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Intelligent packaging (IP) is an enhanced version of traditional packaging systems, providing improved functionality. This technology enhances the communication of food packages with consumers by effectively indicating the shelf life, condition of food inside the package, and history of the product. This could increase the convenience of consumers and upgrade the product's safety. The IP system usually consists of an indicator system that gives an idea about the freshness of the product to the consumers. This color-changing indicator can be derived from natural sources such as fruits and vegetables, which contain pigments like anthocyanins, betalains, and curcumins. Sappan wood (Caesalpinia sappan L.) is a notable source of anthocyanin compounds, such as brazilin. The extract of Sappan wood, which could be extracted by various methods ranging from the traditional boiling method to the novel ultrasonic method, could be incorporated into a packaging film made from a biodegradable material like gelatin. The inclusion of this extract turns the normal gelatin film into a pH-dependent color-indicating film. The film changes color in response to pH shifts, which typically occur during food spoilage. Gelatin serves as a strong and compatible matrix for creating smart packaging films due to its solubility and compatibility with various natural extracts. By utilizing this underused resource, a smart packaging film can be developed, contributing valuable innovation to packaging technology. [ABSTRACT FROM AUTHOR]

The distribution of tiny sensors over a specific area was first proposed in the late 1990s as a concept known as smart dust. Several efforts focused primarily on computing and networking capabilities, but quickly ran into problems related to power supply, cost, data transmission, and environmental pollution. To overcome these limitations, we propose using paper-based (confetti-like) chemosensors that exploit the inherent selectivity of chemical reagents, such as colorimetric indicators. In this work, cheap and biodegradable passive sensors made from cellulose could successfully indicate the presence of hazardous chemicals, e.g., strong acids, by a significant color change. A conventional color digital camera attached to a drone could easily detect this from a safe distance. The collected data were processed to define the hazardous area. Our work presents a combination of the smart dust concept, chemosensing, paper-based sensor technology, and low-cost drones for flexible, sensitive, economical, and rapid detection of hazardous chemicals in high-risk scenarios. [ABSTRACT FROM AUTHOR]

The main goal of this work was to develop bio-based and ecofriendly intelligent films as freshness indicators to monitor European hake (Merluccius merluccius) quality during storage by using a visual, non-destructive, and real-time technique. Locust bean gum (LBG)/κ-carrageenan (Car) films incorporating blueberry extract (BLE) or beetroot extract (BEE) were developed and their effectiveness to detect hake deterioration during 7 days of storage at 4 °C was evaluated. A visible color response from pink to blue was observed on the BLE films at the end of hake storage, which correlated with the hake deterioration profile, namely an increase in pH values (from 6.60 ± 0.04 to 8.02 ± 0.03), total viable count (TVC, from 4.61 ± 0.36 to 8.61 ± 0.21 log CFU/g), and total volatile basic nitrogen content (TVB-N, from 10.21 ± 1.97 to 66.78 ± 4.81 mg/100 g) beyond the spoilage threshold. The results of this study are very promising, since it was possible to develop a new effective intelligent bio-based responsive indicator film incorporating natural dye BLE, which has the potential to contribute to food waste reduction and improve food safety by detecting the hake freshness status. [ABSTRACT FROM AUTHOR]

In this work, a previously unknown aldazine, N’-[4-((E)-{(2Z)-[(12-{[(1E)- (dimethylamino)methylene]amino]amino}-2,3-dihydro-1H-benzo[b]xanthene4-yl)methylene]hydrazone}methyl]-2,3-dihydro-1H-benzo[b]xanthene-12-yl]-N,Ndimethylimidoforma-mide was synthesized by reacting the corresponding aldehyde with hydrazine hydrate. The spectral characteristics of the two azomethine dyes were studied: N,N-dimethyl-N’-{4-[(E)-(phenylimino)methyl]-2,3-dihydro-1H-xanthen-9- yl}imidoformamide and N’-[4-((E)-{(2Z)-[(12-{[(1E)-(dimethylamino)methylene]amino]- 2,3-dihydro-1H-benzo[b]xanthen-4-yl)methy-lene]hydrazono}methyl]-2,3-dihydro-1Hbenzo[b]xanthen-12-yl]-N,N-dimethylimidoformamide. Both dyes exhibit a bathochromic shift in their absorption maxima at lower pH levels. The observed deepening of the color can be attributed to the protonation of the azomethine nitrogen atom and the change in the hybridization of the orbital that carries the unpaired electron pair of the azomethine nitrogen atom, switching from the sp² orbital to the unhybridized p-orbital, which is capable of conjugation with the xanthene fragment. The color of N,N-dimethyl-N’-{4- [(E)-(phenylimino)methyl]-2,3-dihydro-1H-xanthen-9-yl}imidoformamide changes from yellow to red as the pH decreases, while the color of N’-[4-((E)-{(2Z)-[(12-{[(1E)- (dimethylamino)methylene]amino]-2,3-dihydro-1H-benzo[b]xanthen4-yl)methylene]hydrazono}methyl]-2,3-dihydro-1H-benzo[b]xanthen-12-yl]-N,Ndimethylimidoformamide shifts from red to blue. The synthesized dyes have potential as pH indicators in acidic environments. These dyes demonstrate a color change not only in response to pH reduction but also in the presence of transition metal salts. [ABSTRACT FROM AUTHOR]

The safety of food products is of prime importance for consumers and manufacturers. Many means can be used to validate a food product's safety before it is consumed. This study is about the preparation, characterization and evaluation of a generally recognized as safe (GRAS) sensitive colorimetric sensor that detects volatile gases (TVB‐N) resulting from fish spoilage, thus indicating the pH variation of packaged fish products. This is performed by coating a thin layer of ink sensors on the surface of the supporting matrix (corona‐treated PET). Various visual pH indicators were prepared based on black rice anthocyanin as an FDA‐approved dye. Black rice, which contains more than 80% cyanidin‐3‐glucoside, is the most prevalent anthocyanin component. Because of its low toxicity and high concentration, it can be utilized as a natural food colourant. pH indicators based on black rice can show distinct colours in various pH: from red (low pH) to violet (4–6) and deep purple/blue (6–7), blue (7–9) to yellowish/light brown (9–13) throughout the acid–base reaction by the analyte. The ink formulation was prepared by incorporating a binder system (PVOH‐PEG) for higher surface wettability, a crosslinking agent (citric acid) for higher adhesion, an antifoaming agent (natural vanillin) and acetic acid as a pH fixing agent. Corona treatments affected substrate surface chemistry in this study. The samples with thermal treatment passed the ASTM D3330 tape test, the 8000 passages for dry sponge and the 25 passages for wet sponge through the abrasion method. Anthocyanin concentration in formulated ink based on calculation by UV–vis spectra is 0.240 mg/100 g. Sensitivity tests towards TVB‐N gases were carried out at a temperature of 4°C to evaluate the performance of colorimetric films with formulated ink along with thermal treatment (temperature: 165°C, time: 5 min) using the volatile gases emitted by the fish sample inside the package. [ABSTRACT FROM AUTHOR]

