Next Article in Journal
A Rationally Designed, Spiropyran-Based Chemosensor for Magnesium
Previous Article in Journal
Simultaneous Analysis of Sensor Data for Breath Control in Respiratory Air
Article Menu

Export Article

Chemosensors 2018, 6(2), 16; doi:10.3390/chemosensors6020016

Metal Oxide Nanostructures in Food Applications: Quality Control and Packaging
Sensor Lab, Department of Information Engineering, University of Brescia, Via Valotti, 9, 25133 Brescia, Italy
IBBR-CNR, Via Madonna del Piano, 10, 50019 Sesto Fiorentino, Florence, Italy
Nano Sensor Systems s.r.l., Via Branze, 38, 25123 Brescia, Italy
Author to whom correspondence should be addressed.
Received: 26 February 2018 / Accepted: 12 April 2018 / Published: 14 April 2018


Metal oxide materials have been applied in different fields due to their excellent functional properties. Metal oxides nanostructuration, preparation with the various morphologies, and their coupling with other structures enhance the unique properties of the materials and open new perspectives for their application in the food industry. Chemical gas sensors that are based on semiconducting metal oxide materials can detect the presence of toxins and volatile organic compounds that are produced in food products due to their spoilage and hazardous processes that may take place during the food aging and transportation. Metal oxide nanomaterials can be used in food processing, packaging, and the preservation industry as well. Moreover, the metal oxide-based nanocomposite structures can provide many advantageous features to the final food packaging material, such as antimicrobial activity, enzyme immobilization, oxygen scavenging, mechanical strength, increasing the stability and the shelf life of food, and securing the food against humidity, temperature, and other physiological factors. In this paper, we review the most recent achievements on the synthesis of metal oxide-based nanostructures and their applications in food quality monitoring and active and intelligent packaging.
metal oxide; nanostructures; gas sensor; food quality; antimicrobial activity; food packaging

1. Introduction

The monitoring and control of food quality have become important issues. The consumers and the manufacturers are paying more attention to the modern and advanced methods to check the quality of agricultural and food products and to keep them safe for a long time. Besides, the monitoring, control, and maintaining of the quality of food during its transportation from producer to consumer is another important issue. Different analytical methods for food quality control, such as the liquid chromatography–mass spectrometry [1], and surface plasmon resonance [2], have been applied. However, the aforementioned techniques have several limitations. The data acquisition and elaboration processes are slow; the instruments have relatively big dimensions and are not useful to fabricate small-size, portable systems for the real-time analysis. In this regard, the chemical sensors are very promising structures for the manufacturing of small-size and portable monitoring systems to perform real-time food quality analysis. The rotten foods produce toxin gases [3]. In addition, the metabolic activities of microorganisms in dairy foods may contribute to the breakdown of chemical compounds into volatile organic compounds (VOCs) [4]. Therefore, the detection of presence of toxins and VOCs is necessary to avoid the hazards that are related to the food spoilage. Metal oxide based gas sensors are sensitive to a wide range of gases and VOCs. This feature makes them very attractive structures for their integration into the food quality monitoring systems [5,6,7]. Chemical gas sensors based on metal oxide nanomaterials have been used to evaluate and discriminate the quality and standards of all kinds of food, dairy products, and beverages [8,9,10]. They can be used to investigate the shelf life, freshness, and maturity of fruits, vegetables, and grains [11,12,13], and to assess the real-time process monitoring, including the harvesting, processing and storage [14].
The packaging technology is another important subject of research and plays a key role in food protection and storage. The active packaging involves the usage of metal oxide nanostructures in food packaging material that prolongs the shelf life, safety, and quality of the packaged product. The modern model of packaging is the intelligent packaging system with the multifunctional possibilities, such as the sensing, recording, and communication providing information about the possible problems. The spoiled food creates poison and the vapors that can be detected by the chemical gas sensors. The identification of emitted vapors from the food (milk, cheese, meat, fish, fruits, vegetables, eggs, and drinks) will be possible in order to avoid future dangers at the beginning of the spoiling process. Monitoring and control of the humidity and temperature during the food packaging and transport are important as well. Some metal oxides have a good response to the humidity changes [15,16,17]. This feature of oxide materials can be used for the fabrication of humidity sensors and their integration into food quality monitoring systems in order to overcome the problems that are related to the spoilage of food.
The fabrication of small-size sensing systems based on metal oxide gas sensors and their combination with the modern communications tools is a prospective way to perform qualitative and quantitative multi-component analysis of food products. These kind of systems can be activated and controlled by an operator responsible for organizing the intelligent food packaging, storage, and transport from the producer to consumer [6]. In addition, metal oxides can be used for the development of innovative food packaging materials due to their thermal stability, optical and catalytic properties, non-toxicity, and antimicrobial activities [18]. The research studies that have been published over the last years regarding the application of the metal oxide nanostructures in food quality control and packaging indicate that the interest on oxide materials and the investigation of their functional properties have appreciably increased. Figure 1 reports the number of publications with the topics “Metal oxide* AND food quality control OR food monitoring OR food packaging” since 2000 till 2018 March, retrieved from the “Web of Knowledge” database. This trend demonstrates the growing interest in the aforementioned fields.
This paper aims to provide an overview of the most recent achievements on metal oxides-based nanostructures in different food applications, including the quality monitoring, the active and intelligent food packaging, the antimicrobial activities, and the improved nutrition. We have discussed various nanofabrication technologies and strategies, showing their advantages and disadvantages. We have highlighted the achievements and the challenges in the application of nanostructured metal oxides for the food industry.

2. Metal Oxide Nanostructures Growth and Fabrication Methods

Preparation methods of metal oxide nanostructures have been developed towards the shape, size and crystallinity control of the material. The structures can be prepared by several chemical and physical methods. These synthesis techniques of the nanomaterials are based on the top-down and bottom-up approaches. The top-down approach is advantageous in the semiconductor industry and it has been used for the fabrication of computer chips and other products. This approach is mainly based on the lithographic techniques and has limited capabilities [19]. Instead, the bottom-up approaches are in the development stage and the researchers continue to carry out experiments to improve these techniques. The schematic of top-down and bottom-up approaches is presented in Figure 2.
The studies have shown that the bottom-up preparation methods may offer unique capabilities in nanofabrication. Based on this approach, the metal oxide nanostructures can be synthesized in the shape of nanowires, nanorods, nanotubes, nanobelts, etc. [5,20,21]. The assembly of molecular building blocks or chemical synthesis through the vapor phase transport, electrochemical deposition, and solution-based or template-based growth are on the basis of preparation procedures. These procedures may include the vapor-solid or vapor-liquid-solid growth, chemical or physical vapor deposition, metal organic chemical vapor deposition, and the thermal oxidation of metals [21,22,23,24]. The vapor phase deposition method is mainly performed at elevated temperatures under the gas flow in a chamber [23,25]. Great efforts have been made for the fabrication of one dimensional (1D) and thin film metal oxide nanostructures using the chemical vapor deposition (CVD) method, which involves the formation of nanomaterials onto the substrate by the chemical reactions of vapor phase precursors [5,26,27,28]. In this case, the reactions can be enhanced by higher frequency radiation and plasma [26,29,30]. The structure and morphology of the prepared materials depend on the substrate temperature, composition, and the chemistry of the vapor phase. Further improvements of the CVD process allowed for the fabrication of doped 1D metal oxides [26,30,31]. However, the growth rate of the nanostructure can be decreased depending on the doping concentrations [26]. Some dopants can affect the crystal quality of the material and the material growth may become disordered due to the phase separation [30].
Atomic layer deposition (ALD) can also be used for the fabrication of 1D metal oxide materials. ALD is a modification of the CVD, in which gaseous precursors are introduced sequentially to the surface of the substrate and the reactor is purged with an inert gas to remove the unreacted precursor and the reaction byproducts [5,32]. This is a very precise template-based technique to grow well-ordered structures with uniform dimensions. The template material, its preparation and post-growth removal procedure have crucial effects on the fabrication of materials. The most used template for the ALD is the anodic aluminum oxide (AAO) [6]. Well-ordered nanotubular arrays, nanorods, nanopillars, and nanochannels were obtained using the ALD method. The diameter of the structures can be controlled by varying the pattern dimensions. Similarly, it is possible to increase the length of the obtained structures by repeating the deposition cycles [33,34,35].
Vapor-liquid-solid or vapor-solid growth mechanism can be involved in the physical vapor deposition (PVD) procedure for the fabrication of metal oxide nanomaterials as well. The deposition process is carried out in the furnace that is connected with a vacuum pump. The catalyst on the substrate, temperature, and pressure during the material fabrication affect the morphology of the obtained structures [5,32,36]. This is an effective method to obtain metal oxide nanowires, nanorods, nanoneedles, etc. [37,38]. The thermal oxidation of metallic layers can be used in order to obtain single crystalline metal oxide nanowires and nanorods [24,39,40]. This method may be included in the PVD category. The thermal oxidation procedure is the simplest in the PVD category and it can be carried out under atmospheric pressure. The growth conditions can be controlled by modifying the preparation procedure, the temperature, and time, as well as the metal-catalyst and gas atmosphere. Nevertheless, the fabrication procedure at high temperatures can limit the choice of the substrates, especially the use of polymeric flexible films that have relatively low-temperature stability. In this regard, the electrochemical anodization of metallic films is an effective method for the fabrication of 1D oxide materials on flexible polymeric substrates. The anodization procedure is performed in a two-electrode system electrochemical cell. This procedure consists of the oxidation and etching of the metallic films. The metals can be anodized in normal ambient conditions at room temperature [22]. Well-ordered and highly aligned tubular arrays and porous structures can be obtained by means of the anodization method. The length and diameter of the structures are controlled by a variation of the electrolyte composition, the reaction time, and the anodization voltage [41,42,43]. The synthesis procedure at relatively low temperatures allows for fabricating the nanomaterials on flexible polymeric substrates [44,45]. More complex architectures (Figure 3) can be obtained by coupling the electrochemical anodization and the thermal decomposition methods [45].
Chemical methods, such as the spin-coating, dip-coating, and sol-gel have been applied for the preparation of metal oxide thin films and nanoparticles [46,47,48]. The aforementioned methods are very convenient for the fabrication of composite structures due to the availability of precursor materials [47,48,49]. The morphology, alignment, density, aspect ratio, and crystalline quality of the materials that were prepared by sol-gel are directly related to the seed layer parameters [46]. Recent investigations have shown that the hydrothermal growth using different chemical solutions is another efficient method for the preparation of pure and doped oxide materials with various shapes (nanorods, nanofibers, nanowires, and nanosheets) [50,51,52,53]. The morphology of the structures during the preparation process is changed depending on the solution composition, the reaction temperature, and time [6,54].
To prepare the hierarchically assembled poly- and single-crystalline 1D metal oxide nanostructures, the ALD, PVD, CVD, and thermal oxidation methods have been well developed comparing to the chemical approaches. Meanwhile, the template-assisted approach, such as the ALD, makes the integration of the material difficult with the existing planar structures. The growth rate and the crystallinity of the nanostructures that are prepared through the vapor phase transport can be reduced depending on the dopant material type and concentration. The anodization is a cost-effective and precise method to obtain well-ordered and doped nanotubes or nanoporous structures at room temperature without the use of any vacuum technique. Nevertheless, the anodized materials are mainly amorphous and they can be crystallized by post-growth thermal treatment. The doping and functionalization of metal oxides with the different materials can be successfully performed by means of the hydrothermal growth. In this case, the structure synthesis is performed at high temperatures, which limits the choice of substrates.

