The Application of Organic and Inorganic Nanoparticles Incorporated in Edible Coatings and Their Effect on the Physicochemical and Microbiological Properties of Seafood

Abstract

Recent bibliographic research highlights the innovative application of organic and inorganic nanoparticles in edible coatings for seafood preservation. Given the high susceptibility of seafood to spoilage, incorporating nanoparticles into coatings presents a promising solution. These nanoparticles possess significant antioxidant and antimicrobial properties, which contribute to maintaining the quality and extending the shelf life of seafood products. This study reviews various materials and synthesis techniques for nanoparticles, assessing their characteristics and suitability for food applications. It emphasizes the role of nanotechnology in enhancing the mechanical properties of biopolymer-based coatings, which are biodegradable and non-toxic, thus promoting environmental sustainability. The findings indicate that nanoparticle-infused coatings effectively improve the physicochemical properties of seafood, such as pH stabilization and the reduction in total nitrogenous volatile bases, while also inhibiting microbial growth. This multifaceted approach not only addresses food waste and safety concerns but also supports the fishing industry by enhancing product quality. Overall, this research underscores the potential of nanoparticle coatings as a viable strategy for seafood preservation, paving the way for future innovations in sustainable food packaging solutions.

1. Introduction

Fish catch and aquaculture production are significant, with Mexico being ranked 17th worldwide and fourth in Latin America [1,2]. National fish production is concentrated in the northwest of the country, with Sonora emerging as a key state [3]. While fish is highly nutritious and flavorful, its susceptibility to spoilage limits its shelf life [4]. Consequently, the food industry has been exploring alternatives to maintain food freshness, with packaging emerging as a promising avenue due to extensive research and development efforts [5], Resulting in the utilization of polymers to create coatings or films that extend the shelf life of seafood.

Nanotechnology involves the manipulation, design, production, or application of nanomaterials for various purposes [6,7,8,9]. Recent studies have highlighted the benefits of incorporating nanoparticles into coatings, such as their antioxidant and antimicrobial properties, which are conducive to food preservation and play a significant role in the food industry and aquaculture production [8,10]. Presently, nanotechnology in the food industry is primarily focused on developing diverse materials for coating due to the enhanced mechanical properties like strength and stability offered by nanoparticles compared to micro and macroscale materials [10,11].

Future advancements are expected to leverage composite materials to further improve food shelf life [12]. Selecting nanomaterials for incorporation into coatings requires consideration of compound migration into food, emphasizing the importance of assessing potential migration and toxic effects [13]. There is also a growing interest in polymer technology for creating biodegradable and edible films that promote a circular economy with minimal environmental impact [14]. Nanoparticles serve as reinforcement to enhance the mechanical and barrier properties of new packaging materials, particularly biopolymers, which play a significant role in reducing petroleum-based materials [13].

Biopolymers, as edible coatings, do not release harmful substances into food and effectively aid in food preservation [10,15]. However, questions have arisen regarding ensuring human and environmental safety. Thus, there is a need to explore how incorporating nanoparticles into coatings and films can extend the shelf life of seafood, aiming to outline the primary materials used for producing nanoparticles and coatings and describe the impact of nanoparticles in coatings on the properties of seafood products, benefitting society at large, particularly workers in the fishing industry.

The development of nanoparticle coatings for seafood preservation has experienced considerable progress over the years. Initially, research focused on leveraging nanotechnology to enhance the properties of edible coatings, emphasizing extending food shelf life and reducing waste. As the field has evolved, there has been a growing interest in integrating biopolymers and nanoparticles to create sustainable, environmentally friendly solutions in seafood packaging. Moving forward, the field is poised to advance further by developing more effective coatings with enhanced properties and a heightened ability to ensure food safety and seafood preservation sustainably.

This research plays a crucial role in advancing the understanding of how organic and inorganic nanoparticles, when incorporated into edible coatings, can significantly benefit seafood preservation. By focusing on the physicochemical and microbiological properties of seafood, this study sets itself apart from the existing literature, which often treats nanoparticles and coatings in isolation. The multi-faceted approach adopted here not only enhances the properties of these coatings but also addresses pressing issues such as food waste, consumer safety, and environmental sustainability. Integrating innovations in nanotechnology into seafood packaging is expected to improve product quality, extend shelf life, and reduce spoilage, which are of paramount importance given the vulnerability of seafood products. Moreover, the findings from this research could pave the way for further innovations in packaging solutions that are not only effective but also environmentally responsible.

This study aims to analyze the latest advancements in applying nanotechnology in the food industry, particularly focusing on the development of nanoparticle coatings for seafood preservation [16]. The significance of this research lies in its potential to enhance food shelf life, reduce food waste, ensure food safety, and explore sustainable, environmentally friendly packaging alternatives. Understanding and analyzing recent developments in this field are crucial for fostering innovation and devising effective solutions for seafood preservation.

2. Nanotechnology

2.1. Potential Application of Nanoparticles in Food

Figure 1 illustrates the diverse applications of nanotechnology in the field of food science and technology, highlighting several key points. Firstly, nanotechnology can impact the various processes that food undergoes, particularly in terms of deterioration, by enhancing stability and durability through nanobiotechnology, nanoscale reactions, molecular synthesis, and heat and mass transfer. Secondly, it involves the development of nanoparticles, nanoemulsions, nanocomposites, and nanostructures that can be integrated into products or packaging. Thirdly, it includes the incorporation of nanomaterials during product formulation, packaging, or storage. Lastly, nanosensors or nanotracers can be utilized to enhance food safety and security.

Recent studies have explored the potential applications of nanotechnology in the food industry, recognizing it as a highly promising technology with significant potential [8,17]. These applications span across processing, packaging, quality control, as well as the production of functional foods and nutraceuticals [18]. The primary focus of this research lies in the integration of nanoparticles into coatings and their role in preserving food components and extending shelf life.

2.2. Materials Used for the Development of Nanoparticles

Nanoparticles are produced from a variety of materials, each offering unique properties and functionalities that are beneficial to the food industry. These materials can be broadly categorized into organic and inorganic sources. Organic materials often include polysaccharides, proteins, and lipids, which are favored for their biocompatibility and biodegradability [6]. On the other hand, inorganic materials such as silver, zinc oxide, titanium dioxide, copper oxide, carbon and graphene are utilized for their stability, durability, and enhanced barrier properties [19].

Table 1. Materials, techniques, and characteristics involved in developing nanoparticles for packaging systems.