Active food packaging can protect food from microbial contamination, whereas smart food packaging can be used to monitor food freshness and changes in its quality in real time. Curcumin, the main active substance of turmeric, exhibits preservation effects in part due to its antibacterial, antioxidant, and UV blocking properties. Furthermore, it can act as a photosensitizer to produce reactive oxygen species under radiation at specific wavelengths, thereby destroying bacterial cell membranes via an antibacterial effect. In addition, curcumin can also be used as a pH indicator to monitor and evaluate the deterioration of food in real time. In fact, this compound has been widely used in active and smart food packaging. In this study, the structure of curcumin, as well as its physical and chemical properties, were evaluated. The working mechanism of curcumin as an antibacterial, antioxidant, and UV blocking agent, as well as a photosensitizer and pH indicator in active and smart food active packaging, and the relevant research progress, are discussed. Suggestions for further research and development of curcumin in food packaging are also presented. Thus, this study provides a theoretical foundation for research on curcumin in food packaging in the future. [ABSTRACT FROM AUTHOR]

An ammonium chloride–Congo red (NH4Cl-CR) solution is presented as a potential sensing solution for aldehydes. Monofunctional aldehydes such as formaldehyde, acetaldehyde, benzaldehyde, and isobutyraldehyde caused changes in the pH of the sensing solution, producing a color transition from red-orange to violet to blue. This distinguished them from the other compounds, thereby acting as a qualitative test for the functional group. The NH4Cl-CR solution was also employed in making filter paper-based and silica gel-based sensors for formaldehyde and acetaldehyde vapors. These sensors responded positively towards the aldehyde gases through a color transition from pink to blue. The NH4Cl-CR mixture provides a simple and easy-to-handle reagent for the detection of both liquid and gaseous aldehydes which has potential applications in environmental monitoring.

Methyl orange (p-Me2NC6H4N=NC6H4SO3Na; MO) is one of commonly used azo dyes known as an acid-base indicator, along with phenolphthalein. The chemical structural changes of MO with respect to its acid-base equilibrium in aqueous solutions have been learnt in chemical education. The reaction equations vary among analytical chemistry textbooks. Thus, details on the structures of MO are overviewed from historical perspectives for teaching materials in chemistry. Since protonation of MO potentially occurs not only at the azo group (-N=N-) but also at the dimethylamino group (Me2N-), two different chemical species can be considered; i.e., azonium (-N=NH+-) and ammonium (Me2NH+-). In fact, these tautomers of the two protonated MO species exist, and their equilibrium constants have been reported previously. However, ammonium species has not been presented as protonated MO in most textbooks. Misunderstandingly, another confusion concerning the 'resonance' between ammonium and quinonediiminium (p-Me2N+=C6H4=N-NHC6H4SO3-) of MO is also presented; exactly, there should be among azonium and quiononediiminium. In order to avoid misconceptions about the chemical structures of MO, these cases should be introduced to chemical educators and learners. Methyl orange (MO), as shown in Fig. 1, is an azo compound commonly used as an indicator of the neutralization, along with phenolphthalein. Since the proposal of the name of methyl orange and its use as an indicator by Lunge (1881), MO has been used not only as an acid-base indicator in analytical chemistry (Baker, 1964), but also as a learning material in chemical education (Shimada et al., 1992). MO undergoes a structural change from red in strongly acidic aqueous solutions to yellow at a pH 4 or higher (Barbosa, 2005). [ABSTRACT FROM AUTHOR]

Fresh meat and fish are widely consumed foods with short and very short shelf lives, respectively. Efficient supply chains and the judicious use of food packaging are the most effective means of extending shelf life and thus reducing food waste and improving food safety. Food packaging that allows for the use of a modified atmosphere (MAP) is effective in extending the period where the food is both palatable and safe. However, monitoring the state of aging and the onset of spoilage of the product poses challenges. Microbial counts, pH measurements, and sensory evaluations are all informative but destructive and are therefore only useful for monitoring quality via sampling. More attractive would be a technology that can follow the progress of ageing in an individual product while leaving the food packaging intact. Here, we present a pH indicator to be placed inside each package that may be read by the naked eye. It is a colorimetric indicator with a matrix made of pure amylose (AM; 99% linear α-glucans) and cellulose nanofibers (CNFs). Suitable mechanical properties of films cast of the two polysaccharides were achieved via the optimization of the blending ratio. The films were loaded with either of two pH indicators: anthocyanin extracts from red cabbage (RCA) and the synthetic dye neutral red (NR). Mechanical, thermal, permeability, microstructural, and physical properties were tested for all composite films. Films with 35% CNF (35AC-RCA) and (35AC-NR) were selected for further study. Minced meat was packaged under MAP conditions (70% O2 + 30% CO2), while minced fish was packaged under MAP (70% N2 + 30% CO2) and stored at 5 °C for 20 days. Microbial growth, pH, and sensory scores of the minced meat systems differentiated between fresh (0–6 days) and medium-fresh (7–10 days), and minced fish between fresh (0–10 days) and medium-fresh (11–20 days). The total color difference showed that the RCA indicator was able to differentiate between fresh (red) and medium-fresh (pink-red) minced meat, while for minced fish, this indicator discriminated between three stages: fresh (red), medium-fresh (pink-red), and spoiled (pink-blue). The NR indicator failed to discriminate the freshness of either meat or fish under the effect of MAP. Pearson correlation statistical models showed a correlation between color change of the indicator, pH, content of gases, and gas content. In summary, RCA immobilized in an AM + 35% CNF nanocomposite film can monitor the freshness of packaged minced meat/fish under the effect of MAP via color change that may be evaluated with the naked eye. [ABSTRACT FROM AUTHOR]

An ammonia-sensitive, easy-to-use, pH-responsive food packaging indicator was developed using drop-coated filter paper combined with hydrothermally generated glucose-derived carbon dots (G-CQDs). The stability and efficacy of the prepared G-CQD were confirmed by TEM, zeta potential, and optical and luminescent investigations. The multifunctional G-CQD exhibited potent antibacterial activity against S. enterica, E. coli, L. monocytogenes, and S. aureus and high antioxidant efficacy against ABTS (~ 99%) and DPPH (~ 90%) radicals. The paper indicator coated with G-CQD showed discoloration from pale yellow to reddish brown according to pH 2–12 adjustment, and ammonia in the range of 0.1–250 μM could be detected. As an indicator of spoilage, the indicator's ability to indicate the quality of fish and shrimp was evaluated during storage at 28 °C for 24 h. A noticeable variation in the color of the packing indicator from light yellow to dark brown (fish) and blackish brown (shrimp) was observed concurrently with a rise in total volatile basic nitrogen and a pH change of the packaged sample. The G-CQD-based indicators can be a simple and inexpensive approach for suppliers and customers to visually assess the freshness of fish and shrimp in their supply chain. [ABSTRACT FROM AUTHOR]