3. Food Quality Control

This section reports the recent developments in metal oxide chemical sensor devices for their applications in food analysis, in particular, the food quality control, process monitoring, authenticity, and freshness determination. The sensing mechanism of metal oxides is related to the adsorption and desorption processes of different gaseous compounds on the structure surface, followed by the changes in the material electrical conductance (or resistance). The sensing mechanism is described in more detail in our previous works [5,6]. Recent studies have shown that the metal oxide nanomaterials-based gas sensors can be used for the assessment of food products. Chemical sensors and more complex systems have been used to detect the gases that are present in the rotten or spoiled food.
Trimethylamine (TMA) is a gaseous compound that is formed naturally due to the biodegradation of fish and animal products. TMA detection may give useful information to determine the fish and the seafood freshness. TiO2, WO3, and ZnO with different shapes showed a good response towards TMA [55,56,57,58]. The functionalization of WO3 nanorods, ZnO (Figure 4) and MoO3 by Au improved the material’s response due to the catalytic effect of Au [56,58,59]. Introduction of Cr3+ in 1D ZnO nanostructures or their coupling with Cr2O3 and In2O3 can enhance the response and selectivity of the materials towards TMA [57,60,61]. In addition, the heterostructure based on p-type Cr2O3 and SnO2 nanowires showed a good and selective response towards low concentrations of TMA [62]. Lou et al. fabricated the α-Fe2O3/TiO2 hierarchical heterostructure with a good sensing performance when compared with the pure Fe2O3 and TiO2 1D nanostructures [63]. Dimethylamine (DMA) and ammonia (NH3) are the other substances that are responsible for fishy odors, and directly related to the fish quality [64]. During the last years, only a couple of works have been published on metal oxide-based DMA sensors. Investigations have shown that 1D ZnO materials have very good sensing properties for the fabrication of DMA gas sensors [65,66]. However, there is no detailed information in the literature on the studies of other metal oxide materials for their application in DMA detection. Hence, the perspectives of the application of other oxide materials in the fabrication of DMA sensors are still not clear. Besides the fish quality control, NH3 was used as an analyte to determine the shelf life and spoilage of other meat products [67]. The sensing performance of oxide materials towards NH3 was improved by combining them with polymers. SnO2 nanosheets and ZnO nanorods were polymerized by the polypyrrole [68,69]. The response of the polypyrrole-SnO2 composite towards a low concentration of NH3 was improved because of the p-n junction that was formed at the interface of two materials [68]. Excellent conjunction and interaction between the polypyrrole chains and the ZnO nanorods improved the charge transfer in the composite enhancing the structure response [69]. Moreover, both of the composite materials showed a selective response towards NH3 at room temperature (RT), which is an important achievement to fabricate low power consumption sensing devices. The coupling of TiO2 and ZnO with the polyaniline also improved the response and selectivity of the materials at RT [70,71]. The functionalization of ZnO nanorods by Au enhanced the sensing performance of the structure at RT, and in the meantime, decreased the response and recovery time of ZnO [72]. Li et al. improved the response of SnO2 nanotubes towards NH3 at RT by fabricating a SnO2/SnS2 composite material [73]. This improvement was attributed to the heterojunction that was formed at the boundaries of SnO2 and SnS2 crystallites and the higher work function of SnS2 as compared with SnO2.
Hydrogen sulfide (H2S) is produced from eggs and egg products due to their heating. Moreover, low concentrations of H2S contribute to the flavor of heated proteinaceous foods, such as beef, chicken, fish, and milk products, and its production increases at higher temperatures. The detection of H2S can give useful information to identify the overcooked and rotten food [74]. Various oxide materials and their compositions have been studied for the fabrication of H2S sensors [75,76,77,78,79,80,81,82,83,84]. Porous metal oxide nanostructures, such as TiO2, NiO, and CuO are very attractive materials for H2S detection [75,76,77,85]. They have shown a good response towards low concentrations of H2S. In addition, the porous NiO and CuO with p-type conductivity could detect H2S in ppb level at relatively low operating temperatures [76,77]. TiO2 nanoparticles have been used for the functionalization of Fe2O3 nanorods [83]. The obtained structure showed a better sensing performance when compared to the pristine Fe2O3 nanorods. The enhancement was related to the modulation conduction channel width and potential barrier height of the material. The functionalization and doping of ZnO have been proven as the promising strategies to improve the material response towards H2S [86,87]. Guo et al. fabricated a composite material based on ZnO and SnO2 [80]. The obtained ZnO/SnO2 heterogeneous nanospheres showed selective and high response in the presence of low concentrations of H2S. Ag-loaded yolk-shell SnO2 nanostructures showed a high and reversible response towards H2S [81]. Yang et al. reported the synthesis of Ag2O/SnO2 porous structures with the stable and selective response towards H2S in ppb level [82]. The H2S sensing performance of a p-n junction based on Co3O4-SnO2 nanocomposite was improved with an increase in the structure annealing temperature [79]. CuO/V2O5 hybrid nanowires showed a better response towards H2S when compared with the pristine V2O5 nanowires [78].
Fruits and vegetables are perishable products with a very short shelf life. The detection of VOCs is an accessible way for the monitoring of changes in the fresh produce. The majority of the latest studies have been carried out to develop metal oxide sensors for the detection of ethanol and acetone. SnO2, ZnO, TiO2, Cr2O3, WO3, Co3O4, NiO, and In2O3 based nanostructures with different morphologies have been studied for the ethanol [4,88,89,90,91,92] and acetone detection. Reported results have shown that the functionalization and introduction of specific dopant materials can improve the response, selectivity, and recovery time of oxide materials. Furthermore, the composite structures based on metal oxides have shown a promising sensing performance for their application in ethanol and acetone sensing devices. Table 1 summarizes the recent achievements in sensing properties of the metal oxide-based structures for the food quality analysis.
The presence of VOCs in food is a complex aroma bouquet, which includes different compounds due to the aging and bacterial putrefaction of food. In this regard, the fabrication of a more complex and multicomponent system is a proper way for the precise monitoring of food quality and discrimination. The concept of this artificial system is called Electronic nose (EN). An EN consists of different metal oxide gas sensors, where each sensor has particular application requirements with a specific response and selectivity to recognize simple or complex gaseous compounds.
Konduru et al. used SnO2 and WO3 based sensors array to differentiate ethanol, acetone, acetonitrile, and ethyl acetate for the onion quality evaluation. The fabricated EN sensing system was able to detect the presence of the two key volatile compounds that were emitted by diseased onions, and in the meantime, to differentiate them at two concentration levels [97]. An EN based on SnO2 chemical sensors was applied for the identification of the geographical origin of licorice roots [98]. E-nose results were compared to the results that were obtained by the other techniques. The investigations showed that this is an effective and non-destructive method for the authentication of licorice roots. Pacioni et al. used SnO2 sensors array that was functionalized with different metals to obtain a good and selective response towards acetaldehyde, ethanol, acetone, dimethylsulfide, and ethylacetate for the discrimination of truffle-flavored oils [99]. The SnO2 is the most studied metal oxide material for the fabrication of gas sensors. The material has a good response towards different gases. Therefore, the SnO2 based chemical sensors have been mostly used for the fabrication of EN systems. The ENs based on SnO2 gas sensors have been applied for the classification of black tea and the diagnosis of Enterobacteriaceae in vegetable soups, to study the global aromatic profile of coffee, as well as for the meat and fish freshness control. The applications of EN systems based on SnO2 and the other metal oxides are summarized in Table 2. Unfortunately, the composition of oxide materials in some studies on EN systems was not presented. This fact makes it difficult to perform a more detailed comparison of the results that were reported in the literature.
The recent studies of oxide materials are mainly focused on the nanostructures and the thin films, with an increasing attention to improve the sensing performance of the material at relatively low operating temperatures for the prototype sensing devices [100,101,102]. Furthermore, the water molecules can be formed on the surface of metal oxides due to the adsorption of some reducing gases [103]. Therefore, to obtain the gas sensors with stable and reversible response, the sensor device should operate above room temperature to avoid the effects that are related with the water molecules. The aforementioned issues should be considered when comparing the operating temperature and the power consumption of the sensing devices. The different sensing behaviors that were reported for the doped and functionalized oxide materials towards different gaseous compounds are encouraging, and together with the use of ENs, will reduce the problem of the selectivity. The accurate control of the structures shape, composition and dimensions will contribute towards the synthesis of new and interesting nanomaterials, which will open unexplored possibilities for future sensing technologies for food quality control applications.