Materials	Type/Technique	Characteristics	Application	Ref.
Casein/mequindox	Nanoencapsulation by sonication technique	The development of nanoparticles enhances the encapsulation efficiency and bioavailability of mequindox	Use of these nanoparticles in oral pharmaceuticals	[20]
Casein/silver (Ag), gold (Au) and copper oxide (CuO)	Three types of nanoparticles (Ag, Au, and Cu) were synthesized using casein as a reducing agent in a green process	Casein serves as a stabilizer in nanoparticle preparation, but each nanoparticle exhibits different morphologies, indicating dependence on the precursor used	-	[21]
Copper/aqueous extract of Rosa Andeli or Gardenia jasminoides leaves	Nanoparticles by green synthesis method	Rosa Andeli nanoparticles demonstrate superior antibacterial activity compared to those from Gardenia jasminoides	Potential application in drug-resistant bacteria	[22]
Copper (Cu)/Kigelia Africana fruit extract	Nanoparticles by green synthesis method	The extract enhanced nanoparticle synthesis and demonstrated strong antimicrobial activity	Potential application as therapeutic drug for microbial infections	[23]
Curcumin/rosemary oil	Nanoemulsions by a single sonication technique	The nanoemulsions inhibit efficiently the pathogenic bacteria P. aeruginosa, E. coli, and S. typhimurium	The nanoemulsions are used to increase the shelf life of rainbow trout fillets	[11]
Epigallocatechin gallate-grafted-chitosan	Nanoparticle by nanoprecipitation	The nanoparticle is made from chitosan modification to improve antioxidant and antibacterial activity compared to chitosan nanoparticles	Potential uses in biomedical, food packaging, nutraceutical, and pharmaceutical fields	[24]
Iron (Fe3O4)	Nanoparticles by biosynthesis using Satureja hortensis essential oil	The nanoparticles present cubic morphological structure and exhibit antimicrobial activity and anticancer effect against selected cell lines	Potential medicine drug	[25]
Silver (Ag)/essential oil of crown imperial leaves, bulbs and petals	Nanoparticle synthesis with essential oil as reduction agent	Essential oils may be an effective component in nanoparticle production and their application possess significant antibacterial activity	Potential application in medicine, pharmaceutical and food industry	[26]
Silver (Ag)/extract of (Mentha viridis) plant and Prunus domestica gum	Nanoparticle by green synthesis method	This NP presents an excellent antifungal and antibacterial activity and a moderate antioxidant activity	Future applications in medicine, medical devices, and antioxidant system	[27]
Silver (Ag)/safflower extract	Nanoparticles by green synthesis using safflower (Carthamus tinctorius L.) waste extract	Green synthesis enhances nanoparticle development and shows strong activity against S. aureus and P. fluorescens	Potential use in the food and medicine sectors	[28]
Soy isoflavone/whey protein	Soy isoflavone nanoencapsulated by emulsification evaporation method	The nanoencapsulation of soy isoflavone is improved with whey protein and presents an excellent stability, bioactivity and bioaccessibility	Potential application in functional food and pharmaceutical	[29]
Soy protein	Nanoparticles by enzymatic hydrolysis	The inclusion of three enzymes Flavorzyme, Alcalase and Protamex improve the development of the nanoparticles and exhibit better antioxidant activity than peptides of soy protein	Potential application in food, cosmetics and pharmaceuticals	[30]
Starch	Nanoparticles by ultra-sonication and mild alkali hydrolysis	This methodology proved to be useful and simple for the preparation of nanoparticles, also demonstrated enhanced stability and antioxidant activity	Potential application in food and pharmaceuticals	[31]
Starch/water soluble yellow mustard mucilage	Nanocapsules loaded with thymol and carvacrol by electrospray	Spherical structure, with high efficiency of encapsulation and uniform diameter	Elaboration of antimicrobial food packaging	[32]
Tea polyphenol, soybean oil	Nanoencapsulation of tea polyphenol to form a nanoemulsion by ultrasound-assisted method	The nanoemulsions present excellent antioxidant activity, inhibition of α-glucosidase and α-amylase and inhibit bacterial growth better than poly phenols	Food and nutraceutical industry	[33]
Titanium oxide (TiO2)	Nanoparticles synthesis with propolis extract	The nanoparticles showed antimicrobial activity, anticancer activity against human cancer cells and proved safe in low doses in albino male rats	Biomedical applications	[34]
Titanium oxide (TiO2) and zinc oxide (ZnO) with silver (Au) decorated	Nanoparticle by hydrothermal method	The nanocomposites exhibited antimicrobial activity against E. coli, S. aureus and C. albicans, anti-inflammatory activity using in vitro assays and significant anticancer activity through in vitro cytotoxicity assay	Biomedical applications	[35]
Zein/fucoidan complex and resveratrol	Nanoencapsulation of resveratrol	The zein/fucoidan nanocarrier system demonstrated controlled resveratrol release during in vitro digestion and showed low cytotoxicity	Potential use in the nutraceutical and pharmaceutical industries	[36]
Zein stabilized with pectin, xanthan gum and sodium alginate	Nanoencapsulation doxorubicin by flash nanoprecipitation	These nanoparticles demonstrated good stability for two weeks, and using alginate as a stabilizer showed excellent encapsulation efficiency	Potential use for delivering hydrophobic drugs	[37]
Zinc oxide (ZnO)	Nanoparticles by biosynthesis from essential oil of Eucalyptus globulus	The nanoparticles exhibited a potential antibacterial activity and biofilm inhibition. The use of essential oil showed an improvement in green synthesis	Potential application in medicine to combat resistant bacteria and inhibit bacterial biofilms	[38]

displays the various materials employed in the production of nanoparticles, along with their respective properties and applications in the food sector.

2.2.1. Organic Materials

(a) Polysaccharides are linear or branched macromolecules composed of multiple monosaccharide units linked by glycosidic bonds [39]. They are commonly utilized in the production of edible coatings [6,40]. Through the application of nanotechnology, nanoparticles based on polysaccharides have been developed for incorporation into packaging materials.

(b) Proteins are linear polymers consisting of L-α-amino acids, exhibiting a diverse array of structures and functions [39]. They offer various advantages such as high digestibility, cost-effectiveness, and the ability to interact with a wide range of compounds and nutrients [41]. Protein nanoparticles hold significant potential as their properties can be enhanced in nanoscale sizes, including improved stability, antioxidant activity, and non-toxicity [39,42].

(c) Lipids encompass compounds derived from animal and vegetable fats, such as waxes, acylglycerides, and fatty acids, utilized in the formation of edible films and coatings [19,43]. Unlike polysaccharides and proteins, lipids are not classified as biopolymers [44]. Lipid nanoparticles consist of a core surrounded by one or more surfactant materials, such as nanoemulsions, liposomes, and polymer nanoparticles [39]. Essential oils, concentrated volatile and aromatic lipids with therapeutic properties, are crucial compounds used in the food industry. The incorporation of essential oils in coatings enhances food preservation due to their antibacterial, antifungal, antioxidant, antimutagenic, and anticarcinogenic attributes [41,45].

The active components of essential oils, terpenes, and phenolic compounds are organically derived aromatic compounds with one or more aromatic rings and multiple hydroxyl groups [46]. Phenolic compounds, including anthocyanins, flavonoids, and turmeric, naturally occurring in plants, exhibit various biological activities such as antioxidant, antimicrobial, anti-inflammatory, anticancer, and nutraceutical properties [47,48]. Nanoencapsulation can prevent the rapid degradation of these compounds post extraction [41].

2.2.2. Inorganic Materials

(a) Metal-based nanoparticles have fading properties, which allow them to enhance light absorption and scattering [6,19,41]. The most used metals for the development of nanoparticles in the food industry are silver, gold, and copper.

(b) Metal oxides used in the food industry must be classified as food additives by the FDA and exhibit properties like those of metals [6,19,39].

2.3. Potential Toxicity of Nanoparticles

Nanoparticles (NPs) present significant advantages for the food industry, particularly in enhancing food preservation and safety. However, it is crucial to understand their potential toxicity and the migration of nanoparticles from packaging to food [49]. As the application of nanotechnology expands, concerns regarding the safety and health implications of NPs have intensified.

The unique properties of NPs, such as their increased surface area and reduced size, contribute to their heightened chemical reactivity and toxicity compared to bulk materials. This characteristic allows NPs to penetrate cells, tissues, and organs more easily, raising significant safety concerns [50,51]. Numerous studies have identified multiple mechanisms through which NPs can induce toxicity, including the generation of reactive oxygen species (ROS), mitochondrial damage, and inflammatory responses, which may lead to apoptosis and DNA damage [52].

Specific types of nanoparticles, such as silver nanoparticles (AgNPs), are widely utilized for their antibacterial properties in various products, including food packaging. However, research indicates that AgNPs can exhibit toxic effects on cultured mammalian cells, necessitating a deeper understanding of their safety profiles [53]. Factors influencing NP toxicity include size, shape, surface charge, and agglomeration state, all of which play critical roles in their interactions with biological systems [50].

Moreover, the environmental impact of NPs cannot be overlooked. Studies have shown that NPs can be absorbed and transported by terrestrial plants, leading to phytotoxic effects that may threaten human health through the food chain. The presence of NPs in edible plants can interfere with growth and cellular structures, underscoring the need for comprehensive risk assessments [54].

The field of nanotoxicology is essential for evaluating the safety of NPs and understanding their potential health impacts. Traditional toxicity assessments often face challenges, such as interference from the nanoparticles themselves in conventional cytotoxicity assays. Therefore, advanced techniques like metabolomics are being explored to provide a clearer understanding of NP interactions with biological systems [55]. In conclusion, as research continues to reveal the complex toxicological profiles of nanoparticles, it is imperative to establish robust evaluation models to fully comprehend their risks and implications for human health and the environment [52].

