Cellulose Acetate Nanofibres Containing Alizarin as a Halochromic Sensor for the Qualitative Assessment of Rainbow Trout Fish Spoilage

Deep learning models with optimized fluorescence spectroscopy to advance freshness of rainbow trout predicting under nonisothermal storage conditions

This study established long short-term memory (LSTM), convolution neural network long short-term memory (CNN_LSTM), and radial basis function neural network (RBFNN) based on optimized excitation-emission matrix (EEM) from fish eye fluid to predict freshness changes of rainbow trout under nonisothermal storage conditions. The method of residual analysis, core consistency diagnostics, and split-half analysis of parallel factor analysis was used to optimize EEM data, and two characteristic components were extracted. LSTM, CNN_LSTM, and RBFNN models based on characteristic components of EEM used to predict the freshness indices. The results demonstrated the relative errors of RBFNN models with an R2 above 0.96 and relative errors less than 10% for K-value, total viable counts, and volatile base nitrogen, which were better than those of LSTM and CNN_LSTM models. This study presents a novel approach for predicting the freshness of rainbow trout under nonisothermal storage conditions.

Development of halochromic electrospun labels for non-invasive shelf life assessment of rainbow trout (Oncorhynchus mykiss): Incorporation of barberry anthocyanin extract in protein-based smart packaging

Using barberry (Berberis vulgaris L.) as a natural dye in combination with electrospinning technology represents a promising approach for the development of intelligent packaging systems. In this study, the influence of different concentrations of zein (16, 18, and 20%) and barberry anthocyanin-rich powder (BARP) (16, 18, and 20%) on the surface tension and rheological properties of the solution were evaluated. The most favorable nanofibers (NFs) were obtained from a solution containing 18% (w/w) zein under constant voltage. The surface morphology, size, and color-changing properties of electrospun NFs derived from zein polymers containing different concentrations of BARP (16, 18, and 20%) under various electrical fields (20, 22, and 24 kV) were evaluated. The Fourier-transform infrared spectroscopy analysis confirmed the interaction of BARP within the zein-based NFs. The results indicated that the concentration of BARP had a noticeable impact on the physicochemical properties of the NFs. Furthermore, efficacy of the appropriately fabricated halochromic label was evaluated for monitoring the packed rainbow trout fillet during refrigerated storage. On the 10th day, a noticeable visual color turned from pink to pale yellow was observed in response to pH variations. Additionally, the TVN value confirmed the effectiveness of halochromic electrospun labels for non-invasive assessment of fish fillet quality.

Carbon dots embedded bacterial cellulose membrane as active packaging: Toxicity, in vitro release and application in minced beef packaging

Antimicrobial bacterial cellulose (BC) membranes incorporated with carbon dots (CDs) were developed to improve the shelf life and ensure the safety of minced beef during 9 days of storage at 4 °C. An ex-situ method was used to develop BC-CDs with different CDs loading capacities (16.50, 22.50, and 38.50 mg/cm3). Only BC-CDs38.50 membrane exhibited toxicity in human embryonic kidney cells, and BC-CDs membranes had the slowest release rate of CDs in 95% ethanol. Significant differences were noted in the chemical and sensory attributes of samples packaged with BC-CDs16.50 and BC-CDs22.50, compared to the control. The microbial counts in samples with BC-CDs were significantly lower than those in samples with pristine BC membranes or the control. Notably, the BC-CDs22.50 membrane exhibited a substantial reduction (4.7 log10 CFU/g) in Escherichia coli counts by the end of storage. These findings highlight the potential of BC-CDs membranes as effective antimicrobial materials in meat packaging.

