pH-responsive color indicator films based on methylcellulose/chitosan nanofiber and barberry anthocyanins for real-time monitoring of meat freshness

Pectin-based color indicator films incorporated with spray-dried Hibiscus extract microparticles

Colorimetric films incorporated with anthocyanins as an indicator for freshness monitoring have aroused growing interest recently. The pH-sensing colorimetric film were developed based on pectin (HM), containing aqueous hibiscus extract microparticles (HAE). HAE microparticles were obtained by spray drying with different wall materials (Inulin -IN, maltodextrin- MD and their combination). The films were obtained on large scale by continuous casting. These films were characterized for physicochemical analysis, morphological structure, thermal and barrier properties, antioxidant activity, and color change at different pH. The addition of HAE microparticles caused relevant changes to HM-based films, such as in mechanical behavior and improved barrier property (11-22% WVTR reduction) depending on the type of wall material used and the concentration added. It was verified with the thermal stability of films, with a slight increase being observed. The color variation of smart films was entirely pH-dependent. Overall, the proposed color indicator films showed unique features and functionalities and could be used as an alternative natural pH indicator in smart packaging systems.

pH-Responsive Color Indicator of Saffron (Crocus sativus L.) Anthocyanin-Activated Salep Mucilage Edible Film for Real-Time Monitoring of Fish Fillet Freshness

Researchers have been focusing increasingly on preparing innovative packaging films made from renewable and biodegradable materials in recent years. This research set out to fabricate and analyze pH-sensitive edible films based on salep mucilage combined with anthocyanin from saffron (Crocus sativus L.) (SAAs). A casting technique was developed with varying concentrations of SAAs (0, 2.5, 5, 7.5, and 10%v/v) pH-sensitive edible films. The surface morphology, physicochemical, barrier, and mechanical properties, as well as the pH sensitivity of films, were investigated. The results showed SAAs increased thickness, water solubility, moisture content, and oxygen permeability (O2P) up to 199.03 µm, 63.71%, 14.13%, and 47.73 (cm3 µm m−2 day−1 kPa−1), respectively, of the pH-sensitive salep mucilage edible indicator films. As expected, the SAAs concentration from 0% to 10%v/v decreased tensile strength, transparency, and contact angle to 11.94 MPa, 14.27%, and 54.02°, respectively. Although achieving the highest elongation at the break (108%) and the lowest water vapor permeability (WVP) (1.39 g s−1 m−1 Pa−1 × 10−11), the pH-sensitive edible indicator film containing 5 %v/v of SAAs showed the best results. An investigation of pH sensitivity revealed that the solution’s pH variation altered the SAAs color. When the pH was raised from 3 to 11, the SAAs’ color shifted from pink to brown. The SAAs-halochromic salep mucilage edible indicator film was employed as a label in an experiment to track the degradation of fish fillets stored at 4 °C, revealing that the halochromic indicator changed color from yellow to brown as the fish was stored. Our findings show that SAAs-loaded salep mucilage indicator films help monitor real-time food deterioration.

Development of an Indicator Film Based on Cassava Starch-Chitosan Incorporated with Red Dragon Fruit Peel Anthocyanin Extract

The increase in new technology and consumer demand for healthy and safe food has led to the development of smart packaging to help consumers understand food conditions in real time. The incorporation of red dragon fruit peel anthocyanin into cassava starch and chitosan films was used in this study as a color indicator to monitor food conditions. This indicator film was generated using the solvent-casting method. The mechanical, morphological, and physicochemical characterizations of the film were studied, and food freshness monitoring was carried out. The results showed that adding red dragon fruit peel anthocyanin increased up to 94.44% of the antioxidant activity. It also improved its flexibility, indicated by the lowest tensile strength (3.89 ± 0.15 MPa) and Young's modulus (0.14 ± 0.01 MPa) and the highest elongation at break (27.62 ± 0.57%). The indicator film was sensitive to pH, which was indicated by its color change from red to yellow as pH increased. The color of the film also changed when it was used to test the freshness of packaged shrimp at both room and chiller temperatures. According to the results, the indicator film based on cassava starch-chitosan incorporated with red dragon fruit peel anthocyanin showed its potential as a smart packaging material.

Colorimetric Indicators Based on Anthocyanin Polymer Composites: A Review

This review explores the colorimetric indicators based on anthocyanin polymer composites fabricated in the last decade, in order to provide a comprehensive overview of their morphological and compositional characteristics and their efficacy in their various application fields. Notably, the structural properties of the developed materials and the effect on their performance will be thoroughly and critically discussed in order to highlight their important role. Finally, yet importantly, the current challenges and the future perspectives of the use of anthocyanins as components of colorimetric indicator platforms will be highlighted, in order to stimulate the exploration of new anthocyanin sources and the in-depth investigation of all the possibilities that they can offer. This can pave the way for the development of high-end materials and the expansion of their use to new application fields.

