Traditional and Recent Alternatives for Controlling Bacterial Foodborne Pathogens in Fresh Horticultural Commodities—A Review

Abstract

Fresh horticultural products have proven to be an excellent source of minerals, vitamins, and functional compounds for human consumption, resulting in horticultural production evolving from a local to a worldwide condition. However, during their commercialization, there can be side effects, such as the risk of contamination of foodborne illness outbreaks caused largely by bacterial microorganisms. To reduce their incidence, there exist conventional strategies that include mainly chemical and physical methods. Some of them have already been adopted by the horticultural food industry, while others are still under investigation, such as biological control. In recent years, research about the development and application of coatings has increased. There is a growing trend to design and evaluate active formulations based on naturally and non-toxic occurring compounds with antimicrobial effects against foodborne pathogens including, among others, essential oils, plant extracts, organic acids, and chitosan. Furthermore, nanomaterial-based formulations have also been recently tested, resulting in excellent materials to control them. Nevertheless, it is paramount to assess the safety and risk of these materials associated with human consumption. In this review, the current situation of foodborne pathogens in fruit and vegetables, the traditional control methods, and the future development of coating formulations with new materials are reviewed. In addition, the overall action mechanisms of the antimicrobial coating components were briefly described.

1. Introduction

1.1. Quality Parameters

Fruit, vegetables, grains, and seeds have been linked to improved health, since they contain, among other substances, different vitamins, minerals, fiber, and antioxidants. Because of these, many countries have undertaken various initiatives to encourage consumers to eat more of these products and, therefore, horticultural commodities have become one of the most dynamic product areas in domestic and international agricultural trade. During recent years, the average worldwide import–export of fresh horticultural commodities has constantly increased. Currently, the largest export–importers of fruit and vegetables are the EU, the United States, and Japan, plus many other countries such as India, Mexico, and China. Domestically, there is also a constant expansion of new areas subjected to horticultural production, with a continuous commercial exchange of horticultural goods among regions. In addition, advances in production, postharvest handling and processing, and logistical technologies have played a facilitating role.

However, in spite of the existent programs, based on the principles of hazard analysis critical control point (HACCP) systems, such as good agricultural, production, processing and manufacturing, storage, packing, and transport practices, domestic and international trade in fruit and vegetables has brought serious challenges, since as new foods and new sources of food become available, new opportunities for foodborne disease transmission arise [1,2]. Avendaño et al. [3] have mentioned that the number of foodborne disease outbreaks is constant and, in some cases, increasing, particularly in fresh and minimally processed horticultural products. Also, various authors agree that fruit and vegetables and, in particular, leafy greens, sprout seeds, and ready-to-eat vegetables that are consumed raw currently present the greatest concern in terms of microbiological hazards [4,5].

Moreover, the number of foodborne illness cases has increased worldwide due to several factors including, among others, internationalization, commerce, changes in consumer habits and climate conditions, and food safety practices. The World Health Organization [6] stated that contaminated food has caused above 600 million widespread cases of illness per year, with children under 5 years old among the most affected. In particular cases, such as in the United States, there exists 9.4 million cases of foodborne illnesses [7], while in some countries in Europe, reports highlighted 5175 outbreaks [8]. Also, in China, from the 19,517 outbreaks, there were 235,754 cases of severe illnesses [9], and in the Middle East and North Africa, it was calculated that approximately 100 million people within the population were infected by a foodborne illness [10].

Foodborne illness outbreaks related to fresh horticultural commodities usually bring harmful, longer-term economic and health consequences. The implicated producer, company, and/or country may be hit with a serious lawsuit, as well as tighter sanitary control measures if it wishes to reintroduce its horticultural product back into the export market; moreover, there is a risk that consumers will lose trust in the product and thus be hesitant to include it once again in their diet.

Although outbreaks with identified microbial etiology are predominantly of bacterial origin, there are some other implicated microorganisms, including norovirus and hepatitis A, and some parasites, that may also cause serious diseases or even death. For the fresh horticultural produces (leafy greens and fresh fruit), they are at high risk for contamination by norovirus because little or no processing is applied, and they can be contaminated at any step of the pre and postharvest stages [11]. In the case of parasites, they are also responsible for serious outbreaks. In general, the main foodborne parasites are helminths and protozoa, such as, among others, Cryptosporidium spp., Entamoeba histolytica, Giardia duodenalis, Cyclospora cayetanensis, Toxoplasma gondii, and Ascaris lumbricoides, with fresh fruit and vegetables being an important vehicle for their transmission [12,13,14].