Functional Polymeric Membranes with Antioxidant Properties for the Colorimetric Detection of Amines

Herein, the ability of highly porous colorimetric indicators to sense volatile and biogenic amine vapors in real time is presented. Curcumin-loaded polycaprolactone porous fiber mats are exposed to various concentrations of off-flavor compounds such as the volatile amine trimethylamine, and the biogenic amines cadaverine, putrescine, spermidine, and histamine, in order to investigate their colorimetric response. CIELAB color space analysis demonstrates that the porous fiber mats can detect the amine vapors, showing a distinct color change in the presence of down to 2.1 ppm of trimethylamine and ca. 11.0 ppm of biogenic amines, surpassing the limit of visual perception in just a few seconds. Moreover, the color changes are reversible either spontaneously, in the case of the volatile amines, or in an assisted way, through interactions with an acidic environment, in the case of the biogenic amines, enabling the use of the same indicator several times. Finally, yet importantly, the strong antioxidant activity of the curcumin-loaded fibers is successfully demonstrated through DPPH● and ABTS● radical scavenging assays. Through such a detailed study, we prove that the developed porous mats can be successfully established as a reusable smart system in applications where the rapid detection of alkaline vapors and/or the antioxidant activity are essential, such as food packaging, biomedicine, and environmental protection.

A Novel Indicator Based on Polyacrylamide Hydrogel and Bromocresol Green for Monitoring the Total Volatile Basic Nitrogen of Fish

An intelligent indicator was developed by immobilizing bromocresol green (BCG) within the polyacrylamide (PAAm) hydrogel matrix to monitor the total volatile basic nitrogen (TVB-N) content of fish. The FTIR analysis indicated that BCG was effectively incorporated into the PAAm through the formation of intermolecular hydrogen bonds. A thermogravimetric analysis (TGA) showed that the PAAm/BCG indicator had a mere 0.0074% acrylamide monomer residue, meanwhile, the addition of BCG improved the thermal stability of the indicator. In vapor tests with various concentrations of trimethylamine, the indicator performed similarly at both 4 °C and 25 °C. The total color difference values (ΔE) exhibited a significant linear response to TVB-N levels ranging from 4.29 to 30.80 mg/100 g at 4 °C (R2 = 0.98). Therefore, the PAAm/BCG indicator demonstrated stable and sensitive color changes based on pH variations and could be employed in smart packaging for real-time assessment of fish freshness.

Recent Development of Polymer Nanofibers in the Field of Optical Sensing

In recent years, owing to the continuous development of polymer nanofiber manufacturing technology, various nanofibers with different structural characteristics have emerged, allowing their application in the field of sensing to continually expand. Integrating polymer nanofibers with optical sensors takes advantage of the high sensitivity, fast response, and strong immunity to electromagnetic interference of optical sensors, enabling widespread use in biomedical science, environmental monitoring, food safety, and other fields. This paper summarizes the research progress of polymer nanofibers in optical sensors, classifies and analyzes polymer nanofiber optical sensors according to different functions (fluorescence, Raman, polarization, surface plasmon resonance, and photoelectrochemistry), and introduces the principles, structures, and properties of each type of sensor and application examples in different fields. This paper also looks forward to the future development directions and challenges of polymer nanofiber optical sensors, and provides a reference for in-depth research of sensors and industrial applications of polymer nanofibers.

pH-sensitive smart indicators based on cellulose and different natural pigments for tracing kimchi ripening stages

Five natural pigments including water-soluble [butterfly pea (BP), red cabbage (RC), and aronia (AR)] and alcohol-soluble [shikonin (SK) and alizarin (ALZ)] were extracted, characterized, and loaded onto cellulose for preparing pH-sensitive indicators. The indicators were tested their color response efficiency, gas sensitivity, response to lactic acid, color release, and antioxidant activity. Cellulose-water soluble indicators showed more obvious color changes than alcohol-soluble indicators in lactic acid solution and pH solutions (1-13). All cellulose-pigment indicators exhibited prominent sensitivity to ammonia compared to acidic vapor. Antioxidant activity and release behavior of the indicators were influenced by pigment type and simulants. Kimchi packaging test was carried out using original and alkalized indicators. The alkalized indicators were more effective in showing visible color changes during kimchi storage than the original indicators, and cellulose-ALZ displayed the most distinct color change from violet (fresh kimchi, pH 5.6, acidity 0.45 %) to gray (optimum fermented kimchi, pH 4.7, acidity 0.72 %), and to yellow (over fermented kimchi, pH 3.8, acidity 1.38 %) which followed by BP, AR, RC, SK respectively. The findings of the study suggest that the alkalization method could be used to show noticeable color changes in a narrow pH range for application with acidic foods.