On-package ratiometric fluorescent sensing label based on AIE polymers for real-time and visual detection of fish freshness

Freshness is an important parameter of fish quality. This study aims to develop a ratiometric fluorescent sensing label that is responsive to volatile amines, affording real-time and visual detection of fish freshness. For developing of the sensing label, an aggregation-induced emissive (AIE) polymer was prepared from the stimuli-responsive polymer polymethacrylic acid and the AIE molecule tetraphenylethylene and coated on to filter paper with rhodamine B as an internal reference. By exploiting the ratiometric response, the freshness of fish could be identified clearly and easily according to the color of on-package label, which changes from pink (fresh) to dark blue. The difference was linearly correlated with the total volatile basic nitrogen (TVB-N, R² = 0.995 and 0.994 at 25 °C and 4 °C, respectively) in the range of 15-25 mg/100 g for the salmon samples, which indicated that the sensing label feasibly and non-destructively quantified TVB-N.

Characterization of electrospun nanofibers and solvent-casted films based on Centaurea arvensis anthocyanin-loaded PVA/κ-carrageenan and comparing their performance as colorimetric pH indicator

In this research, PVA/Ҡ-carrageenan-based colorimetric indicators incorporated with Centaurea arvensis anthocyanin (CAE) were fabricated by two electrospinning and solvent casting methods and their performance as pH indicators were assessed. Chemical immobilization of CAE on PVA and PVA/Ҡ-carrageenan matrixes was approved by FT-IR analysis. According to SEM images, Ҡ-carrageenanaddition improved the homogeneity of films and decreased the diameter of nanofibers. The crystalline structure and thermal properties of polymeric matrixes were affected by anthocyanin incorporation. CAE had an adverse effect on mechanical properties of films and nanofibers. The preparation method and type of solid matrix affected the responsiveness and the tonality of responded color. Electrospun nanofibers showed high responsiveness (10 s) than colorimetric films (15-40 min) to pH changes. The indicators displayed color variations from heather violet to green over the 2-12 pH range. The designed indicators have potential to be applied as visual pH label in food intelligent packaging.

Design and Preparation of a Biobased Colorimetric pH Indicator from Cellulose and Pigments of Bacterial Origin, for Potential Application as Smart Food Packaging

Nowadays, worldwide challenges such as global warming, pollution, unsustainable consumption patterns, and scarcity of natural resources are key drivers toward future-oriented bioeconomy strategies, which rely on renewable biobased resources, such as bacterial pigments and bacterial cellulose (BC), for materials production. Therefore, the purpose of this study was to functionalize bacterial cellulose with violacein, flexirubin-type pigment, and prodigiosin and test their suitability as pH indicators, due to the pigments’ sensitivity to pH alterations. The screening of the most suitable conditions to obtain the BC-pigment indicators was achieved using a full factorial design, for a more sustainable functionalization process. Then, the pH response of functionalized BC to buffer solutions was assessed, with color changes at acidic pH (BC-violacein indicator) and at alkaline pH (BC-violacein, BC-prodigiosin, and BC-flexirubin-type pigment indicators). Moreover, the indicators also revealed sensitivity to acid and base vapors. Furthermore, leaching evaluation of the produced indicators showed higher suitability for aqueous foods. Additionally, color stability of the functionalized BC indicators was carried out, after light exposure and storage at 4 °C, to evaluate the indicators’ capacity to maintain color/sensitivity. Thus, BC membranes functionalized with bacterial pigments have the potential to be further developed and used as pH indicators.

Poly-l-lactic acid (PLLA)/anthocyanin nanofiber color indicator film for headspace detection of low-level bacterial concentration

Since bacterial contamination is a significant threat to humans, early detection is essential to safeguard dietary safety and physical health. Here, a nanofiber color indicator film based on poly-l-lactic acid (PLLA) as the support and anthocyanin as the indicator material was prepared by electrostatic spinning. It was found that the PLLA/0.8CY nanofiber color indicator film was hydrophobic (the water contact angle of 102.4°) and contained uniform nanofibers with an average diameter of 750 nm. In addition, the film's humidity insensitivity, reusability, color stability, and ammonia sensitivity (the limits of detection 35.39 ppm) made the film environmentally friendly and more accurate and faster for bacterial detection. The film was able to sense 102 CFU/mL of gram-positive and negative bacteria after the model strain E. coli and L. monocytogene. Thus, the PLLA/0.8CY nanofiber color indicator film was able to perform headspace nondestructive detection of low-level bacterial contamination.

