Food Preservation Research Articles

Recent advances in natural food preservatives: a sustainable solution for food safety and shelf life extension

Recent advances in natural food preservatives: a sustainable solution for food safety and shelf life extension

Chemical Composition, Biological Activity, and Application of Rosa damascena Essential Oil as an Antimicrobial Agent in Minimally Processed Eggplant Inoculated with Salmonella enterica

Rosa damascena is mostly grown for its usage in the food, medical, and perfume industries, while it is also used as an attractive plant in parks, gardens, and homes. The use of R. damascena essential oil may yield new results in relation to the antimicrobial activity of essential oils and their use mainly in extending the shelf life of foods. This study investigates the chemical composition and antimicrobial properties of Rosa damascena essential oil (RDEO) using gas chromatography–mass spectrometry (GC-MS) and various bioassays to explore its potential applications in food preservation and microorganism growth control. The GC-MS analysis revealed that RDEO is predominantly composed of phenylethyl alcohol (70%), which is known for its antimicrobial and aromatic properties. Additionally, other significant constituents were identified, including nerol, citronellol, and geraniol, which may contribute to the EOs overall bioactivity. The antimicrobial activity was assessed through the minimal inhibition concentration against five Candida yeast strains, four Gram-positive, and four Gram-negative bacteria, including biofilm-forming Salmonella enterica. Determination of minimum inhibitory concentrations (MIC) revealed the strongest effects of RDEO’s on Gram-negative species, with MIC50 values as low as 0.250 mg/mL for S. enterica. Moreover, an in situ assessment utilizing fruit and vegetable models demonstrated that the vapor phase of RDEO significantly suppressed microbial growth, with the most substantial reductions observed on kiwi and banana models. As a result of our study, the antimicrobial effect of RDEO on the microbiota of sous vide processed eggplant was detected, as well as an inhibitory effect on S. enterica during storage. The insecticidal activity against Megabruchidius dorsalis Fahreus, 1839, was also studied in this work and the best insecticidal activity was found at the highest concentrations. These results suggest that RDEO has the potential to serve as a natural antimicrobial agent in food preservation and safety applications, providing an alternative to synthetic preservatives.

Development of gel-like, high encapsulation efficiency and antibacterial cinnamaldehyde-loaded Pickering emulsion stabilized by EGCG enhanced whey protein isolate-gum arabic ternary nanocomplex

Pickering emulsions (PEs) loaded with essential oils have proven to be a promising delivery system in food preservation, thus attracting increasing research attention. In this study, epigallocatechin gallate (EGCG) enhanced whey protein isolate(WPI)-gum Arabic(GA) ternary spherical nanocomplex (WGE) was fabricated by thermal and pH double-induced method and used to stabilize antibacterial, antioxidant and sustained release Pickering emulsions loaded with cinnamaldehyde. The WGE nanocomplex exhibited biphasic surface wettability (78.2±2.8°), 1.73 times that of WPI, as well as outstanding interfacial tension (5.60 mN/m), 44.6 % lower than that of WPI-GA, mainly due to the electrostatic interactions between WPI and GA and enhanced surface hydrophobicity causing by EGCG, indicating its superb ability to stabilize Pickering emulsions. Using WGE nanocomplex as the Pickering emulsion stabilizer, PEs template was constructed. Confocal laser scanning microscopy (CLSM) showed the formation of a dense oil-water interface layer and gel-like network structure, which demonstrated good storage stability against creaming and coalescence, benefiting to cinnamaldehyde encapsulation. Finally, cinnamaldehyde was encapsulated effectively using this PEs pattern with high encapsulation efficiency under different conditions. The cinnamaldehyde Pickering emulsions (CPEs) demonstrated superior antioxidant ability against DPPH (>85 %) and ABTS (>78 %), as well as effective antibacterial capability against E. coli (>99.9999 %) and S. aureus (>99.99 %) than pure cinnamaldehyde. Moreover, CPEs showed slow sustained-release ability, which could satisfyingly prolong the biological activity of cinnamaldehyde. Therefore, the WGE stabilized cinnamaldehyde Pickering emulsions fabricated in this work might provide a promising alternative for the delivery of antibacterial and controlled release essential oils in the food industry.