Alizarin: Prospects and sustainability for food safety and quality monitoring applications

Active and intelligent food packaging has emerged to ensure food safety, quality, or spoilage monitoring and extend the shelf life of food. The development of intelligent packaging has accelerated significantly in recent years with a focus on monitoring changes in the quality of packaged products in real-time throughout the food supply chain. As one of the popular natural colorants, alizarin has attracted much consideration due to its excellent functional properties and quality to color change under varying pH. Alizarin is an efficient and cost-effective biomaterial with numerous biological features such as antioxidant, antibacterial, non-cytotoxic, and antitumor. This review focuses on an in-depth summary and prospects for alizarin as a natural and safe colorant that has the potential to be incorporated into intelligent packaging to track the freshness of packaged foodstuffs. The use of alizarin as an intelligent packaging agent shows huge potential for the application of food packaging and brings it one step closer to real-time monitoring of food quality throughout the supply chain. Finally, various limitations and future requirements are discussed to underscore the importance of developing alizarin-based intelligent functional food packaging systems.

Application of smart packaging for seafood: A comprehensive review

Nowadays, due to the changes in lifestyle and great interest of consumers in a healthy life, people have started increasing their seafood consumption. But due to their short shelf life, experts are looking for a new packaging called smart packaging (SMP) for seafood. There are different indicators/sensors in SMP; one of the effective indices is time-temperature, which can show consumers the best time of using seafood based on their shelf life and experienced temperature. Another one is radio-frequency identification (RFID) that is a transmission device that represents a separate form of the electronic information-based SMP systems. RFID does not belong to any of the categories of markers or sensors; it is an auto recognition system that applies cordless sensors to indicate segments and collect real-time information without manual interposition. This review covers the use of SMP in all marine foods, including fish, due to its high consumption and high content of polyunsaturated fatty acids, eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3), which are the considerable factors of n-3 polyunsaturated fatty acids for human.

Preparation of Colorimetric Sensor Array System to Evaluate the Effects of Alginate Edible Coating on Boiled-Dried Anchovy

The colorimetric sensor array (CSA) is a simple, rapid, and cost-effective system widely used in food science to assess food quality by identifying undesirable volatile organic compounds. As a prospective alternative to conventional techniques such as total volatile basic nitrogen, peroxide value, and thiobarbituric acid reactive substance analysis, the CSA system has garnered significant attention. This study evaluated the quality of edible-coated food products using both conventional and CSA methods in order to demonstrate that the CSA approach is a feasible alternative to conventional methods. Boiled-dried anchovies (BDA) were selected as the model food product, and the sample's quality was assessed as a function of storage temperature and incubation period using conventional techniques and the CSA system. The surface of BDA was coated with an edible alginate film to form the surface-modified food product. The conventional methods revealed that an increase in storage temperature and incubation time accelerated the lipid oxidation process, with the uncoated BDA undergoing lipid oxidation at a faster rate than the coated BDA. Utilizing multivariate statistical analysis, the CSA approach essentially yielded the same results. In addition, the partial least square regression technique revealed a strong correlation between the CSA system and conventional methods, indicating that the CSA system may be a feasible alternative to existing methods for evaluating the quality of food products with surface modifications.

On-package indicator films based on natural pigments and polysaccharides for monitoring food quality: a review

Deterioration of food quality and freshness is mainly due to microbial growth and enzyme activity. Chilled fresh food, especially meat and seafood, as well as pasteurized products, rapidly lose quality and freshness during packing, distribution and storage. Real-time food quality monitoring using on-package indicator films can help consumers make informed purchasing decisions. Interest in the use of intelligent packaging systems for monitoring safety and food quality has increased in recent years. Polysaccharide-based films can be developed into on-package indicator films due to their excellent film-forming properties and biodegradability. Another important component is the use of colorants with visible color changes at various pH levels. Currently, natural pigments are receiving increased attention because of their safety and environmental friendliness. This review highlights the recent findings regarding the role of natural pigments, the effects of incorporating natural pigments and polysaccharides on properties of indicator film, current application and limitations of on-package indicator films based on polysaccharides in some foods, problems and improvement of physical properties and color conversion of indicator film containing natural pigments, and development of polysaccharide-based pH-responsive films. © 2022 Society of Chemical Industry.