The object of this study was the production of a film based on gelatin and chitosan nanofiber (CNF) and containing β-cyclodextrin/Viola odorata L. (β-CD/viola) inclusion complex to monitor fish freshness and spoilage. As a result, the addition of CNF improved the surface morphology and crystalline structure of the films. The addition of the β-CD/viola complex had no adverse effect on the surface morphology and crystalline structure of the film. In addition, gelatin-based films containing β-CD/viola complex had better water vapor permeability, mechanical properties, and antioxidant activity compared to pure gelatin films. The films incorporated with β-CD/viola complex showed considerable sensitivity against pH changes and ammonia gas, and their color changed from slightly brutal pink to green by increasing pH from 2 to 12. Furthermore, the developed smart colorimetric film is used as an indicator for monitoring Kilka fish spoilage. At the end of the storage time of fish, the color of the indicator film changed from khaki to yellow-green, and its color sensitivity (SRGB) was increased to 9.93%. In conclusion, the gelatin-CNF film containing β-CD/viola complex showed a significant potential for monitoring food spoilage. [ABSTRACT FROM AUTHOR]

The global carbon dioxide in the atmosphere is predicted to rise due to fossil fuel emissions during the next century. Carbon dioxide is soluble in water and partially dissociates into bicarbonate and carbonate, releasing protons that decrease the pH. This change in pH is expected to play a critical role in some earth systems, such as the hydrosphere, where ocean acidification affects the survival of marine organisms. This study used aqueous solutions consisting of water with sodium bicarbonate, Miller's lysogeny broth, Roswell Park Memorial Institute 1640 medium, and Dulbecco's Modified Eagle Medium to develop a colourimetric method for the quantification of dissolved carbon dioxide. Various environmental testing conditions were studied using a fluorescent microplate spectrophotometer. The temperature varied between 27 and 42 °C, and the carbon dioxide levels ranged from 0.20 to 10% v/v in the air. The data showed that the amount of dissolved carbon dioxide decreased by 50% in broth solutions, while the reduction in water samples was approximately 18% when the temperature rose from 27 to 42 °C. Furthermore, the composition of the solutions impacted the amount of gas dissolved. The highest amount of dissolved carbon dioxide was observed in the water sample with the lowest salinity, which reached 20,000 ppm CO2 at 27 °C. The lowest amount of dissolved carbon dioxide concentrations was obtained in Miller's lysogeny broth with the highest salinity level, which reached 1200 ppm under the same conditions. The results obtained can be considered a robust estimation method to calculate the amount of dissolved carbon dioxide under different conditions. [ABSTRACT FROM AUTHOR]

The main goal of this work was to develop bio-based and ecofriendly intelligent films as freshness indicators to monitor European hake (Merluccius merluccius) quality during storage by using a visual, non-destructive, and real-time technique. Locust bean gum (LBG)/κ-carrageenan (Car) films incorporating blueberry extract (BLE) or beetroot extract (BEE) were developed and their effectiveness to detect hake deterioration during 7 days of storage at 4 °C was evaluated. A visible color response from pink to blue was observed on the BLE films at the end of hake storage, which correlated with the hake deterioration profile, namely an increase in pH values (from 6.60 ± 0.04 to 8.02 ± 0.03), total viable count (TVC, from 4.61 ± 0.36 to 8.61 ± 0.21 log CFU/g), and total volatile basic nitrogen content (TVB-N, from 10.21 ± 1.97 to 66.78 ± 4.81 mg/100 g) beyond the spoilage threshold. The results of this study are very promising, since it was possible to develop a new effective intelligent bio-based responsive indicator film incorporating natural dye BLE, which has the potential to contribute to food waste reduction and improve food safety by detecting the hake freshness status.

Salinity impacts important processes in plants, reducing their yield. The effect of salinity on the cytosolic pH (pHcyt) has been little studied. In this research, we employed transgenic tobacco plants expressing the pH sensor Pt-GFP to investigate the alterations in pHcyt in cells across various root zones. Furthermore, we examined a wide spectrum of NaCl concentrations (ranging from 0 to 150 mM) and assessed morphological parameters and plant development. Our findings revealed a pattern of cytosolic acidification in cells across all root zones at lower NaCl concentrations (50, 100 mM). Interestingly, at 150 mM NaCl, pHcyt levels either increased or returned to normal, indicating a nonlinear effect of salinity on pHcyt. Most studied parameters related to development and morphology exhibited an inhibitory influence in response to NaCl. Notably, a nonlinear relationship was observed in the cell length within the elongation and differentiation zones. While cell elongation occurred at 50 and 100 mM NaCl, it was not evident at 150 mM NaCl. This suggests a complex interplay between stimulating and inhibitory effects of salinity, contributing to the nonlinear relationship observed between pHcyt, cell length, and NaCl concentration. [ABSTRACT FROM AUTHOR]

Novel green intelligent films based on basil seed gum (BSG)/chitosan containing red cabbage extract (RCA) (0, 2.5, 5, and 10, % (v/v)) as a colorimetric indicator for food freshness detection were fabricated by casting method. The physicochemical, barrier, mechanical, and antioxidant characteristics, as well as sensitivity to pH and ammonia gas of smart edible packaging films, were investigated. The interaction of anthocyanin extract as a natural dye with biopolymers in films characterized by FTIR spectroscopy and SEM images revealed their suitable compatibility. The film with maximum anthocyanin content (10% (v/v)) appeared robust color changes against various pH and ammonia gas levels. The color of indicator films when exposed to alkaline, neutral and acidic buffers are indicated with green, blue, and red colors, respectively. The DPPH radical scavenging activity of smart BSG/chitosan films improved from 23% to 90.32% with increasing RCA content from 2.5 to 10% (v/v). Generally, the incorporation of RCA in film structure enhanced their solubility, WVP, ΔE, turbidity, and flexibility, and reduced tensile strength. The observations successfully confirmed the efficacy of pH‐sensitive indicator smart film based on BSG/chitosan for evaluation of fish spoilage during storage. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) is a major public health concern, but the mechanisms underlying its viral particle formation are not well understood. In this study, we established a system for producing virus-like particles (VLPs) by expressing four structural proteins that make up SARS-CoV-2 virus particles in cells and used a spike (S) protein fused with the HiBiT peptide as a marker for evaluating VLP production. Using this system, we confirmed that the E protein plays an important role in VLP release. Both the co-expression of VPS4A K173Q and ORF3A and treatment with bafilomycin A1 enhanced VLP release. These results suggest that VLPs are released in an endosomal sorting complex required for transport-independent manner and that lysosomal dysfunction is required for the efficient release of VLPs. Screening various E protein mutants revealed that the F56/Y57/Y59 amyloidization motif and the D72/L73/L74/V75 PDZ-binding motif (PBM) are critical for E protein function in VLP release. We also found that E protein expression led to an increase in the pH of lysosomes and that the N15 residue required for viroporin activity, the C40/C43 consensus sequence, or the K63 dibasic motif are required for its function. However, amyloidization or PBM mutations did not affect lysosomal deacidification, suggesting that the mechanisms of E protein activity during VLP formation and lysosomal deacidification are distinct. Overall, this study highlights the importance of the E protein in SARS-CoV-2 viral particle formation, and the results may be useful in the development of drugs that inhibit this process. IMPORTANCE Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), the virus responsible for coronavirus disease 2019 (COVID-19), has caused a global public health crisis. The E protein, a structural protein found in this virus particle, is also known to be a viroporin. As such, it forms oligomeric ion channels or pores in the host cell membrane. However, the relationship between these two functions is poorly understood. In this study, we showed that the roles of E protein in virus particle and viroporin formation are distinct. This study contributes to the development of drugs that inhibit SARS-CoV-2 virus particle formation. Additionally, we designed a highly sensitive and high-throughput virus-like particle detection system using the HiBiT tag, which is a useful tool for studying the release of SARS-CoV-2. [ABSTRACT FROM AUTHOR]