However, for the purpose of this review article and the research expertise of the authors, the information presented has been aimed only towards the documented published literature of bacterial foodborne pathogens.

1.2. Occurrence of Foodborne Pathogens in Horticultural Commodities

Currently, fruit and vegetables are grown and processed in diverse and complex ways, ranging from in-field packing to pre-cut and bagged products that have been associated with multiple foodborne illness outbreaks in various regions of the world [2]. As mentioned above, bacteria are the main pathogens that cause foodborne illnesses, and they include, among others, Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, Campylobacter jejuni, Bacillus, and Shigella spp., all of which may be found in numerous fresh, pre-cut, and processed horticultural commodities and juices [15].

For example, E. coli has been associated with leafy green vegetables, including spinach and cilantro, and sprout seeds such as radishes and alfalfa. Various serotypes of Salmonella have been linked to the consumption of melons, tomato, mango, and different pepper cultivars, while L. monocytogenes is reported to be found in lettuce, broccoli, and coleslaw [4,5,16].

The source of contamination for fruit and vegetables with these microorganisms is variable; however, this may occur during pre and postharvest handling, as well as in retail markets, foodservice facilities, or the home [1,17].

Several lines of evidence support the view that field contamination may occur associated with animal density, soil, water irrigation, human settlement, landfills, etc., while contamination during postharvest is more associated with inefficient workplace hygiene and handling operations, including poor sanitary practices, inappropriate precooling, etc. At distribution, contamination is also associated with, among other factors, inadequate operator practices, lack of hygienic facilities, and unsafe storage temperatures [2].

Some foodborne bacteria reported in various countries from the last ten years (2013 to 2024) are presented in

Table 1. Summary (2013–2024) of bacteria implicated in foodborne outbreaks in affected countries on fresh and minimally processed agricultural products.

Year	Country	Pathogenic Bacteria	Agricultural Product	References
2013	Sweden	E. coli O157:H7	Mixed salad	[18]
2013	Canada	E. coli O157:H7	Lettuce	[19]
2013	United States	S. Saintpaul	Cucumber (Cucumis sativus)	[20]
2013	Unites States	E. coli O157:H7	Lettuce	[21]
2013–2014	Norway	S. Coeln	Mixed salad	[22]
2013–2014	Republic of Korea	E. coli O6	Kimchi (Brassica pekinensis)	[23]
2014	Finland	Y. pseudotuberculosis	Grated carrot	[24]
2014	Noway	Y. enterocolítica O9	Mixed salad	[25]
2014	United States	S. Newport	Cucumber	[26]
2014	United States	E. coli O157:H7	Celery (Apium graveolens)	[27]
2014	Luxemburg	Staphylococcus aureus	Mixed salad	[28]
2015	Canada	E. coli O157:H7	Leafy vegetables	[29]
2015–2016	United States	Salmonella Poona	Cucumber	[30]
2016	Australia	S. Hvittingtoss	Melon	[31]
2016	Australia	S. Anatum	Lettuce	[32]
2017	Canada	E. coli O157:H7	Romain lettuce	[33]
2017	United States	E. coli O157:H7	Romain lettuce	[34]
2018	Canada, United States	E. coli O157:H7	Romain lettuce	[35]
2018	Austria, Denmark, Finland, Sweden, England	Listeria monocytogenes	Frozen corn	[36]
2019	Norway	S. Agbeni	Snack mix	[37]
2019	New Zeland	S. Typhimurium	Alfalfa sprouts (Medicago sativa)	[38]
2019	Sweden	S. Typhimurium	Tomato (Solanum lycopersicum)	[39]
2019	United States	S. Uganda	Papaya	[40]
2019	United States	S. Carrau	Melon	[41]
2019	Italy, Sweden, Denmark	Y. enterocolítica	Spinach	[42]
2020	United States	S. Javiana	Cut fruit	[43]
2021	United States	S. Typhimurium	Mixed salad	[44]
2021	United States	S. Oranienburg	Onion (Allium cepa)	[45]
2022	United States	S. Typhimurium	Alfalfa sprouts	[46]
2023	United States	S. Thompson	Diced onion	[47]
2023	United States	S. Newport	Cantaloup	[48]
2024	United States	Salmonella	Organic basil (Ocimum basilicum)	[49]
2024	United States	E. coli O157:H7	Onion	[50]
2024	United States	E. coli O157:H7	Baby carrots	[51]

.

