to pH, the sensor realized sensitive spoilage detection of food containing protein. This study provides a new multifunctional food packaging sensing device and a greater understanding of the optimization and application of related devices.

Development of halochromic electrospun labels for non-invasive shelf life assessment of rainbow trout (Oncorhynchus mykiss): Incorporation of barberry anthocyanin extract in protein-based smart packaging

Using barberry (Berberis vulgaris L.) as a natural dye in combination with electrospinning technology represents a promising approach for the development of intelligent packaging systems. In this study, the influence of different concentrations of zein (16, 18, and 20%) and barberry anthocyanin-rich powder (BARP) (16, 18, and 20%) on the surface tension and rheological properties of the solution were evaluated. The most favorable nanofibers (NFs) were obtained from a solution containing 18% (w/w) zein under constant voltage. The surface morphology, size, and color-changing properties of electrospun NFs derived from zein polymers containing different concentrations of BARP (16, 18, and 20%) under various electrical fields (20, 22, and 24 kV) were evaluated. The Fourier-transform infrared spectroscopy analysis confirmed the interaction of BARP within the zein-based NFs. The results indicated that the concentration of BARP had a noticeable impact on the physicochemical properties of the NFs. Furthermore, efficacy of the appropriately fabricated halochromic label was evaluated for monitoring the packed rainbow trout fillet during refrigerated storage. On the 10th day, a noticeable visual color turned from pink to pale yellow was observed in response to pH variations. Additionally, the TVN value confirmed the effectiveness of halochromic electrospun labels for non-invasive assessment of fish fillet quality.

Colorimetric Films Based on Polyvinyl Alcohol and Anthocyanins Extracted from Purple Tomato to Monitor the Freshness of Shrimp

Anthocyanin extracts from purple tomato (PTA) were incorporated with polyvinyl alcohol (PVA), resulting in a series of colorimetric PVA/PTA films with PTA concentrations of 0%, 1%, 3%, and 5% (based on PVA). The role of anthocyanin on color response, Fourier-transform infrared (FTIR), thickness, water content, mechanical properties, antioxidant activity, and water vapor permeability (WVP) through the films was examined. In addition, its application in smart packaging to assess the freshness of shrimp was studied. It was found that the tensile strength, contact angle and WVP of PVA/PTA films increases with the addition of more PTA, while the elongation at break and water content decreased. FTIR analysis showed that there are interactions between PTA and the PVA matrix. The addition of anthocyanins caused significant improvement in the antioxidant properties of PVA films. Furthermore, the total volatile alkaline nitrogen (TVB-N), total plate count (TPC), and pH value of shrimp were monitored after 4 days of refrigeration, and the color change of the indexes was recorded. The PVA/PTA films changed color from purple to yellow-green during the storage time of 0-4 days for shrimp. This suggests that the film could be used in smart packaging as a real-time freshness indicator for shrimp.

Functionalization of bamboo fibers with lawsone dye (Lawsonia inermis) to produce bioinspired hybrid color composite with antibacterial activity

There is great interest in using eco-friendly functional colorants with antibacterial activity to produce colorful textile and plastic products. In this study, we designed, produced, and analyzed a novel multifunctional hybrid color composite colorant with antimicrobial properties, prepared from plant-based products. The new functional color composite was prepared by stabilizing lawsone dye onto amino-silanized cellulose from bamboo fibers. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy were performed to examine the possible interactions between the lawsone dye and silanized bamboo fibers. The color performance, morphology, chemical stability, and thermal stability of the prepared color composite were evaluated using scanning electron microscopy (SEM), UV-Vis spectrophotometry, and thermogravimetric analysis (TGA). The results were compared to those for pure lawsone dye. Modification of amino-silanized bamboo fibers with lawsone dye led to the formation of a light brown colorant that is more resistant to organic solvents (e.g. acetone, ethanol) and elevated temperatures than raw natural dye. Importantly, the designed bamboo fiber/lawsone system (BF-APTES-L) benefits from the synergistic combination of lawsone and bamboo fibers, showing strong antibacterial activity compared to the control sample of bamboo-as evidenced by noticeably inhibited growth of E. coli, S. aureus, and B. subtilis.

Biodegradable cellulose/curcumin films with Janus structure for food packaging and freshness monitoring

The development of renewable, hydrophobic, and biodegradable intelligent packaging materials as an alternative to petroleum-based plastic products has become a new research focus in recent years, but remains a challenge. Herein, regenerated cellulose/curcumin composite films were fabricated by dispersing hydrophobic curcumin uniformly in a hydrophilic cellulose matrix using an aqueous alkali/urea solvent based on the pH-driven principle of curcumin. In addition, a unilateral hydrophobic modification was carried out using chemical vapor deposition of methyltrichlorosilane to obtain Janus structure. The composite films exhibited high transparency in the visible light spectrum, excellent antioxidation, thermal stability, mechanical strength, gas barrier properties, and antibacterial activity. Furthermore, the films demonstrated the capability to lower the overall levels of volatile basic nitrogen in stored fish. The color of the films shifted from a pale yellow to a reddish-brown over time during storage. The composite films can be completely degraded after approximately 98 days in soil with an average environmental temperature of 29 °C. This work provided a facile strategy to prepare biodegradable cellulose/curcumin films with Janus structure as packaging materials which could preserve the freshness of food products while offering visual monitor of their freshness in real-time.

Intelligent active films of sodium alginate and konjac glucomannan mixed by Lycium ruthenicum anthocyanins and tea polyphenols for milk preservation and freshness monitoring

To achieve real-time monitoring of food freshness, a pH-responsive film based on sodium alginate-konjac glucomannan loaded with Lycium ruthenicum anthocyanins (LRA) was prepared, with the addition of tea polyphenols (TP) to enhance the stability of LRA. The surface structure of the films was observed by AFM. The results of FTIR and molecular docking simulation showed that LRA and TP were bound to polysaccharide by hydrogen bonds. The mechanical properties, barrier properties, and antioxidant/antibacterial properties of the films were significantly improved and the films showed obvious color response to pH. Notably, the AFM images showed TP and LRA could lead to more severe damage to the bacterial structure. The results of molecular docking simulation suggested that TP and LRA could act on different components of the bacterial cell wall, indicating their synergistic mechanism in antimicrobial activity. Moreover, the stability of LRA was improved due to the interactions of TP and polysaccharides with LRA. The aggregates formed by TP and LRA were clearly observed by AFM. Finally, the film showed excellent preservation and freshness monitoring effect in milk. In conclusion, TP-LRA-SA-KGM intelligent film exhibited excellent performance and represented a promising novel food packaging material with potential applications.

