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.

Application of bacterial nanocellulose decorated with zeolitic imidazolate framework (ZIF-L) as a platform for food freshness monitoring.

Recently, the food freshness indicator (FFI) has garnered great interest from consumers and food producers. A novel FFI based on bacterial nanocellulose (BNC)/zeolitic imidazolate framework-L (ZIF-L) and grape anthocyanins was developed and characterized using field emission scanning electron microscopy, Fourier-transform infrared, X-ray diffraction, water contact angle, and BET techniques. The results confirmed that the BNC fibrils were decorated by in situ growth of ZIF-L, with a 3D flower-shaped structure and randomly multiple sharp-edged petals, and hydroxyl and oxygenated heterocycle aromatic ring functional groups on its surface. The reversibility, color stability performance, and moisture sorption of FFI were studied and its applicability in a two-layer arrangement as a visual freshness monitoring of shrimp and minced beef was evaluated. The FFI was able to distinguish (ΔE > 5) the fresh, medium fresh, and spoiled minced meat and shrimp visually during 10 and 4 days of storage at 4 °C, respectively. Also, monitoring of food chemical and microbiological parameters approved the correlation of food spoilage with the color parameters of FFI. These results confirmed the function of ZIF-L in the fabrication of highly pH-sensitive food intelligent packaging material.

Development of curcumin incorporated composite films based on chitin and glucan complexes extracted from Agaricus bisporus for active packaging of chicken breast meat.

Composite films were prepared by combining different concentrations of curcumin with chitin and glucan complexes (CGCs) extracted from Agaricus bisporus via a solution casting method. The developed curcumin doped CGC (CGC/Cu) films were characterized in terms of surface, optical, structural, barrier, mechanical, antioxidant, and antimicrobial properties. The biodegradability of CGC/Cu films was determined in soil for 14 days. The incorporation of curcumin significantly affected the surface morphology and improved light barrier properties, radical scavenging activity, and total phenolic content of the films. The CGC/Cu films containing different concentrations of curcumin showed antibacterial activity against Escherichia coli, while antibacterial activity against Staphylococcus aureus was not observed with the developed films. Afterward, the microbial properties of the fresh chicken breast were examined during refrigerated storage for 10 days. The shelf-life of chicken samples wrapped in the developed film was extended at least 40 % compared to the control sample. In conclusion, curcumin incorporated CGC based films can serve as a promising biodegradable active packaging material to improve the shelf-life of meat products.

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 CDs under UV irradiation improved the tested properties of FG films. The kinetic colorimetric responses of FG films against ammonia vapor were 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 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.

Monitoring freshness of chicken breast by using natural halochromic curcumin loaded chitosan/PEO nanofibers as an intelligent package.

Intelligent packaging is important to get information about real time quality of foods. The objective of this study was to develop an electrospun nanofiber halochromic pH sensor film using curcumin, chitosan (CS) and polyethylene oxide (PEO) to monitor chicken freshness. Conductivity and rheological behavior of CS/PEO/curcumin solutions were measured to understand the effect of solution properties on the morphology of the fibers. The morphological characteristics of nanofiber films were investigated by Field Emission Scanning Electron Microscopy (FESEM). Average diameter of the fibers was found to be between 283 ± 27 nm and 338 ± 35 nm. It was concluded that increasing CS amount in nanofibers decreased the diameter of the fibers. Thermal analysis and water vapor permeability features of the pH sensor were also examined. Color changes of curcumin loaded CS/PEO nanofiber film was evaluated on chicken breast package at 4 °C. The color of nanofiber film changed from bright yellow to reddish color which provided an opportunity to detect color changes by even the naked eyes of the untrained consumer. As a quality indicator, surface pH changes of the chicken breast and TVB-N (total volatile basic nitrogen) were measured. At the end of the day 5, pH value of 6.53 ±0.08 and TVB-N concentration of 23.45 ±3.35 mg/100 g indicated that food was at the edge of the acceptance level. As a result, curcumin loaded nanofiber satisfied the expectation and gave an opportunity to visualize real time monitoring of chicken spoilage.

Robust Covalent Coupling Scheme for the Development of FRET Aptasensor based on Amino-Silane-Modified Graphene Oxide.

In recent years, numerous aptamers have been physisorbed on graphene oxide (GO) to develop fluorescence resonance energy transfer-based aptasensors using the fluorescence quenching property of GO. However, physisorbed aptasensors show poor signal reversibility and reproducibility as well as nonspecific probe displacement, and thereby are not suitable for many analytical applications. To overcome these problems when working with complex biological samples, we developed a facile and robust covalent surface functionalization technique for GO-based fluorescent aptasensors using a well-studied adenosine triphosphate binding aptamer (ABA). In the scheme, GO is first modified with amino-silane, and further with glutaraldehyde to create available carbonyl groups for the covalent attachment of a fluorophore and an amino dual modified ABA. The surface modification method was characterized by ζ-potential, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). The linearity, sensitivity, selectivity, and reversibility of the resulting GO-based covalent aptasensor was determined and systematically compared with the physisorbed aptasensor. Although both sensors showed similar performance in terms of sensitivity and linearity, better selectivity and higher resistance to nonspecific probe displacement was achieved with the developed covalent ABA sensor. The surface modification technique developed here is independent of the aptamer sequence, and therefore could be used universally for different analytical applications simply by changing the aptamer sequence for the target biomolecule.

Integration of a Genetically Encoded Calcium Molecular Sensor into Photopolymerizable Hydrogels for Micro-Optrode-Based Sensing.

Genetically encoded molecular-protein sensors (GEMS) are engineered to sense and quantify a wide range of biological substances and events in cells, in vitro and even in vivo with high spatial and temporal resolution. Here, we aim to stably incorporate these proteins into a photopatternable matrix, while preserving their functionality, to extend the application of these proteins as spatially addressable optical biosensors. For this reason, we examined the fabrication of 3D hydrogel microtips doped with a genetically encoded fluorescent biosensor, GCaMP3, at the end of an optical fiber. Stable incorporation parameters of GCaMP3 into a photo-cross-linkable monomer matrix were investigated through a series of characterization and optimization experiments. Different precursor-solution formulations and irradiation parameters of in situ photopolymerization were tested to determine the factors affecting protein stability and sensor reproducibility during photoencapsulation. The microstructure and performance of hydrogel microtips were controlled by varying UV irradiation intensity as well as the molecular weight and concentration of the photocurable monomer, PEGDA (polyethylene glycol diacrylate), in precursor solution. Protein-doped hydrogel micro-optrodes (microtip sensors) were fabricated successfully and reproducibly at the distal end of optical fiber. Under optimized conditions, the bioactivity of GCaMP3 within a hydrogel matrix of micro-optrodes remained similar to that of the protein-free matrix in buffer. The limit of detection of protein optrodes for free calcium was also determined to be 4.3 nM. The hydrogel formulation and fabrication process demonstrated here using microtip optrodes can be easily adapted to other conformation-dependent protein biosensors and can be used in sensing applications.