2. Control of Bacterial Foodborne Pathogens in Horticultural Commodities During Postharvest

Postharvest treatments are indispensable to reduce the presence of microorganisms and minimize the risk of contamination. The simple action of washing is sometimes efficient for removing bacteria from smooth and homogenous surfaces. For example, incidence of L. monocytogenes on the surface of romaine lettuce was reduced 1.0 log¹⁰ CFU g⁻¹ by water immersion. Similarly, E. coli growth on cucumber was reduced from 100,000 to 25,000 CFU mL⁻¹, while in tomatoes it was reduced from 10,000 to 700 CFU mL⁻¹ [52,53].

Other postharvest treatments used today include the application of different methods, such as chemical and non-chemical treatments, whereas biological strategies are still under investigation.

2.1. Chemical Control

Chemical treatments are commonly applied postharvest to disinfect fruit and vegetables, particularly in the food industry. Such methods reportedly reduce the microbial load and maintain the overall quality of the treated commodity; however, their efficiency may be compromised in those products whose texture is rough and porous, such as strawberries and cantaloupes, making bacterial colonies difficult to control [54,55]. Chlorination and oxidation are two methods that involve the application of chemical agents such as, among others, sodium hypochlorite, hydrogen peroxide, chlorine dioxin, and ozone [56].

2.1.1. Chlorination

Sodium hypochlorite (NaClO) is commonly applied due to its low cost, effectiveness, and absence of side effects. It is used in a wide range of horticultural commodities and can be applied at different temperatures. Its mechanism of action generally involves damage to the membrane causing cell lysis. Bacterial viability is affected by inactivation of enzymes and the electron transport chain [57]. Broad evidence exists concerning its bactericidal effect against Salmonella spp., E. coli O157:H7, L. monocytogenes, Y. enterocolitica, and coliforms [58].

Calcium hypochlorite Ca(ClO₂) is also a low-cost disinfectant with a wide antimicrobial margin. Its effects against, among others, E. coli O157:H7 and various serotypes of Salmonella in lettuce, broccoli, and alfalfa have been evaluated. Studies have shown that their bactericidal effects are enhanced when combined with acetic and citric acid [59,60].

2.1.2. Oxidizers

Hydrogen peroxide (H₂O₂) is a strong oxidizing agent. It is considered to be a natural germicidal agent, commonly used in several fruit and vegetables worldwide. Its positive effects have been demonstrated when applied alone or combined with other physical treatments against E. coli, Salmonella, and L. monocytogenes [61,62].

Hypochlorous acid (HClO) results from the combination of sodium hypochlorite and water. It is considered the most effective antimicrobial form. It has been applied in fresh and fresh-cut products to reduce a wide variety of pathogenic bacteria of fruit and vegetables. For example, Feng et al. (2024) [63] reported that the combination HClO + ultrasound treatment had the highest reduction in microorganisms count, with corresponding values of 2.76 log CFU/g and 2.23 log CFU/g of mold and yeast and the total bacterial counts, respectively, compared to the control (running water) with values of 0.46 log CFU/g for mold and yeast and 0.24 log CFU/g for bacteria.

For an appropriate application, the water must have a pH ranging from 5.0 to 6.0, which the content of free HClO exceeds 90%. At pH 11, it decreases drastically to reach 10% of free chlorine [64]. Furthermore, when HClO reacts with organic matter, it produces harmful gases such as chlorine and other byproducts like trihalomethanes, haloacetic acid, haloketons, and chloropricrin [65].

Ozone (O₃) is a well-known powerful oxidizer which stops microorganism development effectively. This compound is considered to have a much stronger oxidization effect than other common disinfectants such as chlorine and hypochlorite. The possibility of forming byproducts that further damage people’s health is remote [66]. Ozone acts as an oxidant on bacterial cell wall components, destroying the membrane and causing serious loss of cellular content and death. Studies indicate that this compound has serious effects on E. coli O157:H7, S. enterica, L. monocytogenes, and Listeria sp. [67,68].

