A starch-based pH-sensing and ammonia detector film containing betacyanin of paperflower for application in intelligent packaging of fish

High water resistance starch based intelligent label for the freshness monitoring of beverages

The traditional starch-based intelligent freshness labels struggle to maintain long-term structural stability when exposed to moisture. To solve this problem, we prepared composite crosslinked labels using phytic acid for double crosslinking of corn starch and soybean isolate proteins, with anthocyanin serving as the chromogenic dye. The mechanical properties, hydrophobic characteristics, and pH responsivity of these crosslinked labels were assessed in this study. The prepared double-crosslinked labels showed reduced moisture content (15.96%), diminished swelling (147.21%), decreased solubility (28.55%), and minimized water permeability, which suggested that they have enhanced hydrophobicity and densification. The crosslinked labels demonstrated the ability to maintain morphological stability when immersed in water for 12 h. Additionally, the mechanical properties of the crosslinked labels were enhanced without compromising their pH-sensing capabilities, demonstrated a color response visible to the naked eye for milk and coconut water freshness monitoring, suggesting great potential for application in beverages freshness monitoring.

A sensing label or gel loaded with an NIR emission fluorescence probe for ultra-fast detection of volatile amine and fish freshness

A simple benzopyran-based fluorescence probe DCA-Apa detection of volatile amine has been synthesized. DCA-Apa can recognize volatile amines by dual channel mode (changing from blue to light yellow in sunlight, and from weak pink to orange under 365 nm) in pure water system. DCA-Apa has the advantages of ultra-fast response (∼6 s), NIR emission (655 nm), and a good fluorescence response for many amines. The sensing label or gel loaded with DCA-Apa was prepared by the dipping or mixing method using filter paper or gelatin as solid carriers, which can identify volatile amine vapor and monitor the freshness of salmon by colorimetric and fluorescent dual channels. When the color of the label changes to light yellow-green or the fluorescence of the label becomes orange fluorescence (365 nm UV lamp), it indicates that the fish has rotted. The two-channel method makes up for the deficiency of the single colorimetric method, and establishes a theoretical foundation for more precise assessment of fish freshness.

Development of dual-channel starch-based film incorporated with betanin@β-cyclodextrin inclusion complex and berberine for indicating shrimp freshness

In this study, the β-cyclodextrin encapsulated betanin (BET@β-CD) with improved thermal stability and retention as well as the berberine (BBR) with aggregate induced luminescence effect were incorporated into corn amylose (CA) biomatrix to develop colorimetric/fluorescent dual-channel smart film. Results shown that the added functional components were uniformly distributed in the film matrix. The high tensile strength (78.87%), low water solubility (31.15%) and water vapor permeability (1.24 × 10-10 g Pa-1 s-1 m-1) of the film predicted its acceptable stability. It was worth mentioning that the film displayed excellent responsiveness to volatile ammonia (0.025-25 mg/mL) with at least 4 times recyclability. Application experiment demonstrated that the film can achieve macroscopic dynamic monitoring of the freshness of shrimps stored at 25 °C, 4 °C, -20 °C under daylight (red to yellow) and UV light (yellow-green to blue-green). Thus, the study suggests an attractive and effective strategy for constructing dual-mode smart packaging materials for food freshness detection.

Ammonia/pH super-sensitive colorimetric labels based on gellan gum, sodium carboxymethyl cellulose, and dyes for monitoring freshness of lamb meat

This study aimed to develop an ammonia and pH super-sensitive label by incorporating methyl red and bromothymol blue (MR-BTB, MB) into gellan gum/sodium carboxymethyl cellulose (GG/CMC-Na, GC). Furthermore, E-nose as an auxiliary tool combined with the labels to monitor meat freshness. Results showed that MB had more color change than pure MR or BTB, and the detection limit of ammonia about the MR-BTB (1:2) group was only 2.82 ppm. The addition of MB significantly increased tensile strength, moisture content, and water solubility, but decreased elongation at break and transmittance of the GC label (p < 0.05). The result of FTIR and SEM indicated the formation of hydrogen bonds and well compatibility between MB and GC. Furthermore, the color of the GC-10.0MB label was constantly obviously changing during meat storage, indicating that the GC-10.0MB label had great potential for monitoring the freshness of the lamb meat. A high correlation was found between ΔE of GC-10.0MB label and TVB-N (R2 = 0.9092) and pH (R2 = 0.9114) of meat. Interestingly, the high correlation between ΔE of GC-10.0 MB label and the response value of S2 (R2 = 0.7531), S6 (R2 = 0.9921), and S7 sensor (R2 = 0.8325) of E-nose was also found.