Electrospun nanofibers fabricated by natural biopolymers for intelligent food packaging

An "intelligent" or smart packaging is able to continuously monitor physicochemical and/or biological variations of packaged food materials, providing real-time information concerning their quality, maturity, and safety. Electrospun nanofiber (ENF) structures, nowadays, reckon as versatile biomaterial platforms in designing intelligent packaging (IP) systems. Natural biopolymer-based ENF traits, for example, surface chemistry, rate of degradation, fiber diameter, and degree of alignment, facilitate the development of unique, tunable IP, enhancing food quality, and safety. In this review, after a brief overview of the electrospinning process, we review food IP systems, which can be utilized to detect variations in food features, for example, those based on alterations in temperature, O2 level, time, humidity, pH, or microbial contamination. Different intelligent approaches that are applicable in engineering IP materials are then highlighted, that is, indicators, data carriers, and sensors. The latest research on the application of ENFs made with natural biopolymers in food IP and their performance on different packaged food types (i.e. meat, fruits and vegetables, dairy products, etc.) are underlined. Finally, the challenges and outlook of these systems in the food industry are discussed.

Colorimetric Indicators Based on Anthocyanin Polymer Composites: A Review

This review explores the colorimetric indicators based on anthocyanin polymer composites fabricated in the last decade, in order to provide a comprehensive overview of their morphological and compositional characteristics and their efficacy in their various application fields. Notably, the structural properties of the developed materials and the effect on their performance will be thoroughly and critically discussed in order to highlight their important role. Finally, yet importantly, the current challenges and the future perspectives of the use of anthocyanins as components of colorimetric indicator platforms will be highlighted, in order to stimulate the exploration of new anthocyanin sources and the in-depth investigation of all the possibilities that they can offer. This can pave the way for the development of high-end materials and the expansion of their use to new application fields.

Recent Progress in Amine Gas Sensors for Food Quality Monitoring: Novel Architectures for Sensing Materials and Systems

The increasing demand for food production has necessitated the development of sensitive and reliable methods of analysis, which allow for the optimization of storage and distribution while ensuring food safety. Methods to quantify and monitor volatile and biogenic amines are key to minimizing the waste of high-protein foods and to enable the safe consumption of fresh products. Novel materials and device designs have allowed the development of portable and reliable sensors that make use of different transduction methods for amine detection and food quality monitoring. Herein, we review the past decade's advances in volatile amine sensors for food quality monitoring. First, the role of volatile and biogenic amines as a food-quality index is presented. Moreover, a comprehensive overview of the distinct amine gas sensors is provided according to the transduction method, operation strategies, and distinct materials (e.g., metal oxide semiconductors, conjugated polymers, carbon nanotubes, graphene and its derivatives, transition metal dichalcogenides, metal organic frameworks, MXenes, quantum dots, and dyes, among others) employed in each case. These include chemoresistive, fluorometric, colorimetric, and microgravimetric sensors. Emphasis is also given to sensor arrays that record the food quality fingerprints and wireless devices that operate as radiofrequency identification (RFID) tags. Finally, challenges and future opportunities on the development of new amine sensors are presented aiming to encourage further research and technological development of reliable, integrated, and remotely accessible devices for food-quality monitoring.

Nanocellulose as a promising substrate for advanced sensors and their applications

Nanocellulose has broad and promising applications owing to its low density, large specific surface area, high mechanical strength, modifiability, renewability. Recently, nanocellulose has been widely used to fabricate flexible, durable and environmental-friendly sensor substrates. In this contribution, the construction and characteristics of nanocellulose-based sensors are comprehensively reviewed. Various nanocellulose-based sensors are summarized and divided into colorimetric, fluorescent, electronic, electrochemical and SERS types according to the sensing mechanism. This review also introduces the applications of nanocellulose-based sensors in the fields of biomedicine, environmental monitoring, food safety, and wearable devices.

