Ammonia-sensitive cellulose acetate-based films incorporated with Co-BIT microcrystals for smart packaging application

Intelligent pH-responsive ratiometric fluorescent nanofiber films for visual and real-time seafood freshness monitoring

In this study, polyvinyl alcohol (PVA)-based ratiometric fluorescence nanofiber films with salicylamide (SA) as the response signal, rhodamine B (RhB) as the internal reference were prepared using electrospinning technique, and reducing their water solubility by glutaraldehyde (G) crosslinked. The RhB and SA were successfully immobilized in the PVA substrate. Moreover, RhB and SA improved the water resistance, water vapor barrier, and mechanical strength of the nanofiber films, among the PVA nanofiber films containing RhB and 400 mg SA (PVA/RhB/4SA-G) showed the best packaging performance. Meanwhile, it exhibited high sensitivity to ammonia (limit of detection was 0.97 ppm), and could effectively distinguish the freshness states of shrimp stored at 4 and 25 °C by displaying a distinct shift from light pink to bright purple fluorescence. Moreover, the migration studies confirmed the safety of PVA/RhB/4SA-G. Therefore, the fabricated PVA/RhB/4SA-G can be utilized as a promising intelligent packaging for monitoring seafood freshness in real-time.

Enhanced ammonia-sensitive intelligent films based on a metal-organic framework for accurate shrimp freshness monitoring

Sensitive intelligent films can be used to accurately monitor food freshness. In this study, a cellulose acetate curcumin-loaded cyclodextrin (CD)-based metal-organic framework intelligent film (CA-Cur@CD-MOF) was developed to monitor shrimp freshness at different spoilage stages in real time. The mechanical, barrier, optical, and ammonia-sensitive properties of this film were studied. Notably, this film demonstrated effective ammonia-sensitive color development, reaching a ΔE value of 8.5 in 2 min under an ammonia atmosphere of approximately 0.4 mM. This intelligent film exhibits good DPPH free radical scavenging ability, high thermal stability, and excellent theoretical limit of detection (LOD). Interestingly, shrimp can be classified as "fresh", "sub-fresh", and "spoilage" during the monitoring of shrimp freshness. Furthermore, a significant correlation (R2 = 0.9641) was observed between the TVB-N and ΔE value for this film. Therefore, this intelligent film is promising for the real-time monitoring of freshness of shrimp and other protein-rich foods.

Colorimetric ammonia-sensing nanocomposite films based on starch/sodium alginate and Cu-Phe nanorods for smart packaging application

The development of colorimetric ammonia-sensing smart packaging materials with real-time freshness detection ability are crucial for ensuring food safe. This research involved the construction of Cu-based framework (Cu-Phe) nanorods with colorimetric ammonia-sensing ability through an easy-to-perform aqueous solution method, and their subsequent utilization as nano inclusions in starch/sodium alginate (ST/SA) substrate to foster the creation of high-performance smart packaging materials. Research findings revealed that the addition of Cu-Phe nanorods (3, 6, 9 wt%) within ST/SA substrate led to the formation of compatible nanocomposite films with significantly augmented physical performance and functionality. Especially, the film containing 9 wt% Cu-Phe presented the highest tensile strength (30.32 MPa), elongation at break (19.12 %), UV-shielding efficacy (blocking >99 % of UV passage), water vapor barrier effectiveness (1.90 × 10-6 g/m·h·Pa) and oxygen barrier ability (2.26 × 10-3 g/m2·s). In addition, the developed ST/SA/Cu-Phe nanocomposite film possessed excellent antibacterial activity (over 99.9 %) against Escherichia coli and Staphylococcus aureus, superior colorimetric ammonia-sensing ability, and long-term colour stability. Also of note, the Cu-Phe added ST/SA nanocomposite film allowed for detecting prawn and pork freshness reduction in real-time via discernible colour transition, suggesting its extensive promise for smart packaging applications.

Applied research and recent advances in the development of flexible sensing hydrogels from cellulose: A review

Flexible wearable smart sensing materials have gained immense momentum, and biomass-based hydrogel sensors for renewable and biologically safe wearable sensors have attracted significant attention in order to meet the growing demand for sustainability and ecological friendliness. Cellulose has been widely used in the field of biomass-based hydrogel sensing materials, being the most abundant biomass material in nature. This review mainly focuses on the types of cellulose hydrogels, the preparation methods and their applications in smart flexible sensing materials. The structure-functional properties-application relationship of cellulose hydrogels and the applications of various cellulose hydrogels in flexible sensing are described in detail. Then it focuses on the methods and mechanisms of cellulose hydrogel flexible sensors preparation, and then summarizes the research of cellulose hydrogel sensors for different types of stimulus response mechanisms to pressure, pH, biomolecules, ions, temperature, humidity, and light. The applications of cellulose hydrogels as flexible sensing materials in biomedical sensing, smart wearable and environmental monitoring are further summarized. Finally, the future development trend of cellulose hydrogels is briefly introduced and the future development of cellulose hydrogel sensing materials is envisioned.