Intelligent Food Packaging: Quaternary Ammonium Chitosan/Gelatin Blended Films Enriched with Blueberry Anthocyanin-Derived Cyanidin for Shrimp and Milk Freshness Monitoring

Blueberry anthocyanin-derived cyanidin (BAC) was used to prepare a series of responsive food freshness packaging films by compounding it with quaternary chitosan (QC) and gelatin (G). The fundamental properties, pH sensitivity, and functional attributes of the films were examined. The BAC solutions exhibited notable variations in color (from red to pink to violet) under different pH conditions. The incorporation of BAC resulted in improved UV-vis shielding capabilities but compromised the mechanical strength of the films (with tensile strength values from 85.02 to 44.89 MPa, elongation at break from 13.08% to 3.6%, and water vapor transmission rates from 5.24 × 10-9 to 7.80 × 10-9 g m-1 s-1 Pa-1). The QC-G-BAC films, containing 5-15 wt% BAC, exhibited noticeable color changes in acidic/ammonia environments within a short timeframe, easily discernible to the naked eye. Furthermore, the inclusion of BAC significantly enhanced the antioxidant and antimicrobial properties of the films. The addition of 5-15 wt% BAC to QC-G-BAC films could be employed for assessing the freshness of fresh shrimp (from red to dark red) and pasteurized milk (from red to dark earthy yellow). Among them, the total color difference (ΔE) of QC-G-BAC5 film was significantly correlated with the pH, acidity, and total colony count of pasteurized milk (R = 0.846, -0.930, -0.908, respectively). This new concept in smart packaging offers a straightforward and user-friendly freshness indicator.

Plant betalains-mixed active/intelligent films for meat freshness monitoring: A review of the fabrication parameters

The plant pigments called betalains are nutritionally safe polar compounds. They are subdivided into betaxanthins (having orange to yellow hues) and betacyanins (purple to red violet hues). Betacyanins change color with a change in pH, particularly in the range 6-8 and 9-11. Perishable foods like fish, chicken, beef, pork, and others tend to release total volatile base-nitrogen (TVB-N) during storage or deterioration, which leads to a change in the pH of pH-sensitive materials in the vicinity. pH-sensitive pigment-incorporated polymeric films with inherent active properties (or active/intelligent films) are increasingly being studied as an alternative to synthetic pH indicators to detect the accumulation of TVB-N by changing its color to indicate the stage of perishable food spoilage. There are many methods of developing such films under different conditions using different bio-based biodegradable polymer(s) and biocompatible plasticizer combinations. Among the reported methods, solution casting method has been the preferred one in most studies covered in this review. This method can be carried out under mild conditions. As such, betacyanins-incorporated polymeric films essentially require mild processing conditions because of their heat sensitivity, which will invariably affect the performance in food freshness monitoring. In this review, film fabrication parameters like temperature and duration of dissolution of polymers, plasticizer concentration, pH of the film-forming solution, film drying, and conditioning/aging, have been critically appraised based on the available literature. The lack of studies on the safety of active/intelligent films has been systematically highlighted in this review to focus future studies on this area.

Graphical abstract

Nelumbo nucifera flower extract incorporated alginate/polyvinyl alcohol films as a sustainable pH indicator for active food packaging applications

In recent years, there has been a growing demand for environmentally friendly smart packaging materials. Therefore, in this study, we developed an eco-friendly pH-sensitive indicator film through the solvent casting process, incorporating alginate, polyvinyl alcohol, garlic, and Nelumbo nucifera flower extract. The effect of extract on the chemical and physical properties of the film were extensively studied using various characterization techniques. XRD and FTIR reveal the strong interaction between the polymers and the extract. The incorporation of the extract influenced various parameters such as swelling behavior, water solubility, and moisture content, while also improving the film's thermal stability, biodegradability, as well as its antioxidant and antimicrobial properties. Interestingly, the film exhibited a color change in response to pH change. During shrimp storage, the film showed a visible transition from purple to green, indicating shrimp spoilage. Additionally, the film's ability to detect freshness was confirmed by measuring total volatile basic nitrogen (TVBN). These findings suggest that the PVA/alginate/garlic/Nelumbo nucifera film shows promise as an intelligent packaging material for real-time food monitoring applications.