3. Methodologies Used for the Development of Nanoparticles

3.1. Nanoencapsulation

Nanoencapsulation is defined as the technique responsible for encapsulating substances at the nanometer scale [7,56]. These are trapped inside another, thus forming a capsule [57]. Nanocapsules or nanospheres are composed of a series of thin layers, usually spherical in shape, capable of storing gases, liquids, or solids inside them, known as the nucleus, active or internal phase [7,58]. Nanoencapsulation is usually a complex technique compared to microcapsules due to the difficulty of obtaining the proper morphology [56]. Figure 2 shows the different systems and morphology of the nanocapsules.

In general, this technique aims to stabilize the material with an enveloping wall; adjusting the structure of the material promotes its proper release and prevents the migration of unwanted components [59]. Likewise, it can be considered as a tool that protects bioactive molecules such as antioxidants, antimicrobials, vitamins, phytosterols, lutein, fatty acids, lycopene, etc., and live cells, as probiotics [56,57].

The nanoencapsulation of active compounds allows their biofunctional properties to be improved, which can be useful in the food industry. It is important to mention that to perform this procedure there is no universal technique, since each compound or food has a different molecular structure [59]. Due to structural diversity, foods have distinctive characteristics from each other, which limits the standardization of a single method for all types of foods.

Nanoencapsulation is a critical technique that enhances the stability and bioavailability of sensitive bioactive compounds in various applications, especially in the food industry. By trapping these compounds within protective nanocapsules, it effectively prevents degradation and improves their functionality. However, the process is complex due to the unique molecular structures of different compounds and foods, which limits the standardization of encapsulation methods. Ongoing research is essential to overcome these challenges and optimize nanoencapsulation for diverse applications while ensuring consistent quality and performance.

3.2. Nanoprecipitation

Nanoprecipitation, also known as solvent displacement or interfacial deposition, is used to encapsulate bioactive compounds just like the earlier method [56,60]. It is one of the most promising technologies of choice for the development of nanospheres and nanocapsules [61]. Moreover, nanoencapsulation can play a vital role in developing nanoparticles as it enhances the stability and bioavailability of the encapsulated compounds, allowing them to retain their functional properties even under adverse conditions. This process protects sensitive bioactive compounds from degradation and controls their release profiles in various applications.

Likewise, it is considered a simple and fast technique; it can be performed in a single step and does not require much energy [62,63]. It consists of a mixture of two phases, an organic (solvent) where the polymer is dissolved and an aqueous one (water and surfactants) [60]. Precipitation occurs when displacement of the solvent occurs and the polymer chains begin to fold, leaving the active compound encapsulated [62].

As for the solvent, it must be organic; normally the following are used: acetone, isopropanol, acetic acid, ethanol, and acetone–isopropanol, while the aqueous phase is composed of water and methanol (surfactant) [60]. The mechanism of formation of nanoparticles by this method is based on the theory of nucleation that involves a few steps: nucleation of particles, growth, and aggregation [61]. Figure 3 shows how this process occurs.

Barreras [61] explains that nanoencapsulation, following the theory of nucleation, is conducted in several steps. First, nucleation occurs; by adding the polymer–solvent solution (organic phase) to the aqueous phase, the polymer reaches the critical saturation limit, causing the polymer–solvent interface to break. Second, growth begins; during this stage, there is a release of energy and the particles by condensation or coagulation are attached to the nucleus. Third, aggregation occurs, and again energy is released; it is crucial that this stage is controlled to homogenize the nanoparticles and achieve uniformity in the structure.

Nanoprecipitation is a straightforward and efficient method for producing nanoparticles through solvent displacement. This technique facilitates the encapsulation of bioactive compounds in a single step and requires minimal energy, making it suitable for large-scale applications. The well-defined nucleation, growth, and aggregation process allows for control over nanoparticle characteristics. However, the choice of solvents can pose environmental and toxicity concerns, necessitating further investigation into safer alternatives. Overall, while nanoprecipitation offers significant advantages, addressing its environmental impact remains critical for its widespread adoption.

3.3. Electrospraying

Electrospraying is a method that involves converting a liquid solution into small particles at nano- and microscale using an electric field [64,65]. Using this technique, simple nanoparticles, nanocapsules and polymeric fibers can be obtained [66]. To achieve the formation of the spray, it is necessary to apply a magnetic field, the droplets must have a nanometer size and must be highly charged with the compound of interest [67].

One of the modifications of this method is coaxial electrospraying. With this technique, nanocapsules can be produced efficiently and, without altering their bioactivity, a uniform particle size is also obtained compared to the other methods [68]. Figure 4 shows a schematic of a coaxial electro sprinkler. The elaboration of nanoparticles obtained by this method have better properties of bioactivity, segmentation, and release [69,70].

In Figure 4, the axial electro sprinkler is depicted with two main fluid inputs: the core fluid and the shell fluid, which are essential for the nanocapsule formation process. The core fluid contains the active compound, while the shell fluid provides the protective layer around the core. The diagram also illustrates the collector, where the produced nanoparticles are deposited, and the voltage source that facilitates the electrospraying process. Additionally, the inset highlights the structure of the nanocapsule, showing the core and its covering, which emphasizes the encapsulation mechanism. This detailed representation is crucial for understanding the electrospraying process and the resulting nanoparticle characteristics.

Electrospraying is an innovative method that utilizes electric fields to create nanoparticles and nanocapsules with uniform sizes, a key factor for ensuring consistent performance in applications. The coaxial electrospraying technique further enhances this capability, allowing for efficient production of nanocapsules while maintaining the bioactivity of sensitive compounds. Despite its advantages, the method requires careful control of processing parameters to achieve the desired nanoparticle characteristics effectively. Continued optimization and research will enhance the practicality of electrospraying in food technology and other fields, promoting the development of more effective nanoparticle formulations.

4. Biopolymers as a Base for Coatings and Films

Currently, synthetic plastics are the most used for food packaging [71]. The reason for this is due to their durability, versatility, and functionality (1). Plastics can be said to be petroleum-based polymers in which polyethylene terephthalate (PET), polyvinylchloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyamide (PA) are included [71]. Some of these can be defined as a thin and flexible wrap [72].

As an alternative for packaging, the use of biopolymers has been implemented, which can replace the use of synthetic plastics by being more environmentally friendly [71]. Lately, biopolymer-based films have become the focus of research for the development of new packaging, since they are not toxic, and the product of their degradation is not toxic either [73].

Biopolymers can also be classified into three main categories as shown in Figure 5. First, those produced by biomass, which are polysaccharides, proteins, and lipids. Second, those produced by microorganisms like polyhydroxyalkanoate (PHA) and that include polyhydroxybutyrate (PHB) and polyglycolic acid (PGA). Third, those produced by chemical synthesis such as polylactic acid (PLA). Next, each classification will be discussed.

4.1. Biopolymers Produced by Biomass

The biopolymers used for the development of biodegradable films and coatings are polysaccharides, proteins, and lipids [17,75], which can be extracted from industrial waste such as agroforestry and fisheries [71,75]. These biopolymers are also known by the term “biobased,” referring to the derivation of the material from biomass [74].

4.1.1. Polysaccharides

Polysaccharides are hydrophilic and have low permeability to water vapor but are selectively permeable to O₂ and CO₂ gases; they also resist lipid migration [44]. Thus, the characteristics that the coating assumes will directly depend on the properties of the polysaccharide. Below are the main polysaccharides used for the development of edible coatings and the properties that support the packaging and storage of food.

(a) Chitosan is considered a safe substance and is GRAS rated by the FDA [76]. This compound is one of the most used to make edible coatings, since it is biodegradable, non-toxic, biocompatible and has antioxidant, antimicrobial, and antifungal activity [44,77]. It should be noted that its antimicrobial activity allows it to act against Gram-positive and Gram-negative bacteria [76,77]. Because of these characteristics, it is considered an excellent material for food packaging.