Smart films fabricated from natural pigments for measurement of total volatile basic nitrogen (TVB-N) content of meat for freshness evaluation: A systematic review

Major databases were searched from January 2012 to August 2021 and 54 eligible studies were included in the meta-analysis to estimate the overall mean of total volatile basic nitrogen (TVB-N) in meat. The mean of TVB-N was 24.96 mg/100 g (95 % CI:23.10-26.82). The pooled estimate of naphthoquinone, curcumin, anthocyanins, alizarin and betalains were 25.98 mg/100 g (95 %CI:19.63-32.33), 30.03 mg/100 g (95 %CI: 24.15-35.91), 24.92 mg/100 g (95 %CI: 22.55-27.30), 23.37 mg/100 g (95 %CI:19.42-27.33) and 19.50 mg/100 g (95 %CI:17.87-21.12), respectively. Meanwhile, subgroups based on meat types showed that smart film was most used in aquatic products at 27.19 mg/100 g (95 %CI:24.97-29.42), followed by red meat at 19.69 mg/100 g (95 %CI:17.44-21.94). Furthermore, 4 °C was the most storage temperature used for testing the performance of smart films at 25.48 mg/100 g (95 %CI:23.05-27.90), followed by storage at 25 °C of 25.65 mg/100 g (95 %CI:22.17-29.13). Substantial heterogeneity was found across the eligible studies (I² = 99 %, p = 0.00). The results of the trim-and-fill method demonstrated publication bias was well controlled.

Development of halochromic indicator film based on arrowroot starch/iota-carrageenan using Kyoho skin extract to monitor shrimp freshness

Increasing trends in food safety awareness drive consumer demands for fresher healthier diets and has led to the development of low-cost pH-sensitive indicator films to evaluate deterioration levels in fresh foods. Arrowroot starch/iota-carrageenan-based films were combined with 10, 30, 50% Kyoho skin extract (KSE) to produce indicator films with halochromic abilities. The KSE indicator films were characterized based on their physico-mechanical, functional, and crystallinity properties; thermal stability; and their pH-dependent color changes in in situ anthocyanin-based monitoring of shrimp freshness. All KSE indicator films displayed compact structure under scanning electron microscope analysis and increased tensile strength, exhibited UV-vis barrier ability, and presented low water wettability. Moreover, FTIR signaled strong hydrogen bond interactions among polymers and KSE that strengthened peak crystallinity in XRD analysis and lowered weight loss at melting temperature, which indicated thermal stability of the indicator films. Furthermore, pH-sensitivity of the indicator films integrated with natural KSE anthocyanin demonstrated color changes from purple to red under acidic conditions, purple to green in an ammonium environment, and yellow appeared in high alkaline conditions. Finally, this study demonstrated the food packaging and halochromic capacity of biopolymer-based pH-sensitivity of the KSE indicator films in real-time monitoring of shrimp at room storage temperatures.

Poly (lactic acid)-based pH responsive membrane combined with chitosan and alizarin for food packaging

A poly (lactic acid) (PLA) -based functional partition composite membrane (PLA/CA) containing chitosan (CS) and alizarin (AL) was designed by solution casting method. The PLA/CA membrane contains the antibacterial zone of the edge part (PLA/CS) and the pH response detection zone of the central part (PLA/AL). At the same time, the environmentally friendly plasticizer tributyl citrate (TBC) was added to make the prepared PLA/CA composite membrane have good flexibility and high transparency. The results of FE-SEM and FTIR showed that CS and AL were uniformly dispersed in PLA matrix and had good compatibility with PLA. The antioxidant activities of PLA/CS and PLA/AL composite films were 43.3 % and 72.8 %, respectively. At the same time, the inhibitory rates of PLA/CS membrane against Escherichia coli and Staphylococcus aureus were as high as 87.91 % and 75.17 %, respectively. PLA/AL films exhibit excellent UV barrier properties. When the environmental pH (ammonia and acetic acid vapor) changed repeatedly, the PLA/AL membrane showed reversible color change of yellow under acidic condition and purple under alkaline condition. During the packaging and storage of chicken breast meat, the freshness of chicken breast meat can be detected by the color change of functional PLA/CA composite membrane.