Novel oxidation indicator films based on natural pigments and corn starch/carboxymethyl cellulose

The existing oil oxidation detection methods are unsuitable for consumers to identify oil oxidation in a domestic setting. This study aims to develop indicator films detecting the degree of lipid oxidation with the naked eye. Purple sweet potato pigment (PSP) was chosen as a color indicator due to its response to hydrogen peroxide. The novel oxidation indicator films were prepared using corn starch, carboxymethyl cellulose (CMC), and varying concentrations of PSP. Fourier transform infrared spectroscopy spectra and scanning electron microscopy analysis confirmed the successful dispersion of PSP in the films. Thermal stability, light resistance, ultraviolet light resistance, mechanical resistance, and flexibility of films containing PSP were improved, enhancing the potential application in detecting oxidized substances. All the films exhibited noticeable color changes when exposed to different concentrations of hydrogen peroxide. These differences were more pronounced with higher levels of PSP. When these films were used to determine the degree of lipid oxidation, the ∆E value of the CS-PSP-0.25 % film showed a linear relationship (R2 = 0.929) with the peroxide value, unlike other films. Therefore, it is reliable to infer the peroxide value of edible oil by observing the color of the films, which helps customers avoid consuming expired oils.

Quality Characteristics of Raspberry Fruits from Dormancy Plants and Their Feasibility as Food Ingredients

The raspberry (Rubus idaeus L.) is a soft red fruit consumed worldwide due to its bitter-sweet taste and phenolics-associated health benefits. During plant dormancy, raspberry fruits are discarded. However, this work hypothesised that these fruits have the chemical quality to be valorised, which would mitigate their waste if adequately stabilised. This can be achieved by drying. The Pacific Deluxe and Versailles varieties were dried by freeze- and convective-drying (30 °C and 40 °C). The freeze-dried fruits preserved their colour, drupelets structure, and phenolic content. Convective-drying promoted a significant fruit darkening, which was more evident at 30 °C due to the longer drying process, and a loss of drupelets structure. Both temperatures promoted a similar decrease in phenolic content, as determined by HPLC, although the ABTS●+ antioxidant activity at 40 °C was lower (IC50 = 9 compared to 13 μg AAE/mg dry weight). To incorporate dried raspberries into muffin formulations, while keeping their red colour, it was necessary to change the raising agent from sodium bicarbonate to baker's yeast. Sensory analysis by a non-trained panel revealed good acceptance, showing that fresh or dried raspberry fruits from dormancy had suitable characteristics for use as food ingredients.

Potential Application of Ovalbumin Gel Nanoparticles Loaded with Carvacrol in the Preservation of Fresh Pork

Plant essential oil has attracted much attention in delaying pork spoilage due to its safety, but its low antibacterial efficiency needs to be solved by encapsulation. Our previous research had fabricated a type of ovalbumin gel nanoparticles loaded with carvacrol (OCGn-2) using the gel-embedding method, which had a high encapsulation rate and antibacterial activity. The main purpose of this study was to further evaluate the stability and slow-release characteristics of OCGn-2 and potential quality effects of the nanoparticles on the preservation of fresh pork pieces during 4 °C storage. The particle test showed that the nanoparticles had better heat stability below 85 °C and salt stability below 90 mM. The in vitro release study indicated that the carvacrol in OCGn-2 followed a Fickian release mechanism. The pork preservation test suggested that the OCGn-2 coating treatments could remarkably restrict the quality decay of pork slices compared to free carvacrol or a physical mixture of ovalbumin and carvacrol treatment. Nano-encapsulation of ovalbumin is beneficial to the sustained release, enhanced oxidation resistance, and improved antibacterial activity of carvacrol. The study suggested that ovalbumin gel nanoparticles embedded with carvacrol could be applied as an efficient bacterial active packaging to extend the storage life of pork.

Preparation of an elderberry anthocyanin film and fresh-keeping effect of its application on fresh shrimps

A smart packaging film was developed employing the pH-indicating activity of elderberry anthocyanins to solve the problem of refrigerated food freshness monitoring. The effect of elderberry anthocyanins on the properties of gellan gum, gelatin composite films and preservation of fresh shrimp as an indicator of freshness was investigated. The results showed that the elderberry anthocyanin-gellan gum/gelatin film had improved on film thickness (7.8×10-2 mm), TS (tensile strength) (14.57×103 MPa), WVP (water vapor permeability) (36.96×10-8 g/m·s·Pa), and a reduced EAB (elongation at break) (17.92%), and water solubility (water-soluble time of 60.5 s). SEM (scanning electron microscopy) and FTIR (infrared spectrum analysis) showed excellent compatibility between its components. Moreover, the elderberry anthocyanin film exhibited good mechanical properties and pH indication effects. Therefore, the film can be considered suitable for maintaining the quality of fresh shrimp. The results could provide a reference for research and development into new active intelligent packaging films.

Development of smart packaging halochromic films embedded with anthocyanin pigments; recent advances

Nowadays, innovative biodegradable packaging based on pH-sensitive natural dyes is being developed. These smart systems quickly inform the food quality to the consumer and monitor fresh foods in real-time. Smart packaging protects food against ambiance risks and simultaneously sends information to users for variations and alterations in the packaging settings. Anthocyanin (ACY), among the natural dyes used as indicators serves as water-soluble flavonoid pigments which made reflection in light in the red-blue range and can detect chemical and microbial alterations in foods based on their pH-susceptible conditions; on the other hand, they have considerable antimicrobial and antioxidant functions that result in the longer shelf life of food products. They also have beneficial properties including anti-cancer and anti-inflammatory functions, avoidance of heart diseases, overweight, and diabetes. Hence, this paper deals with the characteristics of smart packaging films based on anthocyanins, as well as their application in various food industries.