Chitosan is a particularly good option for use in food systems. Apart from the properties described above, coatings made from this compound have good mechanical resistance and good gas permeability: O₂ and CO₂ [77,78]. Finally, these coatings prolong the shelf life by keeping sensory characteristics such as color, flavor, and nutrients for longer [76].

(b) Cellulose is the most abundant biopolymer in nature, found in fruits, vegetables and in various plant structures (leaves and trunks) [79,80]. The most used cellulose derivatives in the food industry are carboxymethylcellulose (MCM), methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) [40]. Since 1980, cellulose has been used for edible coatings [57,80]. Cellulose coatings do not supply odor or color, and cellulose-derived compounds (MCM, MC and HPMC) are transparent, flexible, lipid-resistant but sensitive to water [80,81,82] Like chitosan, it is biodegradable and inexpensive [71]. It is a material that supplies an efficient barrier to O₂, although it presents a weak barrier against water vapor [57,80].

(c) Starch is composed of 25% amylose and 75% amylopectin [81,83]. It is found in rice, corn, potato, cassava, etc. [75]. Edible starch coatings are environmentally friendly, odorless, plentiful, and economical [83,84]. These are good for use in packaging thanks to their mechanical characteristics like plasticity and permeability to O₂ and lipids; they are also soluble in water [81,83]. Based on their characteristics, starch-based coatings are used in fried foods, as they prevent oxidation and color changes due to their permeability to fat [85].

(d) Alginate is composed of R-D-mannuronate and α-L-guluronic acid in different proportions in the chain (1–4) [81,86]. Alginate coatings are economical, biocompatible, non-toxic, tensile resistant, but do not boast good barrier properties [87]. This type of compound has been used to package frozen foods [73,86].

(e) Pectin is an anionic polysaccharide with a vertebral structure of α-d-galacturonic acid bound by a 1–4 bond [81,88]. The use of this polysaccharide in coatings is based on the ability to form gels, thus creating a more stable coating at temperature and pH; it is transparent, and with moderate permeation to O₂ and CO₂ [79,88].

4.1.2. Proteins

Proteins are defined as natural polymers capable of forming amorphous three-dimensional structures stabilized by non-covalent interactions [79]. A great advantage of protein-based coatings is that the raw material for their development can be obtained from by-products of animal or vegetable origin [89]. However, the ability to form containers depends directly on their molecular characteristics [90].

As there is a wide variety of proteins, each one will have different parameters, such as molecular weight, conformation, flexibility, and thermal stability [90]. These aspects can help improve a feature in the final product. The most used proteins are the following: soy, zein, gelatin, albumin, and collagen [79,91].

(a) Gelatin is a protein derived from the selective hydrolysis of collagen and is one of the most widely used (1). Gelatin-based coatings are a particularly suitable alternative to plastics [81,92]. These are economical, flexible, transparent, oxygen permeable and good bioactive compound carriers (1).

(b) Zein is a prolamine-like protein derived from corn gluten [81,93]. It is insoluble in water, but at remarkably high or extremely low pH, this condition changes [57]. Some of its most important characteristics are its resistance to bacteria activity, antioxidant, and adhesive properties [81,94]. Zein coatings can be used as carriers due to the antioxidant and antimicrobial activity properties mentioned above.

(c) Soy protein is classified as a globulin, is found in soybeans and this is 38% to 44% of them [79,95]. The characteristics of the coating are flexibility and permeability to O₂; this last quality prevents the oxidation of food lipids [96].

4.1.3. Lipids

Lipids are compounds that integrate aliphatic or aromatic hydrocarbon chains, and are soluble in non-polar solvents [78]. Lipid films are thick, brittle, opaque, unstable, also have low mechanical strength, cannot form cohesive or independent films, are susceptible to lipid oxidation and bring flavor to the product [44,78,85].

Despite the above, they have excellent moisture, steam, and migration barrier properties; they can also be used to develop active compounds [40,44]. Lipids are used for incorporation into other biopolymers; this technique is widely used to improve the properties of a coating [97]. The most common materials for the manufacture of films or coatings are waxes and essential oils [75].

(a) Essential oils are extracts derived from natural resources such as rosemary, oregano, thyme, sage, basil, ginger, turmeric, garlic, walnut, cloves, and fennel [40]. These have volatile compounds, especially terpenes, and have antimicrobial, antioxidant, antifungal, anti-inflammatory, anticancer activities, among others [81]. Recently, studies have shown that the incorporation of essential oils improves sensory characteristics and prolongs shelf life due to the antimicrobial power against pathogenic bacteria in food [98,99,100,101].

(b) Waxes have a high molecular weight since they are formed by esters of long-chain aliphatic acids and a long-chain aliphatic alcohol [81]. They also have a small hydrophilic part and are insoluble in water [79]. Waxes have been used to protect fruits and vegetables since the early twelfth century, where their main function was to slow the transpiration of the product to preserve its characteristics [102]. The most used in the food industry are beeswax, candelilla wax and carnauba wax [79].

4.2. Biopolymers Produced by Chemical Synthesis

Polylactic acid (PLA)

According to Khosravi [103], the importance of using PLA consists of three points. First, PLA is biodegradable, it does not generate polluting waste such as plastics. Second, it is a non-toxic product and does not generate problems in the consumer due to the migration of its components. Third, it comes from a natural and abundant source, and is economical. Finally, the characteristics it brings are like those of plastics, so it can imitate polymers such as polyvinyl chloride, polypropylene, polystyrene, and polyethylene of different densities [81]. The production of PLA containers can be understood as a life cycle as shown in Figure 6.

4.3. Biopolymers Produced by Microorganisms

Polyhydroxyalkanoates (PHA)

Polyhydroxyalkanoates are polyester biopolymers produced by bacterial fermentation; an example of this is Pseudomonas aeruginosa [97,102]. Notably, microorganisms naturally synthesize PHA polymers with sufficient bioavailability from carbon-rich sources [104]. Figure 7 shows the pathway of PHA synthesis from a fatty acid source. Therefore, the use of these is a practical alternative to be applied in different food packaging systems [97].

5. Composite Coatings with Nanoparticles

Because nanoparticles cannot be used on their own to make coatings, biopolymers need to be used as a base. As mentioned in the earlier topic, there are diverse types of biopolymers and each of them has certain characteristics. So, the incorporation of nanoparticles to a base composed of their composites results in obtaining the composite coatings. These have improved properties which will be explained throughout this chapter. One of the main desirable characteristics of composite coatings is biodegradability; it is also required that they should be harmless.

5.1. Intelligent and Active Packaging with Nanoparticles

5.1.1. Intelligent Packaging

Intelligent packaging represents a transformative approach to food preservation, providing real-time information on the state of the food [105]. These systems respond to various environmental stimuli, allowing consumers to gauge the current condition of the food [8]. The primary functions of intelligent packaging include detecting, recording, checking, and communicating the status of food products, which aids in the control of storage and distribution [59].

The integration of nanotechnology into the development of intelligent packaging systems primarily involves the creation of nanosensors and nanotracers [106]. Recent advancements highlight the effectiveness of these tools in detecting contaminants produced by biochemical or microbial changes, such as pathogenic microorganisms, toxins, pesticides, and allergenic compounds [8,9,59,107,108]. In addition to these factors, intelligent packaging can monitor changes in color, smell, and texture, supporting its application in demonstrating food freshness [8].

(a) Nanosensors play a critical role in monitoring the internal and external conditions of food items and their containers [107]. These sensors detect chemical or structural changes through interactions with the food, generating optical signals reflected in the packaging [108]. For instance, O₂ indicators are examples of nanosensors that utilize photosynthesizers to signal the presence of oxygen through colorimetric indicators [107]. Moreover, sensors sensitive to CO₂ can detect gas production due to food deterioration, utilizing colorimetry or fluorescence [105]. Recent studies have illustrated the utility of such sensors, including a novel PVA/PLA indicator that provides visible color responses to CO₂ levels in mushroom packaging, enabling users to assess freshness effectively [6]. Figure 8 shows these nanosensors.