Development of gelatin/PVA based colorimetric films with a wide pH sensing range winery solid by-product (Vinasse) for monitor shrimp freshness

Anthocyanins were extracted from a winery solid by-product (Vinasse) and added to fish gelatin (FG) and polyvinyl alcohol (PVA) matrices to create freshness monitoring labels. Three different colorimetric indicator smart films [PWE = polyvinyl alcohol with wine extract (WE), FWE = fish gelatin with WE, and PFWE = polyvinyl alcohol and FG blended film with WE] were generated and examined for their suitability to monitor the freshness of shrimp. The mechanical and optical properties, ammonia sensitivity, and colorimetric analysis of smart films were determined. Fourier transform-infrared spectroscopy (FTIR) was used to evaluate the interaction of anthocyanins with FG and PVA and changes in the film's chemical composition with storage. The film surfaces were characterized with atomic force microscopy (AFM). The incorporation of WE enhanced the films' flexibility by providing plasticizer and surfactant properties. The PWE film showed the best color stability. The FWE film showed the least amount of total color change with exposure to ammonia gas and was deemed suitable for refrigerated food packaging. The color of all indicator films showed significant changes suggesting that PWE, FWE, and PFWE films can be utilized in the intelligent packaging application for protein-rich foods to detect spoilage.

Development of pH-responsive konjac glucomannan/pullulan films incorporated with acai berry extract to monitor fish freshness

In this work, konjac glucomannan (KGM)-based film reinforced with pullulan (PL) and acai berry extract (ABE) was developed by solvent casting method. The as-prepared films performed pH-sensitive properties, which can be potentially applied for fish freshness detection. Rheology, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) were used to characterize chemical structure and morphology of ABE-loaded KGM/PL (KP) films (KP-ABE). FT-IR spectrum indicated that hydrogen bond dominated the formation of KP-ABE films. Adding PL contributed to enhanced mechanical properties of KGM film with increased tensile strength (TS) from 21.25 to 50.27 MPa and elongation at break (EAB) from 10.64 to 19.19 %. Incorporating ABE upgraded flexibility, UV-shielding, thermostability, water barrier (decreased Water vapor permeability (WVP) from 2.07 to 1.67 g·mm/m²·day kPa), antioxidant, and antibacterial ability of KP films, but weakened TS. In addition, KP-ABE films can reflect fish freshness in real time through color variability. Therefore, KP-ABE films exhibited potential applications in intelligent food packaging materials.

Fabrication of intelligent/active films based on chitosan/polyvinyl alcohol matrices containing Jacaranda cuspidifolia anthocyanin for real-time monitoring of fish freshness

The present work describes the natural anthocyanin from Jacaranda cuspidifolia (JC) flower immobilized within a biopolymer matrix composed of chitosan (CS) and polyvinyl alcohol (PVA) gave novel intelligent/active packaging films (CPC). We introduced microwave irradiation to prepare polymeric composite films noticed faster mixing of the polymers and extract take place than the conventional method. The prepared composite films are characterized by various analytical and spectroscopic techniques. The smooth SEM images demonstrated CS/PVA matrix miscibility and compatibility with anthocyanin for the film formation. The addition of anthocyanin to the CS/PVA films significantly reduced UV-Vis light transmission, while causing a slight decrease in the films transparency. An increased anthocyanin concentration on polymer films showed improved oxygen permeability (77.09 %), moisture retention capacity (11.64 %), and water vapor transmission rate (43.10 %) substantially. Additionally, the prepared CPC smart films exhibited strong antioxidant (97.92 %) as well as antibacterial activities against common foodborne pathogens such as S. aureus, and E. coli. Furthermore, the prepared smart films demonstrated pink color in acidic, while grey to yellowish in basic solvent. Further, the color response of the freshness label was consistent with the spoilage Total Volatile Basic-Nitrogen (TVB-N) content determined in the fish samples with varied time period. The CPC smart films also showed promising application in terms of monitoring freshness of the fish fillets at room temperature. The obtained results suggested that, the prepared CPC smart films have potential to be used as quality indicator in the marine food packaging system.