Smart Indicator Film Based on Sodium Alginate/Polyvinyl Alcohol/TiO2 Containing Purple Garlic Peel Extract for Visual Monitoring of Beef Freshness

The aim of this study was to prepare a novel pH-sensitive smart film based on the addition of purple garlic peel extract (PGE) and TiO2 nanoparticles in a sodium alginate (SA)/polyvinyl alcohol (PVA) matrix to monitor the freshness of beef. FT-IR spectroscopy revealed the formation of stronger interaction forces between PVA/SA, PGE, and TiO2 nanoparticles, which showed good compatibility. In addition, the addition of PGE improved the tensile strength and elongation at break of the composite film, especially in different pH environments, and the color response was obvious. The addition of 1% TiO2 nanoparticles significantly improved the mechanical properties of the film, as well as the light barrier properties of the film. PGE could effectively be uniformly dispersed into the composite film, but it also had a certain slow-release effect on the release of PGE. PGE had high sensitivity under different pH conditions with rich color changes, and the color showed a clear color change from red to yellow-green when the pH increased from 1 to 14. The same change was observed when it was added to the film. In particular, by applying this film to the process of beef preservation, we judged the freshness of beef by monitoring the changes in the TVB-N value and pH value during the storage process of beef and found that the film showed obvious color changes during the storage process of beef, from blue (indicating freshness) to red (indicating non-freshness), and finally to yellow-green (indicating deterioration), which indicated that the color change of the film and the freshness of the beef maintained a highly consistent.

Food freshness monitoring using poly(vinyl alcohol) and anthocyanins doped zeolitic imidazolate framework-8 multilayer films with bacterial nanocellulose beneath as support

Multilayer intelligent freshness labels based on bacterial nanocellulose (BNC), poly(vinyl alcohol) (PVA), and anthocyanins doped zeolitic imidazolate framework-8 (A-ZIF-8) nanocrystals were developed in this study. First, optical, structural, thermal, and surface characterizations of A-ZIF-8 nanocrystals were performed, and the successful incorporation of anthocyanins into ZIF-8 nanocrystals was demonstrated. Next, A-ZIF-8 was added into PVA, and multilayer films were fabricated by spin-coating PVA/A-ZIF-8 layers onto BNC. The effect of the number of deposition cycles on the barrier, mechanical, thermal, morphological, and colorimetric properties of multilayer labels was investigated. The ammonia sensing, mechanical, and barrier properties of the films were shown to be tuned by the number of the PVA/A-ZIF-8 layers on the BNC. Among the developed films, BNC-2PVA/A-ZIF-8 films with the best colorimetric sensitivity toward volatile ammonia were used to monitor the freshness of skinless chicken breasts. The changes in the ΔE and a* values of BNC-2PVA/A-ZIF-8 film demonstrated a good correlation with the microbial and TVB-N levels in samples over 10 days of storage at 4 °C.

A Novel Indicator Based on Polyacrylamide Hydrogel and Bromocresol Green for Monitoring the Total Volatile Basic Nitrogen of Fish

An intelligent indicator was developed by immobilizing bromocresol green (BCG) within the polyacrylamide (PAAm) hydrogel matrix to monitor the total volatile basic nitrogen (TVB-N) content of fish. The FTIR analysis indicated that BCG was effectively incorporated into the PAAm through the formation of intermolecular hydrogen bonds. A thermogravimetric analysis (TGA) showed that the PAAm/BCG indicator had a mere 0.0074% acrylamide monomer residue, meanwhile, the addition of BCG improved the thermal stability of the indicator. In vapor tests with various concentrations of trimethylamine, the indicator performed similarly at both 4 °C and 25 °C. The total color difference values (ΔE) exhibited a significant linear response to TVB-N levels ranging from 4.29 to 30.80 mg/100 g at 4 °C (R2 = 0.98). Therefore, the PAAm/BCG indicator demonstrated stable and sensitive color changes based on pH variations and could be employed in smart packaging for real-time assessment of fish freshness.

Microwave-induced rapid 4D change in color of 3D printed apple/potato starch gel with red cabbage juice-loaded WPI/GA mixture

This study aimed to explore the feasibility of utilizing microparticle mixture (MCPs) comprised of whey protein isolate (WPI), gum Arabic (GA), and freeze-dried red cabbage juice (FDRCJ) as a smart material to realize a rapid color change of 3D printed apple/potato starch gel in response to microwave heating stimulation. The particle size, morphology and thermal stability of WPI/FDRCJ/GA microparticles were examined. Then, the rheology, texture properties and printability of Apple/potato starch gel affected by different concentrations of WPI/FDRCJ/GA microparticles (0, 15, 30, 45, 60% (w/w)) were studied. Results showed that the WPI/FDRCJ/GA microparticles were more thermally stable than pure materials, indicating that the heat-sensitive anthocyanin and other compounds present in FDRCJ were effectively protected by the wall materials (WPI/GA). Moreover, the addition of various microparticle concentrations decreased the samples' mechanical properties but had no significant influence on their loss modulus, viscosity, or printing accuracy. As the microwave heating time increased, the lightness (L*) and yellowness (b*) of microparticle-added samples decreased while the redness (a*) significantly increased (p < 0.05), resulting in a gradual color change from yellow/brown to red. These findings could be useful to produce novel colorful and appealing 4D healthy food products that stimulate consumer appetite.