Additionally, electroplating is a technique used to create nanosensors by employing an electric current to deposit a thin layer of metal onto the surface of an object. Electroplating plays a vital role in the development of nanosensors for food packaging. These nanosensors are integrated into packaging materials to monitor food quality, detect spoilage, and ensure safety by sensing environmental conditions like temperature, humidity, or the presence of harmful bacteria. Electroplating is used to create highly sensitive, conductive films on these nanosensors, enhancing their performance and precision. The metal coating, typically made of silver, gold, or other conductive materials, ensures that the nanosensors can efficiently transmit signals, offering real-time monitoring and improving food safety. This innovative approach can extend shelf life, reduce food waste, and provide consumers with added confidence in the safety of their packaged foods [109].

(b) Nanotracers, often presented as barcodes or QR codes on packaging, enhance food traceability [59,107]. These tools can be scanned to retrieve product information rapidly, supported by systems like radio frequency identification (RFID), which transfers product data for automatic tracking [107]. The application of intelligent indicators has also extended to using natural pigments such as anthocyanins and betalains, providing a visual assessment of food quality and spoilage [13]. Figure 9 shows this type of nanotracer.

Recent innovations highlight the potential of smart packaging to extend food shelf life through various mechanisms. For instance, electrospun gelatin nanofibers incorporating black elderberry extract, Au nanoparticles (AuNPs), and SnO₂ have been developed as intelligent packaging layers for hake fish fillets. These fibers demonstrated enhanced thermal stability and the ability to indicate spoilage through a rapid color change upon exposure to volatile compounds [110].

Furthermore, the creation of active composite films utilizing chitosan, zinc oxide nanoparticles, and sweet purple potato extract has shown promising results. These films exhibited improved mechanical properties and effective pH-sensing capabilities to detect chicken freshness, revealing the potential for smart and active packaging solutions [111].

Technological advancements continue to propel the packaging industry towards smarter, connected systems that enable real-time monitoring and improve consumer interaction. While challenges remain, the prospects for intelligent packaging are optimistic, with ongoing research aiming to enhance food safety, quality, and the consumer experience [6,13].

5.1.2. Active Packaging

Another application of nanotechnology is the development of active packaging systems, which play a crucial role in extending the shelf life of food. These systems engage directly with food products, absorbing unwanted elements such as carbon dioxide, moisture, oxygen, odors, and ethylene, while also releasing substances that combat oxidation and microbial growth, thus aiding in food preservation [6]. To create this type of packaging, it is essential that there is an interaction with the food [44]. Based on the migration of active components, active packaging can be divided into two categories [112].

On one hand, there are non-migratory systems, which are prepared by adding active compounds to the surface. On the other hand, migratory systems incorporate active compounds into the coating or film itself, typically releasing antioxidants or antimicrobial agents directly into the food [113]. In addition to these, other active ingredients such as moisture regulators, sequestrants, and gas emitters for CO₂ and O₂ are utilized [8]. However, the most used active packaging systems include antioxidants and antimicrobials, which are vital for maintaining food quality and safety.

(a) Antioxidant Activity. Antioxidants used in active packaging often consist of diverse biopolymers and nanoparticles that mitigate oxidation. These antioxidant agents interact with free radicals and oxygen promoters of oxidation reactions, donating electrons to neutralize the radicals and prevent further reactions [91]. This process is illustrated in Figure 10.

Incorporating oxygen-scavenging nanoparticles enhances packaging effectiveness by reducing the amount of O₂. Traditionally, synthetic antioxidants such as butylated hydroxytoluene and hydroxyanisole were used. However, a shift towards incorporating natural compounds, including phenols in the form of nanoemulsions or nanocapsules, is gaining traction [105]. Table 2 provides examples of improvements in the antioxidant activity of composite coatings.

Natural antioxidants sourced from plants exhibit remarkable properties but face challenges due to susceptibility to heat-induced instability and photodegradation. Nevertheless, their inclusion in active packaging contributes to improved gas-barrier properties and overall food quality [6].

(b) Antimicrobial Activity. The incorporation of nanoscale antimicrobial agents in packaging coatings has significantly enhanced antimicrobial activity compared to their microscale counterparts [114]. The nanometric size of these agents allows them to penetrate bacterial cell membranes, disrupting microorganisms and protecting food from spoilage [9]. Commonly used antimicrobial agents include silver and gold nanoparticles due to their high antibacterial activity [85]. While the precise mechanism of action remains under debate, several studies propose a mechanism as illustrated in Figure 11.

Ali [115] suggests that nanoparticles accumulate on the bacterial cell surface and interact with membrane proteins. The affinity of Au and Ag NPs for nitrogen and sulfur allows them to adhere to these membrane proteins, causing a disturbance to the outer layer. This disruption promotes the entry of nanoparticles into the cell, thereby damaging vital cellular processes by interacting with proteins and DNA. Studies have identified that nanoparticles can compromise cellular integrity through several mechanisms, including aggregation within the cell wall, interactions with DNA, RNA, and proteins that damage cellular processes, and the generation of reactive oxygen species (ROS) that release ions and further damage DNA [115,116]. Furthermore, nanoparticles can interact with thiol groups (-SH), leading to protein denaturation and enzymatic deactivation, which may cause disassembly of ribosomal subunits, disrupting protein synthesis and resulting in cell lysis. Table 2 illustrates composite coatings that enhance antimicrobial potential.

5.1.3. Recent Research Highlights the Capabilities of Active Packaging Systems Utilizing Nanoparticles and Their Effects on Food Preservation

(a) Basil Oil-Encapsulated NPs: A study examined the encapsulation of basil oil in silica nanoparticles, which were then combined with chitosan films. The resulting composite demonstrated antimicrobial inhibition against both Gram-positive and Gram-negative bacteria, highlighting the effectiveness of natural compounds in enhancing food safety [117].

(b) Copper Oxide NPs (CuO): Research on poly(butylene adipate-co-terephthalate) blended with thermoplastic starch showed that the incorporation of CuO NPs improved the thermal stability and barrier properties of the films. These bio-nanocomposite films displayed effective antibacterial activity against Escherichia coli, indicating their potential for food packaging applications [118].

(c) Eugenol-Loaded NPs: In another study, eugenol-loaded sodium caseinate and trimethyl chitosan composite nanoparticles were found to enhance the antibacterial and antioxidant properties of gelatin films, making them suitable for meat packaging while preserving texture and color [119].

(d) Curcumin-Zein-EGCG-Carrageenan NPs: The fabrication of nanoparticles using curcumin, zein, EGCG, and carrageenan resulted in composite films with enhanced antioxidant activity. These films exhibited a color change in response to changes in pH or ammonia concentration, which serve as an indicator of food freshness [120].

Table 2. Antioxidant and antimicrobial activity in coatings and films composed with nanoparticles.