4. Food Packaging and Antimicrobial Actions

In this section, the most active metal oxide nanostructures that have been exploited for use in the food packaging systems are reviewed, along with their structure, effects, and applications.
TiO2 nanoparticles are good photocatalysts and antimicrobial agents that are used in food packaging [118,119,120,121]. They act upon the food spoilage bacteria through lipid peroxidation that is caused by the production of reactive oxygen species (ROS) molecules under visible and UV, DNA damage via hydroxyl radicals, resulting in cell death [122,123]. TiO2 based bio-nanocomposites have been used as the efficient packaging materials for various oxygen-sensitive food products [124]. An interesting work on TiO2 based bio-nanocomposite film as a packaging material for soft white cheese was presented by Youssef et al. [125]. The material consisting of chitosan, poly (vinyl alcohol), and TiO2 nanoparticles (CS/PVA/TiO2) exhibited good mechanical properties and antimicrobial activities against Gram-positive, Gram-negative bacteria, fungi, and coliform. In another study, they used ZnO nanoparticles, chitosan (CH), and carboxymethyl cellulose (CMC), namely CH/CMC/ZnO nanocomposite, as a packaging material for the same cheese [126]. It showed similar properties as the TiO2-based material. The CS/PVA/TiO2 bio-nanocomposites displayed hydrophobic property and when used as a packaging material for the soft white cheese, the moisture content of the cheese significantly increased with increasing storage period. In case of CH/CMC/ZnO packaged cheese, the textural parameters of the cheese reduced with the storage time and few changes were also reported as compared to the control and blank. The films had a significant impact on pathogenic microbial strains presented with the inhibition zone ranging from 5 to 15 mm. A poly(vinyl-chloride) PVC/TiO2 nanocomposite bears an efficient food packaging property, mechanical strength, and antimicrobial properties [127]. He et al. prepared a TiO2-protein/polysaccharide (marine red alga) nanocomposite film, wherein the TiO2 nanoparticles enhanced the tensile strength of the film, showed an antimicrobial action against the food pathogen bacteria E. coli and S. aureus, and maintained the quality and shelf life of cherry tomatoes when being used as a coating material [128]. By increasing the TiO2 content in starch/TiO2 bio-nanocomposite, the hydrophobicity of the nanocomposite increased, and its thermal, mechanical, and UV light-shielding properties were enhanced [129].
The nano-TiO2-low density polyethylene (LDPE) packaging showed promising results in maintaining the quality and shelf life of Pacific white shrimp [130]. The TiO2-LDPE nanocomposite material inhibited the growth of spoilage bacteria and lowered the polyphenol oxidase (PPO) activity. It was able to retard the decrease of whiteness and water holding capacity, and reduced the total viable counts (TVC). Bodaghi et al. demonstrated the ability of TiO2-LDPE nanocomposite film to inhibit the microorganisms Pseudomonas spp. and Rhodotorula mucilaginosa that are responsible for fruit and vegetable spoilage [131]. The same group developed an LDPE/clay-TiO2 nanocomposite film showing strong mechanical and barrier properties, and convincing antimicrobial activities against the aforementioned classes of microorganisms [132]. Such film is useful in horticulture product packaging. Similarly, mesoporous TiO2/SiO2 nanocomposite with different concentrations of nanoparticles was used to degrade ethylene under UV light as a measure to ensure the shelf life of mature green tomatoes. This could be a successful photooxidative packaging film model for the fresh fruits and vegetables, and their postharvest management [133]. Chitosan/TiO2 nanocomposite film also demonstrated ethylene photodegradation that helped in the prolongation of tomato storage [134]. TiO2 nanoparticles were exploited to construct a biodegradable nanocomposite film that was aimed at preserving the microbial and sensory qualities of lamb meat during storage [135]. The whey protein isolate (WPI)/cellulose nanofiber (CNF)/TiO2 nanoparticles/rosemary essential oil (REO) nanocomposite film was successful in reducing the bacterial load containing food pathogens, such as L. monocytogenes, S. enteritidis, E. coli O157:H7, S. aureus, and P. fluorescens, thus increased the shelf life of the meat. Another biodegradable nanocomposite film that was fabricated by incorporating jackfruit filum polysaccharide (JFPS)-TiO2 nanoparticles displayed reduced moisture content, transparency, and total soluble matter [136]. The JFPS/TiO2 nanocomposite showed an excellent antimicrobial action that was essential for active food packaging.
In view of the food preservation and safety, various methods and composite materials have been employed for the long-term food storage. AgCl-TiO2 nanocomposite material was used to study the anti-quorum sensing mechanism [137]. Quorum sensing system has been linked to the biofilm formation in food spoilage bacteria. In this study, the anti-quorum sensing activity of the bioactive AgCl-TiO2 material in the model bacteria Chromobacterium violaceum was confirmed by the absence of signaling molecule oxo-octanoyl homoserine lactone during bacterial growth, endorsing the potential use of AgCl-TiO2 nanomaterial in the food packaging industry. Peter et al. developed Ag/TiO2-SiO2-coated food packaging film for the preservation of fresh green lettuce during storage [138]. The obtained results showed its ability to reduce the level of lettuce spoilage, known as botrytis blight that is caused by Botrytis cinerea. The antimicrobial action of TiO2 nanomaterial is explained by its capacity to produce charge carriers when exposed to UV light, which initiates redox reaction on the microbial cell surface that eventually inhibits the microbial cell. Ag/TiO2 nanocomposite-based packaging extended the shelf life and microbial safety of the white bread by inhibiting the growth of yeast, molds and Gram-positive bacteria B. cereus and B. subtilis [139]. In another study, the microbiological and chemical characteristics of the white bread during storage in paper packages using Ag/TiO2-SiO2, Ag/N-TiO2, or Au/TiO2 in comparison with the non-modified paper packages were investigated [140]. The tensile and breaking resistance of the paper packages decreased with an increase in the composite content. The Ag/TiO2-SiO2 based-paper showed the best properties; all three of them exhibited superior water retention and the nanocomposites containing Ag nanoparticles extended the shelf life of the bread together with a strong antimicrobial action.
Poly lactic acid (PLA) nanocomposite films prepared from TiO2 and Ag nanoparticles were applied to study their antimicrobial properties and shelf life of Yunnan cottage cheese [141]. The obtained results showed the essential antimicrobial properties of the PLA/TiO2 and PLA/TiO2+Ag packaging films and the packed cheese exhibited better retention in pH value, lactic acid bacteria (LAB) count, and sensory quality. TiO2-potato starch blend films were studied where TiO2 nanoparticles reduced the water solubility, water vapor permeability, and moisture uptake of the film [142]. The overall functional properties of the film were improved, illustrating its potential for food packaging. Likewise, a soluble soybean polysaccharide (SSPS)/TiO2 bio-nanocomposite showed excellent heat seal strength and biocidal activities fulfilling the requisites for a food coating and packaging material [143]. Other TiO2-based nanocomposite films that were applicable in active and intelligent food packaging are: fish bilayer gelatin/agar film containing TiO2 [144], wheat gluten/cellulose nanocrystals/TiO2 nanocomposite [145], and TiO2/LDPE film assuring the food safety and quality [146]. A chitosan-TiO2 nanocomposite that was prepared for packaging red grapes was successful in preventing the microbial infection and elongating the shelf life of the grapes [147]. It should be noted that the nanocomposites showed better mechanical properties and enhanced hydrophilicity or high-water permeability. It was efficient against both Gram-positive and Gram-negative bacteria by provoking the leakage of cellular substances through the damaged membrane. Similarly, TiO2 and Ag-doped TiO2 nanoparticles were reported to show photocatalytic antibacterial performance under visible-light irradiation [148]. The viability of the test microorganisms: Gram-positive S. aureus and Gram-negative P. aeruginosa, E. coli bacteria was reduced to zero at 3% and 7% doping concentrations of Ag-TiO2 nanoparticles. TiO2 offers a good supporting material for the doping of Ag nanoparticles due to its small size and high surface area. A novel bio-nanocomposite material that was developed from wheat gluten, nanocellulose, and TiO2 nanoparticles coated in kraft paper sheets for food packaging applications showed good antibacterial properties against Gram-positive and Gram-negative bacteria expressed in terms of reduction% of surviving number (CFU) of the tested organisms [145]. A simple example of active food packaging procedure exploiting the polymer nanocomposites is shown in Figure 5.
ZnO nanoparticles are effective antimicrobial agents when they are present in reduced particle size and dimension. They demonstrate an excellent antimicrobial activity against the food pathogens, like Salmonella, Klebsiella, and Shigella via the generation of ROS and the loss of membrane integrity. ZnO nanoparticles also exhibit antibacterial action against spores that are high temperature and pressure resistant [149]. Among the ZnO/LDPE, TiO2/LDPE, and ZnO-TiO2/LDPE nanocomposite films that were studied against E. coli in fresh calf minced meat, ZnO/LDPE films were identified as the best materials to prevent bacterial growth and to improve the shelf life of the meat [150]. An active emulsified film that was based on carboxymethyl cellulose-chitosan-oleic acid (CMC-CH-OL) with ZnO nanoparticles that were produced by the casting method was found to be active against the fungi Aspergillus niger, and its extensibility increased [151]. The nanocomposite film was effectively applied to increase the shelf life of sliced white bread [152]. All active coatings reduced the number of yeasts and molds in the bread. An active polymer bilayer polyethylene/polycaprolactone (PE/PCL) film that was modified with ZnO or ZnO/casein complex extended the shelf life of food [153]. The addition of ZnO nanoparticles enhanced the barrier, mechanical, thermal properties, and antimicrobial actions of the nanocomposite film. This helps in protecting the food products during their transport. Therefore, such a nanocomposite material is preferred for food packaging when low water loss from packaging is favorable. The use of polyethylene films with chitosan-ZnO nanocomposite for active food packaging prevented the microbial contamination after 24 h incubation and extended the shelf life of food [154]. ZnO nanoparticles that were introduced into the chitosan matrix showed a 42% increase in solubility (water affinity) and an 80% reduction in swelling of the resultant nanocomposite materials. The mechanical, thermal, and antimicrobial effect of TiO2 and ZnO added PET-poly(ethylene terephthalate) and PBS-poly(butylene succinate) blend thin film was shown by Threepopnatkul et al. [155]. The PET/PBS thin film with TiO2 seemed to be effective against E. coli and S. aureus than that with ZnO, showcasing the use of the material for food packaging applications.
A comprehensive list of metal oxide nanomaterials and nanocomposites in active food packaging and analysis is given in Table 3. Since the advent of innovative metal oxide nanostructured materials in food packaging, this field continues to grow and evolve. Whereas, these metal oxide nanocomposites serve as a boon in active and intelligent packaging research. There have been concerns about the safety, sustainability, and potential health risks and hazards of the materials that were used. The nanomaterials, when utilized as food additives, could transfer to the food matrix from the nanocomposite. Given the alterations in the nanomaterial surface and properties due to the chemical and physical transformations, the determination of such nanomaterials in a complex food matrix still poses a challenge. Hence, the important concerns that are related to the application of nanocomposites in food packaging are about the size, quantity, and physiochemical properties of the nanomaterials than the polymers, enzymes, or antimicrobial agents that are used to synthesize the nanocomposites. This provides a room for the improvement in key properties and functionalities of the nanomaterials for the food packaging applications.

5. Conclusions

In summary, we provide a comprehensive review of recent research activities on the synthesis and application of metal oxide materials in food quality control and active and intelligent packaging. During the last years, the major part of research on the fabrication of metal oxide nanomaterials has been devoted to the improvement of the synthesis procedures for the modification of the shape and size of the structure and the incorporation of dopant or mixture materials onto the obtained structures. Investigations suggest that the move to the nanoscale can significantly increase the response of the material. The doping and fabrication of composite structures is favorable to improve the selectivity of the material. Numerous studies have showed that the gas sensors that are based on metal oxides nanomaterials are very attractive structures. This is due to their promising gas sensing properties caused by their low dimensionality and high surface-to-volume ratio. However, the advantages and disadvantages in the fabrication methods of metal oxide nanostructures should be considered, estimating the preparation speed, cost, and reproducibility.
The EN systems can be used for the selective detection of VOCs and other gaseous compounds, which is very important for the precious determination of quality changes in the food products. ZnO, TiO2, NiO, Cr2O3, WO3, CuO, Fe2O3, Co3O4, V2O5, and In2O3 nanostructures have shown attractive sensing performances for the fabrication of chemical sensors and their applications in food quality control systems. Moreover, SnO2 has been widely and successfully used in EN systems for the food quality analysis.
The recent studies on metal oxide nanocomposites-based food packaging emphasize the essential role of metal oxide nanomaterials in the fabrication of nanocomposite films coupling the polymer matrices, such as PE, PVC, PLA, chitosan, cellulose, and starch. The obtained bio-nanocomposite structures exhibit antimicrobial actions and effective mechanical, thermal, and barrier properties. Their application in active and intelligent food packaging ensures the food quality and safety and an increased shelf-life of food products.


The authors are thankful to Craig Evans from the Department of Information Engineering (University of Brescia) for revision of English.

Author Contributions

The authors contributed equally to this work.

Conflicts of Interest

The authors declare no conflict of interest.