A review on improving the sensitivity and color stability of naturally sourced pH-sensitive indicator films

Naturally sourced pH-sensitive indicator films are of interest for real-time monitoring of food freshness through color changes because of their safety. Therefore, natural pigments for indicator films are required. However, pigment stability is affected by environmental factors, which can in turn affect the sensitivity and color stability of the pH-sensitive indicator film. First, natural pigments (anthocyanin, betalain, curcumin, alizarin, and shikonin) commonly used in pH-sensitive indicator films are presented. Subsequently, the mechanisms behind the change in pigment color under different pH environments and their applications in monitoring food freshness are also described. Third, influence factors, such as the sources, types, and pH sensitivity of pigments, as well as environmental parameters (light, temperature, humidity, and oxygen) of sensitivity and color stability, are analyzed. Finally, methods for improving the pH-sensitive indicator film are explored, encapsulation of natural pigments, incorporation of a hydrophobic film-forming matrix or function material, and protective layer have been shown to enhance the color stability of indicator films, the addition of copigments or mental ions, blending of different natural pigments, and the utilization of electrospinning have been proved to increase the color sensitivity of indicator films. This review could provide theoretical support for the development of naturally sourced pH-sensitive indicator films with high stability and sensitivity and facilitate the development in the field of monitoring food freshness.

Natural colorant incorporated biopolymers-based pH-sensing films for indicating the food product quality and safety

The current synthetic plastic-based packaging creates environmental hazards that impact climate change. Hence, the topic of the current research in food packaging is biodegradable packaging and its development. In addition, new smart packaging solutions are being developed to monitor the quality of packaged foods, with dual functions as food preservation and quality indicators. In the creation of intelligent and active food packaging, many natural colorants have been employed effectively as pH indicators and active substances, respectively. This review provides an overview of biodegradable polymers and natural colorants that are being extensively studied for pH-indicating packaging. A comprehensive discussion has been provided on the current status of the development of intelligent packaging systems for food, different incorporation techniques, and technical challenges in the development of such green packaging. Finally, the food industry and environmental protection might be revolutionized by pH-sensing biodegradable packaging enabling real-time detection of food product quality and safety.

Sustainable strategies for using natural extracts in smart food packaging

The growing demand for sustainable and eco-friendly food packaging has prompted research on innovative solutions to environmental and consumer health issues. To enhance the properties of smart packaging, the incorporation of bioactive compounds derived from various natural sources has attracted considerable interest because of their functional properties, including antioxidant and antimicrobial effects. However, extracting these compounds from natural sources poses challenges because of their complex chemical structures and low concentrations. Traditional extraction methods are often environmentally harmful, expensive and time-consuming. Thus, green extraction techniques have emerged as promising alternatives, offering sustainable and eco-friendly approaches that minimise the use of hazardous solvents and reduce environmental impact. This review explores cutting-edge research on the green extraction of bioactive compounds and their incorporation into smart packaging systems in the last 10 years. Then, an overview of bioactive compounds, green extraction techniques, integrated techniques, green extraction solvents and their application in smart packaging was provided, and the impact of bioactive compounds incorporated in smart packaging on the shelf lives of food products was explored. Furthermore, it highlights the challenges and opportunities within this field and presents recommendations for future research, aiming to contribute to the advancement of sustainable and efficient smart packaging solutions.

Eggshell membrane as a novel and green platform for the preparation of highly efficient and reversible curcumin-based colorimetric sensor for the monitoring of chicken freshness

Herein, for the very first time, we report a paper-like biomass, eggshell membrane (ESM), as a suitable platform for the fabrication of a colorimetric sensor (E-Cot). Green ethanolic extract, curcumin (CUR), was used as a sensing material to coat with the ESM. The present E-Cot effectively changed its color (yellow to red) in the real-time monitoring for chicken spoilage. The E-Cot exhibits barrier properties due to its inherent semi-permeability characteristics. Interestingly, the E-Cot showed a significant change in total color difference value (ΔE, 0 days - 0.0-39.6, after 1 day - 39.6-42.1, after 2 days - 42.1-53.6, after 3 days- 53.6-60.1, and after 4 days - 60.1-66.3, detectable by the naked eye) in the real-time monitoring for chicken freshness. In addition, the present E-Cot smart colorimetric sensor is reversible with a change in pH, and the sensor can be reused. Further, the hydrophobic nature of the E-Cot was confirmed by water contact angle analysis (WCA, contact angle of 101.21 ± 8.39). Good antibacterial, barrier, and optical properties of the present E-Cot were also found. Owing to the advantages such as green, efficient, cost-effective, biodegradable, reusable, sustainable, and simple preparation, we believe that the present E-Cot would be a more attractive candidate.