Polymer	Nanoparticle	Properties	Coating or Film	Reference
Bovine serum albumin (BSA)	Selenium (Se)	Exhibited antimicrobial activity against several food-borne bacteria, with inhibition observed at 0.5 µg/mL for Listeria monocytogenes and Staphylococcus epidermidis. The average diameter of SeNPs was 22.8 ± 4.7 nm.	Coating	[121]
Carboxymethyl cellulose	Silver (Ag), zinc oxide (ZnO) and copper oxide (CuO)	The incorporation of metallic nanoparticles enhances mechanical properties. Films containing Ag and ZnO inhibited the growth of both S. aureus and E. coli, while those with CuO only inhibited E. coli	Film	[122]
Cellulose paper	Silver (Ag)	Enhanced antimicrobial efficacy against Bacillus cereus and Staphylococcus aureus, with maximum inhibition of 24 mm and 22 mm, respectively. Coated paper maintained the appearance and firmness of stored tomato fruit	Coating	[123]
Chitosan	Titanium dioxide (TiO2)	Greater antioxidant power compared to the use of TiO2 macroparticles and chitosan alone	Film	[51]
	Resveratrol nanoencapsulated	The NPs significantly enhanced the aqueous solubility of trans-resveratrol by 150-fold and increased its bioavailability by 3.5-fold. The coating diminished dehydration, inhibited microbe growth, and extended shelf life of strawberries	Edible coating	[124]
	Silver (Ag) with tea polyphenols	Excellent antioxidant and antibacterial activity, better than chitosan film	Film	[125]
	Silver (Ag)	Showed high antimicrobial activity against Fusarium oxysporum and other fungi with minimum inhibitory concentrations of 41.7 μg/mL. They were non-phytotoxic, enhancing germination and chlorophyll levels in early plant development.	Coating	[126]
	Silver (Ag)	High antifungal activity	Film	[127]
	Rosemary essential oil nanoemulsions	High antimicrobial activity, helped inhibit the growth of pathogenic microorganisms	Coating	[11]
	Turmeric essential oil nanoemulsions	High antimicrobial activity, helped inhibit the growth of pathogenic microorganisms, in smaller quantities compared to rosemary	Coating
	Gelatin and silver (Ag)	The shelf life of carrot pieces was enhanced by composite films containing nanoparticles, which exhibited ideal characteristics for food packaging	Film	[128]
	Essential oil of citrus extract and cinnamon and silver	The composite films exhibited strong activity against L. monocytogenes, S. Typhimurium, and A. niger, effectively delaying the decomposition of irradiated strawberries	Film	[64]
Ethyl vinyl acetate (EVA)	Zinc oxide (ZnO), rosemary and montmorillonite extract	High antioxidant and antimicrobial activity compared to EVA	Film	[129]
Eugenol vinyl-based resins	Silica	Coatings exhibited adequate antioxidant capacity and reduced eugenol release to prolong beneficial effects, scavenging free radicals effectively during testing with food simulants	Coating	[130]
Glucose oxidase modified (GO)	Silver (Ag) and zinc oxide (ZnO)	The incorporation of GO with Ag and ZnO enhanced the activity of the enzymes, maintaining fruit quality parameters such as total suspended solids and firmness. GO/ZnO showed the best results in extending shelf life	Spray coating	[131]
Methylcellulose	Copper oxide (CuO)/gelatin as stabilized	Presented antibacterial activity and a small migration of the nanoparticles when evaluating the storage of cheese with the films	Film	[132]
Molecularly imprinted polymer (MIP)	Gold (AuNPs) and black phosphorus nanocomposites (BPNS)	The MIP/BPNS-AuNPs provided a broad detection range (0.005–10 μM) for pefloxacin with a low detection limit (0.80 nM) and high sensitivity (3.199 μA μM−1). The sensor maintained stable signals over 35 days	Sensor platform	[133]
Nanocellulose	Dextran-coated silver	Dextran enhanced the dispersion of silver nanoparticles and helped preserve food by inhibiting bacterial growth	Film	[134]
Pectin	Cellulose nanocrystals (CNC-NPs)	The incorporation of CNC-NPs significantly improved barrier properties, reducing water vapor and oxygen permeability by 12.6% and 22.3%, respectively, while also providing antioxidant properties	Coating	[135]
	Chlorophyll of black mulberry leaf encapsulated with carboxymethylcellulose/silica	Antioxidant and antibacterial activity concerning DPPH radical and E. coli and S. aureus bacteria, respectively	Film	[136]
Polydimethylsiloxane (PDMS)	Silicon dioxide (SiO2)	The spiky SiO2 nanoparticles created superhydrophobic coatings with contact angles of 165.4° and high transparency (96.93% transmittance). The coatings were resilient to UV irradiation, water, and elevated temperatures	Coating	[137]
Polylactic acid (PLA)	Zinc oxide (ZnO) with zataria essential oil	Higher antioxidant and antimicrobial power than PLA alone	Film	[45]
	Zinc oxide (ZnO) with peppermint essential oil	Higher antioxidant and antimicrobial power than PLA alone but lower than PLA with zataria oil	Film
Starch	PVA and Ag NPs	Enhanced antibacterial and antiviral activities, with complete virus inactivation within 1 min. The coated paper also exhibited improved water resistance and tensile strength	Coating	[138]
Starch and carboxymethylcellulose	Epigallocatechin-3-gallate, cysteine, and cinnamaldehyde (ECCNPs)	The incorporation of ECCNPs improved UV resistance, physical properties, antioxidative, and antibacterial activity of the coating. It effectively prolonged the shelf life of strawberries and oranges	Coating	[139]
Zein	Turmeric nanocapsules with chitosan	High oxidation resistance	Film	[140]
	Chitosan/cinnamon essential oil	The addition of nanoparticles increased the antibacterial activity against S. aureus and E. coli bacterial	Film	[141]
	Catechin/β-cyclodextrin inclusion complex NPs	The addition of nanoparticles enhanced the film structure and exhibited strong antioxidant activity	Film	[142]

Table 2. Antioxidant and antimicrobial activity in coatings and films composed with nanoparticles.

Polymer	Nanoparticle	Properties	Coating or Film	Reference
Bovine serum albumin (BSA)	Selenium (Se)	Exhibited antimicrobial activity against several food-borne bacteria, with inhibition observed at 0.5 µg/mL for Listeria monocytogenes and Staphylococcus epidermidis. The average diameter of SeNPs was 22.8 ± 4.7 nm.	Coating	[121]
Carboxymethyl cellulose	Silver (Ag), zinc oxide (ZnO) and copper oxide (CuO)	The incorporation of metallic nanoparticles enhances mechanical properties. Films containing Ag and ZnO inhibited the growth of both S. aureus and E. coli, while those with CuO only inhibited E. coli	Film	[122]
Cellulose paper	Silver (Ag)	Enhanced antimicrobial efficacy against Bacillus cereus and Staphylococcus aureus, with maximum inhibition of 24 mm and 22 mm, respectively. Coated paper maintained the appearance and firmness of stored tomato fruit	Coating	[123]
Chitosan	Titanium dioxide (TiO2)	Greater antioxidant power compared to the use of TiO2 macroparticles and chitosan alone	Film	[51]
	Resveratrol nanoencapsulated	The NPs significantly enhanced the aqueous solubility of trans-resveratrol by 150-fold and increased its bioavailability by 3.5-fold. The coating diminished dehydration, inhibited microbe growth, and extended shelf life of strawberries	Edible coating	[124]
	Silver (Ag) with tea polyphenols	Excellent antioxidant and antibacterial activity, better than chitosan film	Film	[125]
	Silver (Ag)	Showed high antimicrobial activity against Fusarium oxysporum and other fungi with minimum inhibitory concentrations of 41.7 μg/mL. They were non-phytotoxic, enhancing germination and chlorophyll levels in early plant development.	Coating	[126]
	Silver (Ag)	High antifungal activity	Film	[127]
	Rosemary essential oil nanoemulsions	High antimicrobial activity, helped inhibit the growth of pathogenic microorganisms	Coating	[11]
	Turmeric essential oil nanoemulsions	High antimicrobial activity, helped inhibit the growth of pathogenic microorganisms, in smaller quantities compared to rosemary	Coating
	Gelatin and silver (Ag)	The shelf life of carrot pieces was enhanced by composite films containing nanoparticles, which exhibited ideal characteristics for food packaging	Film	[128]
	Essential oil of citrus extract and cinnamon and silver	The composite films exhibited strong activity against L. monocytogenes, S. Typhimurium, and A. niger, effectively delaying the decomposition of irradiated strawberries	Film	[64]
Ethyl vinyl acetate (EVA)	Zinc oxide (ZnO), rosemary and montmorillonite extract	High antioxidant and antimicrobial activity compared to EVA	Film	[129]
Eugenol vinyl-based resins	Silica	Coatings exhibited adequate antioxidant capacity and reduced eugenol release to prolong beneficial effects, scavenging free radicals effectively during testing with food simulants	Coating	[130]
Glucose oxidase modified (GO)	Silver (Ag) and zinc oxide (ZnO)	The incorporation of GO with Ag and ZnO enhanced the activity of the enzymes, maintaining fruit quality parameters such as total suspended solids and firmness. GO/ZnO showed the best results in extending shelf life	Spray coating	[131]
Methylcellulose	Copper oxide (CuO)/gelatin as stabilized	Presented antibacterial activity and a small migration of the nanoparticles when evaluating the storage of cheese with the films	Film	[132]
Molecularly imprinted polymer (MIP)	Gold (AuNPs) and black phosphorus nanocomposites (BPNS)	The MIP/BPNS-AuNPs provided a broad detection range (0.005–10 μM) for pefloxacin with a low detection limit (0.80 nM) and high sensitivity (3.199 μA μM−1). The sensor maintained stable signals over 35 days	Sensor platform	[133]
Nanocellulose	Dextran-coated silver	Dextran enhanced the dispersion of silver nanoparticles and helped preserve food by inhibiting bacterial growth	Film	[134]
Pectin	Cellulose nanocrystals (CNC-NPs)	The incorporation of CNC-NPs significantly improved barrier properties, reducing water vapor and oxygen permeability by 12.6% and 22.3%, respectively, while also providing antioxidant properties	Coating	[135]
	Chlorophyll of black mulberry leaf encapsulated with carboxymethylcellulose/silica	Antioxidant and antibacterial activity concerning DPPH radical and E. coli and S. aureus bacteria, respectively	Film	[136]
Polydimethylsiloxane (PDMS)	Silicon dioxide (SiO2)	The spiky SiO2 nanoparticles created superhydrophobic coatings with contact angles of 165.4° and high transparency (96.93% transmittance). The coatings were resilient to UV irradiation, water, and elevated temperatures	Coating	[137]
Polylactic acid (PLA)	Zinc oxide (ZnO) with zataria essential oil	Higher antioxidant and antimicrobial power than PLA alone	Film	[45]
	Zinc oxide (ZnO) with peppermint essential oil	Higher antioxidant and antimicrobial power than PLA alone but lower than PLA with zataria oil	Film
Starch	PVA and Ag NPs	Enhanced antibacterial and antiviral activities, with complete virus inactivation within 1 min. The coated paper also exhibited improved water resistance and tensile strength	Coating	[138]
Starch and carboxymethylcellulose	Epigallocatechin-3-gallate, cysteine, and cinnamaldehyde (ECCNPs)	The incorporation of ECCNPs improved UV resistance, physical properties, antioxidative, and antibacterial activity of the coating. It effectively prolonged the shelf life of strawberries and oranges	Coating	[139]
Zein	Turmeric nanocapsules with chitosan	High oxidation resistance	Film	[140]
	Chitosan/cinnamon essential oil	The addition of nanoparticles increased the antibacterial activity against S. aureus and E. coli bacterial	Film	[141]
	Catechin/β-cyclodextrin inclusion complex NPs	The addition of nanoparticles enhanced the film structure and exhibited strong antioxidant activity	Film	[142]