  1. Di Stefano, V.; Avellone, G.; Bongiorno, D.; Cunsolo, V.; Muccilli, V.; Sforza, S.; Dossena, A.; Drahos, L.; Vékey, K. Applications of liquid chromatography–mass spectrometry for food analysis. J. Chromatogr. A 2012, 1259, 74–85. [Google Scholar] [CrossRef] [PubMed]
  2. Vezočnik, V.; Hodnik, V.; Anderluh, G. Surface plasmon resonance analysis of food toxins and toxicants. In Analysis of Food Toxins and Toxicants; John Wiley & Sons, Ltd: Hoboken, NJ, USA, 2017; pp. 195–216. [Google Scholar]
  3. McCarthy, M.J.; McCarthy, K.L. Advanced Sensors, Quality Attributes, and Modeling in Food Process Control; Springer: Boston, MA, USA, 2013; pp. 499–517. [Google Scholar]
  4. Galstyan, V.; Comini, E.; Kholmanov, I.; Ponzoni, A.; Sberveglieri, V.; Poli, N.; Faglia, G.; Sberveglieri, G. A composite structure based on reduced graphene oxide and metal oxide nanomaterials for chemical sensors. Beilstein J. Nanotechnol. 2016, 7, 1421–1427. [Google Scholar] [CrossRef] [PubMed]
  5. Galstyan, V.; Comini, E.; Ponzoni, A.; Sberveglieri, V.; Sberveglieri, G. ZnO quasi-1D nanostructures: Synthesis, modeling, and properties for applications in conductometric chemical sensors. Chemosensors 2016, 4, 6. [Google Scholar] [CrossRef]
  6. Galstyan, V. Porous TiO2-based gas sensors for cyber chemical systems to provide security and medical diagnosis. Sensors 2017, 17, 2947. [Google Scholar] [CrossRef] [PubMed]
  7. Moseley, P.T. Progress in the development of semiconducting metal oxide gas sensors: A review. Meas. Sci. Technol. 2017, 28, 082001. [Google Scholar] [CrossRef]
  8. Baldwin, E.A.; Bai, J.; Plotto, A.; Dea, S. Electronic noses and tongues: Applications for the food and pharmaceutical industries. Sensors 2011, 11, 4744–4766. [Google Scholar] [CrossRef] [PubMed]
  9. Sliwinska, M.; Wisniewska, P.; Dymerski, T.; Namiesnik, J.; Wardencki, W. Food analysis using artificial senses. J. Agric. Food Chem. 2014, 62, 1423–1448. [Google Scholar] [CrossRef] [PubMed]
  10. He, X.J.; Hwang, H.M. Nanotechnology in food science: Functionality, applicability, and safety assessment. J. Food Drug Anal. 2016, 24, 671–681. [Google Scholar] [CrossRef] [PubMed]
  11. Wilson, A. Diverse applications of electronic-nose technologies in agriculture and forestry. Sensors 2013, 13, 2295–2348. [Google Scholar] [CrossRef] [PubMed]
  12. Baietto, M.; Wilson, A. Electronic-nose applications for fruit identification, ripeness and quality grading. Sensors 2015, 15, 899–931. [Google Scholar] [CrossRef] [PubMed]
  13. Sekhon, B.S. Nanotechnology in agri-food production: An overview. Nanotechnol. Sci. Appl. 2014, 7, 31–53. [Google Scholar] [CrossRef] [PubMed]
  14. Dasgupta, N.; Ranjan, S.; Mundekkad, D.; Ramalingam, C.; Shanker, R.; Kumar, A. Nanotechnology in agro-food: From field to plate. Food Res. Int. 2015, 69, 381–400. [Google Scholar] [CrossRef]
  15. Parthibavarman, M.; Hariharan, V.; Sekar, C. High-sensitivity humidity sensor based on SnO2 nanoparticles synthesized by microwave irradiation method. Mater. Sci. Eng. C 2011, 31, 840–844. [Google Scholar] [CrossRef]
  16. Wang, Y.; Zhao, X.J.; Feng, Z.M.; Lu, G.Y.; Sun, T.; Xu, Y. Crystalline-phase-induced formation of fibre-intube TiO2-SnO2 fibres for a humidity sensor. CrystEngComm 2017, 19, 5528–5531. [Google Scholar] [CrossRef]
  17. Hsu, C.L.; Su, I.L.; Hsueh, T.J. Tunable schottky contact humidity sensor based on S-doped ZnO nanowires on flexible pet substrate with piezotronic effect. J. Alloys Compd. 2017, 705, 722–733. [Google Scholar] [CrossRef]
  18. Reig, C.S.; Lopez, A.D.; Ramos, M.H.; Ballester, V.A.C. Nanomaterials: A map for their selection in food packaging applications. Packag. Technol. Sci. 2014, 27, 839–866. [Google Scholar] [CrossRef]
  19. Andrews, D.; Scholes, G.; Wiederrecht, G. Comprehensive Nanoscience and Technology, Volume 1: Nanomaterials; Elsevier Science Bv: Amsterdam, The Netherlands, 2011; pp. 1–635. [Google Scholar]
  20. Galstyan, V.; Comini, E.; Faglia, G.; Sberveglieri, G. TiO2 nanotubes: Recent advances in synthesis and gas sensing properties. Sensors 2013, 13, 14813–14838. [Google Scholar] [CrossRef] [PubMed]
  21. Spencer, M.J.S. Gas sensing applications of 1d-nanostructured zinc oxide: Insights from density functional theory calculations. Prog. Mater. Sci. 2012, 57, 437–486. [Google Scholar] [CrossRef]
  22. Galstyan, V.; Vomiero, A.; Comini, E.; Faglia, G.; Sberveglieri, G. TiO2 nanotubular and nanoporous arrays by electrochemical anodization on different substrates. RSC Adv. 2011, 1, 1038–1044. [Google Scholar] [CrossRef]
  23. Choi, M.J.; Cho, C.J.; Kim, K.C.; Pyeon, J.J.; Park, H.H.; Kim, H.S.; Han, J.H.; Kim, C.G.; Chung, T.M.; Park, T.J.; et al. SnO2 thin films grown by atomic layer deposition using a novel sn precursor. Appl. Surf. Sci. 2014, 320, 188–194. [Google Scholar] [CrossRef]
  24. Shaik, U.P.; Krishna, M.G. Single step formation of indium and tin doped ZnO nanowires by thermal oxidation of indium-zinc and tin-zinc metal films: Growth and optical properties. Ceram. Int. 2014, 40, 13611–13620. [Google Scholar] [CrossRef]
  25. Li, W.; Li, Y.; Du, G.; Chen, N.; Liu, S.; Wang, S.; Huang, H.; Lu, C.; Niu, X. Enhanced electrical and optical properties of boron-doped ZnO films grown by low pressure chemical vapor deposition for amorphous silicon solar cells. Ceram. Int. 2016, 42, 1361–1365. [Google Scholar] [CrossRef]
  26. Hu, P.; Han, N.; Zhang, D.; Ho, J.C.; Chen, Y. Highly formaldehyde-sensitive, transition-metal doped ZnO nanorods prepared by plasma-enhanced chemical vapor deposition. Sens. Actuators B Chem. 2012, 169, 74–80. [Google Scholar] [CrossRef]
  27. Manuel, M.-M.; Ana, B.; Zineb, S.; Juan, P.E.; Angel, B.; Jose, C.; Gonzalez-Elipe, A.R. Vertical and tilted Ag-NPS@ZnO nanorods by plasma-enhanced chemical vapour deposition. Nanotechnology 2012, 23, 255303. [Google Scholar]
  28. Haddad, K.; Abokifa, A.; Kavadiya, S.; Chadha, T.S.; Shetty, P.; Wang, Y.; Fortner, J.; Biswas, P. Growth of single crystal, oriented SnO2 nanocolumn arrays by aerosol chemical vapour deposition. CrystEngComm 2016, 18, 7544–7553. [Google Scholar] [CrossRef]
  29. Panigrahi, J.; Behera, D.; Mohanty, I.; Subudhi, U.; Nayak, B.B.; Acharya, B.S. Radio frequency plasma enhanced chemical vapor based ZnO thin film deposition on glass substrate: A novel approach towards antibacterial agent. Appl. Surf. Sci. 2011, 258, 304–311. [Google Scholar] [CrossRef]
  30. Wang, J.; Dong, X.; Zhang, B.; Zhang, Y.; Wang, H.; Shi, Z.; Zhang, S.; Yin, W.; Du, G. P-type NiZnO thin films grown by photo-assist metal–organic chemical vapor deposition. J. Alloys Compd. 2013, 579, 160–164. [Google Scholar] [CrossRef]
  31. Ye, Z.; Wang, T.; Wu, S.; Ji, X.; Zhang, Q. Na-doped ZnO nanorods fabricated by chemical vapor deposition and their optoelectrical properties. J. Alloys Compd. 2017, 690, 189–194. [Google Scholar] [CrossRef]
  32. Comini, E.; Baratto, C.; Faglia, G.; Ferroni, M.; Vomiero, A.; Sberveglieri, G. Quasi-one dimensional metal oxide semiconductors: Preparation, characterization and application as chemical sensors. Prog. Mater. Sci. 2009, 54, 1–67. [Google Scholar] [CrossRef]
  33. Zhang, Y.; Liu, M.; Ren, W.; Ye, Z.-G. Well-ordered ZnO nanotube arrays and networks grown by atomic layer deposition. Appl. Surf. Sci. 2015, 340, 120–125. [Google Scholar] [CrossRef]
  34. Lim, Y.T.; Son, J.Y.; Rhee, J.S. Vertical ZnO nanorod array as an effective hydrogen gas sensor. Ceram. Int. 2013, 39, 887–890. [Google Scholar] [CrossRef]
  35. Huang, Y.J.; Pandraud, G.; Sarro, P.M. The atomic layer deposition array defined by etch-back technique: A new method to fabricate TiO2 nanopillars, nanotubes and nanochannel arrays. Nanotechnology 2012, 23, 485306. [Google Scholar] [CrossRef] [PubMed]
  36. Lahiri, R.; Ghosh, A.; Dwivedi, S.M.M.D.; Chakrabartty, S.; Chinnamuthu, P.; Mondal, A. Performance of erbium-doped TiO2 thin film grown by physical vapor deposition technique. Appl. Phys. A 2017, 123, 573. [Google Scholar] [CrossRef]
  37. Comini, E.; Baratto, C.; Concina, I.; Faglia, G.; Falasconi, M.; Ferroni, M.; Galstyan, V.; Gobbi, E.; Ponzoni, A.; Vomiero, A.; et al. Metal oxide nanoscience and nanotechnology for chemical sensors. Sens. Actuators B Chem. 2013, 179, 3–20. [Google Scholar] [CrossRef]
  38. George, A.; Kumari, P.; Soin, N.; Roy, S.S.; McLaughlin, J.A. Microstructure and field emission characteristics of ZnO nanoneedles grown by physical vapor deposition. Mater. Chem. Phys. 2010, 123, 634–638. [Google Scholar] [CrossRef]
  39. Dlugosch, T.; Chnani, A.; Muralidhar, P.; Schirmer, A.; Biskupek, J.; Strehle, S. Thermal oxidation synthesis of crystalline iron-oxide nanowires on low-cost steel substrates for solar water splitting. Semicond. Sci. Technol. 2017, 32, 084001. [Google Scholar] [CrossRef]
  40. Kim, D.; Leem, J.Y. Catalyst-free synthesis of ZnO nanorods by thermal oxidation of Zn films at various temperatures and their characterization. J. Nanosci. Nanotechnol. 2017, 17, 5826–5829. [Google Scholar] [CrossRef]
  41. Comini, E.; Galstyan, V.; Faglia, G.; Bontempi, E.; Sberveglieri, G. Highly conductive titanium oxide nanotubes chemical sensors. Microporous Mesoporous Mater. 2015, 208, 165–170. [Google Scholar] [CrossRef]