Meat 4.0: Principles and Applications of Industry 4.0 Technologies in the Meat Industry

Meat 4.0 refers to the application the fourth industrial revolution (Industry 4.0) technologies in the meat sector. Industry 4.0 components, such as robotics, Internet of Things, Big Data, augmented reality, cybersecurity, and blockchain, have recently transformed many industrial and manufacturing sectors, including agri-food sectors, such as the meat industry. The need for digitalised and automated solutions throughout the whole food supply chain has increased remarkably during the COVID-19 pandemic. This review will introduce the concept of Meat 4.0, highlight its main enablers, and provide an updated overview of recent developments and applications of Industry 4.0 innovations and advanced techniques in digital transformation and process automation of the meat industry. A particular focus will be put on the role of Meat 4.0 enablers in meat processing, preservation and analyses of quality, safety and authenticity. Our literature review shows that Industry 4.0 has significant potential to improve the way meat is processed, preserved, and analysed, reduce food waste and loss, develop safe meat products of high quality, and prevent meat fraud. Despite the current challenges, growing literature shows that the meat sector can be highly automated using smart technologies, such as robots and smart sensors based on spectroscopy and imaging technology.

Development of highly stable color indicator films based on κ-carrageenan, silver nanoparticle and red grape skin anthocyanin for marine fish freshness assessment

Color indicator films for fish freshness were fabricated by incorporating κ-carrageenan (CAR) polymer with red grape skin extract (GSE) as a pH-sensing agent and silver nanoparticles (AgNPs) as an antimicrobial agent. Anthocyanins in GSE exhibited distinguished pH responsive color changes. GSE and AgNPs were well compatible with CAR with intramolecular interactions, approved by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis, thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). GSE-containing films displayed distinguished color changes in response to pH variations and volatile ammonia. Enhanced UV blocking ability and strong antioxidant activity were revealed for GSE included films without sacrificing the physico-chemical properties of the CAR film. Films containing AgNPs showed improved mechanical strength and strong antimicrobial ability against both Escherichia coli and Staphylococcus aureus. The CAR/AgNPs/GSE film displayed a distinctive color change corresponding to changes in the total volatile basic nitrogen (TVB-N) of fish during storage. In addition, the CAR/AgNPs/GSE film showed excellent color stability to consecutive UV exposure and its storage time at 25 °C is expected to be at least 240 days, which indicates that it has high potential as an intelligent food freshness indicator film.

Monitoring dynamic changes in chicken freshness at 4 °C and 25 °C using pH-sensitive intelligent films based on sodium alginate and purple sweet potato peel extracts

A pH-sensitive intelligent indicator film was developed and used for monitoring dynamic changes in chicken freshness at 4 °C and 25 °C by immobilizing 0.2 %-1.0 % purple sweet potato peel extracts (PPE) with sodium alginate (SA). The films presented a wide range of colors from red-pink to green-yellow at 2-13, and the films with less PPE were more sensitive to ammonia. The color of films with 0.6 % PPE changed from pink to blue when used in monitoring chicken freshness at 4 °C (5 d) and 25 °C (60 h), which corresponded to changes in total volatile base nitrogen from 5.35 (5.35) mg/100 g to 16.2 (19.9) mg/100 g. Scanning electron microscopy and X-ray diffraction revealed that PPE improved the compactness and crystallinity of SA films, while Fourier transform infrared spectroscopy revealed hydrogen bonds between SA and PPE. Compared to SA films, the water vapor and light barrier abilities of films with 0.6 % were significantly improved (P < 0.05), there was no significant effect on tensile strength (P > 0.05), and the elongation of 0.6 % PPE films (P < 0.05) was decreased. Thus, PPE can serve as an excellent indicator of intelligent films for monitoring the freshness of meat products.

Electrospun chitosan/polyethylene oxide nanofibers mat loaded with copper (II) as a new sensor for colorimetric detection of tetracycline

Using electrospun chitosan/polyethylene oxide nanofibers mat (CS/PEO NFM) as carrier, Cu@CS/PEO NFM, a new tetracycline (TC) solid-state colorimetric sensor, were simply prepared by directly immobilizing Cu²⁺ on surface of CS/PEO NFM. After immersing in TC solutions, Cu@CS/PEO NFM can display visible color changes to the naked eye within 5.0 min, and the TC concentration-dependent color changes can also be quantitatively analyzed with a smartphone. Because Cu²⁺ can enhance the adsorption of CS/PEO NFM for TC, Cu@CS/PEO NFM possess a more sensitive response ability to TC, ensuring that the colorimetric sensing detection will not be interfered by other coexisting drugs. Due to the reversible combination of chitosan and Cu²⁺, the colorimetric sensing ability of Cu@CS/PEO NFM can be regenerated even after being reused at least 4 times. In addition, the naked eye detection limit of Cu@CS/PEO NFM-based colorimetric sensing is 65 μg kg^-1, which does not exceed the maximum residue limit in milk samples set by China (100 μg kg^-1). The obtained results fully indicated the practical application value of this method in preventing the hazard of TC residues.