Purple cabbage, turmeric, magenta, amaranth, and red beet contain colour anthocyanins. These colours change according to pH environments. This research aims to explore the potential of utilizing various plant species, such as purple cabbage, turmeric, magenta, amaranth, and red beet, to develop pH indicator paper. The colour solutions of these plants were extracted with deionized water. The extracted solutions were analyzed by IR spectra and UV-Vis spectra. The peak of OH, C=O, and C-O in IR spectra changed in alkaline, neutral, and acidic environments, respectively. The maximum absorption wavelengths of the extracted solutions in UV-Vis spectra were 533 nm and 600 nm in alkaline and neutral environments, respectively. The pH indicator paper was created by impregnating plain white computer paper with extract solutions to achieve uniform colouration. These prepared pH indicator papers were used to detect the pH of household chemicals, including milk, soap, toothpaste, and various fruits and vegetables. The study demonstrates that these plant species exhibit excellent sensitivity to different pH values, possess good durability, and remain unaffected by environmental factors. The developed pH indicator paper holds promising practical applications for testing the pH of diverse chemicals. In this study, the pH indicator paper was employed to determine the acidity or alkalinity levels of commonly found household items, including fruits, beverages, and cleaning solutions. The results highlight the versatility and convenience of utilizing plant-based pH indicator paper for monitoring pH variations in daily life applications. [ABSTRACT FROM AUTHOR]

Hg and Cd are the two most toxic heavy metal ions that could be found in aqueous solutions. In this study, a chemosensor based on 5-(4-((4-nitrophenyl) diazenyl) phenyl)-1,3,4-oxadiazole-2-thiol (DOT) was reported to detect these ions simultaneously. DOT showed high selectivity towards Hg ion by changing the color of the solution from beige to gold-yellow at different concentrations of Hg ion. In comparison, other relevant metals, such as Li+, Na+, K+, Cs+, Mg2+, Ca2+, Al3+, Fe2+, Ag+, Cu2+, Pb2+, Ni2+, Zn2+, Cr3+, Fe3+, Pb4+, Mn2+, and Cd2+ did not affect the color of the DOT solution as the interfering ions. Despite no changes in the color of DOT solution in the presence of Cd ion, a solution containing DOT-Hg complex was changed from gold-yellow to orange by adding Cd ion, providing an approach for detecting Hg and Cd ion simultaneously with UV–Vis and Fluorescent spectroscopy. DOT exhibited a high association constant with a detection limit of 0.05 μM for Hg and Cd ions in an aqueous solution. The results of quantum mechanics (QM) calculations were also consistent with the experimental observations, which indicated that changes in the band gap could explain the various colors of DOT complex with metal ions.

Freshness is one of the main factors affecting consumers' purchase of food. The freshness indicator labels of packaged fresh green bell pepper (Capsicum annuum L.) and greengrocery (Brassica chinensis L.) were constructed, and pH-sensitive indicator labels based on the dye of anthocyanin and the mixing dye of methyl red and bromothymol blue were prepared in this study. At the same time, the color, chlorophyll content and vitamin C content of vegetables were measured in order to explore the applicability of indicator labels in the cool chain transportation of vegetables. Compared with the nature dye, the chemical dye-type indicator labels are more sensitive to pH changes. The results showed that the mixed indicator intelligent label had the best indication effect, and the MB 2 (mixing 1 g/L methyl red and bromothymol blue solutions at a ratio of 3:2 with a concentration of 70 mL/L in indicator film solution) indicator label could effectively indicate the freshness changes in vegetables during storage. Meanwhile, the color changes of the MB 2-type indicator label were correlated with the colors change of the sample, changes in nutrients, and changes in CO2 content inside the packaging. In addition, freshness detection models for green bell pepper and greengrocery by using color information of MB 2 intelligent labels were established. Hence, this pH-sensitive label can be applied as a promising intelligent packaging for non-destructively monitoring the freshness of respiratory and non-respiratory climacteric vegetables. [ABSTRACT FROM AUTHOR]

Chitosan (CS), as a biocompatible and biodegradable nature polymer, has excellent antibacterial property. Poly(ethylene oxide) (PEO), as a biomaterial with thermal stability, biocompatibility and biodegradability, has good spinnability. Anthocyanin, as a natural colorant agent with different molecular structures under different pH values, has good antibacterial and antioxidant properties and can be applied as a pH indicator. Electrospun nanofiber membranes (NFMs) show great application prospects in food packaging due to their unique structural and functional advantages. In this work, anthocyanin/CS/PEO nanofiber membranes (NFMs) for food packaging were batch prepared by the spherical section free surface electrospinning (SSFSE), and their yield reached 5.8 ± 0.4 g/h. The morphology, structure and properties of CS-based NFMs were explored, which showed that they were hydrophilic and had excellent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Among them, anthocyanin/CS/PEO NFMs exhibited better mechanical properties and high antioxidant activity. Furthermore, the color changes of anthocyanin/CS/PEO NFMs at different pH values were investigated, illustrating that they could be used as a visual monitoring food packaging, and their application effects in beef storage were studied. [ABSTRACT FROM AUTHOR]