Antifungal Effects and Postharvest Diseases Control Potential of E, E-2, 4-Nonadienal against Rhizopus stolonifer.

Pathogenic microorganisms are a significant cause of food spoilage, adversely affecting both product quality and human health. This study evaluated the antifungal activities of 34 aldehydes against foodborne and plant pathogenic fungi, identifying 8 promising lead compounds. Among them, E, E-2, 4-nonadienal exhibited optimal effects against Rhizopus stolonifer with an EC50 of 11.29 μg/mL. In vitro assays demonstrated that E, E-2, 4-nonadienal significantly impact R. stolonifer through both direct contact and fumigation. The preliminary mode of action (MOA) studies indicated that it effectively inhibited spore germination, disrupted ergosterol biosynthesis, and induced oxidative stress, affecting the permeability of the fungal cell membrane and altering mycelial morphology. Additionally, E, E-2, 4-nonadienal significantly reduced soft rot in spore-infected stored cherry tomatoes and showed low toxicity. Thus, aldehydes, exemplified by E, E-2, 4-nonadienal, are potential food and agricultural preservatives, offering efficiency, safety, and cost-effectiveness.

Investigating the Synergistic Effects of Carvacrol and Citral-Edible Polysaccharide-Based Nanoemulgels on Shelf Life Extension of Chalkidiki Green Table Olives

Modern bioeconomy and sustainability demands lead food technology in the development of novel biobased edible food preservatives. Herein, the development and characterization of novel polysaccharide (xanthan gum and kappa-carrageenan)-based nanoemulgels (NGs) enhanced with essential oil derivatives; pure citral (CT); pure carvacrol (CV); and various CT:CV ratios (25:75, 50:50, and 75:25) are presented. The obtained NGs are applied as active edible coatings for extending the shelf life of Protected Designation of Origin (PDO) green table olives of Chalkidiki. The zeta potential demonstrated the high stability of the treatments, while light scattering measurement and scanning electron microscopy images confirmed the <100 nm droplet size. EC50 indicated high antioxidant activity for all the tested samples. The fractional inhibitory concentration (FIC) confirmed the synergistic effect of NG with a CT:CV ratio at 50:50 against Staphylococcus aureus and at CT:CV ratios 25:75 and 75:25 against E. coli O157:H7. NG coatings with CT:CV ratios at 50:50 and at 25:75 effectively controlled the weight loss at 0.5%, maintained stable pH levels, and preserved the visual quality of green olives on day 21. The synergistic effect between CT and CV was confirmed as they reduced the spoilage microorganisms of yeasts and molds by 2-log [CFU/g] compared to the control and almost 1 log [CFU/g] difference from pure CT and CV-based NGs without affecting the growth of beneficial lactic acid bacteria crucial for fermentation. NGs with CT:CV ratios at 50:50 and at 25:75 demonstrated superior effectiveness in preventing discoloration and maintaining the main sensory attributes. Overall, shelf life extension was achieved in 21 compared to only 7 of the uncoated ones. Finally, this study demonstrates the potential of polysaccharide-based NGs in mixtures of CT and CV for the shelf life extension of fermented food products.

Synergistic Integration of α-Ag2WO4 into PLA/PBAT for the Development of Electrospun Membranes: Advancing Structural Integrity and Antimicrobial Efficacy.