Effect of kaolin impregnated with calico plant extract on properties of starch films

Starch film has poor tensile properties and poor water resistance. We aimed to improve these properties by adding kaolin impregnated with calico plant extract (CP-Kaolin). UV-Vis spectrophotometry showed that the calico plant extract (CPE) contained 4867.52 mg/L of total phenolic compounds and betacyanins were the predominant constituents. CP-Kaolin was characterized by Fourier transform infrared spectroscopy (FTIR), zeta potential, scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis. FTIR analysis showed that betacyanins were adsorbed on kaolin via hydrogen bonding. Zeta potential analysis confirmed the adsorption of betacyanins on kaolin. The intercalation of betacyanins between kaolin platelets was observed by XRD. SEM revealed that CP-Kaolin was well dispersed and embedded within the starch matrix. It was found that the addition of 10 wt% of CP-Kaolin increased the water resistance, tensile strength and thermal stability of starch film. Moreover, starch film containing 10 wt% of CP-Kaolin was sensitive to the change in pH of the fish during storage. Therefore, the addition of CP-Kaolin improved the properties of starch film and starch film composite with CP-Kaolin could be applied as a smart packaging in the food industry.

Intelligent packaging based on chitosan/fucoidan incorporated with coleus grass (Plectranthus scutellarioides) leaves anthocyanins and its application in monitoring the spoilage of salmon (Salmo salar L.)

The innovation of this study was to develop a novel biodegradable intelligent packaging based on chitosan/fucoidan combined with different amounts (1, 3 and 5 wt% on chitosan basis) of coleus grass (Plectranthus scutellarioides) leaves anthocyanins (CGL) to monitor the spoilage of salmon (Salmo salar L.). The addition of fucoidan improved the barrier and mechanical properties of the chitosan films (CS) due to hydrogen bonds and intermolecular electrostatic interactions. Moreover, the addition of CGL not only improved the physical properties but also improved the biological activity of chitosan/fucoidan film (CF). The DPPH and ABTS radical scavenging activity of CF contained 5 wt% CGL was 1.83 and 1.75 times than CF, respectively. The inhibition zone size of CF films containing 5 wt% CGL (CF-5%CGL) was approximately 2.04 (Escherichia coli) and 2.16 (Staphylococcus aureus) times higher than that of CF. Moreover, CF-CGL displayed obvious color changes in different pH environments and is highly sensitive to ammonia gas. The CF-CGL has visible color changes during the monitoring of salmon spoilage and extended the shelf life of salmon. According to our findings, CF-CGL film might be employed as a possible intelligent packaging material for monitoring and preserving salmon in the future.

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.

Chitosan Film Sensor for Ammonia Detection in Microdiffusion Analytical Devices

Chitosan films have attracted increased attention in the field of sensors because of chitosan's unique chemico-physical properties, including high adsorption capacity, filmability and transparency. A chitosan film sensor was developed through the dispersion of an ammonia specific reagent (Nessler's reagent) into a chitosan film matrix. The chitosan film sensor was characterized to assess the film's properties by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). A gas diffusion device was prepared with the chitosan film sensor, enabling the collection and detection of ammonia vapor from biological samples. The chitosan film sensor color change was correlated with the ammonia concentration in samples of human serum and artificial urine. This method enabled facile ammonia detection and concentration measurement, making the sensor useful not only in clinical laboratories, but also for point-of-care devices and wherever there is limited access to modern laboratory facilities.

Development of a multifunctional food packaging for meat products by incorporating carboxylated cellulose nanocrystal and beetroot extract into sodium alginate films

Consumers' pursuit for safe meat products is challenging to develop smart food packaging with proper mechanical properties and multifunctional properties. Therefore, this work attempted to introduce carboxylated cellulose nanocrystal (C-CNC) and beetroot extract (BTE) into sodium alginate (SA) matrix films to enhance their mechanical properties and endow them with antioxidant properties and pH-responsive capacity. The rheological results showed the C-CNC and BTE were consistently dispersed in the SA matrix. The incorporation of C-CNC made the surface and cross-section of the films rough but still dense, thus significantly improving the mechanical properties of the films. The integration of BTE provided antioxidant properties and pH responsiveness without significantly changing the thermal stability of the film. The highest tensile strength (55.74 ± 4.52 MPa) and strongest antioxidant capacities were achieved for the SA-based film with BTE and 10 wt% C-CNC. Additionally, the films possessed higher UV-light barrier properties after incorporating BTE and C-CNC. More notably, the pH-responsive films discolored when TVB-N value exceeded 18.0 mg/100 g during storage of pork at 4 °C and 20 °C, respectively. Therefore, the SA-based film with enhanced mechanical and functional properties has a high potential for quality detection in smart food packaging applications.

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.