Summary: Anthocyanins have attracted increasing attention for different packaging systems due to having functional features such as biocompatibility, antioxidative activity, visible colour response at varying pH values. In this study, the extract of Aronia melanocarpa as anthocyanins source was incorporated into guar gum films to take advantage of both antioxidant and pH responsive attributes. Aronia addition did not affect the thermal stability of guar gum films. Radical scavenging activity of the films (%) was measured by 2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH) assay, and aronia added films exhibited very strong antioxidant activity (up to 85%). The colour of aronia solution varied from pink to brown with pH ranging from 1 to 13. Similarly, when the films were immersed in buffer solutions at different pH values, the visual colour varied from pink to brownish yellow. ΔE values of GR_AR_3 (guar gum films having the highest aronia concentration) ranged between 23.31 and 40.62 at pH 1–13. This result proved colour change of the films can be even detected by untrained consumers. Furthermore, the films were found to be very sensitive to ammonia vapour. Aronia incorporated guar gum films could be suggested as both antioxidant films to prevent foods oxidation from oxidation and promising intelligent films to monitor the deterioration of foods. [ABSTRACT FROM AUTHOR]

With outstanding AIE effect, TPE-substituted chalcone derivatives were widely used in the field of mechanochromic luminescent materials, chemical sensors, biosensing, etc. However, TPE-substituted chalcones which could function as pH indicator have not yet been reported until now. In this paper, three novel TPE-substituted chalcones were designed and synthesized as pH indicator for the first time. These TPE-substituted chalcones exhibited sensitive pH-chromic properties with continuous end points (pH = 9.77, 10.98 and 11.51 respectively). These pH indicators can be employed in fabrication of pH strips with higher accuracy compared to universal pH strips. Detection of Et3N can also be realized by these TPE-substituted chalcones with advantages in low cost, high sensitivity, easy-handle and real-time. [ABSTRACT FROM AUTHOR]

Whey protein isolate (WPI)-ascorbic acid (AA) solutions were used to generate powders using spray drying technology. The powders changed color during storage. In this study, spray-dried powders with different ratios of WPI to AA were aged under different conditions. Significant redness generation was observed by heating spray-dried WPI-ascorbic acid powders up to 80 °C rapidly, and redness was generated over a longer time (up to 3 to 5 days) at room temperature. This change in redness was used to develop a packaging indicator for tracking temperature and time, which may be used to indicate the degree of food freshness by visual observation. Another application was to make the aged powders into tablets, and red liquid extracts have been leached out of the tablets into aqueous solutions. The colors of the solutions with the aged WPI-AA powders and their red extract changed at different pHs (from 3 to 11). These extracts were coated onto paper to create low toxicity pH indicators for food testing. [ABSTRACT FROM AUTHOR]

In this work, we monitored the fluorescence quantum efficiency (η) and the fluorescence lifetime (τ) of natural dye extracts from the leaves of Tradescantia pallida purpurea. The natural dye was extracted from leaves in aqueous solutions as a function of the potential of hydrogen (pH). The η was determined from conical diffraction (CD) pattern measurements due to thermally-driven self-phase modulation. The fluorescence spectra and time-resolved fluorescence measurements corroborate the CD results, and the average η ≈ 0.28 and τ ≈ 3.1 ns values were obtained in the pH range 3.96–8.02. In addition, the extracted natural dye was tested as a possible colorimetric and/or fluorometric pH indicator in milk.

Sumac (Rhus coriaria) is a natural source of phenolic compounds especially anthocyanins and tannins which makes it a potential active agent and colorimetric indicator. This work aimed to prepare simultaneously antioxidant, antimicrobial, and pH-responsive guar gum (GR) films by incorporating sumac. Moisture content, water vapor permeability (WVP), opacity, color, thermal, antioxidant, antimicrobial properties, and pH-response of the films were analyzed. Sumac addition resulted in WVP and higher opacity values when compared to GR films. Guar gum sumac (GR_S) films showed strong antioxidant activity (up to 99%). Sumac incorporation bestowed the guar gum films with antimicrobial function against Staphylococcus aureus. When the films were immersed in buffer solutions at different pH values, the color of the films changed from pink to brown which proved the GR_S films' colorimetric sensitivity to pH change. Thus, this study demonstrated that GR_S films have the potential to be promising active and pH-sensitive food packaging materials. [ABSTRACT FROM AUTHOR]

In this work, we monitored the fluorescence quantum efficiency (η) and the fluorescence lifetime (τ) of natural dye extracts from the leaves of Tradescantia pallida purpurea. The natural dye was extracted from leaves in aqueous solutions as a function of the potential of hydrogen (pH). The η was determined from conical diffraction (CD) pattern measurements due to thermally-driven self-phase modulation. The fluorescence spectra and time-resolved fluorescence measurements corroborate the CD results, and the average η ≈ 0.28 and τ ≈ 3.1 ns values were obtained in the pH range 3.96–8.02. In addition, the extracted natural dye was tested as a possible colorimetric and/or fluorometric pH indicator in milk. [ABSTRACT FROM AUTHOR]

Colorimetric sensing techniques for point(s), linear and areal array(s) were developed using image sensors and novel image processing software for chemical, biological and medical applications. Monitoring and recording of colorimetric information on one or more specimens can be carried out by specially designed image processing software. The colorimetric information on real-time monitoring and recorded images or video clips can be analyzed for point(s), line(s) and area(s) of interest for manual and automatic data collection. Ex situ and in situ colorimetric data can be used as signals for process control, process optimization, safety and security alarms, and inputs for machine learning, including artificial intelligence. As an analytical example, video clips of chromatographic experiments using different colored inks on filter papers dipped in water and randomly blinking light-emitting-diode-based decorative lights were used. The colorimetric information on points, lines and areas, with different sizes from the video clips, were extracted and analyzed as a function of time. The video analysis results were both visualized as time-lapse images and RGB (red, green, blue) color/intensity graphs as a function of time. As a demonstration of the developed colorimetric analysis technique, the colorimetric information was expressed as static and time-series combinations of RGB intensity, HSV (hue, saturation and value) and CIE L*a*b* values. Both static and dynamic colorimetric analysis of photographs and/or video files from image sensors were successfully demonstrated using a novel image processing software. [ABSTRACT FROM AUTHOR]

Synthetic approach to fluorescent polyaza- and polyoxadiazamacrocycles comprising a structural fragment of 6,7-diamino-2,3-diphenylquinoxaline has been elaborated using Pd-catalyzed amination providing target compounds in yields up to 77%. A series of nine novel N- and N,O-containing macrocyclic ligands differing by the number of donor sites and cavity size has been obtained. These compounds possess well-pronounced fluorescent properties with emission maxima in a blue region in aprotic solvents and high quantum yields of fluorescence, while in proton media, fluorescence shifts towards the green region of the spectrum. Using macrocycles 5c and 5e as examples, we have shown that such compounds can serve as dual-channel (colorimetric and fluorimetric) pH indicators in water media, with pH transition point and response being dependent on the macrocycle structure due to different sequences of protonation steps. [ABSTRACT FROM AUTHOR]