A high-stable and sensitive colorimetric nanofiber sensor based on PCL incorporating anthocyanins for shrimp freshness

A novel bilayer colorimetric film incorporating polycaprolactone (PCL) with clitoria ternatea Linn anthocyanin (CA) via electrospinning was designed. The PCL nanofibers layer acted as a protective layer against harsh environments as the strong hydrophobic with the WCA (water contact angle) values of 101.79°. The PCL-CA layer worked as an indicator for its significant color changes for pH. The sensitivity test verified the ammonia cycler reversibility of the nanofibers is promising for re-use packaging. And the PCL/PCL-CA film was characterized as suitable WVP (water vapour permeability), and the lower velocity of water penetrating. Moreover, higher elongation at break (240.431%), and color stability were achieved. Besides, the film exhibited the color change from pale-blue to yellow-green response as an indication of shrimp spoilage (21 h). These results suggested the potential application of the PCL/PCL-CA film for a reusable freshness sensor tool in food packaging.

A Simple Combination of Active and Intelligent Packaging Based on Garlic Extract and Indicator Solution in Extending and Monitoring the Meat Quality Stored at Cold Temperature

Safety and quality, as the major concerns of meat, are highly dependent on the ingredients and packaging techniques used. A basic combination of active and intelligent packaging is believed to be capable of preserving product quality, extending shelf life, and monitoring product deterioration. Therefore, this study aimed to extend and monitor the beef quality at cold temperatures (4 ± 1 °C). The active packaging applied garlic extract (0%, 15%, and 20% (w/w)) to release anti-microbial agents. Meanwhile, the intelligent paper applied a combination of bromothymol blue (BTB) and phenol red (PR) solutions at pH 5.00. The results showed that beef packed without the addition of garlic extract had already deteriorated on the 6th day of storage while, with the addition of garlic extract (15% and 20%) rotted on the 12th day. The intelligent indication label’s color profile changed from dark yellow (fresh), to reddish-yellow (to be consumed immediately), to faded red (rotten). The color change of the intelligent indicator label in response to all meat deterioration criteria demonstrates a linear correlation for determining the extent of rottenness during storage. Therefore, this simple combination of active paper and intelligent indicator can be used to extend the shelf life and monitor meat quality.

Smart Biopolymer-Based Nanocomposite Materials Containing pH-Sensing Colorimetric Indicators for Food Freshness Monitoring

Nanocomposite biopolymer materials containing colorimetric pH-responsive indicators were prepared from gelatin and chitosan nanofibers. Plant-based extracts from barberry and saffron, which both contained anthocyanins, were used as pH indicators. Incorporation of the anthocyanins into the biopolymer films increased their mechanical, water-barrier, and light-screening properties. Infrared spectroscopy and scanning electron microscopy analysis indicated that a uniform biopolymer matrix was formed, with the anthocyanins distributed evenly throughout them. The anthocyanins in the composite films changed color in response to alterations in pH or ammonia gas levels, which was used to monitor changes in the freshness of packaged fish during storage. The anthocyanins also exhibited antioxidant and antimicrobial activity, which meant that they could also be used to slow down the degradation of the fish. Thus, natural anthocyanins could be used as both freshness indicators and preservatives in biopolymer-based nanocomposite packaging materials. These novel materials may therefore be useful alternatives to synthetic plastics for some food packaging applications, thereby improving the environmental friendliness and sustainability of the food supply.

Fabrication and characterization of a smart film based on cassava starch and pomegranate peel powder for monitoring lamb meat freshness

Nowadays, the development of pH‐sensitive smart edible films using biopolymers and natural plant extracts (especially those rich in anthocyanins) has attracted much attention. Therefore, in this study, the intelligent edible film was produced and characterized using cassava starch and pomegranate peel powder (PPP) and the possibility of using production films to monitor the freshness of lamb meat. The smart films were prepared using different concentrations of PPP (2, 4, 6, and 8% w/w) and the solvent casting method. The results showed that the incorporation of PPP had a significant effect on the mechanical parameters of the starch films. With increasing the levels of PPP, the color of the films became darker and redder. Increasing the PPP levels also led to an increase in total phenol content (TPC) (from 0 to 13 mg GAE (gallic acid equivalent)/g) and antioxidant activity (from 0% to 70% DPPH (1,1‐diphenyl‐2‐picryl hydrazyl) radical scavenging) of the produced films (p < .05). The intelligent film was used in the lamb meat packaging, and the color of the film changed from red to green during the storage period at 25°C. The amount of total volatile basic nitrogen (TVB‐N) in the meat could be detected by color changes of the intelligent films. Finally, this study demonstrated that the film based on cassava starch and PPP could be used as an intelligent and pH‐sensitive film to monitor the freshness of meat and meat products.

