An eco-friendly film of pH-responsive indicators for smart packaging

Advances in biomaterials based food packaging systems: Current status and the way forward

World hunger is getting worse, while one-third of food produced around the globe is wasted and never consumed. It is vital to reduce food waste to promote the sustainability of food systems, and improved food packaging solutions can augment this effort. The utilization of biomaterials in smart food packaging not only enhances food preservation and safety but also aligns with current demands for eco-friendly technologies to mitigate the impacts of climate change. This review provides a comprehensive overview of the developments in the field of food packaging based on the innovative use of biomaterials. It emphasizes the potential use of biomaterials derived from nature including cellulose, chitosan, keratin, etc. for this purpose. Various smart food packaging technologies such as active and intelligent packaging are discussed in detail including scavenging additives, colour-changing environment indicators, sensors, RFID tags, etc. The article also delves into the utilization of edible films and coatings, nanoparticle fillers and 2D materials in food packaging systems. Furthermore, it outlines the challenges and opportunities in this dynamic domain, emphasizing the ongoing need for research and innovation to shape the future of sustainable and smart food packaging solutions to enhance and monitor the shelf-life of food products.

Eco-friendly methylcellulose/zinc alginate film with multi-function properties: thermal stability, flame retardancy and antibacterial activities

The purpose of this study was to synthesize crosslinked films from methylcellulose (MC) and sodium alginate (SA) using a straightforward ion exchange technique in a ZnCl2 coagulation bath. The resulting MC/ZA blend films exhibited significant improvements in thermal stability, with a measured increase of 191 °C in degradation temperature compared to MC film. The introduction of zinc ion (Zn2+) enhanced the flame retardancy of MC/ZA film, achieving a 92.4 % reduction in flammability. The microstructure of the MC/ZA blend film displayed a relatively smooth surface, indicating better biocompatibility between MC and ZA. Additionally, the barrier property of the MC/ZA film was improved, with a 35 % reduction in permeability to water vapor, and the mechanical properties were strengthened, showing a slightly reduction of 5 % in tensile strength. Furthermore, the MC/ZA blend film demonstrated enhanced antibacterial effectiveness, with a 99.99 % of S. aureus and E. coli, implying their suitability for packaging applications involving high oil content foods.

Edible thermochromic beads from flavonoid, fatty acid, and lecithin for smart packaging

Enzymatic browning and microbial growth are two natural phenomena that occur when fruits and vegetables are exposed to abnormal conditions, i.e., temperatures in the range of 12-22 °C, leading to their spoilage. Controlling the temperatures during the supply chain aims to optimize the product's shelf life. Irreversible thermochromic beads were fabricated using a simple extrusion technique containing fatty acid, lecithin, and anthocyanin solution-alginate. The pigmentation durability was adjusted based on electrostatic interactions, as evidenced by the reduction in dye leaching in the case of the produced bead at pH = 6 to less than 0.007 after 45 min. Characterization shows that the chosen combination of fatty acids and the quinonoid molecule is useful for producing thermochromic beads, with a color change at 12 °C-22 °C, from blue to purple. Using the prepared thermochromic beads in the supply chain of fresh-cut salad and brussels sprouts showed a great result for monitoring their freshness after 21 ± 1 min.

Development of curcumin integrated smart pH indicator, antibacterial, and antioxidant waste derived Artocarpus lakoocha starch-based packaging film

Monitoring of food freshness is considered one of the crucial challenges for both customers/consumers and the food industries. In this study, we developed a curcumin-based starch film (F1) for pH-sensitive intelligent food packaging application. The starch was obtained from waste seeds of Artocarpus lakoocha (NS-MJF). The native starch underwent various physical and chemical modifications to yield modified starches (S1 [Autoclave heat treated], S2 [osmotic-pressure treated], S3 [citric acid treated]). The native starch was then used further for the formation of curcumin (2.5 % w/w)-based film (F1). We had analyzed these starches for solubility, colour analysis, biodegradability, oil absorption capacity, and moisture content, etc. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed favourable microstructures. The addition of curcumin to the starch enhanced the contact angle and elongation at the break of the resulting films. Antioxidant and antimicrobial assays, along with real-time freshness monitoring of chicken fillets, were also conducted. Thus, our findings may contribute to the optimization of pH-responsive biopolymer-based films for intelligent poultry packaging, promising advancements in food preservation and safety.