Fabrication, performance, and potential environmental impacts of polysaccharide-based food packaging materials incorporated with phytochemicals: A review

Although food packaging preserves food's quality, it unfortunately contributes to global climate change since the considerable carbon emissions associated with its entire life cycle. Polysaccharide-based packaging materials (PPMs) are promising options to preserve foods, potentially helping the food industry reduce its carbon footprint. PPMs incorporated with phytochemicals hold promise to address this critical issue, keep food fresh and prolong the shelf life. However, phytochemicals' health benefits are impacted by their distinct chemical structures thus the phytochemicals-incorporated PPMs generally exhibit differential performances. PPMs must be thoughtfully formulated to possess adequate physicochemical properties to meet commercial standards. Given this, this review first-time provides a comprehensive review of recent advances in the fabrication of phytochemicals incorporated PPMs. The application performances of phytochemicals-incorporated PPMs for preserving foods, as well as the intelligent monitoring of food quality, are thoroughly introduced. The possible associated environmental impacts and scalability challenges for the commercial application of these PPMs are also methodically assessed. This review seeks to provide comprehensive insights into exploring new avenues to achieve a greener and safer food industry via innovative food packaging materials. This is paramount to preserve not only food shelf life but also the environment, facilitating the eco-friendly development of the food industry.

Polycaprolactone/Starch/Agar Coatings for Food-Packaging Paper: Statistical Correlation of the Formulations' Effect on Diffusion, Grease Resistance, and Mechanical Properties

Paper is one of the most promising materials for food packaging and wrapping due to its low environmental impact, but surface treatments are often needed to improve its performance, e.g., the resistance to fats and oils. In this context, this research is focused on the formulation of a new paper bio-coating. Paper was coated with liquids containing poly(hexano-6-lactone) (PCL), glycerol and variable percentages of starch (5-10% w/w PCL dry weight), agar-agar (0-1.5% w/w PCL dry weight), and polyethylene glycol (PEG) (5% or 15% w/w PCL dry weight) to improve coating uniformity and diffusion. A design of experiments approach was implemented to find statistically reliable results in terms of the best coating formulation. Coated paper was characterized through mechanical and physical properties. Results showed that agar content (1.5% w/w PCL dry weight) has a beneficial effect on increasing the resistance to oil. Furthermore, the best coating composition has been calculated, and it is 10% w/w PCL dry weight of starch, 1.5% w/w PCL dry weight of agar, and 15% w/w PCL dry weight of PEG.

Hybrid biodegradable materials from starch and hydrocolloid: fabrication, properties and applications of starch-hydrocolloid film, gel and bead

The potential for utilizing starch and hydrocolloids as sustainable biomaterials has garnered significant attention among researchers. The biodegradability and functional properties of composite films, gels, and beads, as well as their environmental friendliness, make them attractive options for a variety of applications. However, the hydrophilicity, brittleness, and regeneration limitations of starch materials can be addressed through the incorporation of non-starch hydrocolloids. This article summarizes the formation mechanisms and interactions of starch-hydrocolloid films, gels, and gel beads, evaluates the factors that affect their structural and functional properties, and presents an overview of the progress made in their physicochemical and functional applications. The structure of starch-hydrocolloid composites is primarily formed through hydrogen bond interactions, and the source, proportion, and preparation conditions of the components are critical factors that affect the properties of the biomaterials. Starch-hydrocolloid films are primarily used for extending the shelf life of food products and detecting food freshness. Starch-hydrocolloid gels are utilized as adsorption materials, wound dressings, and flexible sensors, and starch-hydrocolloid beads are primarily employed for the controlled release of bioactive substances. It is clear that starch-hydrocolloid composites have the potential to develop novel advanced materials for various applications in the food, biological, and materials industries.

Recent advances in pH-sensitive indicator films based on natural colorants for smart monitoring of food freshness: a review

As a new type of packaging method, natural pigment-based pH-sensitive indicator film packaging can be used to intelligently monitor food freshness, provide consumers with intuitive food freshness information, and own the advantages of small size, low cost and intuitive accuracy. Based on the introduction of the principle of natural pigment in pH-sensitive indicator film intelligent packaging, this paper reviews the types of natural pigment indicators (such as anthocyanins, curcumin) and film-forming matrix materials, and systematically discusses the research progress of their application in freshness monitoring in various foods, and points out the limitations of this intelligent packaging in practical applications. In order to provide natural pigment in the application and promotion of pH-sensitive indicator film packaging for monitoring food freshness, further research and development works are required to overcome the current limitations. The needs for further research and developments are outlined.

Exopolysaccharide riclin and anthocyanin-based composite colorimetric indicator film for food freshness monitoring

Food freshness monitoring is vital to ensure food safety. Recently, packaging materials incorporating pH-sensitive films have been employed to monitor the freshness of food products in real time. The film-forming matrix of the pH-sensitive film is essential to maintain the desired physicochemical functions of the packaging. Conventional film-forming matrices, such as polyvinyl alcohol (PVA), have drawbacks of low water resistance, poor mechanical properties, and weak antioxidant ability. In this study, we successfully synthesise PVA/riclin (P/R) biodegradable polymer films to overcome these limitations. The films feature riclin, an agrobacterium-derived exopolysaccharide. The uniformly dispersed riclin conferred outstanding antioxidant activity to the PVA film and significantly improved its tensile strength and barrier properties by forming hydrogen bonds. Purple sweet potato anthocyanin (PSPA) was used as a pH indicator. The intelligent film with added PSPA provided robust surveillance of volatile ammonia and changed its color within 30 s in the pH range of 2-12. This multifunctional colorimetric film also engendered discernible color changes when the quality of shrimp deteriorated, demonstrating its great potential as an intelligent packaging material to monitor food freshness.