Characterization of Natural Anthocyanin Indicator Based on Cellulose Bio-Composite Film for Monitoring the Freshness of Chicken Tenderloin

Intelligent packaging with indicators that provide information about the quality of food products can inform the consumer regarding food safety and reduce food waste. A solid material for a pH-responsive indicator was developed from hydroxypropyl methylcellulose (HPMC) composited with microcrystalline cellulose (MCC). MCC at 5%, 10%, 20%, and 30% w/w was introduced into the HPMC matrix and the physical, barrier, thermal, and optical properties of the HPMC/MCC bio-composite (HMB) films were analyzed. At 5, 10, and 20% MCC, improved mechanical, transparency, and barrier properties were observed, where HMB with 20% of MCC (H20MB) showed the best performance. Therefore, H20MB was selected as the biodegradable solid material for fabricating Roselle anthocyanins (RA) pH sensing indicators. The performance of the RA-H20MB indicator was evaluated by monitoring its response to ammonia vapor and tracking freshness status of chicken tenderloin. The RA-H20MB showed a clear color change with respect to ammonia exposure and quality change of chicken tenderloin; the color changed from red to magenta, purple and green, respectively. These results indicated that RA-H20MB can be used as a biodegradable pH sensing indicator to determine food quality and freshness.

Application of Red Cabbage Anthocyanins as pH-Sensitive Pigments in Smart Food Packaging and Sensors

Anthocyanins are excellent antioxidant/antimicrobial agents as well as pH-sensitive indicators that provide new prospects to foster innovative smart packaging systems due to their ability to improve food shelf life and detect physicochemical and biological changes in packaged food. Compared with anthocyanins from other natural sources, red cabbage anthocyanins (RCAs) are of great interest in food packaging because they represent an acceptable color spectrum over a broad range of pH values. The current review addressed the recent advances in the application of RCAs in smart bio-based food packaging systems and sensors. This review was prepared based on the scientific reports found on Web of Science, Scopus, and Google Scholar from February 2000 to February 2022. The studies showed that the incorporation of RCAs in different biopolymeric films could affect their physical, mechanical, thermal, and structural properties. Moreover, the use of RCAs as colorimetric pH-responsive agents can reliably monitor the qualitative properties of the packaged food products in a real-time assessment. Therefore, the development of smart biodegradable films using RCAs is a promising approach to the prospect of food packaging.

Synthesis and Physicochemical Characterization of Polymer Film-Based Anthocyanin and Starch

Colorimetric indicators, used in food intelligent packaging, have enormous promise for monitoring and detecting food quality by analyzing and interpreting the quality data of packaged food. Hence, our study developed and characterized a biopolymer film based on starch and anthocyanin for prospective meat freshness monitoring applications. The developed film was morphologically characterized using different morphology instruments to identify the interaction between anthocyanin and starch. The color differences of the proposed film in response to different pH buffers have also been investigated. The combination of anthocyanin and starch produces a smooth and homogenous surface with an intermolecular hydrogen bond that increases the biopolymer's wavelength. The film indicated bright red at pH 2.0-6.0, bluish-grey at pH 7.0-11.0, and yellowish-green above 11.0 that the naked eye can see. The indicator film shows high sensitivity toward pH changes. The inclusion of anthocyanin increases the biopolymer film's thickness and crystalline condition with low humidity, water solubility, and swelling values. As a result, the polymer film can be employed in the food industry as an affordable and environmentally friendly indication of meat freshness.

An active and pH-responsive film developed by sodium carboxymethyl cellulose/polyvinyl alcohol doped with rose anthocyanin extracts

Many anthocyanins were used in active and pH-responsive packaging. The purpose of the study was to prepare an active and pH-responsive sensitive film based on sodium carboxymethyl cellulose/polyvinyl alcohol (CPVA) by a casting process, which contained rose anthocyanin extracts (RAEs) to monitor the freshness of pork. The concentration of RAEs had an important influence on the physicochemical property of RAEs-CPVA films, especially excellent anti-oxidation and light barrier properties. Importantly, the 160-RAEs-CPVA film had a strong response to pH, showing different color at different pHs. Furthermore, when monitoring the freshness of pork stored at 25 °C, the light green color of the 160-RAEs-CPVA film indicated that the freshness of the pork was higher, while the dark green and orange appearance indicated that the pork was spoiled. Therefore, 160-RAEs-CPVA film can be used as a smart indicator for freshness monitoring of pork.