Preparation of Steamed Purple Sweet Potato-Based Films Containing Mandarin Essential Oil for Smart Packaging

Anthocyanin-rich steamed purple sweet potato (SPSP) is a suitable raw material to produce smart packaging films. However, the application of SPSP-based films is restricted by the low antimicrobial activity of anthocyanins. In this study, SPSP-based smart packaging films were produced by adding mandarin essential oil (MEO) as an antimicrobial agent. The impact of MEO content (3%, 6%, and 9%) on the structures, properties, and application of SPSP-based films was measured. The results showed that MEO created several pores within films and reduced the hydrogen bonding system and crystallinity of films. The dark purple color of the SPSP films was almost unchanged by MEO. MEO significantly decreased the light transmittance, water vapor permeability, and tensile strength of the films, but remarkably increased the oxygen permeability, thermal stability, and antioxidant and antimicrobial properties of the films. The SPSP-MEO films showed intuitive color changes at different acid-base conditions. The purple-colored SPSP-MEO films turned blue when chilled shrimp and pork were not fresh. The MEO content greatly influenced the structures, physical properties, and antioxidant and antimicrobial activities of the films. However, the MEO content had no impact on the color change ability of the films. The results suggested that SPSP-MEO films have potential in the smart packaging of protein-rich foods.

Development of pH-freshness smart label based on gellan gum film incorporated with red cabbage anthocyanins extract and its application in postharvest mushroom

Novel colorimetric films based on gellan gum (GG) containing red cabbage anthocyanins extract (RCAE) were prepared as pH-freshness smart labels for real-time visual detection of mushroom freshness. The GG/RCAE films had excellent pH and ammonia sensitivity. The GG/RCAE-0.2-0.3 films had the highest sensitivity to acetic acid. The SEM micrographs, AFM images, FT-IR and XRD spectra demonstrated that RCAE were successfully combined into the film-forming substrate. The incorporation of RCAE resulted in the increase of thermal stability, opacity and surface hydrophobicity of films. Meanwhile, the GG/RCAE-0.2 film exhibited stronger tensile strength and excellent color stability at 4℃. The color changes of GG/RCAE-0.2 film were visually easier to distinguish during the storage of mushroom. The results showed the GG/RCAE films could be used as pH-freshness smart labels to detect the freshness of fruits and vegetables.

Smart packaging films based on corn starch/polyvinyl alcohol containing nano SIM-1 for monitoring food freshness

There is at present an acute need for the construction of biopolymer-based smart packaging material that can be applied for the real-time visual monitoring of food freshness. Herein, a nano-sized substituted imidazolate material (SIM-1) with ammonia-sensitive and antibacterial ability was effectively manufactured and then anchored within corn starch/polyvinyl alcohol (CS/PVA) blend to construct biopolymeric smart active packaging material. The structure, physical and functional performances of CS/PVA-based films with different content of SIM-1 (0.5, 1.0 and 2.0 wt% on CS/PVA basis) were then explored in detail. Results revealed that the incorporated SIM-1 nanocrystals were equally anchored within the CS/PVA matrix owing to the establishment of potent hydrogen-bonding interactions, which produced an obvious improvement in the compatibility of CS/PVA blend film, as well as its mechanical strength, water/oxygen barrier and UV-screening performances. The constructed CS/PVA/SIM-1 blend films further demonstrated superior long-term color stability property, ammonia-sensitive and antibacterial functions. Furthermore, the CS/PVA/SIM-1 blend films were utilized for effectively monitoring the deterioration of shrimp via observable color alteration. The above findings suggested the potential applications of CS/PVA/SIM-1 blend films in smart active packaging.