The potential of anthocyanin-loaded alginate hydrogel beads for intelligent packaging applications: Stability and sensitivity to volatile amines

pH indicators have emerged as promising tools for real-time monitoring of product freshness and quality in intelligent food packaging applications. However, ensuring the stability of these indicators is critical for practical use. This study aims to evaluate the stability of anthocyanins-loaded alginate hydrogel beads of varying sizes at different temperatures under accelerated light conditions and relative humidity (RH) levels of 53% and 97% during 21 days of storage. Moreover, their sensitivity to the principal spoilage volatiles of muscle food products such as ammonia (NH3), dimethylamine (DMA) and trimethylamine (TMA) was investigated. The half-life of cyanidin-3-glucoside in small hydrogel beads was roughly twice as long as that of the larger beads under accelerated light exposure at 4 °C and they were less likely to undergo noticeable color changes over time. Both sizes of hydrogel beads stored at 97% RH and 4 °C showed color stability over the 21-day period with minimal color variation (|ΔE| ≤ 3). The UV-vis spectra of the purple corn extract exhibited changes across pH 2 to 12, as evidenced by the visible color variations, ranging from pink to green. The limit of detection (LOD) for NH3 was 25 ppm for small beads and 15 ppm for large ones. Both types of beads exhibited similar LOD for DMA and TMA, around 48 ppm. This research showed that alginate hydrogel beads containing anthocyanins from purple corn are a viable option for developing intelligent packaging of muscle foods. Furthermore, the use of hydrogel beads of different sizes can be customized to specific muscle foods based on the primary spoilage compound generated during spoilage.

Investigating the microbial properties of sodium alginate/chitosan edible film containing red beetroot anthocyanin extract for smart packaging in chicken fillet as a pH indicator

The current trend in the production of smart films involves the use of pH-responsive color indicators derived from natural sources. In line with this trend, the aim of this research is to produce edible films from sodium alginate (A) and chitosan (Ch) incorporating red beet anthocyanin (Ac) extract, and to assess the properties of these films and their use as coatings for chicken fillets. The study employed a factorial design to evaluate the effects of treatments C (control), A25%-ch75% (films consisting of 25% sodium alginate and 75% chitosan), and A25%-ch75%-Ac (films consisting of 25% sodium alginate, 75% chitosan, and red beet anthocyanin). The findings indicate that the inclusion of red beet anthocyanin extract did not result in any discernible differences in the FTIR spectra of the film samples. Analysis of the XRD results revealed that the addition of the extract led to a reduction in the crystal structure of the film. Moreover, SEM results demonstrated that the extract caused alterations in the polymer chains and an increase in the porosity of the film matrix. With regard to the chicken fillet samples coated with the film, over time, there was an increase in microbial analysis (total microorganism count and Staphylococcus aureus coagulase-positive) and chemical properties (pH, peroxide, thiobarbituric acid, and nitrogen compounds) for all samples. However, this trend was significantly lower in the samples coated with the Ac extract (P < 0.05). Texture analysis results revealed that the hardness parameter of all samples decreased over the storage period, while the samples containing the Ac extract demonstrated a significant increase in this parameter (P < 0.05). Additionally, the color changes of the pH sensor corresponded to the anthocyanin structure. Based on the results, the smart film composed of sodium alginate/chitosan incorporating red beet anthocyanin extract has the potential to enhance the quality, prolong the shelf life, and decrease the microbial load of chicken fillet when used as a coating. Furthermore, red beet anthocyanin can serve as a suitable indicator for spoilage changes in packaged food products.

A Review on Reinforcements and Additives in Starch-Based Composites for Food Packaging

The research of starch as a matrix material for manufacturing biodegradable films has been gaining popularity in recent years, indicating its potential and possible limitations. To compete with conventional petroleum-based plastics, an enhancement of their low resistance to water and limited mechanical properties is essential. This review aims to discuss the various types of nanofillers and additives that have been used in plasticized starch films including nanoclays (montmorillonite, halloysite, kaolinite, etc.), poly-saccharide nanofillers (cellulose, starch, chitin, and chitosan nanomaterials), metal oxides (titanium dioxide, zinc oxide, zirconium oxide, etc.), and essential oils (carvacrol, eugenol, cinnamic acid). These reinforcements are frequently used to enhance several physical characteristics including mechanical properties, thermal stability, moisture resistance, oxygen barrier capabilities, and biodegradation rate, providing antimicrobial and antioxidant properties. This paper will provide an overview of the development of starch-based nanocomposite films and coatings applied in food packaging systems through the application of reinforcements and additives.

Development of a pH-sensing indicator for shrimp freshness monitoring: Curcumin and anthocyanin-loaded gelatin films

An intelligent pH-sensing indicator containing Roselle (Hibiseus sabdariffa L.) (RS) anthocyanin and curcumin (CR) was developed and characterized as on-package indicator tags to check the freshness of shrimp during the storage at 4°C. FE-SEM and FT-IR analysis showed that RS and CR were successfully immobilized in the gelatin-glycerol film-forming substrate. The addition of various natural dyes increased the thickness and antioxidant action of the colorimetric film. To assess the response to changes in the pH, the colorimetric film was immersed in different buffers. Based on volatile amines secreted by shrimp, a test application of a colorimetric film containing natural dyes at a ratio of CR:RS = 1:4 (v/v) was conducted in shrimp at 4°C. The total volatile basic nitrogen (TVB-N) and the pH of shrimp were monitored during refrigerated storage for 10 days, and the color changes of the indicator were recorded simultaneously. The results indicated that the designed colorimetric film could produce various colors, which are thought to be indicative of the freshness and spoilage of packaged shrimp. Therefore, the target film can be utilized as a promising smart packaging material for monitoring the freshness of shrimp and aquatic products in real time.

A pH-sensitive intelligent packaging film harnessing Dioscorea zingiberensis starch and anthocyanin for meat freshness monitoring

Abundant starch was isolated from Dioscorea zingiberensis C.H. Wright, a novel and underutilized industrial crop resource. In this study, an intelligent packaging film able to indicate food freshness was developed and characterized. D. zingiberensis starch (DZS) was bleached first, and its particle size, total starch content, amylose content, and gelatinization temperature were then measured. Butterfly pea (Clitoria ternatea Linn.) flowers were selected as the source of polyphenols, which rendered the prepared film intelligent and progressively blue-violet. SEM and FT-IR analyses showed the homogeneous dispersion of butterfly pea flower extract (BPE) in the film. The BPE-loaded film showed improved flexibility and resistance to UV and oxidation while maintaining sufficient mechanical strength and physical properties. Moreover, the film underwent a distinguishable color change from red to blue-violet and finally to green-yellow with increasing pH from 2 to 13. Similar color alteration also occurred when the film was exposed to ammonia. When the film was used to monitor the freshness of chicken stored at room temperature, it exhibited an obvious color change, implying its deterioration. Therefore, the newly developed BPE-DZS film, which was produced from readily accessible natural substances, can serve as an intelligent packaging material, indicating food freshness and prolonging shelf life.