Electrospinning as a Promising Process to Preserve the Quality and Safety of Meat and Meat Products

Fresh and processed meat products are staple foods worldwide. However, these products are considered perishable foods and their deterioration depends partly on the inner and external properties of meat. Beyond conventional meat preservation approaches, electrospinning has emerged as a novel effective alternative to develop active and intelligent packaging. Thus, this review aims to discuss the advantages and shortcomings of electrospinning application for quality and safety preservation of meat and processed meat products. Electrospun fibres are very versatile, and their features can be modulated to deliver functional properties such as antioxidant and antimicrobial effects resulting in shelf-life extension and in some cases product quality improvement. Compared to conventional processes, electrospun fibres provide advantages such as casting and coating in the fabrication of active systems, indicators, and sensors. The approaches for improving, stabilizing, and controlling the release of active compounds and highly sensitive, rapid, and reliable responsiveness, under changes in real-time are still challenging for innovative packaging development. Despite their advantages, the active and intelligent electrospun fibres for meat packaging are still restricted to research and not yet widely used for commercial products. Industrial validation of lab-scale achievements of electrospinning might boost their commercialisation. Safety must be addressed by evaluating the impact of electrospun fibres migration from package to foods on human health. This information will contribute into filling knowledge gaps and sustain clear regulations.

A review on colorimetric indicators for monitoring product freshness in intelligent food packaging: Indicator dyes, preparation methods, and applications

Intelligent food packaging system exhibits enhanced communication function by providing dynamic product information to various stakeholders (e.g., consumers, retailers, distributors) in the supply chain. One example of intelligent packaging involves the use of colorimetric indicators, which when subjected to external stimuli (e.g., moisture, gas/vapor, electromagnetic radiation, temperature), display discernable color changes that can be correlated with real-time changes in product quality. This type of interactive packaging system allows continuous monitoring of product freshness during transportation, distribution, storage, and marketing phases. This review summarizes the colorimetric indicator technologies for intelligent packaging systems, emphasizing on the types of indicator dyes, preparation methods, applications in different food products, and future considerations. Both food and nonfood indicator materials integrated into various carriers (e.g., paper-based substrates, polymer films, electrospun fibers, and nanoparticles) with material properties optimized for specific applications are discussed, targeting perishable products, such as fresh meat and fishery products. Colorimetric indicators can supplement the traditional "Best Before" date label by providing real-time product quality information to the consumers and retailers, thereby not only ensuring product safety, but also promising in reducing food waste. Successful scale-up of these intelligent packaging technologies to the industrial level must consider issues related to regulatory approval, consumer acceptance, cost-effectiveness, and product compatibility.

Fabrication of a "progress bar" colorimetric strip sensor array by dye-mixing method as a potential food freshness indicator

Colorimetric sensing is a low-cost, intuitive method for monitoring the freshness of food. We prepared a colorimetric strip sensor array by mixing different amounts of bromophenol blue (BPB) and bromocresol green (BCG). As results of NH₃ simulation, the array strip turned from yellow to blue, and the number of blue spots increased with the increasing NH₃, like a progress bar. Although the actual color is quite different, the color-changing trend was consistent with the simulated model calculated by a computer. The progress bar results remained stable under three lighting conditions. Furthermore, in the Cod preservation experiment, the color-changing progress of the strip sensor array is consistent with the simulation and can indicate Cod freshness while providing more distinguish levels. Therefore, a "progress bar" indicator built by this strategy possess the potential of realizing nondestructive, more accurate, and commercially available food quality monitoring through the naked eye and smart equipment recognition.