  42. Ellis, B.L.; Knauth, P.; Djenizian, T. Three-dimensional self-supported metal oxides for advanced energy storage. Adv. Mater. 2014, 26, 3368–3397. [Google Scholar] [CrossRef] [PubMed]
  43. Galstyan, V.; Comini, E.; Faglia, G.; Sberveglieri, G. Synthesis of self-ordered and well-aligned Nb2O5 nanotubes. CrystEngComm 2014, 16, 10273–10279. [Google Scholar] [CrossRef]
  44. Galstyan, V.; Vomiero, A.; Concina, I.; Braga, A.; Brisotto, M.; Bontempi, E.; Faglia, G.; Sberveglieri, G. Vertically aligned TiO2 nanotubes on plastic substrates for flexible solar cells. Small 2011, 7, 2437–2442. [Google Scholar] [CrossRef] [PubMed]
  45. Galstyan, V.; Comini, E.; Baratto, C.; Faglia, G.; Sberveglieri, G. Nanostructured ZnO chemical gas sensors. Ceram. Int. 2015, 41, 14239–14244. [Google Scholar] [CrossRef]
  46. Rana, A.u.H.S.; Chang, S.-B.; Chae, H.U.; Kim, H.-S. Structural, optical, electrical and morphological properties of different concentration sol-gel ZnO seeds and consanguineous ZnO nanostructured growth dependence on seeds. J. Alloys Compd. 2017, 729, 571–582. [Google Scholar] [CrossRef]
  47. Valerio, L.R.; Mamani, N.C.; de Zevallos, A.O.; Mesquita, A.; Bernardi, M.I.B.; Doriguetto, A.C.; de Carvalho, H.B. Preparation and structural-optical characterization of dip-coated nanostructured co-doped ZnO dilute magnetic oxide thin films. Rsc Adv. 2017, 7, 20611–20619. [Google Scholar] [CrossRef]
  48. Richard, D.; Romero, M.; Faccio, R. Experimental and theoretical study on the structural, electrical and optical properties of tantalum-doped ZnO nanoparticles prepared via sol-gel acetate route. Ceram. Int. 2018, 44, 703–711. [Google Scholar] [CrossRef]
  49. Zhang, Z.; Yin, C.; Yang, L.; Jia, W.; Zhou, J.; Xu, H.; Cao, D. H2 response characteristics for sol–gel-derived WO3-SnO2 dual-layer thin films. Ceram. Int. 2017, 43, 6693–6699. [Google Scholar] [CrossRef]
  50. Yao, S.; Qu, F.; Wang, G.; Wu, X. Facile hydrothermal synthesis of WO3 nanorods for photocatalysts and supercapacitors. J. Alloys Compd. 2017, 724, 695–702. [Google Scholar] [CrossRef]
  51. Cao, S.; Zhao, C.; Han, T.; Peng, L. Hydrothermal synthesis, characterization and gas sensing properties of the WO3 nanofibers. Mater. Lett. 2016, 169, 17–20. [Google Scholar] [CrossRef]
  52. Yu, Z.; Qu, X.; Yang, W.; Peng, J.; Xu, Z. A facile hydrothermal synthesis and memristive switching performance of rutile TiO2 nanowire arrays. J. Alloys Compd. 2016, 688, 37–43. [Google Scholar] [CrossRef]
  53. Yin, M.; Yao, Y.; Fan, H.; Liu, S. WO3-SnO2 nanosheet composites: Hydrothermal synthesis and gas sensing mechanism. J. Alloys Compd. 2018, 736, 322–331. [Google Scholar] [CrossRef]
  54. Sun, K.C.; Qadir, M.B.; Jeong, S.H. Hydrothermal synthesis of TiO2 nanotubes and their application as an over-layer for dye-sensitized solar cells. RSC Adv. 2014, 4, 23223–23230. [Google Scholar] [CrossRef]
  55. Perillo, P.M.; Rodríguez, D.F. Low temperature trimethylamine flexible gas sensor based on TiO2 membrane nanotubes. J. Alloys Compd. 2016, 657, 765–769. [Google Scholar] [CrossRef]
  56. Liu, L.; Song, P.; Yang, Z.; Wang, Q. Highly sensitive and selective trimethylamine sensors based on WO3 nanorods decorated with Au nanoparticles. Phys. E Low-Dimens. Syst. Nanostruct. 2017, 90, 109–115. [Google Scholar] [CrossRef]
  57. Chu, X.; Zhou, S.; Dong, Y.; Sun, W.; Ge, X. Trimethylamine gas sensor based on Cr3+ doped ZnO nanorods/nanoparticles prepared via solvothermal method. Mater. Chem. Phys. 2011, 131, 27–31. [Google Scholar] [CrossRef]
  58. Meng, F.; Zheng, H.; Sun, Y.; Li, M.; Liu, J. Trimethylamine sensors based on Au-modified hierarchical porous single-crystalline ZnO nanosheets. Sensors 2017, 17, 1478. [Google Scholar] [CrossRef] [PubMed]
  59. Zhang, J.; Song, P.; Li, Z.; Zhang, S.; Yang, Z.; Wang, Q. Enhanced trimethylamine sensing performance of single-crystal MoO3 nanobelts decorated with au nanoparticles. J. Alloys Compd. 2016, 685, 1024–1033. [Google Scholar] [CrossRef]
  60. Woo, H.-S.; Na, C.; Kim, I.-D.; Lee, J.-H. Highly sensitive and selective trimethylamine sensor using one-dimensional ZnO-Cr2O3 hetero-nanostructures. Nanotechnology 2012, 23, 245501. [Google Scholar] [CrossRef] [PubMed]
  61. Lee, C.-S.; Kim, I.-D.; Lee, J.-H. Selective and sensitive detection of trimethylamine using ZnO-In2O3 composite nanofibers. Sens. Actuators B Chem. 2013, 181, 463–470. [Google Scholar] [CrossRef]
  62. Kwak, C.-H.; Woo, H.-S.; Lee, J.-H. Selective trimethylamine sensors using Cr2O3-decorated SnO2 nanowires. Sens. Actuators B Chem. 2014, 204, 231–238. [Google Scholar] [CrossRef]
  63. Lou, Z.; Li, F.; Deng, J.; Wang, L.; Zhang, T. Branch-like hierarchical heterostructure (α-Fe2O3/TiO2): A novel sensing material for trimethylamine gas sensor. ACS Appl. Mater. Interfaces 2013, 5, 12310–12316. [Google Scholar] [CrossRef] [PubMed]
  64. Chun, H.-N.; Kim, B.; Shin, H.-S. Evaluation of a freshness indicator for quality of fish products during storage. Food Sci. Biotechnol. 2014, 23, 1719–1725. [Google Scholar] [CrossRef]
  65. Du, J.; Wang, H.; Zhao, R.; Xie, Y.; Yao, H. Surfactant-assisted synthesis of the pencil-like zinc oxide and its sensing properties. Mater. Lett. 2013, 107, 259–261. [Google Scholar] [CrossRef]
  66. Zhang, L.; Zhao, J.; Lu, H.; Li, L.; Zheng, J.; Zhang, J.; Li, H.; Zhu, Z. Highly sensitive and selective dimethylamine sensors based on hierarchical ZnO architectures composed of nanorods and nanosheet-assembled microspheres. Sens. Actuators B Chem. 2012, 171, 1101–1109. [Google Scholar] [CrossRef]
  67. Wojnowski, W.; Majchrzak, T.; Dymerski, T.; Gębicki, J.; Namieśnik, J. Portable electronic nose based on electrochemical sensors for food quality assessment. Sensors 2017, 17, 2715. [Google Scholar] [CrossRef] [PubMed]
  68. Li, Y.; Ban, H.; Yang, M. Highly sensitive NH3 gas sensors based on novel polypyrrole-coated SnO2 nanosheet nanocomposites. Sens. Actuators B Chem. 2016, 224, 449–457. [Google Scholar] [CrossRef]
  69. Jain, S.; Karmakar, N.; Shah, A.; Kothari, D.C.; Mishra, S.; Shimpi, N.G. Ammonia detection of 1-d ZnO/polypyrrole nanocomposite: Effect of CSA doping and their structural, chemical, thermal and gas sensing behavior. Appl. Surf. Sci. 2017, 396, 1317–1325. [Google Scholar] [CrossRef]
  70. Tai, H.; Jiang, Y.; Xie, G.; Yu, J.; Chen, X.; Ying, Z. Influence of polymerization temperature on NH3 response of pani/ TiO2 thin film gas sensor. Sens. Actuators B Chem. 2008, 129, 319–326. [Google Scholar] [CrossRef]
  71. Das, M.; Sarkar, D. One-pot synthesis of zinc oxide-polyaniline nanocomposite for fabrication of efficient room temperature ammonia gas sensor. Ceram. Int. 2017, 43, 11123–11131. [Google Scholar] [CrossRef]
  72. Shingange, K.; Tshabalala, Z.P.; Ntwaeaborwa, O.M.; Motaung, D.E.; Mhlongo, G.H. Highly selective NH3 gas sensor based on au loaded ZnO nanostructures prepared using microwave-assisted method. J. Colloid Interface Sci. 2016, 479, 127–138. [Google Scholar] [CrossRef] [PubMed]
  73. Li, R.; Jiang, K.; Chen, S.; Lou, Z.; Huang, T.; Chen, D.; Shen, G. SnO2/SnS2 nanotubes for flexible room-temperature NH3 gas sensors. RSC Adv. 2017, 7, 52503–52509. [Google Scholar] [CrossRef]
  74. Warren, M.W.; Larick, D.K.; Ball, H.R. Volatiles and sensory characteristics of cooked egg-yolk, white and their combinations. J. Food Sci. 1995, 60, 79–84. [Google Scholar] [CrossRef]
  75. Perillo, P.; Rodríguez, D. TiO2 nanotubes membrane flexible sensor for low-temperature H2S detection. Chemosensors 2016, 4, 15. [Google Scholar] [CrossRef]
  76. Yu, T.; Cheng, X.; Zhang, X.; Sui, L.; Xu, Y.; Gao, S.; Zhao, H.; Huo, L. Highly sensitive H2S detection sensors at low temperature based on hierarchically structured nio porous nanowall arrays. J. Mater. Chem. A 2015, 3, 11991–11999. [Google Scholar] [CrossRef]
  77. Li, Z.; Wang, N.; Lin, Z.; Wang, J.; Liu, W.; Sun, K.; Fu, Y.Q.; Wang, Z. Room-temperature high-performance H2S sensor based on porous CuO nanosheets prepared by hydrothermal method. ACS Appl. Mater. Interfaces 2016, 8, 20962–20968. [Google Scholar] [CrossRef] [PubMed]
  78. Yeh, B.-Y.; Jian, B.-S.; Wang, G.-J.; Tseng, W.J. CuO/V2O5 hybrid nanowires for highly sensitive and selective h2s gas sensor. RSC Adv. 2017, 7, 49605–49612. [Google Scholar] [CrossRef]
  79. Jiang, P.; Zhang, H.; Chen, C.; Liang, J.; Luo, Y.; Zhang, M.; Cai, M. Co3O4-SnO2 nanobox sensor with a pn junction and semiconductor-conductor transformation for high selectivity and sensitivity detection of H2S. CrystEngComm 2017, 19, 5742–5748. [Google Scholar] [CrossRef]
  80. Guo, W.; Mei, L.; Wen, J.; Ma, J. High-response H2S sensor based on ZnO/SnO2 heterogeneous nanospheres. RSC Adv. 2016, 6, 15048–15053. [Google Scholar] [CrossRef]
  81. Yoon, J.-W.; Hong, Y.J.; Chan Kang, Y.; Lee, J.-H. High performance chemiresistive H2S sensors using Ag-loaded SnO2 yolk-shell nanostructures. RSC Adv. 2014, 4, 16067–16074. [Google Scholar] [CrossRef]
  82. Yang, T.; Yang, Q.; Xiao, Y.; Sun, P.; Wang, Z.; Gao, Y.; Ma, J.; Sun, Y.; Lu, G. A pulse-driven sensor based on ordered mesoporous Ag2O/SnO2 with improved H2S-sensing performance. Sens. Actuators B Chem. 2016, 228, 529–538. [Google Scholar] [CrossRef]