Covalently phenolated-β-lactoglobulin-pullulan as a green halochromic biosensor efficiency monitored Barramundi fish's spoilage

The effect of the covalent binding between anthocyanins extracted from purple potato peels and beta-lactoglobulin (β-Lg) on its ability to fabricate a green/smart halochromic biosensor combined with pullulan (Pul) was studied. The physical, mechanical, colorimetry, optical, morphological, stability, functionality, biodegradability, and applicability of β-Lg/Pul/Anthocyanin biosensors to monitor the Barramundi fish's freshness during storage were entirely evaluated. The docking and multispectral results proved that β-Lg could be successfully phenolated with anthocyanins and subsequently interacted with Pul via H-bonding and other forces which mainly subsequently form the smart biosensors. Phenolation with anthocyanins significantly heightened the mechanical, moisture resistance, and thermal steadiness of β-Lg/Pul biosensors. Anthocyanins also nearly duplicated the bacteriostatic and antioxidant activities of β-Lg/Pul biosensors. The biosensors changed the color associated with the loss in freshness of the Barramundi fish, mostly due to the ammonia production and pH-alteration throughout fish deterioration. Most importantly, β-Lg/Pul/Anthocyanin biosensors are biodegradable and decomposed within ∼30 d of simulated environmental circumstances. Overall, β-Lg/Pul/Anthocyanin smart biosensors could minimize the usage of plastic packaging materials and employ to monitor the freshness of stored fish and fish-stuffs.

Development of intelligent and active potato starch films based on purple corn cob extract and molle essential oil

The present study aims to develop of an active and "intelligent" film that uses potato starch as a polymeric matrix, anthocyanins from purple corn cob as a natural dye, and molle essential oil as an antibacterial compound. The color of anthocyanin solutions is pH-dependent, and the developed films shows a visual color change from red to brown after immersion in solutions with pH values ranging from 2 to 12. SEM and FTIR analyses suggested that anthocyanins have favorable dispersibility and good compatibility with the starch-glycerol matrix. The study found that both anthocyanins and molle essential oil significantly enhanced the ultraviolet-visible light barrier performance; moreover, tensile strength, elongation at break, and elastic modulus reached values of 3.21 MPa, 62.16 %, and 12.87 MPa, respectively. The biodegradation rate in vegetal compost also accelerated during the three-week period, achieving a weight loss of 95 %. Moreover, the film presented an inhibition halo for Escherichia coli, indicating its antibacterial activity. The results suggest that the developed film has the potential to be used as food-packaging material.

A Novel Intelligent Indicator Film: Preparation, Characterization, and Application

The development of intelligent indicator film that can detect changes in food quality is a new trend in the food packaging field. The WPNFs-PU-ACN/Gly film was prepared based on whey protein isolate nanofibers (WPNFs). Anthocyanin (ACN) and glycerol (Gly) were used as the color indicator and the plasticizer, respectively, while pullulan (PU) was added to enhance mechanical properties of WPNFs-PU-ACN/Gly edible film. In the study, the addition of ACN improved the hydrophobicity and oxidation resistance of the indicator film; with an increase in pH, the color of the indicator film shifted from dark pink to grey, and its surface was uniform and smooth. Therefore, the WPNFs-PU-ACN/Gly edible film would be suitable for sensing the pH of salmon, which changes with deterioration, as the color change of ACN was completely consistent with fish pH. Furthermore, the color change after being exposed to grey was evaluated in conjunction with hardness, chewiness, and resilience of salmon as an indication. This shows that intelligent indicator film made of WPNFs, PU, ACN, and Gly could contribute to the development of safe food.

Progress and Prospective of the Industrial Development and Applications of Eco-Friendly Colorants: An Insight into Environmental Impact and Sustainability Issues

Color is the prime feature directly associated with the consumer's attraction and choice of their food. The flavor, safety, and nutritional value of any food product are directly associated with the food color. Natural and synthetic colorants (dyes and pigments) have diversified applications in various sectors such as food, feed, pharmaceutical, textiles, cosmetics, and others. Concerning the food industry, different types of natural and synthetic colorants are available in the market. Synthetic food colorants have gained popularity as they are highly stable and cheaply available. Consumers worldwide prefer delightful foodstuffs but are more concerned about the safety of the food. After its disposal, the colloidal particles present in the synthetic colorants do not allow sunlight to penetrate aquatic bodies. This causes a foul smell and turbidity formation and gives a bad appearance. Furthermore, different studies carried out previously have presented the toxicological, carcinogenic effects, hypersensitivity reactions, and behavioral changes linked to the usage of synthetic colorants. Natural food colorings, however, have nutraceutical qualities that are valuable to human health such as curcumin extracted from turmeric and beta-carotene extracted from carrots. In addition, natural colorants have beneficial properties such as excellent antioxidant properties, antimutagenic, anti-inflammatory, antineoplastic, and antiarthritic effects. This review summarizes the sources of natural and synthetic colorants, their production rate, demand, extraction, and characterization of food colorants, their industrial applications, environmental impact, challenges in the sustainable utilization of natural colorants, and their prospects.

Novel color stability and colorimetry-enhanced intelligent CO2 indicators by metal complexation of anthocyanins for monitoring chicken freshness

This study aims to improve the color stability of anthocyanins and develop a CO2-sensitive indicator based on black goji anthocyanin (BGA) extract. Although the BGA extracts showed distinct color changes, such as red-purple-blue, their intrinsic color diminished after 24 h. A metal complexation method was used for the high color stability of BGA. BGA extracts were chelated with various concentrations of Al3+ [0 - 20% (w/w)]. It showed high color stability and strong intensity in a dose-dependent manner. A CO2-sensitive indicator sachet was developed using hydroxypropyl methylcellulose hydrogel, based on 5% (w/w) Al3+-BGA complexes. The indicator was applied to the chicken breast and detected its spoilage after 3 days with its changing color to greyish blue, due to the microbial growth to 7.00 log CFU/g. These results demonstrated the possibility of chelated anthocyanin complexes as indicating dyes and the ability to monitor the food quality changes through noticeable color changes.