The rising resistance of various pathogens and the demand for materials that prevent infections drive the need to develop broad-spectrum antimicrobial membranes capable of combating a range of microorganisms, thereby enhancing safety in biomedical and industrial applications. Herein, we introduce a simple and efficient technique to engineer membranes composed of polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) biopolymers and α-Ag2WO4 particles using an electrospinning technique. The corresponding structural, thermal, mechanical, and antimicrobial properties were characterized. X-ray diffraction (XRD) patterns confirmed the integration of crystalline α-Ag2WO4 within the polymer matrix. Scanning electron microscopy (SEM) and Raman confocal microscopy revealed uniformly dispersed α-Ag2WO4 particles in the electrospun fibers, influencing their diameter and surface roughness. Thermal analysis indicated adjustments in the thermal stability and crystallinity of the composites with an increasing α-Ag2WO4 content. Dynamic mechanical analysis (DMA) highlighted variations in storage modulus and glass transition temperatures due to interactions between α-Ag2WO4 and polymer chains, with tensile tests showing an increase in elastic modulus and ultimate tensile strength as the α-Ag2WO4 content increased. Antimicrobial assessments revealed that PLA/PBAT membranes with α-Ag2WO4 showed pronounced antibacterial activity, forming inhibition halos across all samples against Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and Mycobacterium smegmatis (a surrogate for Mycobacterium tuberculosis). These membranes also exhibited potent antiviral activity against bacteriophage phi 6, a surrogate for SARS-CoV-2, suggesting potential applications in combating infections caused by enveloped viruses. The antimicrobial activities are attributed to the generation of reactive oxygen species (ROS) and the controlled release of Ag+ ions. This work underscores the multifaceted capabilities of α-Ag2WO4-enhanced PLA/PBAT membranes in combating bacterial and viral growth, where both durability and microbial resistance are critical. Taken together, our findings provide a solution for obtaining advanced materials to be applied in a wide range of industrial applications, such as filtration systems, food preservation, antimicrobial coatings, protective textiles, and cleaning products.

An Intelligent Indicator Film Based on Food Derived Materials for Real-Time Visual Monitoring of Salmon Freshness

ABSTRACT Determining the freshness of aquatic products during food processing, transportation, and preservation is critical for ensuring food safety and quality. In this study, we developed intelligent indicator films sensitive to nitrogen compounds using sodium alginate, glycerol, and natural pigments. These films exhibited excellent indicating performance in monitoring the freshness of salmon, including total volatile basic nitrogen (TVB-N), thiobarbituric acid-reactive substances (TBARS), and pH levels. Additionally, the intelligent indicator films exhibit both thermal stability and good biocompatibility. This finding paves the way for developing safe and effective food freshness indicators with potential uses in transportation, packaging, and related industries.

Study of the nutritional quality of peas (Pisum sativum L.) under different conservation conditions

Peas (Pisum sativum L.) are among the most widely cultivated legumes, known for their adaptability to dry and warm environments and their high nutritional value. This research aimed to investigate the biochemical diversity of proteins, polyphenols, flavonoids, tannins, and antioxidant activity in a local population of peas from the Mareth oasis in Tunisia under different preservation methods: fresh, frozen, canned, and dried. The hypothesis was that preservation methods significantly impact the nutritional quality of peas, with fresh peas retaining the highest levels of essential nutrients. The results showed that fresh peas had superior nutritional quality, demonstrating the highest concentrations of protein (39 mg/g MF), polyphenols (0.17 mg GAE/g MF), flavonoids (0.086 mg QE/mg MF), and antioxidants (52%). In contrast, dried peas exhibited the lowest nutrient levels, particularly in protein and antioxidant activity. The study highlighted that freezing is an effective method for preserving the nutritional integrity of peas compared to canning and drying, which significantly reduce essential nutrient levels. Understanding the effects of various preservation techniques is crucial for maintaining the nutritional quality of peas. These findings have significant implications for consumers and the food industry, advocating for practices that prioritize the retention of nutrients in preserved peas. This research contributes to the ongoing discourse on food preservation methods and their impact on nutritional quality, providing insights that support better choices in food processing and consumption.