5.2. Properties of Composite Coatings with Nanoparticles

Biopolymers, depending on their nature, can have poor mechanical and barrier properties. It should be noted that the use of nanocomposites in coatings has supplied improvements in their mechanical strength and in their barriers against gases, because, by reducing the size of the particles to a nanometer scale, the coating is thinner, more flexible, and stable [106].

5.2.1. Mechanical Properties

Jeevahan and Chandrasekaran [43] suggest that the importance of nanoparticles in coatings is due to the biopolymer–nanoparticle interaction contributing to the transfer of stress at the interface creating a more resistant coating, while the biopolymer–biopolymer interaction contributes to agglomeration by increasing the volume, thus creating a weaker coating compared to the earlier one.

5.2.2. Barrier Properties

The barrier property of a polymeric material can be described in terms of permeability, which depends on the diffusion coefficient and solubility of the gas in the matrix [39]. Like the mechanical properties, the permeable barrier to gases is improved due to the use of nanomaterials [106], since the continuous exchange between the gases inside and outside the packaging promotes the deterioration of the food [9]. It is important to emphasize improving the barrier properties to prolong the shelf life of any product.

The permeation of gases through composite coatings with nanoparticles follows a mass transport mechanism like that of a semicrystalline matrix [39]. Figure 12 shows the schematic of the permeability mechanism. Following this transfer, Clark [39] mentions that the gas is adsorbed on the surface and then diffuses through the polymer. So, in the biopolymer with nanoparticles, it slows the diffusion of the gas; this is known as high barrier.

5.3. Coating Application Methods

Another important feature to be considered in edible coatings is the ability to adhere to the surface of the food [143]. In addition, the thickness of the coating must be taken care of since it is crucial to control the deterioration of the final product [78]. To apply the coating to the food, two methods are used, immersion or spraying (Figure 13) [81].

5.3.1. Immersion

This method is the most used; however, being in direct contact, the food must go through prior cleaning and disinfection [144]. Ribeiro [78] and Parreidt [145] explain that the process is carried out in four steps: first, the food is immersed in the solution containing the biopolymer; second, the product is drained to remove the excess polymer solution; third, a second immersion occurs in a cross-linking bath for the formation of the gel, and fourth, the product is drained to remove the excess.

5.3.2. Spraying

This method is used to form a semipermeable membrane on the surface of the product [143]. It consists of covering the surface of the food with small droplets [71]. To conduct this process, it is necessary that the coating has certain characteristics such as density, viscosity, and surface tension, which are closely related to the properties of the polymer [78]. One of its advantages is that it requires less material, the thickness is better controlled, and a more uniform coating is obtained [143].

6. Effect of Nanoparticles Incorporated into Coatings Applied to Seafood

6.1. Physicochemical Properties

6.1.1. pH

pH is a crucial factor in the stability and preservation of seafood [57]. In living organisms, muscle tissue has a neutral pH, but this value decreases after death due to halted blood circulation and oxygen depletion. During the post-mortem stage, anaerobic glycolysis occurs, leading to lactic acid production and a gradual decline in pH as ATP levels drop and oxidative metabolism ceases. Fish have a higher pH than meat, while crustaceans often have an even higher pH [145]. The addition of nanoparticles (NPs) aims to slow this pH decline, enhancing food preservation through their antimicrobial properties, which reduce microbial growth.

In a study [146], it is described how some nanoparticles can influence the pH of seafood. Nanoparticles like silver, zinc oxide, and titanium dioxide inhibit spoilage organisms and pathogenic bacteria. By controlling these microbial populations, NPs help minimize the production of alkaline byproducts such as ammonia (NH₃) and trimethylamine, which can lead to off-flavors and spoilage. This stabilization of pH extends the shelf life of seafood products. Innovative uses of nanoparticles include biosynthesized silver nanoparticles frozen to create antimicrobial nano ice, which effectively preserves fish. Nano-sized ice crystals prevent hard crust formation, protecting fish during transport. Additionally, sodium alginate-based ozone (O₃) nano bubbles have been shown to maintain bacterial counts, pH, and total volatile basic nitrogen (TVBN) levels in small yellow croaker, despite some increase in fat oxidation.

Nanospheres, which encapsulate active compounds, and chitosan-based aggregates have been effective in preventing textural deterioration and maintaining pH in fish fillets. Other structures, like polyvinylpyrrolidone-capped liquid gold nanospheres, also contribute to seafood quality improvement. Carbon dots, known for their low toxicity and stability, have demonstrated antimicrobial effects. For example, nano-sized carbon dots from onion extract extended the shelf life of Atlantic mackerel by delaying increases in TVBN, total viable counts (TVC), and pH. In summary, nanoparticles play a significant role in seafood preservation by inhibiting spoilage organisms and stabilizing pH, thereby enhancing the overall quality and freshness of seafood products.

6.1.2. Total Nitrogenous Volatile Bases

The enzymes of the microorganisms responsible for deterioration produce a wide variety of volatile compounds that control the unpleasant tastes [147]. These correspond to the accumulation of ammonia, dimethylamine (DMA), trimethylamine (TMA), among others; these are decided as the content of total nitrogenous volatile bases in fish [44]. The production of total nitrogenous volatile bases causes an alkaline change in the pH of the organism [148,149].