The properties of pH-responsive gelatin-based intelligent film as affected by ultrasound power and purple cabbage anthocyanin dose

A pH-sensitive intelligent film was prepared using gelatin as base substrate and purple cabbage anthocyanins (PCA) as indicator with the aid of ultrasound. Fourier transforms infrared and X-ray diffraction analysis showed that 600 W ultrasound brought changes to characteristic bands of gelatin and PCA, and flattened diffraction peak around 2θ = 20°. Film prepared with 600 W ultrasound exhibited high tensile strength and elongation at break and showed high transition temperature and surface hydrophobicity by differential scanning calorimetry and contact angle analysis. The incorporation of <0.35 % PCA had no effect on mechanical properties of films, but it improved the antioxidative activity. Films with 0.14 %, 0.21 % and 0.28 % PCA suggested pronounced color difference at pH 5-8, in accordance with the sharp ΔE difference. Films with 0.28 % PCA was applied for monitoring chilled-stored fish quality. It showed visible color change from pink to atrovirens during storage. The difference of ΔE at various days was ≥5 and ΔE highly correlated with total volatile basic nitrogen. Therefore, gelatin along with PCA under appropriate ultrasound treatment could prepare intelligent film to preserve and monitor the quality of chilled-stored fish.

Preparation of an indicator film based on pectin, sodium alginate, and xanthan gum containing blueberry anthocyanin extract and its application in blueberry freshness monitoring

An active pH-sensitive film based on pectin-sodium alginate-xanthan gum composite film (PAX) was prepared, containing blueberry anthocyanin extract (BAEs), to monitor the freshness of blueberries. The effects of different contents of BAEs on the microstructure and physical properties of intelligent polysaccharide films were comprehensively evaluated. It was found that 75-BAEs-PAX film had a solid response to pH value and showed different and easily distinguishable colors at different pH values. In addition, when the freshness of blueberries stored at different temperatures (-1 °C, 4 °C, 10 °C, 15 °C, 25 °C) was monitored, the color of 75-BAEs-PAX film changed from purple to light pink from neutral to acidic environment, which was consistent with the change of pH value of blueberries from fresh to spoilage. The Arrhenius equation verified that the difference between the activation energy of the indicator film and the blueberry quality was less than 25 kJ/mol. Therefore, the 75-BAEs-PAX film can be used as an indicator film for blueberries freshness monitoring. In this study, the freshness of blueberries was monitored by BAEs, and the purpose of using ontology to monitor ontology was achieved. The freshness of blueberries was visualized during storage and transportation, which could effectively reduce the waste of blueberries. In the future, the method of ontology monitoring ontology could be extended to other foods.

Alizarin: Prospects and sustainability for food safety and quality monitoring applications

Active and intelligent food packaging has emerged to ensure food safety, quality, or spoilage monitoring and extend the shelf life of food. The development of intelligent packaging has accelerated significantly in recent years with a focus on monitoring changes in the quality of packaged products in real-time throughout the food supply chain. As one of the popular natural colorants, alizarin has attracted much consideration due to its excellent functional properties and quality to color change under varying pH. Alizarin is an efficient and cost-effective biomaterial with numerous biological features such as antioxidant, antibacterial, non-cytotoxic, and antitumor. This review focuses on an in-depth summary and prospects for alizarin as a natural and safe colorant that has the potential to be incorporated into intelligent packaging to track the freshness of packaged foodstuffs. The use of alizarin as an intelligent packaging agent shows huge potential for the application of food packaging and brings it one step closer to real-time monitoring of food quality throughout the supply chain. Finally, various limitations and future requirements are discussed to underscore the importance of developing alizarin-based intelligent functional food packaging systems.

Preparation and characterization of an intelligent film based on fish gelatin and Coleus scutellarioides anthocyanin to monitor the freshness of rainbow trout fish fillet

In this study, a pH-sensitive indicator based on fish gelatin and Coleus scutellarioides anthocyanin extract (CSAE) was prepared and characterized. Films were prepared using the solvent casting method and different levels of CSAE, including 10 ml (CSG1), 20 ml (CSG2), and 30 ml (CSG3), and 0 ml (CSG0) as a control sample. The mechanical, optical, and pH sensing of active films and the release of anthocyanins from the films were investigated. The relationship between the total volatile basic nitrogen (TVB-N) of fish fillets and a* color index of films was studied. By incorporation of CSAE, the flexibility of films increased, while the tensile strength and UV-Vis light transmittance through the films decreased (p < .05). The films containing the CSAE had a darker, yellowish, and reddish color than the control film. There was a significant relationship between the pH variation and the film color. The films had a purple color at acidic pH, and their color changed to green at an alkaline pH, indicating the sensitivity of the produced films to pH changes. There was a significant relationship between the TVB-N value of fish fillets and the a* index of the film during the 16 h storage time. The results showed that by increasing TVB-N values of the fillets, the a* color index decreased, and the films' color changed from purple to colorless. In summary, the active films prepared with fish gelatin and CSAE could be used as pH-sensitive intelligent packaging to display the freshness of fishery products.