  83. Kheel, H.; Sun, G.-J.; Lee, J.K.; Lee, S.; Dwivedi, R.P.; Lee, C. Enhanced H2S sensing performance of TiO2-decorated α-Fe2O3 nanorod sensors. Ceram. Int. 2016, 42, 18597–18604. [Google Scholar] [CrossRef]
  84. Wang, Y.; Liu, B.; Xiao, S.; Wang, X.; Sun, L.; Li, H.; Xie, W.; Li, Q.; Zhang, Q.; Wang, T. Low-temperature H2S detection with hierarchical Cr-doped WO3 microspheres. ACS Appl. Mater. Interfaces 2016, 8, 9674–9683. [Google Scholar] [CrossRef] [PubMed]
  85. Tong, X.; Shen, W.; Chen, X.; Corriou, J.-P. A fast response and recovery H2S gas sensor based on free-standing TiO2 nanotube array films prepared by one-step anodization method. Ceram. Int. 2017, 43, 14200–14209. [Google Scholar] [CrossRef]
  86. Hosseini, Z.S.; Mortezaali, A.; Iraji zad, A.; Fardindoost, S. Sensitive and selective room temperature H2S gas sensor based on Au sensitized vertical ZnO nanorods with flower-like structures. J. Alloys Compd. 2015, 628, 222–229. [Google Scholar] [CrossRef]
  87. Nimbalkar, A.R.; Patil, M.G. Synthesis of highly selective and sensitive Cu-doped ZnO thin film sensor for detection of H2S gas. Mater. Sci. Semicond. Process. 2017, 71, 332–341. [Google Scholar] [CrossRef]
  88. Hyun, S.K.; Sun, G.-J.; Lee, J.K.; Lee, C.; In Lee, W.; Kim, H.W. Ethanol gas sensing using a networked pbo-decorated SnO2 nanowires. Thin Solid Films 2017, 637, 21–26. [Google Scholar] [CrossRef]
  89. Galstyan, V.; Comini, E.; Baratto, C.; Ponzoni, A.; Ferroni, M.; Poli, N.; Bontempi, E.; Brisotto, M.; Faglia, G.; Sberveglieri, G. Large surface area biphase titania for chemical sensing. Sens. Actuators B Chem. 2015, 209, 1091–1096. [Google Scholar] [CrossRef]
  90. Choi, S.; Bonyani, M.; Sun, G.-J.; Lee, J.K.; Hyun, S.K.; Lee, C. Cr2O3 nanoparticle-functionalized WO3 nanorods for ethanol gas sensors. Appl. Surf. Sci. 2018, 432, 241–249. [Google Scholar] [CrossRef]
  91. Tan, J.; Dun, M.; Li, L.; Zhao, J.; Tan, W.; Lin, Z.; Huang, X. Synthesis of hollow and hollowed-out Co3O4 microspheres assembled by porous ultrathin nanosheets for ethanol gas sensors: Responding and recovering in one second. Sens. Actuators B Chem. 2017, 249, 44–52. [Google Scholar] [CrossRef]
  92. Ben Amor, M.; Boukhachem, A.; Labidi, A.; Boubaker, K.; Amlouk, M. Physical investigations on Cd doped NiO thin films along with ethanol sensing at relatively low temperature. J. Alloys Compd. 2017, 693, 490–499. [Google Scholar] [CrossRef]
  93. Jeong, Y.J.; Koo, W.-T.; Jang, J.-S.; Kim, D.-H.; Kim, M.-H.; Kim, I.-D. Nanoscale PtO2 catalysts-loaded SnO2 multichannel nanofibers toward highly sensitive acetone sensor. ACS Appl. Mater. Interfaces 2018, 10, 2016–2025. [Google Scholar] [CrossRef] [PubMed]
  94. Shen, J.-Y.; Wang, M.-D.; Wang, Y.-F.; Hu, J.-Y.; Zhu, Y.; Zhang, Y.X.; Li, Z.-J.; Yao, H.-C. Iron and carbon codoped WO3 with hierarchical walnut-like microstructure for highly sensitive and selective acetone sensor. Sens. Actuators B Chem. 2018, 256, 27–37. [Google Scholar] [CrossRef]
  95. Wang, C.; Liu, J.; Yang, Q.; Sun, P.; Gao, Y.; Liu, F.; Zheng, J.; Lu, G. Ultrasensitive and low detection limit of acetone gas sensor based on W-doped NiO hierarchical nanostructure. Sens. Actuators B Chem. 2015, 220, 59–67. [Google Scholar] [CrossRef]
  96. Mishra, R.K.; Murali, G.; Kim, T.-H.; Kim, J.H.; Lim, Y.J.; Kim, B.-S.; Sahay, P.P.; Lee, S.H. Nanocube In2O3@RGO heterostructure based gas sensor for acetone and formaldehyde detection. RSC Adv. 2017, 7, 38714–38724. [Google Scholar] [CrossRef]
  97. Konduru, T.; Rains, G.; Li, C. A customized metal oxide semiconductor-based gas sensor array for onion quality evaluation: System development and characterization. Sensors 2015, 15, 1252–1273. [Google Scholar] [CrossRef] [PubMed]
  98. Russo, M.; Serra, D.; Suraci, F.; Di Sanzo, R.; Fuda, S.; Postorino, S. The potential of e-nose aroma profiling for identifying the geographical origin of licorice (Glycyrrhiza glabra L.) roots. Food Chem. 2014, 165, 467–474. [Google Scholar] [CrossRef] [PubMed]
  99. Pacioni, G.; Cerretani, L.; Procida, G.; Cichelli, A. Composition of commercial truffle flavored oils with GC–MS analysis and discrimination with an electronic nose. Food Chem. 2014, 146, 30–35. [Google Scholar] [CrossRef] [PubMed]
  100. Zhang, J.; Liu, X.H.; Neri, G.; Pinna, N. Nanostructured materials for room-temperature gas sensors. Adv. Mater. 2016, 28, 795–831. [Google Scholar] [CrossRef] [PubMed]
  101. Joshi, N.; Hayasaka, T.; Liu, Y.; Liu, H.; Oliveira, O.N.; Lin, L. A review on chemiresistive room temperature gas sensors based on metal oxide nanostructures, graphene and 2D transition metal dichalcogenides. Microchim. Acta 2018, 185, 213. [Google Scholar] [CrossRef] [PubMed]
  102. Liu, X.; Ma, T.; Pinna, N.; Zhang, J. Two-dimensional nanostructured materials for gas sensing. Adv. Funct. Mater. 2017, 27, 1702168. [Google Scholar] [CrossRef]
  103. Barsan, N.; Schweizer-Berberich, M.; Gopel, W. Fundamental and practical aspects in the design of nanoscaled SnO2 gas sensors: A status report. Fresenius J. Anal. Chem. 1999, 365, 287–304. [Google Scholar] [CrossRef]
  104. Lelono, D.; Triyana, K.; Hartati, S.; Istiyanto, J.E. Classification of indonesia black teas based on quality by using electronic nose and principal component analysis. In Advances of Science and Technology for Society; Nuringtyas, T.R., Roto, R., Widyaparaga, A., Mahardika, M., Kusumaadmaja, A., Sholihun, Hadi, N., Eds.; AIP: College Park, MD, USA, 2016; Volume 1755. [Google Scholar]
  105. Severini, C.; Derossi, A.; Fiore, A.G.; Ricci, I.; Marone, M. The electronic nose system: Study on the global aromatic profile of espresso coffee prepared with two types of coffee filter holders. Eur. Food Res. Technol. 2016, 242, 2083–2091. [Google Scholar] [CrossRef]
  106. Gobbi, E.; Falasconi, M.; Zambotti, G.; Sberveglieri, V.; Pulvirenti, A.; Sberveglieri, G. Rapid diagnosis of enterobacteriaceae in vegetable soups by a metal oxide sensor based electronic nose. Sens. Actuators B Chem. 2015, 207, 1104–1113. [Google Scholar] [CrossRef]
  107. Ghosh, A.; Ray, H.; Ghosh, T.K.; Das, A.; Bhattacharyya, N. Generic handheld e-nose platform for quality assessment of agricultural produces and biomedical applications. In Proceedings of the Nose2014: 4th International Conference on Environmental Odour Monitoring and Control, Venice, Italy, 14–17 September 2014; Volume 40, pp. 259–264. [Google Scholar]
  108. Sanaeifar, A.; Mohtasebi, S.S.; Ghasemi-Varnamkhasti, M.; Ahmadi, H. Application of mos based electronic nose for the prediction of banana quality properties. Measurement 2016, 82, 105–114. [Google Scholar] [CrossRef]
  109. Trirongjitmoah, S.; Juengmunkong, Z.; Srikulnath, K.; Somboon, P. Classification of garlic cultivars using an electronic nose. Comput. Electron. Agric. 2015, 113, 148–153. [Google Scholar] [CrossRef]
  110. Qiu, S.; Wang, J.; Gao, L. Qualification and quantisation of processed strawberry juice based on electronic nose and tongue. LWT-Food Sci. Technol. 2015, 60, 115–123. [Google Scholar] [CrossRef]
  111. Güney, S.; Atasoy, A. Study of fish species discrimination via electronic nose. Comput. Electron. Agric. 2015, 119, 83–91. [Google Scholar] [CrossRef]
  112. Severini, C.; Ricci, I.; Marone, M.; Derossi, A.; De Pilli, T. Changes in the aromatic profile of espresso coffee as a function of the grinding grade and extraction time: A study by the electronic nose system. J. Agric. Food Chem. 2015, 63, 2321–2327. [Google Scholar] [CrossRef] [PubMed]
  113. Hasan, N.; Ejaz, N.; Ejaz, W.; Kim, H. Meat and fish freshness inspection system based on odor sensing. Sensors 2012, 12, 15542–15557. [Google Scholar] [CrossRef] [PubMed]
  114. Xu, M.; Ye, L.; Wang, J.; Wei, Z.; Cheng, S. Quality tracing of peanuts using an array of metal-oxide based gas sensors combined with chemometrics methods. Postharvest Biol. Technol. 2017, 128, 98–104. [Google Scholar] [CrossRef]
  115. Xu, L.; Yu, X.; Liu, L.; Zhang, R. A novel method for qualitative analysis of edible oil oxidation using an electronic nose. Food Chem. 2016, 202, 229–235. [Google Scholar] [CrossRef] [PubMed]
  116. Tian, X.-Y.; Cai, Q.; Zhang, Y.-M. Rapid classification of hairtail fish and pork freshness using an electronic nose based on the PCA method. Sensors 2012, 12, 260–277. [Google Scholar] [CrossRef] [PubMed]
  117. Dymerski, T.; Gebicki, J.; Wardencki, W.; Namiesnik, J. Application of an electronic nose instrument to fast classification of polish honey types. Sensors 2014, 14, 10709–10724. [Google Scholar] [CrossRef] [PubMed]
  118. Yemmireddy, V.K.; Hung, Y.-C. Effect of binder on the physical stability and bactericidal property of titanium dioxide (TiO2) nanocoatings on food contact surfaces. Food Control 2015, 57, 82–88. [Google Scholar] [CrossRef]
  119. Mofokeng, J.P.; Luyt, A.S. Morphology and thermal degradation studies of melt-mixed poly(hydroxybutyrate-co-valerate) (PHBV)/poly(ε-caprolactone) (PCL) biodegradable polymer blend nanocomposites with TiO2 as filler. J. Mater. Sci. 2015, 50, 3812–3824. [Google Scholar] [CrossRef]