The bacteria Aeromonas spp., Photobacterium phosphoreum, Pseudomonas, Shewanella putrefaciens, and Vibrio ssp are the main producers of volatile compounds through their metabolism [147,150]. During the mechanism of these bacteria, the deamination of proteins is conducted. Alongside the production of trimethylamine is the development of hypoxanthine, which is known to generate bitter tastes in seafood [147]. The determination of trimethylamine is used as a biomarker of spoilage in seafood [151]. Once the origin of the total nitrogenous volatile bases is known, it is important to emphasize that the desired effect of the nanoparticles to counteract this type of deterioration is the antimicrobial activity.

Shahbazi and Shavisi [101] conducted an experiment in which they used sodium alginate coatings with peppermint essential oil and cellulose nanoparticles. The effects of this coating were analyzed in silver carp fillets (Hypophthalmichthys molitrix) for 14 days in refrigeration. The results showed that, both in the treated carp files and in the control files, the content of volatile bases increased progressively. The results of the control at 4 days were no longer suitable for consumption.

However, in the same study, in the treated fillets, the values of the volatile compounds were significantly lower and the fish remained fit for consumption for 13 days. Shahbazi and Shavisi [101] mention that the low value of volatile compounds was due to the presence of the bioactive phenolic compounds of peppermint essential oil.

6.1.3. Thiobarbituric Acid Reactive Substances

Because most seafood products are rich in unsaturated fatty acids (monounsaturated and polyunsaturated), these are more susceptible to lipid oxidation. Unsaturated fatty acids such as oleic and linoleic are more prone to autooxidation [152]. During lipid oxidation, hydroperoxides break down into hydroxykanes, alkanes, and malonaldehyde (MDA) [44]. The latter is one of the most important products in oxidation deterioration [153].

The above-mentioned oxidation by-products can be decided by the method of reactive substances to thiobarbiturate acid [154]. Thiobarbituric acid reacts with different aldehydes; this reaction is not specific to MDA, as it can also react with other compounds [155]. However, the most common reaction is that of MDA with thiobarbituric acid in the presence of an acid and water.

It should be noted that this parameter is important to find in seafood products, because the substances reacting with thiobarbituric acid are harmful to the health of the consumer [156]. There are two crucial points that must be considered to delay the production of these compounds: develop coatings with low oxygen permeability and use compounds with high antioxidant activity or that are oxygen sequestrants [104].

Based on the above, using composite coatings with nanoparticles that have antioxidant activity, and a good oxygen barrier is an exceptionally desirable choice. Since these characteristics will positively influence the physicochemical properties of seafood products. Throughout this work, the importance of these coating properties has been emphasized.

6.2. Microbiological Properties

6.2.1. Deteriorating Bacteria

The total bacterial count stands for the number of all bacteria capable of forming visible colonies in the culture medium at a certain temperature [157]. Deteriorating bacteria are reaching products through contamination [158].

Table 3. Spoilage bacteria present in seafood products.

Bacterium	Characteristics
Brochuthrix	Hemophilic, non-sporulated and immobile
Carnobacterium	Psychotropic, immobile and oxidase positive
Photobacterium	Psychotropic
Pseudoalteromonas	Aerobic, heterotopic, oxidase and catalase positive
Pseudomonas	Positive and non-fermentative oxidase
Shewanella	Oxidase positive, catalase positive and does not ferment glucose

Adaptation by [158].

shows the main deteriorating bacteria present in fish and shellfish.

In the latest advances in packaging systems, the use of biodegradable biopolymers reinforced with nanoparticles stands out [106]. Thus, nanoparticles play a significant role within this sector [159]. In the various investigations developed, the antimicrobial power of coatings has been studied.

Sullivan [160] studies the incorporation of chitosan nanoparticles and carnosolic acid nanoparticles as a novel method for the elaboration of coatings with antimicrobial activity in European hake fillets (Merluccius merluccius). In the study, they saw that the fillets were preserved for longer when the solution of nanoparticles was applied by spraying, and lipid oxidation was reduced.

6.2.2. Pathogenic Microorganisms

Pathogenic bacteria, including Escherichia coli, Salmonella, Campylobacter, Yersinia enterocolitica, and Staphylococcus aureus, pose significant health risks due to food contamination [161]. Each year, around 600 million cases of foodborne illness and 420,000 deaths occur because of these microorganisms [162]. Therefore, developing edible coatings reinforced with nanoparticles (NPs) is crucial for inhibiting microbial growth and extending shelf life.

Recent studies have demonstrated the effectiveness of nanoparticles in combating pathogenic bacteria. For instance, copper oxide nanoparticles (CuO) synthesized from Penicillium chrysogenum exhibited strong antibacterial activity, with minimal inhibitory concentration (MIC) values as low as 3.12 µg/mL against E. coli [163]. Similarly, silver nanoparticles (Ag) have been shown to induce oxidative stress and disrupt bacterial membranes, effectively preventing biofilm formation, which is critical in food spoilage [164].

As antibiotic resistance rises, alternative strategies are necessary. Peptide nucleic acids targeting bacterial metalloenzymes and biofilm-related infections are being explored as potential antibacterial agents [165]. Additionally, cell membrane-coated nanoparticles (MNPs) offer enhanced biocompatibility and targeted action against pathogens, showing promise in treating infections like sepsis [166].

In summary, the integration of nanoparticles into food preservation techniques not only addresses microbial contamination but also enhances food safety and shelf life. Continued research into their effectiveness against pathogenic bacteria is essential for developing innovative preservation and therapeutic strategies.

Finally, as there is no straightforward evidence on the effect of nanoparticles on food properties, the following scheme has been proposed (Figure 14) where their action is proposed. First, the nanoparticles are obtained and then incorporated into a solution with the selected biopolymer (a). Two methods can be used to apply the coating (b), sprinkling or immersion. A thin layer is generated on the surface of the food (c), with the composite coating (d).

Likewise, the nanoparticles of the coating can migrate inside the food, while the diffusion of gases from the food to the outside or vice versa (e) happens. Finally, the nanoparticles attack the bacteria present; as already mentioned above, the antimicrobial activity of these weakens the cell wall and causes bacterial death (f).

7. Future Directions

The application of organic and inorganic nanoparticles in edible coatings for seafood offers a promising avenue for enhancing food preservation. Future research should optimize synthesis methods for consistent quality and explore environmentally friendly, cost-effective green synthesis methods. Developing nanoparticles with enhanced antimicrobial and antioxidant properties can significantly improve the shelf life and safety of seafood products.

Comprehensive regulatory and safety assessments are crucial as the use of nanoparticles in food applications grows. Future studies should address potential toxicity and long-term effects to ensure consumer safety. Scalability and commercialization need to be addressed, including cost-effective production methods and integration into existing food processing systems. Understanding consumer perceptions and market trends is essential for successful implementation.

Interdisciplinary collaboration among food scientists, chemists, microbiologists, and regulatory bodies is necessary to drive innovation and meet industry standards. Assessing the environmental impact of nanoparticle production and disposal is also crucial. Future research should focus on sustainable practices and evaluating the life cycle of nanoparticle-based coatings to minimize their ecological footprint.

By addressing these perspectives, the application of organic and inorganic nanoparticles in edible coatings can be refined and optimized, leading to improved preservation of seafood and other perishable food products.

8. Conclusions

The integration of organic and inorganic nanoparticles into edible coatings signifies a transformative step forward in seafood preservation technology. This research emphasizes the remarkable ability of nanoparticles to enhance both the physicochemical and microbial profiles of seafood products, providing vital antimicrobial and antioxidant properties. By stabilizing pH levels and curbing the development of volatile nitrogenous bases, nanoparticle coatings extend the shelf life of seafood, addressing pressing challenges related to food waste and safety. Additionally, utilizing biodegradable and non-toxic biopolymers in these coatings reflects a commitment to environmental sustainability, which is increasingly prioritized in modern food systems. Future research should focus on refining nanoparticle synthesis techniques, evaluating long-term safety and toxicity, and understanding consumer perceptions of these innovative solutions. The insights derived from this study lay a solid foundation for the development of innovative packaging solutions that not only enhance food quality and safety but also contribute to a more sustainable food supply chain. The application of nanoparticle technology in seafood preservation offers significant potential for improving efficiency and sustainability within the industry.