Fabrication and characterization of polyvinyl alcohol/sodium alginate/zein/ chitosan bilayer film for dynamic visualization of pork quality

The development of real-time and convenient meat freshness indication technology is crucial to ensure food safety. A novel antibacterial visualized intelligent film was designed based on polyvinyl alcohol (PA), sodium alginate (SA), zein (ZN), chitosan (CS), alizarin (AL) and vanillin (VA) using layer-by-layer assembly (LBL) method for real-time and in situ monitoring of pork freshness. The fabricated film had various advantageous properties, including an excellent hydrophobicity with a water contact angle (WCA) of 91.59°, improved color stability, excellent water barrier properties and increased mechanical performance (TS = 42.86 MPa). The fabricated film also demonstrated effective antibacterial properties with a bacteriostatic circle diameter of 13.6 mm for Escherichia coli. Moreover, the film can perceive and visualize the antibacterial effect through color changes, enabling dynamic visual monitoring of the antibacterial effect. A good correlation (R² = 0.9188) between the color changes (ΔE) and total viable count (TVC) of pork was documented. Conclusively, fabricated multifunctional film improves the accuracy and versatility of freshness indication and had great potential for food preservation and freshness monitoring. The outcomes of this research provides a new perspective for the design and development of multifunctional intelligent films.

Design of Biodegradable, Climate-Specific Packaging Materials That Sense Food Spoilage and Extend Shelf Life

The AgriFood systems in tropical climates are under strain due to a rapid increase in human population and extreme environmental conditions that limit the efficacy of packaging technologies to extend food shelf life and guarantee food safety. To address these challenges, we rationally designed biodegradable packaging materials that sense spoilage and prevent molding. We nanofabricated the interface of 2D covalent organic frameworks (COFs) to reinforce silk fibroin (SF) and obtain biodegradable membranes with augmented mechanical properties and that displayed an immediate colorimetric response (within 1 s) to food spoilage, using packaged poultry as an example. Loading COF with antimicrobial hexanal also mitigated biotic spoilage in high-temperature and -humidity conditions, resulting in a four-order of magnitude decrease in the total amount of mold growth in soybeans packaged in silk-COF, when compared to cling film (i.e., polyethylene). Together, the integration of sensing, structural reinforcement, and antimicrobial agent delivery within a biodegradable nanocomposite framework defines climate-specific packaging materials that can decrease food waste and enhance food safety.

pH-dependent color response of cellulose-based time-temperature indicators impregnated with red cabbage extract

Color-based time-temperature indicators (TTIs) can show the time and temperature changes of an environment with a visually recognizable color change. Made from natural dyes, these TTIs are simple, inexpensive and sustainable. In this study, cellulose-based TTI labels were prepared with red cabbage extract of pH2, pH7 and pH9 to determine how pH alter the response of the labels to time and temperature changes. This study also aimed to determine the relationship between color change and time at different temperatures. The color responses of the labels were followed spectrophotometrically by measuring the CIE Lab color coordinates and by giving the total color difference at 4 °C, 23 °C, 40 °C, 80 and 100 °C after increments of time. The best fitting linear or nonlinear regression models of the CIE Lab coordinates, total color difference and time data as a function of temperature were also determined. The labels prepared with red cabbage extract at different pH behaved differently. Opposite to expectations, the acidic, pink colored labels did not have the highest color stability. Our finding was, that the label prepared with the acidic red cabbage extract is the most suitable as time-temperature label for indicating long-term temperature storage and the label prepared with the neutral red cabbage extract is the most suitable as time-temperature label for indicating short-term storage by color change. According to the results the color changes of the labels are predictable with the fitted models with a correlation coefficient between 0.96 and 1.

Enzymatic acylation of cyanidin-3-O-glucoside in raspberry anthocyanins for intelligent packaging: Improvement of stability, lipophilicity and functional properties

Anthocyanins (ACNs) as one category of water-soluble flavonoid pigments are increasingly employed in pH sensing indicator applications for monitoring food freshness. Nevertheless, considering that anthocyanins are sensitive to environmental factors, their practical applications in food industries are still rather limited. In order to improve the stability of anthocyanins and capitalize upon their application in pH-color responsive intelligent packaging, this study aims to graft octanoic aid onto raspberry anthocyanins catalyzed by immobilized Candida antarctica lipase B (Novozymes 435). Structural analyses based on Fourier transform infrared spectroscopy (FTIR), UV-Vis, liquid chromatography-mass spectrometry (LC-MS), and nuclear magnetic resonance (NMR) revealed that octanoic acid was regioselective grafted onto the 6-OH position of its glucoside. The acylation efficiency of C3G by octanoic acid up to 47.1%. The octanoic acid moiety was found to improve lipophilicity, antioxidant activity and stability of C3G. In addition, acylated derivative also maintained the pH-color response characteristics of nature ACNs and exhibited excellent NH3 response properties. These results indicated that acylated anthocyanins exhibit potential application as intelligent packaging indicator for monitoring food freshness.