Ensuring food safety by monitoring freshness is crucial, particularly for high-protein meat products susceptible to spoilage. Smart packaging with pH-sensitive indicators, using natural pigments such as anthocyanin, provides a cost-effective and non-invasive solution. In this work, a novel colorimetric pH sensor based on biopolymer and natural deep eutectic solvents (NADES) is proposed. The NADES composed by Betaine: Glycerol: Water (BGH) was used for the anthocyanin extraction from Brassica oleracea (Purple Cabbage, PC), using the ultrasonic "one-step" method and BGH extraction efficiency was compared with water. Then, the BGH extract was mixed with different concentrations of xanthan gum (XG) 5, 10, 15 and 20%. The biopolymeric materials were characterized in terms of structure, mechanical properties, stability and pH response. The combination containing 10 % of xanthan gum (PC-BGH-XG10) presented suitable features to be used as a sensor. Thus, PC-BGH-XG10 was applied for real-time monitoring of meat spoilage. Interestingly colour changes were visible to the naked eye and they were successfully correlated with microbiological assays. To the best of our knowledge, this is the first integration of NADES and xanthan gum in the development of a colorimetric pH sensor. The proposed approach represents a green strategy for in-situ control of packaged foods intended for final consumption. [Display omitted] • Novel NADES based biopolymeric pH sensor for monitoring meat spoilage was developed. • Anthocyanins from Brassica oleracea were used as a natural dye. • NADES were applied as extractant solvent and also as plasticizer agent. • Sensor colour changes, visible to the naked eye, are a useful tool for consumers. • This is the first integration of NADES and xanthan gum in pH sensor development. [ABSTRACT FROM AUTHOR]

A new pH-sensitive intelligent packaging system was developed composed of extracted and purified basil seed gum (BG) containing aqueous malva sylvestris extract (MS) and varying amounts of synthesized graphene oxide (GO). In the following, the characteristics of prepared films including spectroscopic, physio-mechanical, thermogravimetry, fracture-surface morphology, anthocyanin release, and pH and TVB-N sensitivity, were investigated. Our results revealed that the addition of 0.5 wt % MS into the BG matrix induced pH sensitivity to the film and resulted in a visible color change from pH 2.0 to 14.0; however, it reduced the thermal and physio-mechanical properties. In this regard, the effective presence of the optimum concentration of GO (0.25 wt%) in enhancing the mechanical and thermal properties of the BG-MS films was shown. Moreover, inspecting the release kinetics demonstrated a controllable release for BG-MS-GO film compared to the BG-MS film in 48 h. Furthermore, the total volatile basic nitrogen (TVB-N) content and pH value were shown to be highly correlated with the color changes of the freshness indicator film during the storage of salmon fillets at 25 °C for 36 h. Therefore, it was shown that BG-MS-GO film can be used as a highly effective freshness/spoilage indicator of proteinic products. [ABSTRACT FROM AUTHOR]

Visual pH-responsive packaging material is particularly important in food supply chain safety monitoring due to their non-destructive monitoring method and intuitive result. However, it has always been limited by the instability performance of pH-response components and carriers, which further hinders its wide food safety application. To address these challenges, we selected cellulose with remarkable biocompatibility and mechanical properties as the carrier, and high pH-responsive curcumin to develop a smart packaging material (RC/GC composite film) with real-time food safety monitoring. Compared with pure cellulose film, the RC/GC composite film exhibited excellent mechanical properties (4-fold enhancement) and thermal stability (100 °C increasing). Meanwhile, based on the first reported strategy of curcumin in-situ growth during cellulose film formation, the RC/GC composite film exhibited exceptional antioxidant activity (89.2 %), antimicrobial property (91.6 %), and significant pH-responsive sensitivity (within 15 s). This innovative approach offers a new strategy for easy-to-use and effective monitoring of food spoilage in packaging materials. • In situ grow curcumin in cellulose film within a mixed acid solvent displacement process. • RC/GC film provides rapid discolouration response to ammonia from food spoilage within 15 s. • Curcumin improved strength (4-fold increase) and thermal stability (T max of 354.4 °C) of primitive membranes. [ABSTRACT FROM AUTHOR]

Humidity-induced discoloration from surface coating is promising, but the surface suffers from low stability, due to the lack of covalent interactions between pH indicator, hygroscopic components and fabrics. Here, we report a strategy to fabricate all-polymer-based, highly hygroscopic fabrics with humidity-induced discoloration and pH-induced discoloration simply by covalently coating/polymerizing a reactive pH indicator and a hygroscopic monomer onto fabrics. The resulting fabrics show remarkable and reversible discoloration from blue to yellow, upon increasing relative humidity. The high reusability of the discoloration has been verified by repeating moisture adsorption and desorption over 20 cycles, without obvious deterioration in the discoloration behavior. Moreover, the fabrics display discoloration behaviors upon contacting aqueous solutions and vapors at different pHs. The simple coating, significant and reversible color transition, and the high reusability enable the all-polymer-based, hygroscopic fabrics to be excellent candidates for humidity indication and pH indication. [Display omitted] • Fabrication: Coating from a reactive pH indicator and a hygroscopic monomer. • The coating: Highly hygroscopicity, pH responsive discoloration. • The fabrics: Humidity-induced discoloration, pH-induced discoloration. [ABSTRACT FROM AUTHOR]

In order to quickly and accurately non-destructive real-time monitoring of fish freshness, a visual colorimetric array sensor was constructed in this study based on anodized aluminum flakes as the substrate and 13 indicators selected as gas-sensitive materials. The freshness of turbot during storage was measured by using the constructed colorimetric array sensor. The results showed that the total volatile basic nitrogen (TVB-N) value of turbot reached 32.85 mg/100 g when the storage time was more than 22 h at 25 ℃, and the fish was rotten. At this time, the color of the array points in the colorimetric sensor array changed. The RGB values of sensor array points before and after response were extracted and subtracted, and the clustering analysis and principal component analysis were carried out. The results showed that the colorimetric array sensor was able to accurately distinguish the freshness of fish in different storage time periods. In addition, the array sensor was applied to detect the freshness of carp and American redfish at different storage times, and the results showed that there was no significant difference between the TVB-N values predicted by the colorimetric array sensor and the actual measured values. Therefore, it is feasible to apply the sensor to fish freshness monitoring.

pH indicators have emerged as promising tools for real-time monitoring of product freshness and quality in intelligent food packaging applications. However, ensuring the stability of these indicators is critical for practical use. This study aims to evaluate the stability of anthocyanins-loaded alginate hydrogel beads of varying sizes at different temperatures under accelerated light conditions and relative humidity (RH) levels of 53% and 97% during 21 days of storage. Moreover, their sensitivity to the principal spoilage volatiles of muscle food products such as ammonia (NH3), dimethylamine (DMA) and trimethylamine (TMA) was investigated. The half-life of cyanidin-3-glucoside in small hydrogel beads was roughly twice as long as that of the larger beads under accelerated light exposure at 4 °C and they were less likely to undergo noticeable color changes over time. Both sizes of hydrogel beads stored at 97% RH and 4 °C showed color stability over the 21-day period with minimal color variation (|ΔE| ≤ 3). The UV–vis spectra of the purple corn extract exhibited changes across pH 2 to 12, as evidenced by the visible color variations, ranging from pink to green. The limit of detection (LOD) for NH3 was 25 ppm for small beads and 15 ppm for large ones. Both types of beads exhibited similar LOD for DMA and TMA, around 48 ppm. This research showed that alginate hydrogel beads containing anthocyanins from purple corn are a viable option for developing intelligent packaging of muscle foods. Furthermore, the use of hydrogel beads of different sizes can be customized to specific muscle foods based on the primary spoilage compound generated during spoilage.