Betalains as promising natural colorants in smart/active food packaging

Betalains are water-soluble nitrogen pigments with beneficial effects, including antioxidant, antimicrobial, and pH-indicator properties. The development of packaging films incorporated with betalains has received increasing attention because of pH-responsive color-changing properties in the colorimetric indicators and smart packaging films. As such, intelligent and active packaging systems based on biodegradable polymers containing betalains have been recently developed as eco-friendly packaging to enhance the quality and safety of food products. Betalains could generally improve the functional properties of packaging films, such as higher water resistance, tensile strength, elongation at break, and antioxidant and antimicrobial activities. These effects are dependent on betalain composition (about its source and extraction), content, and the kind of biopolymer, film preparation method, food samples, and storage time. This review focused on betalains-rich films as pH- and ammonia-sensitive indicators and their applications as smart packaging to monitor the freshness of protein-rich foods such as shrimp, fish, chicken, and milk.

Development, application and future trends of starch-based delivery systems for nutraceuticals: A review

As a natural biopolymer, starch is ideally adapted as an encapsulant material for nutraceutical delivery systems due to its unique nature of extensive sources, versatility and high biocompatibility. This review offers an outline of recent advances in the development of starch-based delivery systems. The structure and functional properties of starch in encapsulating and delivering bioactive ingredients are first introduced. Structural modification of starch improves the functionalities and extends the applications of starch in novel delivery systems. Then, various nutraceutical delivery systems are systematically summarized, which include porous starch, starch particle, amylose inclusion complex, cyclodextrin, gel, edible film and emulsion. Next, the delivery process of nutraceuticals is discussed in two parts: digestion and release. Intestinal digestion plays an important role during the whole digestion process of starch-based delivery systems. Moreover, controlled release of bioactives can be achieved by porous starch, starch-bioactive complexation and core-shell structure. Finally, the challenges of the existing starch-based delivery systems are deliberated, and the directions for future research are pointed out. Composite delivery carriers, co-delivery, intelligent delivery, delivery in real food systems, and reuse of agricultural wastes may be the research trends for starch-based delivery systems in the future.

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.

A double-layer smart film based on gellan gum/modified anthocyanin and sodium carboxymethyl cellulose/starch/Nisin for application in chicken breast

In order to overcome this challenge of poor stability of natural anthocyanins in intelligent packaging materials, roselle anthocyanin (RA) was first modified by acetic acid, and then a double-layer smart indication antimicrobial film was developed using modified roselle anthocyanin (MRA)-gellan gum (GG) as the inner layer and sodium carboxymethyl cellulose (CMC)-starch (ST)-Nisin as the outer layer. UV spectra revealed that acetic acid was successfully grafted onto RA, which dramatically improved their thermal stability, antioxidant capabilities, photostability, and pH stability. The bilayer films were successfully prepared, as revealed by scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction measurements. In comparison to GG-MRA and CMC-ST-Nisin films, the water content, water solubility, mechanical characteristics, water vapor barrier, oxygen barrier, and hydrophobicity of GG-MRA@CMC-ST-Nisin films were significantly enhanced. The presence of the outer layer films significantly enhanced the UV-vis light barrier, opacity, antioxidant and antibacterial properties of the inner layer films. When the films were applied to chicken breast, it was found that the indicator films not only monitored the freshness of the chicken in real-time but also that the GG-MRA film and the double-layer film were effective in extending the shelf life of the chicken by 1 and 2 days, respectively, compared to the control group.

Novel ammonia-responsive carboxymethyl cellulose/Co-MOF multifunctional films for real-time visual monitoring of seafood freshness

Nowadays, ammonia-responsive biopolymer-based intelligent active films are of great interest for their huge potential in maintaining and monitoring the freshness of seafood. However, it is still a challenge to create biopolymer-based intelligent active films with favorable color stability, antibacterial and visual freshness indication functions. Herein, cobalt-based metal-organic framework (Co-MOF) nanosheets with ammonia-sensitive and antibacterial functions were successfully synthesized and then embedded into carboxymethyl cellulose (CMC) matrix to develop high performance and multifunctional CMC-based intelligent active films. The influence of Co-MOF addition on the structure, physical and functional characters of CMC film was comprehensively studied. The results showed that the Co-MOF nanofillers were homogeneously embedded within the CMC matrix, bringing about remarkable promotion on tensile strength (from 45.3 to 62.2 MPa), toughness (from 0.7 to 2.3 MJ/m³), water barrier and UV-blocking performance of CMC film. Notably, the obtained CMC/Co-MOF nanocomposite films also presented excellent long-term color stability, antibacterial activity (with the bacteriostatic efficiency of 99.6 % and 99.3 % against Escherichia coli and Staphylococcus aureus), and ammonia-sensitive discoloration performance. Finally, the CMC/Co-MOF nanocomposite films were successfully applied for real-time visual monitoring of shrimp freshness. The above results demonstrate that the CMC/Co-MOF nanocomposite films possess huge potential applications in intelligent active packaging.