  120. Lin, Q.B.; Li, H.; Zhong, H.N.; Zhao, Q.; Xiao, D.H.; Wang, Z.W. Migration of ti from nano-TiO2-polyethylene composite packaging into food simulants. Food Addit. Contam. Part A-Chem. Anal. Control Expos. Risk Assess. 2014, 31, 1284–1290. [Google Scholar] [CrossRef] [PubMed]
  121. Yemmireddy, V.K.; Farrell, G.D.; Hung, Y.C. Development of titanium dioxide (TiO2) nanocoatings on food contact surfaces and method to evaluate their durability and photocatalytic bactericidal property. J. Food Sci. 2015, 80, N1903–N1911. [Google Scholar] [CrossRef] [PubMed]
  122. Pathakoti, K.; Morrow, S.; Han, C.; Pelaez, M.; He, X.; Dionysiou, D.D.; Hwang, H.-M. Photoinactivation of escherichia coli by sulfur-doped and nitrogen–fluorine-codoped TiO2 nanoparticles under solar simulated light and visible light irradiation. Environ. Sci. Technol. 2013, 47, 9988–9996. [Google Scholar] [CrossRef] [PubMed]
  123. Kubacka, A.; Diez, M.S.; Rojo, D.; Bargiela, R.; Ciordia, S.; Zapico, I.; Albar, J.P.; Barbas, C.; dos Santos, V.; Fernandez-Garcia, M.; et al. Understanding the antimicrobial mechanism of TiO2-based nanocomposite films in a pathogenic bacterium. Sci. Rep. 2014, 4, 4134. [Google Scholar] [CrossRef] [PubMed]
  124. Farhoodi, M. Nanocomposite materials for food packaging applications: Characterization and safety evaluation. Food Eng. Rev. 2016, 8, 35–51. [Google Scholar] [CrossRef]
  125. Youssef, A.M.; El-Sayed, S.M.; Salama, H.H.; El-Sayed, H.S.; Dufresne, A. Evaluation of bionanocomposites as packaging material on properties of soft white cheese during storage period. Carbohydr. Polym. 2015, 132, 274–285. [Google Scholar] [CrossRef] [PubMed]
  126. Youssef, A.M.; El-Sayed, S.M.; El-Sayed, H.S.; Salama, H.H.; Dufresne, A. Enhancement of egyptian soft white cheese shelf life using a novel chitosan/carboxymethyl cellulose/zinc oxide bionanocomposite film. Carbohydr. Polym. 2016, 151, 9–19. [Google Scholar] [CrossRef] [PubMed]
  127. Krehula, L.K.; Papić, A.; Krehula, S.; Gilja, V.; Foglar, L.; Hrnjak-Murgić, Z. Properties of uv protective films of poly(vinyl-chloride)/TiO2 nanocomposites for food packaging. Polym. Bull. 2017, 74, 1387–1404. [Google Scholar] [CrossRef]
  128. He, Q.Y.; Huang, Y.; Lin, B.B.; Wang, S.Y. A nanocomposite film fabricated with simultaneously extracted protein-polysaccharide from a marine alga and TiO2 nanoparticles. J. Appl. Phycol. 2017, 29, 1541–1552. [Google Scholar] [CrossRef]
  129. Goudarzi, V.; Shahabi-Ghahfarrokhi, I.; Babaei-Ghazvini, A. Preparation of ecofriendly uv-protective food packaging material by starch/TiO2 bio-nanocomposite: Characterization. Int. J. Biol. Macromol. 2017, 95, 306–313. [Google Scholar] [CrossRef] [PubMed]
  130. Luo, Z.S.; Qin, Y.; Ye, Q.Y. Effect of nano-TiO2-ldpe packaging on microbiological and physicochemical quality of pacific white shrimp during chilled storage. Int. J. Food Sci. Technol. 2015, 50, 1567–1573. [Google Scholar] [CrossRef]
  131. Bodaghi, H.; Mostofi, Y.; Oromiehie, A.; Zamani, Z.; Ghanbarzadeh, B.; Costa, C.; Conte, A.; Del Nobile, M.A. Evaluation of the photocatalytic antimicrobial effects of a TiO2 nanocomposite food packaging film by in vitro and in vivo tests. LWT-Food Sci. Technol. 2013, 50, 702–706. [Google Scholar] [CrossRef]
  132. Bodaghi, H.; Mostofi, Y.; Oromiehie, A.; Ghanbarzadeh, B.; Hagh, Z.G. Synthesis of clay-TiO2 nanocomposite thin films with barrier and photocatalytic properties for food packaging application. J. Appl. Polym. Sci. 2015, 132. [Google Scholar] [CrossRef]
  133. De Chiara, M.L.V.; Pal, S.; Licciulli, A.; Amodio, M.L.; Colelli, G. Photocatalytic degradation of ethylene on mesoporous TiO2/SiO2 nanocomposites: Effects on the ripening of mature green tomatoes. Biosyst. Eng. 2015, 132, 61–70. [Google Scholar] [CrossRef]
  134. Kaewklin, P.; Siripatrawan, U.; Suwanagul, A.; Lee, Y.S. Active packaging from chitosan-titanium dioxide nanocomposite film for prolonging storage life of tomato fruit. Int. J. Biol. Macromol. 2018, 112, 523–529. [Google Scholar] [CrossRef] [PubMed]
  135. Alizadeh Sani, M.; Ehsani, A.; Hashemi, M. Whey protein isolate/cellulose nanofibre/TiO2 nanoparticle/rosemary essential oil nanocomposite film: Its effect on microbial and sensory quality of lamb meat and growth of common foodborne pathogenic bacteria during refrigeration. Int. J. Food Microbiol. 2017, 251, 8–14. [Google Scholar] [CrossRef] [PubMed]
  136. Jin, B.; Li, X.; Zhou, X.; Xu, X.; Jian, H.; Li, M.; Guo, K.; Guan, J.; Yan, S. Fabrication and characterization of nanocomposite film made from a jackfruit filum polysaccharide incorporating TiO2 nanoparticles by photocatalysis. RSC Adv. 2017, 7, 16931–16937. [Google Scholar] [CrossRef]
  137. Naik, K.; Kowshik, M. Anti-quorum sensing activity of AgCl-TiO2 nanoparticles with potential use as active food packaging material. J. Appl. Microbiol. 2014, 117, 972–983. [Google Scholar] [CrossRef] [PubMed]
  138. Peter, A.; Tegla, D.; Giurgiulescu, L.; Cozmuta, A.M.; Nicula, C.; Cozmuta, L.M.; Vagelas, I. Development of Ag/TiO2-SiO2-coated food packaging film and its role in preservation of green lettuce during storage. Carpathian J. Food Sci. Technol. 2015, 7, 88–96. [Google Scholar]
  139. Cozmuta, A.M.; Peter, A.; Cozmuta, L.M.; Nicula, C.; Crisan, L.; Baia, L.; Turila, A. Active packaging system based on Ag/TiO2 nanocomposite used for extending the shelf life of bread. Chemical and microbiological investigations. Packag. Technol. Sci. 2015, 28, 271–284. [Google Scholar] [CrossRef]
  140. Peter, A.; Mihaly-Cozmuta, L.; Mihaly-Cozmuta, A.; Nicula, C.; Ziemkowska, W.; Basiak, D.; Danciu, V.; Vulpoi, A.; Baia, L.; Falup, A.; et al. Changes in the microbiological and chemical characteristics of white bread during storage in paper packages modified with Ag/TiO2–SiO2, Ag/N–TiO2 or Au/TiO2. Food Chem. 2016, 197, 790–798. [Google Scholar] [CrossRef] [PubMed]
  141. Li, W.H.; Li, L.; Zhang, H.; Yuan, M.L.; Qin, Y.Y. Evaluation of pla nanocomposite films on physicochemical and microbiological properties of refrigerated cottage cheese. J. Food Process. Preserv. 2018, 42. [Google Scholar] [CrossRef]
  142. Oleyaei, S.A.; Zahedi, Y.; Ghanbarzadeh, B.; Moayedi, A.A. Modification of physicochemical and thermal properties of starch films by incorporation of TiO2 nanoparticles. Int. J. Biol. Macromol. 2016, 89, 256–264. [Google Scholar] [CrossRef] [PubMed]
  143. Shaili, T.; Abdorreza, M.N.; Fariborz, N. Functional, thermal, and antimicrobial properties of soluble soybean polysaccharide biocomposites reinforced by nano TiO2. Carbohydr. Polym. 2015, 134, 726–731. [Google Scholar] [CrossRef] [PubMed]
  144. Vejdan, A.; Ojagh, S.M.; Adeli, A.; Abdollahi, M. Effect of TiO2 nanoparticles on the physico-mechanical and ultraviolet light barrier properties of fish gelatin/agar bilayer film. LWT-Food Sci. Technol. 2016, 71, 88–95. [Google Scholar] [CrossRef]
  145. El-Wakil, N.A.; Hassan, E.A.; Abou-Zeid, R.E.; Dufresne, A. Development of wheat gluten/nanocellulose/titanium dioxide nanocomposites for active food packaging. Carbohydr. Polym. 2015, 124, 337–346. [Google Scholar] [CrossRef] [PubMed]
  146. Othman, S.H.; Abd Salam, N.R.; Zainal, N.; Basha, R.K.; Talib, R.A. Antimicrobial activity of TiO2 nanoparticle-coated film for potential food packaging applications. Int. J. Photoenergy 2014. [Google Scholar] [CrossRef]
  147. Zhang, X.D.; Xiao, G.; Wang, Y.Q.; Zhao, Y.; Su, H.J.; Tan, T.W. Preparation of chitosan-TiO2 composite film with efficient antimicrobial activities under visible light for food packaging applications. Carbohydr. Polym. 2017, 169, 101–107. [Google Scholar] [CrossRef] [PubMed]
  148. Gupta, K.; Singh, R.P.; Pandey, A.; Pandey, A. Photocatalytic antibacterial performance of TiO2 and Ag-doped TiO2 against S. aureus. P. aeruginosa and E. coli. Beilstein J. Nanotechnol. 2013, 4, 345–351. [Google Scholar] [CrossRef] [PubMed]
  149. Venkatasubbu, G.D.; Baskar, R.; Anusuya, T.; Seshan, C.A.; Chelliah, R. Toxicity mechanism of titanium dioxide and zinc oxide nanoparticles against food pathogens. Colloids Surf. B Biointerfaces 2016, 148, 600–606. [Google Scholar] [CrossRef] [PubMed]
  150. Marcous, A.; Rasouli, S.; Ardestani, F. Low-density polyethylene films loaded by titanium dioxide and zinc oxide nanoparticles as a new active packaging system against escherichia coli O157:H7 in fresh calf minced meat. Packag. Technol. Sci. 2017, 30, 693–701. [Google Scholar] [CrossRef]
  151. Noshirvani, N.; Ghanbarzadeh, B.; Mokarram, R.R.; Hashemi, M.; Coma, V. Preparation and characterization of active emulsified films based on chitosan-carboxymethyl cellulose containing zinc oxide nano particles. Int. J. Biol. Macromol. 2017, 99, 530–538. [Google Scholar] [CrossRef] [PubMed]
  152. Noshirvani, N.; Ghanbarzadeh, B.; Rezaei Mokarram, R.; Hashemi, M. Novel active packaging based on carboxymethyl cellulose-chitosan-ZnO nps nanocomposite for increasing the shelf life of bread. Food Packag. Shelf Life 2017, 11, 106–114. [Google Scholar] [CrossRef]
  153. Rescek, A.; Krehula, L.K.; Katancic, Z.; Hrnjak-Murgic, Z. Active bilayer pe/pcl films for food packaging modified with zinc oxide and casein. Croat. Chem. Acta 2015, 88, 461–473. [Google Scholar] [CrossRef]