The synthesis and characterisation of new dyes based on indolizines bearing catechol groups in their structure is presented. The preparation was carried out through a simple three component one-pot reaction promoted by CuNPs/C, between pyridine-2-carbaldehyde, an aromatic alkyne and a tetrahydroisoquinoline (THIQ) functionalized with catechol groups. The products were isolated in 30%–34% yield, which was considered more than acceptable considering that the catechol hydroxyl groups were not protected prior to reaction. In view of the colour developed by the products and their response to the acidic and basic conditions of the medium, product 3aa was studied by UV-Vis and NMR spectroscopies at different pH values. We concluded that product 3aa suffered two deprotonations at pKa of 4.4 and 9.5, giving three species in a pH range between 2–12, with colours varying from light red to deep orange. The reversibility of the process observed for 3aa at different pH values, together with its changes in colour, make this new family of products attractive candidates to use them as pH indicators.

In recent years, there has been an increase in demand for pH color-changing materials. These materials can visually communicate signals to people by connecting pH changes with color information. Embedding pH indicators into fibers to create flexible color-changing materials is an effective way to develop daily wearable products. For the stability of the indicator and the indirect contact of the indicator with the human body, it is usually necessary to encapsulate it in capsules. In this study, different pH indicators (Thymol Blue-TB, Bromocresol Green-BCG, and Bromocresol Purple-BCP) were mixed into a wide-domain pH color-changing indicator and encapsulated with ethyl cellulose (EC) by the flash nanoprecipitation (FNP) method using a new-type droplet-shaped confined impinging jet mixer. The effects of flow rate, core-to-wall ratio, and mixed solution concentration on the formation of the nanocapsules were investigated. In addition, the morphology, particle size, size distribution, dispersion stability, and encapsulation efficiency were systematically studied. At a core-to-wall ratio of 1:2, a mixed solution with a concentration of 6 mg/mL and a feed flow rate of 40 mL/min produced nanocapsules with an average particle size of 141.83 ± 0.98 nm and a PDI of 0.125 ± 0.01. Furthermore, a zeta potential with a range of −31.83 ± 0.23 mV and an encapsulation efficiency of 75.20 ± 1.72% were observed at 1:2 core-to-wall ratios. It was concluded that the color of the nanocapsules continuously changed from yellow to green and green to blue when the pH range was increased from 3 to 10. The color-changing nanocapsules were then embedded into sodium alginate hydrogel fibers, resulting in the same color-changing trend (pH 3–10) as that obtained for the nanocapsules. This study can be useful for the pH monitoring of various body fluids, such as wound exudate, urine, and sweat. [ABSTRACT FROM AUTHOR]

Soil salinity negatively affects the growth, development and yield of plants. Acidification of the cytosol in cells of glycophytes was reported under salinity, while various types of plant cells can have a specific reaction under the same conditions. Transgenic Arabidopsis plants expressing the pH sensor Pt-GFP in the cytosol were used in this work for determination of morphometric changes and cytosolic pH changes in the superficial cells of Arabidopsis roots under chronic salinity in vitro. We did not find changes in the length of the root cap cells, while there was a decrease in the length of the differentiation zone under 50, 75 mM NaCl and the size of the epidermal cells of the differentiation zone under 75 mM NaCl. The most significant changes of cytosolic pH to chronic salinity was noted in columella (decrease by 1 pH unit at 75 mM NaCl) and epidermal cells of the differentiation zone (decrease by 0.6 and 0.4 pH units at 50 and 75 mM NaCl, respectively). In developed lateral root cap cells, acidification of cytosol by 0.4 units occurred only under 75 mM NaCl in the medium. In poorly differentiated lateral cells of the root cap, there were no changes in pH under chronic salinity. [ABSTRACT FROM AUTHOR]

In this study, blue corn extract (BCE) was added to a corn starch, polyvinyl alcohol (PVA) based smart packaging indicator film. Characterization of physical properties of films by tensile test and color difference test. The color changes of BCE and corn starch/PVA/BCE composite films were investigated in the pH range of 1–14. Scanning electron microscopy images showed good compatibility of BCE with the substrate. BCE significantly increased the tensile strength, elongation at break and water content of the films (p < 0.05). The corn starch/PVA/BCE films had good color stability. The addition of BCE had no significant effect on film thickness (p < 0.05). The corn starch/PVA/BCE film underwent a significant change from red to dark purple during the film application for the preservation and storage of tilapia. The results showed that this pH sensitive film has the potential to indicate the shelf life of tilapia. Practical Application: Smart pH indicator films were prepared by mixing different ratios of blue corn extract with corn starch/PVA substrates. The effects of different ratios of BCE on the physical properties and pH sensitivity of the composite membranes were investigated. During the storage of tilapia, the composite membranes showed a clear change from red to dark purple. [ABSTRACT FROM AUTHOR]

Investigation of the neutralizing behavior of concrete is essential, as it can help reveal the durability properties of concrete structures. In this paper, anthocyanin extracted from February orchid (F. orchid) petals was used to characterize the neutralized (carbonated, leached, and sulfate-attacked) regions of cement-based materials. The durability of F. orchid indicator was evaluated through comparison between discoloring behaviors of fresh and aged F. orchid indicators, and the capability of the new indicator in neutralization characterization was then verified by combining indicator (phenolphthalein, malachite green, indigo carmine, or thymolphthalein) spray, X-ray computed tomography (CT), and the X-ray attenuation method (XRAM). The result in the present study showed that, with a lower color intensity as compared to phenolphthalein/thymolphthalein, F. orchid indicator was less preferable in studying carbonation but a better choice in characterizing leaching and sulfate attack of cement-based materials. In addition, a sharp carbonation front was revealed in the present study, suggesting that the carbonation process in this study was controlled mainly by diffusion. For leaching and sulfate attack, the broader fronts revealed suggested that both processes were co-controlled by diffusion and reaction. The current work serves as a 'leap' toward the application of natural pigments in analyzing the durability of concrete structures. [ABSTRACT FROM AUTHOR]