Application of smart packaging for seafood: A comprehensive review

Nowadays, due to the changes in lifestyle and great interest of consumers in a healthy life, people have started increasing their seafood consumption. But due to their short shelf life, experts are looking for a new packaging called smart packaging (SMP) for seafood. There are different indicators/sensors in SMP; one of the effective indices is time-temperature, which can show consumers the best time of using seafood based on their shelf life and experienced temperature. Another one is radio-frequency identification (RFID) that is a transmission device that represents a separate form of the electronic information-based SMP systems. RFID does not belong to any of the categories of markers or sensors; it is an auto recognition system that applies cordless sensors to indicate segments and collect real-time information without manual interposition. This review covers the use of SMP in all marine foods, including fish, due to its high consumption and high content of polyunsaturated fatty acids, eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3), which are the considerable factors of n-3 polyunsaturated fatty acids for human.

A smart film incorporating anthocyanins and tea polyphenols into sodium carboxymethyl cellulose/polyvinyl alcohol for application in mirror carp

Multifunctional food packaging films were developed based on polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (CMC), tea polyphenol (TP) and black carrot anthocyanin (CA). Results of Zeta potential, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction showed that CA enhanced the stability of the particle dispersion system through hydrogen bonding and electrostatic interactions, promoted the compatibility between TP and PVA-CMC (PC) substrates, and enhanced the binding between the components of the films. Because of the interaction of TP and CA, PC-TP-CA films had better water resistance and water vapor barrier properties, thermal stability, antioxidant and antimicrobial properties. PC-CA and PC-TP-CA films exhibited excellent UV-blocking properties. They also showed distinct color responsiveness in the pH range of 2-13, significant sensitivity to ammonia vapor in a short period of time and excellent color stability over 20 days of storage under different conditions. When the film was applied to fish, it was found that PC-TP-CA film could extend the shelf life of fish by 1-2 days and successfully monitor the freshness of the fish in real-time. Considering all the physical and functional properties, the non-toxic and biodegradable PC-TP-CA film has excellent potential as a new multifunctional food packaging material in the future.

Application of Biosensors, Sensors, and Tags in Intelligent Packaging Used for Food Products-A Review

The current development of science and the contemporary market, combined with high demands from consumers, force manufacturers and scientists to implement new solutions in various industries, including the packaging industry. The emergence of new solutions in the field of intelligent packaging has provided an opportunity to extend the quality of food products and ensures that food will not cause any harm to the consumer's health. Due to physical, chemical, or biological factors, the state of food may be subject to degradation. The degradation may occur because the packaging, i.e., the protective element of food products, may be damaged during storage, transport, or other logistic and sales activities. This is especially important since most food products are highly perishable, and the maintenance of the quality of a food product is the most critical issue in the entire supply chain. Given the importance of the topic, the main purpose of this article was to provide a general overview of the application of biosensors, sensors, and tags in intelligent packaging used for food products. A short history and the genesis of intelligent packaging are presented, and the individual possibilities of application of sensors, biosensors, gas sensors, and RFID tags, as well as nanotechnology, in the area of the packaging of food products are characterized.

A novel pH-sensitive antibacterial bilayer film for intelligent packaging

Intelligent single-layer packaging is widely used in food monitoring and storage. However, most single-layer intelligent packaging has poor mechanical strength and water barrier properties. In this study, a bilayer intelligent detector film based on polyvinyl alcohol-chitosan (PVA-CS)/nano-ZnO/sodium alginate (SA) combined with anthocyanin extract (cyanidin chloride) was prepared using a layer-by-layer solution casting assembly technique. The effects of different levels of anthocyanin extracts on the physical and functional properties of the films, including microstructure, mechanical property, barrier property, pH sensitivity, and antibacterial property, were investigated. The results show that the bilayers exhibit excellent physical properties, lower water vapor permeability, better light transmission and UV-blocking properties, a broader pH sensitivity (ΔE > 10), and good antibacterial activity. In short, the bilayer films studied are superior to the single-layer films in terms of their packaging potential for products with low moisture content, offering new directions for active intelligent packaging and biodegradable materials for the food industry.