2.2. Non-Chemical Control

Physical Control

UV Irradiation is a control treatment able to generate reactive chemical species, including free radicals, in cells. These intermediates have been shown to be involved in various biological effects against pathogenic bacteria, directly affecting their development. The UV irradiation has been applied in different fruit and vegetables to control E. coli O157:H7, Salmonella, and L. monocytogenes with notable results [68,69,70,71,72]. The application of this type of control is a promising technology for various horticultural products and it should be considered even more so in the future; however, the side effects include increasing enzymatic browning of the treated product due to the rupture of the cell membranes [68].

Cold plasma is a recent non-thermal oxidative treatment that can be generated by partially or totally ionizing a gas at low pressure or atmospheric pressure. It has been used in postharvest that has shown high efficacy in controlling pathogenic bacteria, without affecting the characteristics of the products, and its effect has been reported on several pathogenic bacteria including L. monocytogenes, S. enteritidis, and E. coli [73,74,75]. In this last pathogen, the effectiveness of this method has been evaluated, among others, on cherry tomatoes, eggplant, green onion, carrot, cabbage, papaya, apple, molasses, and kiwi, showing notable reductions up to 5 log¹⁰ CFU [76]. It has also been used to improve the effectiveness of other disinfectants such as hydrogen peroxide applied to grape tomatoes, apples, melons, and romaine lettuce against S. Typhimurium and L. innocua [77].

Heat is another physical alternative that has also been evaluated. To date, it has been applied in different horticultural products including, among others, mango, melon, broccoli, and Chinese cabbage to reduce Salmonella spp., E. coli, and L. monocytogenes among others enterobacteria [78,79]. The treatment generally consists of holding the horticultural commodity in a range of temperatures from 50 °C to 96 °C for very short periods of time; however, fruit with a thin cuticle and fragile structure are not suitable for this technology [80].

Modified atmosphere (MA) consists of changing the internal atmosphere of a package containing a horticultural commodity by reducing O₂ and replacing it with another gas such as CO₂ and N. For some fruit and vegetables, this technology allows their storage life to be extended by reducing the respiration rate and ethylene production, thereby controlling the microbial load and delaying the enzymatic deterioration [81]. The inhibitory action of CO₂ depends on the type of microorganism; thus, the aerobic bacteria are very susceptible to high CO₂ concentrations, but this gas may stimulate growth of lactic bacteria. Nevertheless, it has been reported that E. coli O157:H7 and S. enteriditis may survive in an MA environment; therefore, a combined alternative is appropriate [82,83,84].

Some examples of control methods are given in

Table 2. Some examples of chemical and physical control methods for reducing foodborne pathogens in fresh fruit and vegetables during postharvest.

Control Method	Fruit/Vegetable	Treatment Strategy	Pathogen	Final Microbial Load	Refs.
Chemical	Spinach	Sodium hypochlorite (100 ppm, 5 min)	E. coli O157:H7	1.1 UFC g−1	[84]
Chemical	Lettuce	Sodium hypochlorite (200 ppm, 2 min)	E. coli O157:H7	1.0 UFC g−1	[85]
Chemical	Red chard (Beta vulgaris subs. vulgaris)	Sodium hypochlorite (6%, 6 min)	E. coli O157:H7	0.85 UFC g−1	[86]
Chemical	Cabbage, lettuce, mint	Sodium hypochlorite (100 mg Kg−1, 5 min)	E. coli E. coli O157:H7	6 log CFU g−1	[87]
Chemical	Peach	Sodium hypochlorite (21 ppm, 5 s)	Listeria innocua	1.10–2.02 log CFU mL−1	[88]
Chemical	Lettuce	Sodium hypochlorite (1.5 mL L−1, 15 min)	E. coli	0.7 log10 UFC mL−1	[89]
Chemical	Blueberry (Vaccinium corymbosum)	Sodium hypochlorite (100 mg L−1, 5 min)	E. coli O157:H7	4.4 UFC g−1	[59]
Chemical	Papaya	Calcium hypochlorite (10 ppm, 5min)	Salmonella Typhimurium Listeria monocytogenes	1.8 log UFC 1.24 log UFC	[90]
Chemical	Green pepper (Capsicum annum)	Ozone (1.8 mg L−1, 1 min)	Total coliforms	1.0 UFC g−1	[91]
Chemical	Chilli (C. frutescens)	Ozone (800 mg h−1 15 min)	S. Typhimurium E. coli	complete inhibition	[92]
Chemical	Starfruit (Averrhoa carambola) and guava (Psidium guava)	Hydrogen peroxide (5.0%, 1 min)	E. coli ATCC25922 S. aureus (ATCC 25955)	2. 0 -4.0 UFC mL (starfruit), 1.5–2.2 UFC mL (guava)	[93]
Chemical	Strawberries	Levulinic acid 0.5%; or 5 %+ sodium dodecyl sulfate 0.5%; or 2 %(2 min)	Salmonella, Enterococcus faecium, E. coli O157:H7, E. coli P1, and L. monocytogenes	2.0, 2.6, 1.9, 1.8, 2.2-log reductions	[94]
Physical	Cantaloupe	Heat (84 °C, 240 s)	L. innocua	4.0 log10 UFC g−1	[95]
Physical	Chinese cabbage	Heat (55 °C, 3 s)	Enterobacterias	1.0 UFC 102 g−1	[78]
Physical	Grape (Vitis vinifera) and tomato	UV (0.60–6.0 kJ/m2, 1 min)	S. enterica and E. coli O157:H7	2.15–3.1 and 2.3–3.5 log10 CFU g−1, respectively	[96]
Physical	Broccoli (Brasica oleracea)	UV (15 kJ/m2, 37 s)	E. coli, S. enteritidis, and L. monocytogenes	4.1, 2.9, and 4.2 log10 UFC g−1, respectively	[97]
Physical	Peach	UV (442 mJ/cm2, 60 s)	E. coli O157:H7	0.9 log UFC	[98]
Physical	Apple slices	Cold plasma (200 mbar, 3 min)	S. enterica serovar Typhimurium (ATCC 13311)	6 log UFC g−1	[99]
Physical + chemical	Blueberries	Pulsed electric fields (2 kV/cm field strength, 1 ms pulse width, and 100 pulses per s), 2, 4 and 6 min	E. coli K12 and L. innocua	1.0 and 0.5 log CFU/g E. coli and 2.3 and 2.6 log CFU/g L. innocua	[100]