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.

Titanium dioxide nanoparticles as multifunctional surface-active materials for smart/active nanocomposite packaging films

Environmental issues such as plastic packaging and high demand for fresh and safe food has increased the interest for developing smart/active food packaging films with colloidal nanoparticles (NPs). Titanium dioxide nanoparticles (TNPs) are cost effective and stable metal oxide NPs which could be used as a functional nano-filler for biodegradable food packaging due to their excellent biocompatibility, photo catalyzing, and antimicrobial properties. This article has comprehensively reviewed the functional properties and advantages of TNPs-containing smart/active films. The advantage of adding TNPs for ameliorating food packaging materials such as their physical, mechanical, moisture/light barrier, optical, thermal resistance, microstructure and chemical properties as well as, antibacterial, and photocatalytic properties are discussed. Also, the practical and migration properties of administrating TNPs in food packaging material are investigated. The ethylene decomposition activity of TNPs containing active films, could be used for increasing the shelf life of fruits/vegetables after harvesting. TNPs are safe with negligible migration rates which could be used for fabrication of multifunctional smart/active packaging films due to their antimicrobial properties and ethylene gas scavenging activities.

Ixiolirion tataricum anthocyanins-loaded biocellulose label: Characterization and application for food freshness monitoring

A new intelligent pH-sensitive colorimetric label was fabricated by immobilizing Ixiolirion tataricum anthocyanins (ITA) into biocellulose (bacterial nanocellulose; BNC) film and was then studied to determine how it can be used as a label for monitoring freshness/spoilage of shrimp during storage at 4 °C. The formation of new interactions between ITA and BNC film and disruption of crystalline structure of BNC after anthocyanins immobilization were approved by FT-IR and XRD analyses, respectively. According to FE-SEM observations, the porosity of the BNC network decreased after ITA incorporation. The fabricated BNC-ITA label showed a distinct color change from violet to green over the pH range of 4-12. The pH, total volatile basic nitrogen (TVB-N), total psychrophiles count (TPC), and the quantity of biogenic amines (histamine, cadaverine, putrescine, and tyramine) in the shrimp samples and their correlation with color changes on the label were measured over a 4-day storage period. Consistent with changes in levels of TVB-N, TPC, pH, and biogenic amines, a visually distinguishable color change occurred on the BNC-ITA label as blue (fresh), dark green (medium fresh), and kelly green (spoiled). This research showed that ITA as a novel pH-sensitive dye is a promising candidate for developing pH labels for seafood intelligent packaging.

A review on nanomaterials and nanohybrids based bio-nanocomposites for food packaging

With an increasing demand for a novel, eco-friendly, high-performance packaging material "bio-nanocomposites" has attracted great attention in recent years. The review article aims at to evaluating recent innovation in bio-nanocomposites for food packaging applications. The current trends and research over the last three years of the various bio-nanocomposites including inorganic, organic nanomaterials, and nanohybrids, which are suitable as food packaging materials due to their advanced properties such as high mechanical, thermal, barrier, antimicrobial, and antioxidant are described in detail. In addition, the legislation, migration studies, and SWOT analysis on bio-nanocomposite film have been discussed. It has been observed that the multifunctional properties of the bio-nanocomposite materials, has the potential to improve the quality and safety of the food together with no /or fewer negative impact on the environment. However, more studies need to be performed on bio-nanocomposite materials to determine the migration levels and formulate relevant legislation.

Application of Nanotechnology to Improve the Performance of Biodegradable Biopolymer-Based Packaging Materials

There is great interest in developing biodegradable biopolymer-based packaging materials whose functional performance is enhanced by incorporating active compounds into them, such as light blockers, plasticizers, crosslinkers, diffusion blockers, antimicrobials, antioxidants, and sensors. However, many of these compounds are volatile, chemically unstable, water-insoluble, matrix incompatible, or have adverse effects on film properties, which makes them difficult to directly incorporate into the packaging materials. These challenges can often be overcome by encapsulating the active compounds within food-grade nanoparticles, which are then introduced into the packaging materials. The presence of these nanoencapsulated active compounds in biopolymer-based coatings or films can greatly improve their functional performance. For example, anthocyanins can be used as light-blockers to retard oxidation reactions, or they can be used as pH/gas/temperature sensors to produce smart indicators to monitor the freshness of packaged foods. Encapsulated botanical extracts (like essential oils) can be used to increase the shelf life of foods due to their antimicrobial and antioxidant activities. The resistance of packaging materials to external factors can be improved by incorporating plasticizers (glycerol, sorbitol), crosslinkers (glutaraldehyde, tannic acid), and fillers (nanoparticles or nanofibers). Nanoenabled delivery systems can also be designed to control the release of active ingredients (such as antimicrobials or antioxidants) into the packaged food over time, which may extend their efficacy. This article reviews the different kinds of nanocarriers available for loading active compounds into these types of packaging materials and then discusses their impact on the optical, mechanical, thermal, barrier, antioxidant, and antimicrobial properties of the packaging materials. Furthermore, it highlights the different kinds of bioactive compounds that can be incorporated into biopolymer-based packaging.