Graphical Abstract

Biodegradable Active Packaging Material Containing Grape Seed Ethanol Extract and Corn Starch/κ-Carrageenan Composite Film

An active film composed of corn starch/κ-carrageenan and ethanolic grape seed extract (0, 1, 3, and 5 wt% of GSE on corn starch basis) were successfully prepared using the solvent casting technique. The effects of the different concentrations of ethanolic grape seed extract (GSE) on the physicochemical properties, antioxidant properties, and antibacterial properties of CS/κC films were analyzed. The results showed that the addition of GSE inhibited the recrystallization of starch in the composite film. The glass transition temperature of composite film is 121.65 °C. With the addition of GSE, the surface roughness of the composite film increased, and the cross-section displayed a stratification phenomenon. Meanwhile, when GSE was added to the composite film, the tensile strength of the composite film decreased (3.50 ± 0.27 MPa), the elongation at break increased (36.87 ± 2.08%), and the WVP increased (1.58 ± 0.03 g mm/m2·d· kPa). With the increase of the concentration of GSE in the composite film, the a* value and b* value of the composite film increase, the L* value decreases, and the opacity increases. The lipid oxidation test proved that the composite films containing 1% GSE has a significant inhibitory effect on the oxidation of lard (p < 0.05). The above results indicate that the GSE can be used as a food-grade packaging material and has a good application prospect in the food industry.

Preparation and application of a colorimetric film based on sodium alginate/sodium carboxymethyl cellulose incorporated with rose anthocyanins

To monitor the freshness of Penaeus vannamei during storage, a colorimetric film based on sodium alginate/sodium carboxymethyl cellulose incorporated with rose anthocyanins extract (RAE) was prepared. The results showed that the incorporation of RAE increased moisture content, water vapor permeability, and water contact angle of the colorimetric film. FTIR, XRD spectra, and SEM demonstrated that RAE had good compatibility with the film-forming substrate. The colorimetric film presented obvious color variation in the pH range of 2.0-12.0 and was sensitive to volatile ammonia. The colorimetric film exhibited a visual color change from pink to pale yellow to yellowish green during the storage of Penaeus vannamei at 4 °C. Significant correlations were observed between the color change of colorimetric film (ΔE) and the pH value or TVB-N content of Penaeus vannamei (p < 0.05). Therefore, the colorimetric film shows great application potential to monitor the freshness of shrimp as intelligent packaging.

Recent Advances and Applications in Starch for Intelligent Active Food Packaging: A Review

At present, the research and innovation of packaging materials are in a period of rapid development. Starch, a sustainable, low-cost, and abundant polymer, can develop environmentally friendly packaging alternatives, and it possesses outstanding degradability and reproducibility in terms of improving environmental issues and reducing oil resources. However, performance limitations, such as less mechanical strength and lower barrier properties, limit the application of starch in the packaging industry. The properties of starch-based films can be improved by modifying starch, adding reinforcing groups, or blending with other polymers. It is of significance to study starch as an active and intelligent packaging option for prolonging shelf life and monitoring the extent of food deterioration. This paper reviews the development of starch-based films, the current methods to enhance the mechanical and barrier properties of starch-based films, and the latest progress in starch-based activity, intelligent packaging, and food applications. The potential challenges and future development directions of starch-based films in the food industry are also discussed.

Polymeric Packaging Applications for Seafood Products: Packaging-Deterioration Relevance, Technology and Trends

Seafood is a highly economical product worldwide. Primary modes of deterioration include autolysis, oxidation of protein and lipids, formation of biogenic amines and melanosis, and microbial deterioration. These post-harvest losses can be properly handled if the appropriate packaging technology has been applied. Therefore, it is necessary for packaging deterioration relevance to be clearly understood. This review demonstrates recent polymeric packaging technology for seafood products. Relationship between packaging and quality deterioration, including microbial growth and chemical and biochemical reactions, are discussed. Recent technology and trends in the development of seafood packaging are demonstrated by recent research articles and patents. Development of functional polymers for active packaging is the largest area for seafood applications. Intelligent packaging, modified atmosphere packaging, thermal insulator cartons, as well as the method of removing a fishy aroma have been widely developed and patented to solve the specific and comprehensive quality issues in seafood products. Many active antioxidant and antimicrobial compounds have been found and successfully incorporated with polymers to preserve the quality and monitor the fish freshness. A thermal insulator has also been developed for seafood packaging to preserve its freshness and avoid deterioration by microbial growth and enzymatic activity. Moreover, the enhanced biodegradable tray is also innovative as a single or bulk fish container for marketing and distribution. Accordingly, this review shows emerging polymeric packaging technology for seafood products and the relevance between packaging and seafood qualities.