Exploring the Extraction and Application of Anthocyanins in Food Systems

The continued use of synthetic additives in food production and preservation has raised concerns among consumers, given their potential negative health effects. Researchers and food industry experts have been exploring plants with potent functional compounds as an alternative source of natural compounds such as anthocyanins, which can be utilized to produce safe food additives. Given their various biological activities, great potential exists for anthocyanins to be used as additives to preserve food or produce functional foods with health benefits. However, to fully realize the economic and health benefits of anthocyanins, a deep understanding of the different plant sources of anthocyanins, as well as their composition, extraction techniques, and function in various products, is warranted. Therefore, this paper critically reviews the different plant sources of anthocyanins and their application in the food and nutraceutical industries, highlighting emerging extraction techniques, health benefits, and challenges in the use of anthocyanins in the food industry. This review also offers insights that could be used in future research and help establish novel and sustainable methods for manufacturing anthocyanin-based value-added products and ingredients.

Innovative perspectives on bacteriocins: advances in classification, synthesis, mode of action, and food industry applications.

Bacteriocins, natural antimicrobial peptides produced by bacteria, present eco-friendly, non-toxic, and cost-effective alternatives to traditional chemical antimicrobial agents in the food industry. This review provides a comprehensive update on the classification of bacteriocins in food preservation. It highlights the significant industrial potential of pediocin-like and two-peptide bacteriocins, emphasizing chemical synthesis methods like Fmoc-SPPS to meet the demand for bioactive bacteriocins. The review details the mode of action, focusing on mechanisms such as transmembrane potential disruption and pH-dependent effects. Furthermore, it addresses the limitations of bacteriocins in food preservation and explores the potential of nanotechnology-based encapsulation to enhance their antimicrobial efficacy. The benefits of nanoencapsulation, including improved stability, extended antimicrobial spectrum, and enhanced functionality, are underscored. This understanding is crucial for advancing the application of bacteriocins to ensure food safety and quality.

Activity of Bambara Groundnut Seed Coat Extract Against Shewanella Species: Efficacy and Mechanisms of Action

The Bambara groundnut is the indigenous legume in the southern part of Thailand. It contains a seed coat rich in polyphenols, which can serve as natural antimicrobial agents. The extracts from red and white seed coats of Bambara groundnuts, namely RSC and WSC, respectively, were prepared using an ultrasound-assisted extraction process. The extraction yield, total phenolic content (TPC), and antimicrobial activity of both extracts were examined. The RSC extract demonstrated a significantly higher extraction yield (8.35%) than WSC extract (2.34%) (p < 0.05). Furthermore, the TPC of RSC extract (420.98 ± 0.27 mg of gallic acid/g dry extract) was higher than that of WSC extract (28.29 ± 0.91 mg of gallic acid/g dry extract). The RSC extract exhibited stronger inhibition against Shewanella putrefaciens and S. algae than its WSC counterpart. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS) analysis indicated that the RSC extract was rich in flavonoids and polyphenols, while the WSC extract contained more triterpenoid saponins. Time–kill kinetics showed that the RSC extract reduced bacterial loads in a dose-dependent manner. Scanning electron microscopic images revealed that drastic bacterial cell membrane damage with a rough surface and the deformation of cells was caused by the extract. Furthermore, confocal laser scanning microscopic (CLSM) images confirmed the inhibition of S. algae biofilm formation by RSC extract. RSC extract also suppressed bacterial motility, induced protein leakage, and reduced extracellular protease activity, thus highlighting its potent bactericidal effects. These findings suggested that the RSC extract rich in phenolic compounds could serve as an antimicrobial agent and hold promise as a natural preservative for perishable foods, especially seafoods.