Bilayer pH-sensitive colorimetric indicator films based on zein/gellan gum containing black rice (Oryza sativa L.) extracts for monitoring of largemouth bass (Micropterus salmoides) fillets freshness

Anthocyanins as natural pH-sensitive material can be used to determine the freshness of largemouth bass (Micropterus salmoides) fillets. However, it is easily degraded. Using zein as the protective layer to improve the light blocking ability of the film, gellan gum (GG) and black rice extracts (BRE) as the sensing layer, a bilayer colorimetric indicator film for monitoring fish spoilage was developed. The functionality and stability of bilayer film and GG single film were compared. As compared to GG single film, Zein/GG bilayer film had stronger intermolecular interactions, higher mechanical properties, and higher optical barrier properties. Notably, Zein/GG-8 % BRE bilayer film exhibited higher stability than GG-8 % BRE film when the films were exposed to room temperature for 30 days. Zein/GG-8 % BRE bilayer film were further used to monitor freshness of largemouth bass fillets during storage. Zein/GG-8 % BRE bilayer film demonstrated a noticeable color change from red to brown when largemouth bass fillets spoiled. Moreover, the ∆E of films showed a good correlation with TVB-N of largemouth bass fillets (R² = 0.985). Our research results show that the Zein/GG-BRE bilayer indicator film has great potential application prospects in monitoring fish freshness.

Application of intelligent packaging for meat products: A systematic review

BACKGROUND

Today, in response to consumer demand and market trends, the development of new packaging with better performance such as intelligent packaging has become more important. This packaging system is able to perform intelligent functions to increase shelf life, increase safety and improve product quality.

OBJECTIVES

Recently, various types of packaging systems are available for meat products, especially cooked, fresh and processed meats. But because meat products are very perishable, monitoring their quality and safety in the supply chain is very important. This systematic article briefly reviews some of the recent data about the application of intelligent packaging in meat products.

METHODS

The search was conducted in Google Scholar, Science Direct, Elsevier, Springer, Scopus, and PubMed, from April 1996 to April 2021 using a different combination of the following keyword: intelligent packaging, and meat.

RESULTS

The results showed that the intelligent packaging presents several benefits compared to traditional packaging (e.g., antimicrobial, antioxidant, and shelf life extension) at the industrial processing level. Thus, these systems have been applied to improve the shelf life and textural properties of meat and meat products.

CONCLUSIONS

It is necessary to control the number of intelligent compounds that are included in the packaging as they clearly influence the quality and nutritional properties as well as the final cost of the food products.

Antimicrobial Bilayer Film Based on Chitosan/Electrospun Zein Fiber Loaded with Jaboticaba Peel Extract for Food Packaging Applications

This work focused on developing an active bilayer film based on natural extract. Thus, the jaboticaba peel extract (JPE) was produced and characterized and showed promising application as a natural additive in biopolymeric materials. The zein fiber and bilayer films were produced using a chitosan film (casting) and zein fiber (electrospinning), with and without JPE. All samples were evaluated according to thickness, solubility in water, water vapor permeability, and main diameter, and for these, zein fiber, chitosan/zein fiber, and chitosan/zein fiber + 3% JPE showed values of 0.19, 0.51, and 0.50 mm, 36.50, 12.96, and 27.38%, 4.48 × 10^-9, 1.6 × 10^-10, and 1.58 × 10^-10 (g m^-1 Pa^-1 s^-1), and 6.094, 4.685, and 3.620 μm, respectively. These results showed that the addition of a second layer improved the barrier properties of the material when compared to the monolayer zein fiber. The thermal stability analysis proved that the addition of JPE also improved this parameter and the interactions between the components of the zein fiber and bilayer films; additionally, the effective presence of JPE was shown through FTIR spectra. In the end, the active potential of the material was confirmed by antimicrobial analysis since the bilayer film with JPE showed inhibition halos against E. coli and S. aureus.

Preparation of Wide-Domain pH Color-Changing Nanocapsules and Application in Hydrogel Fibers

In recent years, there has been an increase in demand for pH color-changing materials. These materials can visually communicate signals to people by connecting pH changes with color information. Embedding pH indicators into fibers to create flexible color-changing materials is an effective way to develop daily wearable products. For the stability of the indicator and the indirect contact of the indicator with the human body, it is usually necessary to encapsulate it in capsules. In this study, different pH indicators (Thymol Blue-TB, Bromocresol Green-BCG, and Bromocresol Purple-BCP) were mixed into a wide-domain pH color-changing indicator and encapsulated with ethyl cellulose (EC) by the flash nanoprecipitation (FNP) method using a new-type droplet-shaped confined impinging jet mixer. The effects of flow rate, core-to-wall ratio, and mixed solution concentration on the formation of the nanocapsules were investigated. In addition, the morphology, particle size, size distribution, dispersion stability, and encapsulation efficiency were systematically studied. At a core-to-wall ratio of 1:2, a mixed solution with a concentration of 6 mg/mL and a feed flow rate of 40 mL/min produced nanocapsules with an average particle size of 141.83 ± 0.98 nm and a PDI of 0.125 ± 0.01. Furthermore, a zeta potential with a range of -31.83 ± 0.23 mV and an encapsulation efficiency of 75.20 ± 1.72% were observed at 1:2 core-to-wall ratios. It was concluded that the color of the nanocapsules continuously changed from yellow to green and green to blue when the pH range was increased from 3 to 10. The color-changing nanocapsules were then embedded into sodium alginate hydrogel fibers, resulting in the same color-changing trend (pH 3-10) as that obtained for the nanocapsules. This study can be useful for the pH monitoring of various body fluids, such as wound exudate, urine, and sweat.

Intelligent pH indicator composite film based on pectin/chitosan incorporated with black rice anthocyanins for meat freshness monitoring

With the improvement of consumer awareness of food safety and the increasing concern about plastic pollution, the development of novel intelligent packaging film is imminent. This project aims to develop an environmentally friendly pH-sensitive intelligent food packaging film for meat freshness monitoring. In this study, anthocyanin-rich extract from black rice (AEBR) was added to composite film formed by the co-polymerisation of pectin and chitosan. AEBR showed strong antioxidant activity, and different colour responses to different conditions. The mechanical properties of the composite film remarkably improved when AEBR was incorporated into. Besides, the introduction of anthocyanins enables the colour of composite film to change from red to blue with the degree of meat spoilage increased which shows the indicative effect of composite films on meat putrification. Therefore, the AEBR-loaded pectin/chitosan film could be used as an indicator to monitor meat freshness in real-time.