Development and characterization of a novel active and intelligent film based on pectin and betacyanins from peel waste of pitaya (Hylocereus undatus)

In the present study, peel waste of pitaya (Hylocereus spp.) was used to develop a novel active and functional film. The film was developed with a combination of the white-fleshed pitaya peel pectin (WPPP) as a biopolymer and white-fleshed pitaya peel betacyanins (WPPB) as an active constituent, respectively. Furthermore, montmorillonite (MMT), a cheap and environmental-friendly silicate material, was introduced into film matrix as a filler to reduce the moisture sensitivity of the film. The effect of the incorporation of WPPB on the properties of WPPP/MMT films was investigated. The colorimetric response of WPPP/MMT/WPPB to pH and ammonia was examined, respectively. Moreover, WPPP/MMT/WPPB-2 was employed to monitor the freshness of shrimp. The color of the film changed from redness to reddish-brown, and further to brownness, echoing the shrimp turned from fresh to spoiled. Therefore, WPPP/MMT/WPPB-2 composite films showed promise for the applications in monitoring the freshness of shrimp.

Preparation, physicochemical and application evaluation of raspberry anthocyanin and curcumin based on chitosan/starch/gelatin film

Raspberry anthocyanin (RA) from Rubus idaeus L. (Rosaceae) and curcumin (Cur) from Curcuma longa L. (Zingiberaceae) can effectively improve the physicochemical properties of composite films, and as bioactive pigment components, they can impart pH-responsive properties to the film. In this study, RA and Cur were added to chitosan/starch/gelatin composite film (CSG) to prepare CSG-RA, CSG-Cur, CSG-RA/Cur₈₂ and CSG-RA/Cur₇₃ color films by solution casting method. The color films could change color under different pH conditions and had higher antioxidant activities using ABTS (2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)) assay. The results from fourier transform infrared spectroscopy and scanning electron microscopy showed that RA and Cur were well dispersed in the CSG matrix and improved the structure of the composite films. The hydrophobic Cur increased the tensile strength from 6 Mpa (CSG) to 14 Mpa (CSG-Cur), but reduced the elongation at break from 55 % (CSG) to 40 % (CSG-Cur). These color films had a good fresh-keeping effect and freshness monitoring, in particular, CSG-RA/Cur₇₃, had the better opacity, water solubility, thickness, moisture content and water vapor permeability than the other films. Briefly, binary pigment films had the potential to become a pH-sensitive indicator/packing film.

Colorimetric food spoilage monitoring with carbon dot and UV light reinforced fish gelatin films using a smartphone application

The objective of this study was to develop novel colorimetric films for food freshness monitoring. UV light irradiation (365 nm) and carbon dots (CDs) were tested as the potential crosslinkers in the fabrication of anthocyanins doped fish gelatin (FG) films. The effect of crosslinkers on the optical, surface, structural, barrier and mechanical properties of FG films was investigated. The incorporation of CD under UV irradiation improved the tested properties of FG films. The kinetic colorimetric responses of FG films against ammonia vaporwere studied to simulate the food spoilage and determine the ammonia sensitivity of the films. Among the tested films, UV-treated FG films containing 100 mg/l (FG-UV-CD100) indicated the best properties. Later, the color difference of FG-UV-CD100 films was observed to correlate well with microbial growth and TVB-N release in skinless chicken breast samples. At the same time, a custom-designed smartphone application (SmartFood) was also developed to be used with the FG-UV-CD100 film for quantitative estimation of food freshness in real-time. The proposed food freshness monitoring platform reveals a great potential to minimize global food waste and the outbreak of foodborne illness.

Smart packaging films based on locust bean gum, polyvinyl alcohol, the crude extract of Loropetalum chinense var. rubrum petals and its purified fractions

Loropetalum chinense var. rubrum is an ornamental shrub rich in polyphenolic compounds. In this study, polyphenolic compounds were extracted from L. chinense var. rubrum petals (LCP) and further purified on macroporous resin column to afford two fractions. The crude extract of LCP (LCP-CE) and its two purified fractions (LCP-25PF and LCP-50PF) were individually incorporated into locust bean gum/polyvinyl alcohol matrix to develop smart packaging films. The structures, physical and functional properties of the films were compared. Results showed LCP-25PF was mainly composed of anthocyanins, while LCP-50PF was mainly composed of chlorogenic acid and vanillin. LCP-CE, LCP-25PF and LCP-50PF interacted with locust bean gum/polyvinyl alcohol matrix through hydrogen bonds, thereby improving the light and oxygen barrier ability, tensile strength, thermal stability, antioxidant activity and antimicrobial activity of the film. The film containing LCP-25PF showed the lowest water vapor permeability (10.36 × 10^-11 g m^-1 s^-1 Pa^-1) and oxygen permeability (0.42 cm³ mm m^-2 day^-1 atm^-1) but the highest tensile strength (29.76 MPa), antioxidant activity and antimicrobial activity. In addition, the films containing LCP-CE and LCP-25PF had pH-/ammonia-sensitivity and effectively indicated shrimp freshness at 4 °C. Results suggested the film containing LCP-25PF could be used as smart packaging film.