Covalent immobilization of bromocresol purple on cellulose nanocrystals for use in pH-responsive indicator films

This study developed pH-indicator films by combining esterified cellulose nanocrystals (e-CNCs) with activated bromocresol purple (a-BCP) via covalent bonding for pH-sensitive color-changing applications. The e-CNC/a-BCP particles were incorporated into cellulose acetate polymer to prepare pH-sensitive color changing films. Binding of a-BCP to e-CNCs was proven by attenuated total reflection infrared (ATR-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Colorimetric analysis showed that films containing 10% or 15% e-CNC/a-BCP particles had critical color changes either at pH 4-5, or pH 7-8. The films with 10% e-CNC/a-BCP particles also revealed excellent leaching resistance under acidic conditions. Color changes were reversible between pH 2 and 10. These pH-indicator films had visible color changes in response to pH variations, color reversibility, leaching resistance, and sufficient rigidity even though mechanical properties decreased as the e-CNC/a-BCP content increased from 0% to 15%.

Cold atmospheric plasma physically reinforced substances of platelets-laden photothermal-responsive methylcellulose complex restores burn wounds

Patients with irregular, huge burn wounds require time-consuming healing. The skin has an epithelial barrier mechanism. Hence, the penetration and retention of therapeutics across the skin to deep lesion is generally quite difficult and these usually constrain the delivery/therapeutic efficacies for wound healing. Effective burn wound healing also necessitates proper circulation. Conventional polymeric dressing usually exhibits weak mechanical behaviors, obstructing their load-bearing applications. Cold atmospheric plasma (CAP) was used as an efficient, environmentally friendly, and biocompatible process to crosslink methylcellulose (MC) designed for topical administration such as therapeutic substances of platelets (SP) and polyethyleneimine-polypyrrole nanoparticle (PEI-PPy NP)-laden MC hydrogel carriers, and wound dressings. The roles of framework parameters for CAP-treated SP-PEI-PPy NP-MC polymeric complex system; chemical, physical, and photothermal effects; morphological, spectroscopical, mechanical, rheological, and surface properties; in vitro drug release; and hydrophobicity are discussed. Furthermore, CAP-treated SP-PEI-PPy NP-MC polymeric complex possessed augmented mechanical properties, biocompatibility, sustainable drug release, drug-retention effects, and near-infrared (NIR)-induced hyperthermia effects that drove heat-shock protein (HSP) expression with drug permeation to deep lesions. This work sheds light on the CAP crosslinking polymeric technology and the efficacy of combining sustained drug release with photothermal therapy in burn wound bioengineering carrier designs.

Green Coating Polymers in Meat Preservation

Edible coatings, including green polymers are used frequently in the food industry to improve and preserve the quality of foods. Green polymers are defined as biodegradable polymers from biomass resources or synthetic routes and microbial origin that are formed by mono- or multilayer structures. They are used to improve the technological properties without compromising the food quality, even with the purpose of inhibiting lipid oxidation or reducing metmyoglobin formation in fresh meat, thereby contributing to the final sensory attributes of the food and meat products. Green polymers can also serve as nutrient-delivery carriers in meat and meat products. This review focuses on various types of bio-based biodegradable polymers and their preparation techniques and applications in meat preservation as a part of active and smart packaging. It also outlines the impact of biodegradable polymer films or coatings reinforced with fillers, either natural or synthesized, via the green route in enhancing the physicochemical, mechanical, antimicrobial, and antioxidant properties for extending shelf-life. The interaction of the package with meat contact surfaces and the advanced polymer composite sensors for meat toxicity detection are further considered and discussed. In addition, this review addresses the research gaps and challenges of the current packaging systems, including coatings where green polymers are used. Coatings from renewable resources are seen as an emerging technology that is worthy of further investigation toward sustainable packaging of food and meat products.