.

2.3. Biological Control Strategies

Antagonistic microorganisms and natural products derivatives. In this case, biological control may include other microorganisms such as fungi, bacteria, bacteriophages, yeasts, and viruses. The use of lactic acid bacteria has gained interest, too [101]. Other notable natural antimicrobial compounds also include the polymer chitosan [102] and secondary metabolites from plant extracts and essential oils [103].

In the last case, the fumigation with essential oils or their compounds in vapor phase is another experimental method for controlling foodborne bacteria in fruit and vegetables. The antimicrobial activity of essential oils is well known, but their use in fumigation is limited. However, the results obtained so far are promising and postulate it as a good method of preserving fruit and vegetable products [104]. For example, compounds extracted from cinnamon oil in the vapor phase have been evaluated on E. coli, P. aeruginosa, Salmonella, and S. aureus [105], as well as the effect of oregano, thyme, cinnamon, clove, and carrot seed oils on L. monocytogenes [106]. Overall, the reported antimicrobial activity of essential oils in the vapor phase is effective at high concentrations and over short periods. Several authors report that it is necessary to carry out sensory evaluations on fruit and vegetables treated with these compounds to evaluate changes in flavor, since they could cause changes in their sensory attributes [107].

In

Table 3. Some examples of the use of biological control for reducing foodborne pathogens in fresh fruit and vegetables during postharvest.

Fruit/Vegetable	Treatment Strategy	Pathogen	Final Microbial Load	Refs.
Cantaloupe	Antagonist E. coli O157:H7-specific bacteriophages (ECP-100) 6.69 log PFU ml−1	E. coli O157:H7	0.7 UFC mL−1	[108]
Romaine lettuce (Lactuca sativa var. longifolia)	Antagonist E. coli O157:H7-specific phage strains: 38, 39, 41, CEV2, AR1, 42, ECA1, and ECB (107 PFU mL−1)	E. coli O157:H7 and ATCC 43895	1.5 UFC/leaf	[109]
Mushrooms (Agaricus bisporus)	Antagonist Pichia kluyveri 1 × 108 cells/mL + UV-C 6 Kj/m2	Lactococcus lactis subsp. lactis	Disease incidence 40% and natural infection 15%	[110]
Tomato	Chitosan (200 mg) + lactic, acetic, and levulinic acid (2%, 10 min)	S. Montevideo ATCC 8387, S. Newport, S. Saintpaul 02-517-1, and S. Typhimurium ATCC 14028	2.5 log10 UFC/stem	[111]
Black radish (Raphanus sativus var. sativus)	Chitosan (1%) + essential oil (0.2%)	L. monocytogenes ATCC 19115, and 19112	2.4 and 2.1 log10 UFC g−1, respectively	[112]
Swiss chard	Honeybush ethanol extract 6 m L−1	L. monocytogenes and E. coli O157:H7	2.31–2.67 log reductions	[113]
Romain lettuce	Peanut skin extract + benzethonium chloride emulsion 5 mg L-1	L. monocytogenes and E. coli O157:H7	3.0 and 2.8 log reductions	[114]

, various examples of biological control are shown.