A sensitive fluorescence-visualized sensor based on an InP/ZnS quantum dots-sodium rhodizonate system for monitoring fish freshness

A fluorescence-visualized sensor based on 3-mercaptopropionic acid (MPA)-capped indium phosphide/ zinc sulfide quantum dots (InP/ZnS QDs) and sodium rhodizonate (SR) was designed to sensitively monitor fish freshness. MPA-InP/ZnS QDs, which exhibit orange-red fluorescence, were synthesized by a solvothermal method. In the MPA-InP/ZnS QDs-SR system, the fluorescence of MPA-InP/ZnS QDs was quenched by SR due to the combined function of the inner filter effect (IFE) and static quenching effect (SQE) at pH = 3. When ammonia was added, the fluorescence was recovered, and the color changed from colorless to bright orange-red under UV light (365 nm). The sensing performance for volatile amine gas was studied, and the sensor demonstrated good linearity between the fluorescence intensity, the total volatile basic nitrogen (TVB-N) and the total color change (ΔE) of bighead carp stored at room temperature (25 °C) and refrigerated temperature (4 °C). The proposed sensor has potential applications in monitoring fish freshness.

Electrospun Nanofibers: Current Progress and Applications in Food Systems

Electrospinning has the advantages of simple manufacturing equipment, a low spinning cost, wide range of spinnable materials, and a controllable mild process, which can continuously fabricate submicron or nanoscale ultrafine polymer fibers without high temperature or high pressure. The obtained nanofibrous films may have a large specific surface area, unique pore structure, and easy-to-modify surface characteristics. This review briefly introduces the types and fiber structures of electrospinning and summarizes the applications of electrospinning for food production (e.g., delivery systems for functional food, filtration of beverages), food packaging (e.g., intelligent packaging, antibacterial packaging, antioxidant packaging), and food analysis (e.g., pathogen detection, antibiotic detection, pesticide residue detection, food compositions analysis), focusing on the advantages of electrospinning applications in food systems. Furthermore, the limitations and future research directions of the technique are discussed.

Novel colorimetric membranes based on polylactic acid-grafted-citrated methacrylated urethane (PLA-CMU) to monitor cod freshness

Halochromic agent is easy to fall off from the surface of colorimetric membranes during fish freshness monitoring, which would decay the test accuracy. In order to increase its anchoring, citrated methacrylated urethane (CMU) synthesized by using tributyl citrate, β-hydroxyethyl methacrylate and diphenyl-methane-diisocyanate as a halochromic agent was grafted on polylactic acid (PLA). The CMU grafted PLA (PLA-CMU) together with tetrabutylammonium chloride (TBAC) prepared colorimetric membranes via electrospinning. ¹H NMR and FTIR analysis showed successful bonding between CMU and PLA, and PLA-CMU grafting efficiency reached to the maximum value of 11.15%. Moreover, DSC confirmed that PLA-CMU existed low cold-crystallization temperature due to the excellent compatibility of CMU with PLA, which enhanced the anchoring of CMU effectively. Nanofiber-based PLA-CMU/TBAC colorimetric membrane enhanced the probability of molecules being captured due to its porous structure and large specific surface area. In addition, the increase in hydrophilicity of the membrane can provide a microenvironment for liquid phase reaction, exhibiting obvious color-changing sensitivity during cod freshness monitoring, from white color to light orange or pink with the deterioration of cod at 25 °C and 4 °C respectively. The results demonstrate PLA-CMU/TBAC colorimetric membranes would provide a simple and promising strategy for monitoring fish freshness.

Recent Advances in the Development of Smart and Active Biodegradable Packaging Materials

Interest in the development of smart and active biodegradable packaging materials is increasing as food manufacturers try to improve the sustainability and environmental impact of their products, while still maintaining their quality and safety. Active packaging materials contain components that enhance their functionality, such as antimicrobials, antioxidants, light blockers, or oxygen barriers. Smart packaging materials contain sensing components that provide an indication of changes in food attributes, such as alterations in their quality, maturity, or safety. For instance, a smart sensor may give a measurable color change in response to a deterioration in food quality. This article reviews recent advances in the development of active and smart biodegradable packaging materials in the food industry. Moreover, studies on the application of these packaging materials to monitor the freshness and safety of food products are reviewed, including dairy, meat, fish, fruit and vegetable products. Finally, the potential challenges associated with the application of these eco-friendly packaging materials in the food industry are discussed, as well as potential future directions.