Thermal Evaluation of Solar Dryer’s Curve-Front utilized Heat Transfer Analysis

The sun is most sustainable renewable energy, environmentally friendly and utilized for preservation of food and agricultural crops. The main objective of this experiment research work has focused on using renewable energy for evaporated moisture of foods fruit vegetables and herbs by drying system. The heat transfer equation are analyzed to effectively harness the temperature from the sun. Experimental data obtained were used to evaluate the properties of dry air on boundary region condition. Initial, testing was carried out under without load condition, and the result shows that the ambient and dryer’s internal temperature range between 29.3-40.2˚C and 37.4-60.3 ˚C, respectively, in Thailand a latitude of 14°0'48.46" North and longitude of 100°31'49.76" East (recorded average solar radiations and temperature on January 2023 - June 2024), average solar radiations range between 312 W/m2 and 513 W/m2. The indirect natural convection was design and calculated energy base on average temperature not higher than 55˚C, utilized sun daylight at 08:00 a.m. to 04:00 p.m. local time and clear sky or partially cloudy. Second, determination of design parameters; heat energy equation and steam table analysis. Final, utilization of the design under local time, solar radiation and the climatic local conditions and test with ginger slices (represent product in order to examine weight loss). The solar dryer’s curve front shape conduced on without load showed the heat transfer coefficient natural convections range between 3.7 and 4.5 W/m2 ˚C, the energy of dry air analysis range between 54.7 and 155.2 J/s and performance of drying rate range between 0.06 and 0.82 g/s, under increasing and decreasing trends of solar radiations from the time, date and climatic local region condition.

Citronella Oil as Additives in Active Carrageenan -based Food Packaging Films: A Review

The natural degradation process of plastics is slow and harmful to the environment, making biodegradable films a more advantageous option. These films not only reduce environmental pollution but also have the potential to preserve food products and extend their shelf life. This study explores the potential of utilizing iota carrageenan-based films in combination with essential oils for food packaging applications. Iota carrageenan, known for its high elasticity and thixothrophic properties, serves as an ideal base material for film formation. Essential oils, with antioxidant and antimicrobial properties, are incorporated into the packaging material to enhance shelf life and prevent food spoilage. Citronella oil demonstrates effective antimicrobial and antioxidant activities for food preservation. The presence of essential oils acts as plasticizers in the film, improving flexibility but requiring careful consideration of concentration to maintain network strength.

Biodegradable films incorporating Malaysian stingless bee propolis: Development, characterization, and potential for food packaging

Three different Malaysian stingless bee propolis samples were examined using the ethanolic extraction method for total flavonoid (TFC) and phenolic content (TPC), antioxidant, and antibacterial activities. Additionally, the biodegradable films were developed and characterized, this study also aims to enhance the functional qualities for possible use in active food packaging by combining corn starch (CS) with propolis extract (PE). The propolis samples were extracted with 70 % ethanol and analysed through a UV–VIS spectrophotometer for determination of antioxidant, TPC, and TFC. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) was used as scavenging test for free radicals, while Folin-Ciocalteu and aluminium chloride (AlCl3) were used to measure total flavonoid and phenolic contents. The data presented in this study showed significant differences in TPC and TFC identified in each sample ranged from 31.95 to 59.48 mg/mL GAE and 53.88 to 59.49 mg/mL RE, respectively. The findings also showed significant differences in the antibacterial activities of Malaysian stingless bee propolis, especially against Gram-positive bacterial strains. In comparison to the control treatments, the ethanolic propolis extract treatments also improved the film's physiochemical and antibacterial qualities. The incorporation of PE into CS resulted in decreased moisture content of the films from 17.20 % to 14.39 %, whereas the solubility significantly decreased from 17.44 % to 12.14 %. The weight of CS and PE film lowered significantly after 14 days and the weight loss percentage also demonstrated that bioplastic degradation occurred. The propolis extract was able to prevent the growth of foodborne bacteria since the present data revealed that the microbial count was significantly lower than control groups by displaying an acceptable limit of aerobic plate count for red meat products, which is lower than 6 log CFU/g. Propolis from Malaysian stingless bees may offer a viable substitute for synthetic additives in biodegradable food packaging films. Its antimicrobial and antioxidant properties support its application for sustainable food preservation.