3. Coatings for Reducing Foodborne Pathogens

3.1. Functions and Materials for Coating Formulations

Natural or synthetic waxes are commonly used in the food industry. Their benefits include a good visual appearance and gas permeability adequate for weight loss control, maturation, and quality maintenance of coated fruit and vegetables [115]. Currently, new food industry products should incorporate input from materials science and consider environmental issues, hence the tendency is to use renewable, biodegradable, and edible materials derived from plant sources to produce biopolymer coatings. Coatings prolong the storage lifetime of fruit and vegetables, maintain the quality, and ensure the safety, transportation, and storage of fresh and processed food. The commercial applications for fruit and vegetables include, among others, apples, pears, carrots, celery, strawberry, and mushrooms.

Although biodegradable materials have a higher cost compared to synthetic polymers, nowadays, the commercialization of biopolymeric coatings has gained more attention for preserving horticultural commodities [116,117,118].

The main materials that can be integrated into coating formulations are from the continuous matrix, usually composed of polysaccharides (cellulose, starch, chitosan, alginate, carrageenan, pullulan, and various gums), proteins (gluten and milk protein), lipids (peanut, coconut fats, triglycerides, and transesterified oils), and natural and non-natural waxes. Also, plasticizers (glycerol, sorbitol, and polyethylene glycol), emulsifiers, and surfactants (fatty acids, glycerol stearate, and tweens) are used [119].

In recent decades, other strategies have been considered, such as the development of intelligent coatings. To be considered an intelligent coating, its formulation must include active compounds protected by polymeric substances, which may contain, among others, polysaccharides, proteins, and phospholipids. Intelligent coatings can actively respond to certain conditions or stimuli, and their goal is to help detect pH changes, gas release, or inhibit microorganisms, as well as preserve the freshness and organoleptic properties of the products [120,121]. The preparation and application of coatings must be carried out under hygienic conditions to avoid contamination and ensure their effectiveness [122]. The addition of antimicrobial compounds, in addition to providing benefits to fruit and vegetable products, could also prevent contamination of the coating itself [123].

As a new application of active or intelligent food packaging, edible coatings emerged (Figure 1). The edibility and biodegradability are extra functions not present in conventional packaging [124]. An edible coating is applied in a liquid form by immersing the fruit or vegetable in a solution. They are applied as thin layers to the external surface of a fresh fruit or vegetable acting as a barrier generating a modified atmosphere around the product. These coatings protect products from mechanical damage and microbial contamination, reducing moisture, providing a semi-permeable barrier to gases (O₂, CO₂), and maintaining the firmness of the fruit, also giving gloss to the coated fruit and vegetables. Usually, the edible coating is consumed with the coated fruit or vegetable [123,125,126,127,128], thus, coatings added with antioxidant compounds are a viable alternative for minimally processed vegetables, as they help prevent microbial deterioration and enzymatic browning [129]. Overall, to date, their limitations include mainly the high-cost escalation to achieve the desired properties and the lack of regulatory issues.

Among the methods used for coating fruit and vegetables is one known as the dip-layer-by-layer (LbL) deposition technique. In this method, the surface of the fruit or vegetable is submerged in oppositely charged polyelectrolyte solutions with a wash step in between each solution. Another method is spray LbL deposition, in which the droplets of the polyelectrolyte solution are aerosolized in order to coat the surface instead of submerging the fruit or vegetable in a solution of the polyelectrolyte, as in the case of dip LbL. Both methods are rapid and inexpensive. The advantages of spray LbL are that irregular and large surfaces can be coated and less waste is generated due to the smaller amount of solution used. It can be used in commercial applications [130]. The methods are schematized in Figure 2a,b.