Fabrication of halochromic smart films by immobilizing red cabbage anthocyanins into chitosan/oxidized-chitin nanocrystals composites for real-time hairtail and shrimp freshness monitoring

In this study, halochromic smart films were produced, characterized, and applied to monitor the freshness of hairtail and shrimp in real-time. Red cabbage anthocyanins (RCAs) solution illustrated significant color variations (red-pink-blue-green) in different pH environments. RCAs were successfully immobilized into chitosan (CS)/oxidized-chitin nanocrystals (OCN) composites through hydrogen bonding, and cohesive film structures were formed. When the proper concentration of RCAs was incorporated into the composites, improved water vapor permeability (WVP), oxygen permeability (OP), mechanical, UV-blocking, and antioxidant properties were observed. Moreover, the smart films exhibited distinguishable changes of color to ammonia vapor and acidic/alkaline environment within short time intervals, which were easy to discern by naked eyes. Finally, the smart films were applied to monitor the freshness of hairtail (Trichiurus lepturus) and shrimp (Penaeus vannamei). The film color changed significantly during storage time, and three stages of product freshness (fresh, medium fresh, and spoiled) were successfully differentiated. Strong correlations among three freshness indicators and two colorimetric parameters were also identified and analyzed. Overall, the smart system assembled from non-toxic and biodegradable components could contribute to monitoring the freshness of seafood, like hairtail and shrimp, in real-time.

Detection of food spoilage and adulteration by novel nanomaterial-based sensors

Food industry is always looking for more innovative and accurate ways to monitor the food safety and quality control of final products. Current detection techniques of analytes are costly and time-consuming, and occasionally require professional experts and specialized tools. The usage of nanomaterials in sensory systems has eliminated not only these drawbacks but also has advantages such as higher sensitivity and selectivity. This article first presents a general overview of the current studies conducted on the detection of spoilage and adulteration in foods from 2015 to 2020. Then, the sensory properties of nanomaterials including metal and magnetic nanoparticles, carbon nanostructures (nanotubes, graphene and its derivatives, and nanofibers), nanowires, and electrospun nanofibers are presented. The latest investigations and advancements in the application of nanomaterial-based sensors in detecting spoilage (food spoilage pathogens, toxins, pH changes, and gases) and adulterants (food additives, glucose, melamine, and urea) have also been discussed in the following sections. To conclude, these sensors can be applied in the smart packaging of food products to meet the demand of consumers in the new era.

Shelf life extension of aquatic products by applying nanotechnology: a review

Aquatic products are extremely perishable due to their biological composition. Conventional preservation methods such as freezing, chemical treatments, packaging, and so forth are unable to inhibit enzymatic and microbiological spoilage efficiently and/or energy intensive and/or potentially toxic. However, the demand of consumers for aquatic products with long shelf life and high quality has urged the food industries to pursuit highly effective preservation methods for shelf life extension of aquatic products. Nanotechnology-related shelf life prolongation process possess the ability to overcome the drawbacks of conventional preservation technologies due to its unique properties. In this article, the aquatic products spoilage mechanisms, recent application of nanotechnology-related preservation techniques for aquatic products as well as the risk and regulation of nanomaterials have been reviewed. It has been shown that nanotechnology-related preservation techniques can effectively extend the shelf life without impairing the quality of aquatic products. However, the safety of nanotechnology is still remained controversial, therefore, the application of nanotechnology should be considered cautiously.

Application of electrospinning technique in development of intelligent food packaging: A short review of recent trends

Intelligent food packaging refers to packages with the ability to sense foodstuff changes and to inform customers of the packaging content variations. They are often accompanied by smart detecting devices. Providing a suitable platform to include these devices into packaging polymers has always been discussing. Electrospun nanofibers produced through the electrospinning have been recently utilized as an outstanding and novel platforms for this purpose. Thus, the main aim of this study is to investigate recent trends in producing intelligent food packaging using electrospinning technique. In this regard, this paper was categorized into two chief sections, including (a) the principal of electrospinning technique to fabricate fine nanofibers and the parameters affecting the quality of electrospun fibers, and (b) the role of nanofibers as a platform to cover pH indicators in intelligent food packaging.