Development of Shrimp Freshness Indicating Films by Embedding Anthocyanins-Rich Rhododendron simsii Flower Extract in Locust Bean Gum/Polyvinyl Alcohol Matrix

Freshness indicating films containing anthocyanins are one type of smart packaging technology. Anthocyanins in the films can show visual color changes when food spoilage occurs, thereby indicating the freshness degree of food in real-time. Rhododendron simsii is a landscape plant with attractive flowers that are abundant in anthocyanins. In this study, smart packaging films were prepared by embedding 2% and 4% R. simsii flower anthocyanins (RA) in locust bean gum- (LBG) and polyvinyl alcohol- (PVA) based matrices. The micro-structure, barrier, mechanical, thermal, antioxidant, and color-changeable properties of the films were determined. The potential application of the films in indicating the freshness of shrimp at 4 °C was also investigated. Results showed that the RA interacted with the LBG/PVA matrices through hydrogen bonds, which significantly improved the barrier, mechanical, thermal, antioxidant, pH-sensitive, and ammonia-sensitive properties of the films. Meanwhile, the performance of the films was remarkably influenced by the content of the RA. The film containing 4% RA had the highest light blocking ability, tensile strength (38.32 MPa), elongation at break (58.18%), and antioxidant activity, and also showed the lowest water vapor permeability (22.10 × 10^-11 g m^-1 s^-1 Pa^-1) and oxygen permeability (0.36 cm³ mm m^-2 day^-1 atm^-1). The films containing 2% and 4% RA could effectively change their colors when the level of total volatile basic nitrogen in the shrimp exceeded the safe value, which demonstrated the suitability of the films for indicating the freshness degree of shrimp.

Cassava Starch Films with Anthocyanins and Betalains from Agroindustrial by-Products: Their Use for Intelligent Label Development

The development of biodegradable packaging materials has become a widely addressed topic in recent years. Microparticles generated from Brassica oleracea var. capitata f. rubra (red cabbage, RC) and Beta vulgaris L. var. conditiva (beetroot, BR) which contained anthocyanins or betalains, were included in the formulation of edible films based on cassava starch (CS) giving origin to films CSRC, CSBR, or CSBC (mixture of both particles). The inclusion of the filler determined an increase in the stress at rupture from 0.8 MPa (CS) to 1.2 MPa (CSRC) or 1.0 MPa (CSBC), of the contact angle from 2.6° to 13.8° (CSBR) or 19.6° (CSBC). The use of these films for developing a smart label for hake packaging and the study of the TBV-N content, the microbiological characteristics of the muscle, and the color changes of the label with time, allowed us to conclude that the films CSRC and CSBC would be suitable for sensing the deterioration of packaged and chilled hake and that the color change of the label CSBC was completely consistent with fish muscle deterioration. As the microparticles can be obtained from by-products of the production and industrialization of plant tissues, the composite films and the smart labels developed can contribute not only to the development of safe food but also to the addition of value to those residues and to environmental protection.

Enhanced artificial intelligence for electrochemical sensors in monitoring and removing of azo dyes and food colorant substances

It is necessary to determine whether synthetic dyes are present in food since their excessive use has detrimental effects on human health. For the simultaneous assessment of tartrazine and Patent Blue V, a novel electrochemical sensing platform was developed. As a result, two artificial azo colorants (Tartrazine and Patent Blue V) with toxic azo groups (-NN-) and other carcinogenic aromatic ring structures were examined. With a low limit of detection of 0.06 μM, a broad linear concentration range 0.09μM to 950μM, and a respectable recovery, scanning electron microscopy (SEM) was able to reveal the excellent sensing performance of the suggested electrode for patent blue V. The electrochemical performance of an electrode can be characterized using cyclic and differential pulse voltammetry, and electrochemical impedance spectroscopy. Moreover, the classification model was created by applying binary classification assessment using enhanced artificial intelligence comprises of support vector machine (SVM) and Genetic Algorithm (GA), respectively, a support vector machine and a genetic algorithm, which was then validated using the 50 dyes test set. The best binary logistic regression model has an accuracy of 83.2% and 81.1%, respectively, while the best SVM model has an accuracy of 90.3% for the training group of samples and 81.1% for the test group (RMSE = 0.644, R2 = 0.873, C = 205.41, and = 5.992). According to the findings, Cu-BTC MOF (copper (II)-benzene-1,3,5-tricarboxylate) has a crystal structure and is tightly packed with hierarchically porous nanomaterials, with each particle's edge measuring between 20 and 37 nm. The suggested electrochemical sensor's analytical performance is suitable for foods like jellies, condiments, soft drinks and candies.