Sustainable synthesis of PVA@ZnO:Ga3+ nanocomposite films for UV shielding, food preservation, shape memory and anti-counterfeiting applications

Herein, we successfully fabricated transparent and highly flexible polyvinyl alcohol@ZnO:Ga3+ (PVA@ZnO:Ga3+) nanocomposites (NCs) films by simple solution casting method. Upon excitation at 266 nm, both the ZnO:Ga3+ nanoparticles (NPs) and the PVA@ZnO:Ga3+ NCs exhibit a prominent peak at 385 nm and a broad peak around 550 nm. The optimized PVA@ZnO:Ga3+ NCs demonstrated the most effective ultra violet (UV) blockage across the UV-A (99.99 %), UV-B (100 %) and UV-C (100 %) and high energy blue light HEBL (94.63 %). However, PVA alone absorbed <25 % of the light in all UV regions. Packaging of fresh cherry fruit with PVA@ZnO:Ga3+ (0.1 wt%) NCs enhanced the shelf-life up-to 15 days of storage under room temperature. These innovative NCs packaging films could provide a green, environment-friendly and antimicrobial system to combat the shorter shelf life of cherry fruit. The optimized NCs exhibited excellent shape recovery under pH conditions of 1, 7 and 13 and at a temperature of 70 °C, returning to its original shape within 120, 150, 160 and 6 sec, respectively. This emphasizes the NCs remarkable water-induced shape memory ability. Further, PVA@ZnO:Ga3+ NCs security ink offers strong anti-counterfeiting (AC) properties with UV luminescence and stability against UV exposure, aging and temperature effect. It adheres well to various substrates, ensuring long-term durability and resistance to replication. Overall, the results clearly show that ZnO:Ga3+ NPs hold great promise for applications in AC technology, UV blocking and the food packaging industry, thanks to their low cost, biocompatibility, flexibility and transparency.

7-(Diethylamino) coumarin-3-carboxylic acid as a novel antibrowning agent: Activity and mechanism

Browning caused by polyphenol oxidase (PPO) and microorganisms significantly impacts the nutritional quality of fruits and vegetables. This study identified 7-(Diethylamino) coumarin-3-carboxylic acid (7-DCCA) as an effective inhibitor of both PPO and bacteria. Enzyme assays revealed that 7-DCCA competitively inhibits PPO activity with an IC50 value of 0.275 ± 0.002 mM. Fluorescence and molecular simulation methods demonstrated that 7-DCCA forms a complex with PPO through hydrogen bonding and hydrophobic interactions, altering the enzyme's structure and reducing its activity. Thermogravimetric and differential scanning calorimetry (DSC) assays showed that 7-DCCA stabilizes PPO, delaying its thermal decomposition. Antibacterial tests proved that 7-DCCA inhibits Staphylococcus aureus and Escherichia coli by disrupting cell membranes. Additionally, 7-DCCA suppressed PPO and peroxidase activities, delaying phenolic oxidation and preventing browning in fruits and vegetables. Cytotoxicity assays confirmed its safety, with over 85 % cell viability at concentrations up to 0.1 mM. Stability experiments verified that 7-DCCA had greatly light and thermal stability. This study highlighted 7-DCCA as a promising antibrowning agent with potential application in food preservation.

Photocatalytic rice bran protein/carboxymethyl cellulose/ZrO2 fiber produced by microfluidics: Formation mechanism, bacteriostasis and strawberry preservation

Developing cost-effective and environmentally sustainable active packaging materials remains an important challenge. We have developed rice bran protein (RBP)-based fibers incorporating carboxymethyl cellulose (CMC) and ZrO2 nanoparticles (ZrO2 NPs, 0 %–7 %, m/m) using microfluidic spinning. The integration of RBP, CMC, and ZrO2 NPs formed a robust hydrogen bond network that enhanced the fibers' thermal stability and crystallinity, reduced surface hydrophobicity, and aligned the molecular orientation. Under the catalysis of visible light (300 W, 12 h), ZrO2 NPs in the fiber produced reactive oxygen species, which inhibited the oxidative stress resistance system of Bacillus subtilis and destroyed its biofilm and DNA, thus showing excellent antibacterial effect. Additionally, during storage, this fiber also showed the ability to scavenge ethylene, thereby reducing the rate of loss of luminance, hardness and weight of strawberries. This study offers a new idea for RBP fiber in food preservation, antibacterial, and value-added utilization of rice bran by-products.