  154. Al-Naamani, L.; Dobretsov, S.; Dutta, J. Chitosan-zinc oxide nanoparticle composite coating for active food packaging applications. Innov. Food Sci. Emerg. Technol. 2016, 38, 231–237. [Google Scholar] [CrossRef]
  155. Threepopnatkul, P.; Wongnarat, C.; Intolo, W.; Suato, S.; Kulsetthanchalee, C. Effect of TiO2 and ZnO on thin film properties of pet/pbs blend for food packaging applications. Energy Procedia 2014, 56, 102–111. [Google Scholar] [CrossRef]
Figure 1. Number of publications with the topics “Metal oxide* AND food quality control OR food monitoring OR food packaging” since 2000, according to Web of Knowledge database.
Figure 1. Number of publications with the topics “Metal oxide* AND food quality control OR food monitoring OR food packaging” since 2000, according to Web of Knowledge database.
Chemosensors 06 00016 g001
Figure 2. The schematic representation of the top-down and bottom-up approaches for the fabrication of metal oxide nanostructures.
Figure 2. The schematic representation of the top-down and bottom-up approaches for the fabrication of metal oxide nanostructures.
Chemosensors 06 00016 g002
Figure 3. (ac) SEM micrographs with different resolutions and (d) corresponding histograms of thermally annealed ZnO nanoparticles diameter distribution. Reprinted from [45] with permission. Copyright (2015) Elsevier B.V.
Figure 3. (ac) SEM micrographs with different resolutions and (d) corresponding histograms of thermally annealed ZnO nanoparticles diameter distribution. Reprinted from [45] with permission. Copyright (2015) Elsevier B.V.
Chemosensors 06 00016 g003
Figure 4. (a) Responses of the Au-modified hierarchical porous single-crystalline ZnO nanosheets to different concentrations of trimethylamine (TMA) and (b) the corresponding calibration curve. Reprinted from [58] with permission.
Figure 4. (a) Responses of the Au-modified hierarchical porous single-crystalline ZnO nanosheets to different concentrations of trimethylamine (TMA) and (b) the corresponding calibration curve. Reprinted from [58] with permission.
Chemosensors 06 00016 g004
Figure 5. Schematic representation of the active food packaging using metal oxide nanostructure and biodegradable polymeric films.
Figure 5. Schematic representation of the active food packaging using metal oxide nanostructure and biodegradable polymeric films.
Chemosensors 06 00016 g005
Table 1. A selected list of references on metal oxide materials for the fabrication of gas sensors and their application in food quality analysis.
Table 1. A selected list of references on metal oxide materials for the fabrication of gas sensors and their application in food quality analysis.
Material and MorphologyTarget Gas and ConcentrationOperating Temperature (°C)Reference
TiO2 nanotubesTMA, 40–400 ppm-[55]
Au-WO3 nanorodsTMA, 100 ppm280[56]
Au-MoO3 nanobeltsTMA, 5–100 ppm280[59]
Cr3+-ZnO nanorodTMA, 0.01–100 ppm255[57]
ZnO-Cr2O3TMA, 5 ppm400[60]
ZnO-In2O3 nanofibersTMA, 0.05–5 ppm375[61]
Cr2O3-SnO2 nanowireTMA, 0.25–5 ppm450[62]
Au-ZnO porous nanosheetsTMA, 10–300 ppm260[58]
α-Fe2O3/TiO2 nanofibers/nanorodsTMA, 10–200 ppm250–320[63]
ZnO pencil-likeDMA, 5–300 ppm340[65]
ZnO nanorod/nanosheetDMA, 1–1000 ppm370[66]
polypyrrole-SnO2 nanosheetsNH3, 1–10.7 ppmRT[68]
polypyrrole-ZnO nanorodsNH3, 50 ppmRT[69]
Polyaniline-TiO2 thin filmsNH3, 23–141 ppmRT[70]
Polyaniline-ZnO nanoparticlesNH3, 20–100 ppmRT[71]
Au-ZnO nanorodsNH3, 5–100 ppmRT[72]
SnO2/SnS2 nanotubes/nanoparticlesNH3, 20–500 ppmRT[73]
TiO2 nanotubesH2S, 1–50 ppm300[85]
TiO2 nanotubesH2S, 6–38 ppm70[75]
NiO porousH2S, 1 ppb–100 ppmRT-92[76]
CuO porous nanosheetsH2S, 10 ppb–60 ppmRT[77]
TiO2-Fe2O3 nanoparticle-nanorodsH2S, 1–200 ppm300[83]
Au-ZnO nanorodsH2S, 3 ppm25[86]
Cu-ZnO thin filmH2S, 5–50 ppm250[87]
ZnO/SnO2, nanospheresH2S, 0.5–100 ppm300[80]
Ag-SnO2, yolk-shellH2S, 0.25–5 ppm350[81]
Ag2O/SnO2 porousH2S, 300 ppb100[82]
Co3O4-SnO2 nanoboxH2S, 50 ppm180[79]
CuO/V2O5 nanowiresH2S, 7–23 ppm220[78]
PbO-SnO2 nanowiresEthanol, 5–200 ppm300[88]
Reduced graphene oxide-ZnO, nanoparticles, chain-like agglomeratesEthanol, 100–250 ppm250[4]
TiO2 nanotubesEthanol, 10–50 ppm200–500[89]
Cr2O3-WO3, nanoparticle, nanorodsEthanol, 5–200 ppm300[90]
Co3O4 porous nanosheetsEthanol, 1–100 ppm220[91]
Cd-NiO thin filmEthanol, 1000 ppm100[92]
PtO2-SnO2 nanofiberAcetone, 0.6–5 ppm400[93]
Fe-C-WO3 walnut-like particlesAcetone, 0.2–10 ppm300[94]
W-NiO, flower-like spheresAcetone, 10–1000 ppm250[95]
In2O3-reduced graphene oxide, nanocubesAcetone, 5–25 ppm175[96]
Table 2. A list of Electronic nose (EN) systems based on metal oxides for the food quality monitoring.
Table 2. A list of Electronic nose (EN) systems based on metal oxides for the food quality monitoring.
Sensing MaterialTarget GasesApplicationReference
SnO2, WO3Ethanol, acetone, acetonitrile, ethyl acetateOnion quality evaluation[97]
SnO2Ethanol, ethyl acetate, isobutyl alcohol, etc.To identify geographical origin of Licorice roots[98]
SnO2, SnO2-SiO2, Ag-SnO2, Au-SnO2, Pd-SnO2, WO3Acetaldehyde,ethanol, acetone, etc.To distinguish truffle-flavored oils[99]
SnO2Aromatic compoundsClassification of Indonesian black tea[104]
SnO2Alcohols, aldehydes, ketones, etc.To study the global aromatic profile of coffee[105]
SnO2, MoO3Acids, alcoholsDiagnosis of Enterobacteriaceae in vegetable soups[106]
SnO2Aromatic compoundsTo study the quality of tea[107]
Metal oxide sensors, Hanwei Electronics Co., Ltd.Alcohols, NH3Prediction of banana quality[108]
Metal oxide sensors, Hanwei Electronics Co., Ltd. and Figaro Inc.Sulfur compounds, H2S, NH3Classification of garlic cultivars[109]
Metal oxide sensors, PEN2, Airsense Analytics, GermanyAlcohol, NH3, aromatic compoundsStrawberry juice quality control[110]
Metal oxide sensors, Figaro USA Inc.VOCsFish species discrimination[111]
Metal oxide sensors, Alpha M.O.S., FranceOrganic acids, caffeineAromatic profile of Espresso coffee[112]
Metal oxide sensors, Ogam Technology, Futurlec, e2v and Figaro EngineeringVOCs, NH3, alcohol, etc.Meat and fish freshness control[113]
Metal oxide sensors, Alpha M.O.S., FranceEthanol, NH3, VOCsTo trace peanuts quality[114]
Metal oxide sensors, Win Muster Airsense Analytics Inc., GermanyAlcohol, methane, aromatic compoundsAnalysis of edible oil oxidation[115]
Metal oxide sensors, Hangzhou Ke Na Sensors Inc., and Figaro Inc.TMA, DMA, EthanolFreshness control of hairtail fish and pork[116]
Metal oxide sensors, Figaro Inc., JapanEthanol, NH3, VOCsClassification of honey[117]
Table 3. Applications of metal oxide-based nanomaterials in food packaging sector.
Table 3. Applications of metal oxide-based nanomaterials in food packaging sector.
MaterialApplication/ Mode of ActionReference
CS/PVA/TiO2Food packaging[125]
CH/CMC/ZnOFood packaging[126]
PVC/TiO2Food packaging[127]
TiO2-protein/polysaccharide (marine red alga)Quality and shelf life of cherry tomatoes[128]
Starch/TiO2UV-protective food packaging material[129]
TiO2-LDPEQuality and shelf-life of Pacific white shrimp[130]
TiO2-LDPEAntimicrobial actions in fruit and vegetable[131]
LDPE/clay-TiO2Antimicrobial action, horticulture packaging[132]
TiO2/SiO2Degrade ethylene, quality and shelf life of mature green tomatoes[133]
Chitosan/TiO2Ethylene photodegradation, prolongation of tomato storage[134]
WPI/CNF/TiO2/REOMicrobial and sensory qualities of lamb meat, antimicrobial action[135]
JFPS-TiO2Antimicrobial action, active food packaging[136]
AgCl-TiO2Anti-quorum sensing, food packaging[137]
Ag/TiO2-SiO2Preservation of fresh green lettuce, reduction of lettuce spoilage, antimicrobial action[138]
Ag/TiO2Shelf life and microbial safety of white bread, inhibition of yeast, mold and Gram-positive bacteria[139]
Ag/TiO2-SiO2, Ag/N-TiO2 or Au/TiO2Shelf life of white bread, antimicrobial action[140]
PLA/TiO2 and PLA/TiO2+AgShelf-life of Yunnan cottage cheese[141]
Starch/TiO2Reduced water solubility, water vapor permeability and moisture uptake of the film, food packaging function[142]
Soybean polysaccharide/TiO2Heat seal strength, antimicrobial action, food coating and packaging[143]
Fish gelatin/agar bilayer/TiO2Food packaging, food safety[144]
Wheat gluten/CNC/TiO2Food packaging, food safety[145]
TiO2/LDPEFood packaging, food safety[146]
ZnO/LDPE, TiO2/LDPE, and ZnO-TiO2/LDPEAntimicrobial property against E. coli in fresh calf minced meat, shelf life of calf meat[150]
Carboxymethyl cellulose-chitosan-oleic acid/ZnOAntimicrobial action against the fungi Aspergillus niger, increased extensibility[151]
CMC-CH-OL-ZnOShelf life of sliced white bread, active against yeast and molds[152]
polyethylene/polycaprolactone-ZnOShelf life of food, antimicrobial actions, food packaging and transport[153]
Chitosan-TiO2Food packaging, effective packaging of red grapes, shelf life of grapes[147]
TiO2 and Ag-TiO2Photocatalytic antibacterial performance, food packaging[148]
Chitosan-ZnO/polyethyleneFood packaging,antimicrobial properties, shelf life of food[154]
Wheat gluten/nanocellulose/TiO2 coated in craft paperFood packaging, antimicrobial action[145]
TiO2, ZnO-poly(ethyleneterephthalate) and poly(butylene succinate)Food packaging[155]

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (
Chemosensors EISSN 2227-9040 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top