3.2. Coating Effects on Fruit and Vegetable Storage Quality and Presence of Foodborne Pathogens

As mentioned above, the most common materials used in coating formulations are waxes and, more recently, biopolymers (polysaccharides, proteins, and lipids) synthesized in microbial cellulose using a Gram-negative bacterium (Acetobacter aceti) [131]. In this study, two different composite solutions and casting-films were elaborated: microbial cellulose/starch/chitosan and microbial cellulose/starch/sodium alginate incorporating clove extract at concentrations of 1%, 2%, 3%, and 4%. The in vitro antimicrobial activity was tested against S. aureus, Shigella, Salmonella, and E. coli. The highest inhibition was observed for the microbial cellulose/starch/chitosan solution with 4% clove extract against E. coli, and films from the solutions showed inhibition against all bacteria with 3% of clove extract.

Using cellulose, Zhang et al. [132] elaborated hydroxyethyl cellulose/Polyvinyl alcohol/ε-polylysine films for the conservation of green grapes. For the in vitro assay, the inhibitory effect was demonstrated against E. coli and S. aureus with a higher effect against E. coli. For the in vivo study, weight loss, hardness, total soluble solids (TSS), and color were evaluated. The grapes packed in plastic wrap were compared with the elaborated film. The color remained green, they remained fresh and firm, and the TSS were maintained during storage. The shelf life of the green grapes was extended up to 6 days with the use of the packaging film.

Popesku et al. [133] evaluated the effect of edible films based on medium and high molecular weight chitosan and ascorbic or acetic acid, and sea buckthorn or grape seed essential oil incorporation on the shelf life of organic strawberries in cold storage (4 °C and 8 °C). The antimicrobial assay showed a reduction in the microbial load yeast and molds on strawberries. Compared with the control sample (fruit without coating), the ascorbic acid, total polyphenol content, and antioxidant activity were preserved for the high molecular weight chitosan film.

Also, Dinh et al. [134] evaluated the effect of chitosan films incorporated with guava leaf extract. For this, casting films were elaborated for 0–3% guava extract concentration. As guava extract content increased, the antioxidant properties increased, also improving the films’ biodegradability.

Using the dipping technique, tomatoes and bananas were coated. After 21-day storage, the appearance of the coated tomatoes was superior to the uncoated tomato, even better with the inclusion of the guava extract (3%) in the formulation. Also, weight loss was lower (20.42%) than for the uncoated (35.62%) tomatoes. For bananas, ripening was slower due to the presence of the extract (2%). Using 3% of the extract causes an overripening of the fruit due to the presence of phenolic in the extract and in the banana, inducing brown discoloration.

Das et al. [135] prepared a nanoemulsion edible coating solution based on carboxymethyl cellulose (CMC) and cardamom essential oil to study its effectiveness on shelf-life extension for tomatoes. They determined the minimum inhibitory concentrations of the nanoemulsion against E. coli and L. monocytogenes as being 10%. The in vivo evaluation showed a weight loss of 7.32% and firmness reduction of less than 1.3 times; the oxidative stress was reduced, and the antioxidant enzymes were increased due to the application of the coating on the fruit during 15-day storage.

On the other hand, Filgueiras et al. [136] studied the antimicrobial properties and the effect of gelatin-red propolis (5, 10, 15, 20, and 25%) coatings on green grapes preservation. The in vitro study showed that films with 25% red propolis extract showed higher antimicrobial activity against S. aureus. Grapes with gelatin and gelatin-red propolis (25%) were stored for 25 days at 25 °C and 5 °C. The gelatin-red propolis-coated fruit showed lower weight loss and the pH, total titratable acidity, TSS, and color of the grapes increased during storage. For the sensory evaluation, the acceptability index of the refrigerated coated fruit was higher (>78%) than for the control samples (38%).

For avocado, Garcia et al. [137] studied the effect of coatings based on zein nanoparticles, zein and ε-polylysine nanoparticles, zein solution, and ε-polylysine solution on the postharvest preservation of this fruit after 15-day ambient storage. A color change was observed as well as overripening and fungal decay for the control fruit with 14% (v/v) ethanol solution. The lower weight loss was observed for the zein and ε-polylysine nanoparticles solution (20.14%) compared to the control (28.05%). Also, the lowest respiration rate was obtained using this formulation with values of 107.83 mg of CO₂/kg/h, more firmness was maintained (5.01 N) compared to the control (3.67 N), and smaller color difference was observed (3.67), being 15.45 for the control. Also, for avocado, Ngubane et al. [138] evaluated the efficacy of carboxymethyl cellulose-moringa leaf extract (8–16%) to maintain the quality of “Hass” avocado. The fruit was stored at 5.5 ± 1 °C and 90 ± 5% RH for 28 days 7 additional days at 23 °C. It was observed that the phenolics, flavonoids, and antioxidant activity of “Hass” avocado were preserved. The weight loss and firmness were maintained and a delay in color change was observed, as well as a reduction in sugar concentration compared to the control (avocado washed with distilled water).