Large-scale dual-responsive ClO2 controlled-release film for strawberry preservation

Chlorine dioxide (ClO2) exhibits promising potential for the application in food preservation. However, the large-scale production of controlled-release ClO2 films faces challenges. The sodium chlorite microcapsules (Micro-SC) were successfully prepared in this study using polyvinyl alcohol (PVA) as the wall material through the spray drying method. Furthermore, A large-scale preparation of temperature and humidity dual-responsive ClO2 controlled-release films (Micro-SC@EVA) was achieved using melt extrusion. The film could release ClO2 triggered by water vapor for 36 days. The antibacterial effects were significantly enhanced with the increase of microcapsule ratio from 4 % to 8 %. The Micro-SC@EVA film reduced the total viable count and wight loss of strawberries, inhibits ethylene production, and extended the shelf life of by 150 % compared with the control group at 25 °C. The application evaluation results show that the novel approach for the large-scale preparation of ClO2 controlled-release film holds significant implications for food packaging.

A novel ratiometric fluorescent nanosensor based-on UiO-66-NH2 capped carbon dots for nitrite determination

Nitrite is a commonly used food preservative and a water contaminant that has garnered significant attention due to its harmful effects on human health. Developing a simple and sensitive method for determining nitrite levels is crucial for safeguarding public health. In this paper, we present a novel ratiometric fluorescent nanosensor (CDs@UiO-66-NH2), created by combining orange-red-emitting CDs with blue-emitting UiO-66-NH2. This ratiometric probe detects nitrite ions (NO2−) based on the diazotization reaction between the amino group in UiO-66-NH2 and the target NO2−, where the blue emission of UiO-66-NH2 is quenched but the orange-red emission of CDs remains stable. The probe demonstrated a detection range of 0.5–20 μM with a limit of detection (LOD) of 0.157 μM for NO2−. Due to the probe’s distinct color changes in response to NO2−, RGB values can be easily read using a smartphone, enabling ultrasensitive visual detection of NO2− with an LOD of 0.76 μM. This sensor was successfully applied to detect NO2− in environmental water samples. Finally, a smartphone-based RGB reading method using CDs@UiO-66-NH2 for visual quantitative detection of NO2− was proposed, broadening the application of CDs@UiO-66-NH2 in environmental protection.

Novel high-strength, recyclable, microbial-resistant, and freeze-thaw dual topological network hydrogel cooling media

The demand for multifunctional hydrogels, offering high mechanical strength, efficient cooling, and antimicrobial properties, is growing in food preservation. Here, a dual-network (DN) hydrogel PM@Cur, which includes curcumin, is fabricated through chemical crosslinking and hydrogen bonding interactions. The resulting hydrogels can withstand more than five freeze-thaw cycles at −80 °C, and resist brittleness after liquid nitrogen treatment. PM@Cur also exhibits surface hydrophobicity (contact angle >90°) for both water and organic solvents. These properties meet the mechanical, anti-fouling, and recyclable demands for hydrogel coolants. The antimicrobial assays in vitro confirmed that the inclusion of curcumin provided the PM@Cur with photodynamic antimicrobial capacity. Finally, the prepared PM@Cur hydrogel ice cubes have been confirmed to exhibit better anti-melting properties than traditional ice cubes, thus enabling the preservation of strawberries and shrimp. This study presents an innovative solution for producing advanced functional integrated hydrogels, offering a promising and safer option for food coolants.\\.