Digitalization of Colorimetric Sensor Technologies for Food Safety

Colorimetric sensors play a crucial role in promoting on-site testing, enabling the detection and/or quantification of various analytes based on changes in color. These sensors offer several advantages, such as simplicity, cost-effectiveness, and visual readouts, making them suitable for a wide range of applications, including food safety and monitoring. A critical component in portable colorimetric sensors involves their integration with color models for effective analysis and interpretation of output signals. The most commonly used models include CIELAB (Commission Internationale de l'Eclairage), RGB (Red, Green, Blue), and HSV (Hue, Saturation, Value). This review outlines the use of color models via digitalization in sensing applications within the food safety and monitoring field. Additionally, challenges, future directions, and considerations are discussed, highlighting a significant gap in integrating a comparative analysis toward determining the color model that results in the highest sensor performance. The aim of this review is to underline the potential of this integration in mitigating the global impact of food spoilage and contamination on health and the economy, proposing a multidisciplinary approach to harness the full capabilities of colorimetric sensors in ensuring food safety.

A novel dual-channel cassava starch/polyvinyl alcohol-based film for visual monitoring of shrimp freshness

In this study, the polyvinylpyrrolidone-alizarin nanoparticles (PVP-AZ NPs) with favorable water dispersion and the carbon quantum dots (RQDs) with aggregate induced emission effect were synthesized to construct an eco-friendly film for food freshness monitoring. The introduction of PVP-AZ NPs and RQDs enhanced the network structure and thermal stability of the cassava starch/polyvinyl alcohol film, and reduced its crystallinity and light transmittance via non-covalent binding with the film-forming matrix. The developed film exhibited visually recognizable colorimetric and fluorescent responses to ammonia at 0.025-25 mg/mL, and it can be reused at least 6 times. Practical application experiment proved that the film, as an indicator label, can achieve accurate, real-time, and visual dynamic monitoring of the freshness of shrimp stored at 25 °C, 4 °C, and - 20 °C under daylight (orange yellow to purple) and UV light (red to blue). The integration of multivariate detection technology can eliminate the interference of external factors by self-correction to improve sensitivity and reliability, which provides a reference for the development of other food quality and safety monitoring platforms.

Highly flexible carbon nitride-polyethylene glycol-cellulose acetate film with photocatalytic antibacterial activity for fruit preservation

Cellulose acetate film, as a biodegradable and biomass-derived material, has great potential applications in food packaging. However, the poor mechanical and antibacterial properties limit its applications. Herein, a highly flexible carbon nitride-polyethylene glycol-cellulose acetate (CN-PEG-CA) film was successfully prepared by combining graphitic carbon nitride (g-C3N4) photocatalyst with cellulose acetate (CA). The g-C3N4 enables the film with antibacterial activity, as a green photocatalyst. PEG softens the rigid polymer CA and crosslinks CA, PEG, and g-C3N4 together by hydrogen bonding, as a flexible crosslinker. X-ray diffractometer (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectrum (FT-IR) characterizations confirmed the successful preparation of the CN-PEG-CA film. The mechanical property tests demonstrated that adding PEG increased the elongation at break of the film by about 4 times. The composite film had high antibacterial activity, and the bactericidal rates on Escherichia coli and Staphylococcus aureus were 99.98 % and 99.89 %, respectively. It effectively extended the shelf life of strawberries to 96 h and effectively maintained the quality of strawberries during storage. After 96 h, the weight loss rate of strawberries packaged with 15 % CN-PEG-CA film was 21.83 %, vitamin C content was 45.47 %, titratable acidity content was 0.89 %, and color, hardness and total soluble solids were well maintained. And biocompatibility test results showed that the film was safe and nontoxic. From the ecological and economic point of view, the highly flexible and biodegradable films with efficient photocatalytic antibacterial activity synthesized in this paper have great potential in the field of food packaging.

Methylcellulose/chitosan nanofiber-based composites doped with lactoferrin-loaded Ag-MOF nanoparticles for the preservation of fresh apple

Increasing demand for high-quality fresh fruits and vegetables has led to the development of innovative active packaging materials that exhibit controlled release of antimicrobial/antioxidant agents. In this study, composite biopolymer films consisting of methylcellulose (MC) and chitosan nanofibers (ChNF) were fabricated, which contained lactoferrin (LAC)-loaded silver-metal organic framework (Ag-MOF) nanoparticles. The results indicated that the nanoparticles were uniformly distributed throughout the biopolymer films, which led to improvements in tensile strength (56.1 ± 3.2 MPa), thermal stability, water solubility, swelling index, water vapor barrier properties (from 2.2 ± 2.1 to 1.9 ± 1.9 × 10-11 g. m/m2. s. Pa), and UV-shielding effects. The Ag-MOF-LAC2% films also exhibited strong and long-lasting antibacterial activity against E. coli (19.8 ± 5.2 mm) and S. aureus (20.1 ± 3.2 mm), which was attributed to the slow release of antimicrobial LAC from the films. The composite films were shown to maintain the fresh appearance of apples for at least seven days, which was attributed to their antimicrobial and antioxidant activities. Consequently, these composite films have the potential in the assembly of innovative active packaging materials for protecting fresh fruits and vegetables. However, further work is required to ensure their safety and economic viability.

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.