Intelligent labels manufactured by thermo-compression using starch and natural biohybrid based

This work aims to develop intelligent labels based on cassava starch and biohybrid pigments by thermo-compression. The biohybrid pigment (BH) was developed by the adsorption of anthocyanins (ACNs) extracted from the jambolan fruit (Syzygium cumini L.) into montmorillonite (Mt) in order to improve its stability. The effect of the addition of biohybrid on the physicochemical properties of the thermo-pressed starch labels was evaluated. ACNs from jambolan extract show a visible pH-dependent color-changing ability at pH 1 - 12, and the adsorption did not modify the color property. The intelligent labels presented a homogeneous surface, and the BH was well dispersed in the starch matrix. The presence of BH increased the solubility in the water of starch labels. Chemical structure characterization revealed that the BH interacted with starch matrices through hydrogen bonds. Furthermore, the thermal stability of starch labels increased with the presence of BH. Hence, the purple color of intelligent labels was preserved at high temperatures. Finally, labels containing BH show visible changes from purple to a blue color when exposed to ammonia vapor, which simulates the degradation of meat products. Thus, the label content jambolan pigments will be used to control meat deterioration.

Active-intelligent and biodegradable sodium alginate films loaded with Clitoria ternatea anthocyanin-rich extract to preserve and monitor food freshness

The aim of this study was to develop and characterize sodium alginate films loaded with 10-40 % Clitoria ternatea extract (CTE) and apply to monitoring the quality of milk, pork and shrimp. Films loaded with CTE showed high light barrier capacity and improved tensile strength by 3.8 times over control films. The incorporation of CTE in alginate films improved the thermal stability of the materials due to intermolecular interactions and crosslinking of polymeric networks. The addition of 40 % of CTE generated films with antibacterial action against E. coli. The alginate films showed biodegradable characteristics in soil and beach sand in 15 days. The food simulant test revealed that the loaded films show good compatibility with aqueous and acidic foods due to the release of higher levels of polyphenols and anthocyanins. The films showed great colorimetric potential due to their ability to change color at different pH (pink-green), ammonia gas (blue-green) and sterilization process (blue-yellow). When the film loaded with 40 % CTE (F40) was applied to monitor the freshness of milk and meat products (shrimp and pork), its blue color changed to purple and green, respectively. Therefore, the F40 has great potential to be used as a biodegradable indicator of freshness.

Active/intelligent packaging films developed by immobilizing anthocyanins from purple sweetpotato and purple cabbage in locust bean gum, chitosan and κ-carrageenan-based matrices

Active/intelligent packaging films were developed by incorporating purple sweetpotato anthocyanins (PSA) and purple cabbage anthocyanins (PCA) in locust bean gum/polyvinyl alcohol (LP), chitosan/polyvinyl alcohol (CP) and κ-carrageenan/polyvinyl alcohol (KP) film matrices. The joint effect of anthocyanins' source and polysaccharides' nature on the structure and functionality of the films was determined. Results showed PSA and PCA interacted with film matrices through hydrogen bonds and/or electrostatic interactions, resulting in improved film uniformity. PSA and PCA did not remarkably alter the water vapor permeability and tensile strength of the films; however, significantly improved the light barrier ability, antioxidant activity, pH-sensitivity and ammonia-sensitivity of films. For the films containing the same anthocyanins (PSA or PCA), LP-based films had relatively higher light barrier ability and storage stability, while CP-based had relatively weaker color changeable ability. When PSA and PCA were immobilized in the same film matrix, the films containing PCA had higher light barrier ability and antioxidant activity than the films containing PSA. Among the films, LP-PCA film exhibited a good potential to monitor the freshness of shrimp. Results suggested the structure and functionality of the films were influenced by the source of anthocyanins and the nature of polysaccharides.