Smart packaging can provide real-time information about changes in food quality and impart a protective effect to the food product by using active agents. This study aimed to develop a smart bilayer film (alginate/agar) with a cellulose nanosphere (CNs) from corncob. The bilayer films were prepared using 1.5% (w/w) sodium alginate with 0.25% (w/v) butterfly pea extract incorporated (indicator layer) and 2% (w/w) agar containing 0.5% (w/v) catechin–lysozyme (ratio 1:1) (active layer). The CNs were incorporated into the alginate layer at different concentrations (0, 5, 10, 20, and 30% w/w-based film) in order to improve the film's properties. The thickness of smart bilayer film dramatically increased with the increase of CNs concentration. The inclusion of CNs reduced the transparency and elongation at break of the smart bilayer film while increasing its tensile strength (p < 0.05). The integration of CNs did not significantly affect the solubility and water vapor permeability of the smart bilayer film (p > 0.05). The smart bilayer film displayed a blue film with a glossy (without CNs) or matte surface (with CNs). The developed bilayer film shows excellent pH sensitivity, changing color at a wide range of pHs, and has a good response to ammonia and acetic acid gases. The film possesses exceptional antimicrobial and antioxidant activities. The integration of CNs did not influence the antibacterial activity of the film, despite the presence of a higher level of DPPH in film containing CNs. The smart bilayer film was effectively used to monitor shrimp freshness. These findings imply that smart bilayer films with and without CNs facilitate food safety and increase food shelf life by monitoring food quality. [ABSTRACT FROM AUTHOR]

Plant root absorbs water and nutrients from the soil, and the root apoplastic fluid (AF) is an important intermediate between cells and the surrounding environment. The acid growth theory suggests that an acidic AF is needed for cell wall expansion during root growth. However, technical limitations have precluded the quantification of root apoplastic fluid pH (AF‐pH). Here, we used Green‐enhanced Nano‐lantern (GeNL), a chimeric protein of the luciferase NanoLuc (Nluc) and the green fluorescent protein mNeonGreen (mNG), as a ratiometric pH indicator based on the pH dependency of bioluminescence resonance energy transfer efficiency from Nluc to mNG. Luminescence spectrum of GeNL changed reciprocally from pH 4.5 to 7.5, with a pKa of 5.5. By fusing GeNL to a novel signal peptide from Arabidopsis thaliana Cellulase 1, we localised GeNL in A. thaliana AF. We visualised AF dynamics at subcellular resolution over 30 min and determined flow velocity in the maturation zone to be 0.97± 0.06 μm/s. We confirmed that the developing root AF is acidic in the pH range of 5.1−5.7, suggesting that the AF‐pH is tightly regulated during root elongation. These results support the acid growth theory and provide evidence for AF‐pH maintenance despite changes in ambient pH. Summary statement: We visualised and quantified the pH dynamics by localising a bioluminescent ratiometric indicator to the root apoplastic fluid (AF) of Arabidopsis thaliana. The AF‐pH was dynamically acidified as the root developed regardless of different ambient pH, suggesting a strict regulation of AF‐pH. [ABSTRACT FROM AUTHOR]

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Polymerase chain reaction (PCR) is the gold standard for molecular diagnoses due to its high sensitivity and accuracy. However, conventional PCR exhibits limitations including extended analysis time and complicated sample treatment. To shorten the analysis time of standard three-step PCR, we employed a two-step PCR allowing for fast amplification of nucleic acid in a chip format. Moreover, to realize a fully-integrated and on-site visual discrimination of opportunistic and multidrug-resistant pathogens, namely, Enterococcus faecium and Acinetobacter baumannii. DNA was extracted using FTA card, and pH-dependent color changes of the PCR amplicons were monitored by using phenolphthalein as a pH indicator. The overall reaction took less than 35 min and exhibited high selectivity and sensitivity confirmed by the limit of detection of approximately 10 3  CFU/mL for E. faecium. In addition, carbapenem-resistant A. baumannii was successfully detected demonstrating the clinical applicability of the introduced technique using a thermoplastic chip. E. faecium both in bacterial cell culture solution and a contaminated surface were also successfully detected proving the feasibility of the chip-based detection system and paving the way for a facile discrimination of opportunistic pathogens prevalent in hospitals and our environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Annually, about one-third of the food produced around the world is wasted due to spoilage. Food contamination and spoilage, along with the use and disposal of nondegradable packaging materials, impact human health and have huge economic and sustainability implications. Achieving sustainability within the food system requires innovative solutions to reduce the environmental footprint. Herein, we describe the formulation, scalable manufacturing, and characterization of three-dimensional (3D)-printed sensors prepared from a mixture of edible biopolymer hydrogels, 8% alginate, and 10% gelatin and nanocellulose (CNC) as a reinforcement filler. We demonstrate that incorporating CNC improves the overall mechanical performance of the printed film and enables the stabilization of pH-responsive dyes for monitoring the release of total volatile basic nitrogen (TVB-N), an indicator of food freshness. Mechanical performance enhancement includes increases of 43% in load-depth indentation, 28.2% in hardness, and 17.4% in elastic modulus. This enhancement facilitates its use as a smart label technology, enabling the visual assessment of spoilage when placed inside packaging over a period of 3 days at room temperature. The 3D-printed film exhibits excellent durability, flexibility, shape memory, and robustness, along with pH responsiveness, showing distinctive color changes over the pH range of 2 to 13. These performances are demonstrated in packaged meat and fish, enabling monitoring over several days and illustrating potential as a real-time freshness indicator. The material formulations developed in this work are biodegradable, eco-friendly, and inexpensive, making them suitable candidates for smart and sustainable food packaging.

Freshness is one of the main factors affecting consumers’ purchase of food. The freshness indicator labels of packaged fresh green bell pepper (Capsicum annuum L.) and greengrocery (Brassica chinensis L.) were constructed, and pH-sensitive indicator labels based on the dye of anthocyanin and the mixing dye of methyl red and bromothymol blue were prepared in this study. At the same time, the color, chlorophyll content and vitamin C content of vegetables were measured in order to explore the applicability of indicator labels in the cool chain transportation of vegetables. Compared with the nature dye, the chemical dye-type indicator labels are more sensitive to pH changes. The results showed that the mixed indicator intelligent label had the best indication effect, and the MB 2 (mixing 1 g/L methyl red and bromothymol blue solutions at a ratio of 3:2 with a concentration of 70 mL/L in indicator film solution) indicator label could effectively indicate the freshness changes in vegetables during storage. Meanwhile, the color changes of the MB 2-type indicator label were correlated with the colors change of the sample, changes in nutrients, and changes in CO2 content inside the packaging. In addition, freshness detection models for green bell pepper and greengrocery by using color information of MB 2 intelligent labels were established. Hence, this pH-sensitive label can be applied as a promising intelligent packaging for non-destructively monitoring the freshness of respiratory and non-respiratory climacteric vegetables.