Today, the incorporation of nanomaterials and food additives like antimicrobials and antioxidants into edible coating is a new way to give additional properties to the coating to improve the safety and shelf-life of fruit and vegetables [139,140]. The incorporation of antimicrobial agents for controlled release from biodegradable edible coatings is a new alternative to extend their shelf-life. The efficiency of an antimicrobial package depends on the package–food interactions and environmental conditions present therein, as well as on the diffusion of the antimicrobial agent through the packaging material [141,142].

The antibacterial properties of essential oils on foodborne pathogens have been known for a long time [103,143,144,145]. The lime, thyme, oregano, cinnamon, ginger, and clove essential oils, and allium species, spices, and herbs, among others, have attracted greater interest as an alternative to synthetic products [146,147,148,149].

3.3. Nanotechnology-Based Coatings: Regulatory and Safety Concerns

The edible films and coatings are composed of materials that have different interactions to achieve good moisture and gas barriers. Thus, it is important to assess the safety and risk of these materials associated with human consumption at the concentrations at which they are applied.

Regulatory organizations such as the Food and Drug Administration (FDA) in the United States approve substances when they are considered as Generally Recognized as Safe (GRAS). Under this classification, there are still a huge number of factors that must be considered, including, among others, the quantity of fresh horticultural commodity consumed, whether it is with or without skin, and the coating formulation and thickness [150]. Recently, The European Food Safety Authority (EFSA) has assessed the safety of nanomaterials. Also, the Codex Alimentarius Commission and the International Organization for Standardization (ISO), have developed some guidelines for nanomaterials used in food packaging [151].

The use of nanocoatings is still limited, due to regulatory safety and toxicity. Nanoparticles (Nps) are small and have high reactivity. A major concern is that they can migrate from the packaging materials into food and penetrate the human body through ingestion causing inflammation, damage, oxidative stress, and disruption of cellular function in vitro and in vivo, with possible toxicological effects mainly targeting the liver, kidneys, and gastrointestinal tract. The life cycle of the NPs in the human body depends on the organ exposed. Also, when the packaging is disposed of, these nanomaterials can be incorporated into soil and aquatic environment [152].

Nowadays, most of the information related to nanotoxicology is related to synthetic NPs, and few studies have been conducted for natural NPs. Factors like temperature, pH, acidic environment, and mechanical damage of the packaging influence the NP’s migration towards the food with which it is in contact. To assess the toxicity of NPs, in vitro and in vivo analytical methods are used. Cytotoxicity, genotoxicity, and oxidative stress are the most common methods in which culture cells are exposed to different NPs concentrations. For in vivo, the studies are conducted in animal models with NP’s direct administration, and analytical methods including microscopy, dynamic light scattering, and omics technologies [151].

In vitro studies of the cytotoxicity of silicon dioxide NPs added as additives to edible coatings showed that depending on particle size, time, and concentration, the cell viability decreased with affectations in the integrity of cell membrane [153]. These nanoparticles are not included in the FDA list, although silicon dioxide has been used in contact with food. In another study, a daily intake between 5 mg/kg/d and 25 mg/kg/d of polystyrene nanoparticles (Nano-PS) was supplied to female mouses for 8 weeks. It resulted in an increase in oxidative stress and a decrease in the number of mouse ovarian follicles and fertility, as well as cell apoptosis [154].

For the in vivo models, it was demonstrated that different concentrations of copper oxide nanoparticles (400 mg/kg body weight/day) cause damage to the liver and kidneyd in rats over 4 weeks [155]. Another study on female rats fed with SiO₂ NPs of 20–30 nm in size for 20 days showed no pathological effect on the liver, kidneys, or lungs for a dose of 300 mg/kg bw/day. However, for higher doses, hyperemia in the kidneys and lungs, as well as necrosis, was observed [156].

The toxicity and genotoxicity of chitosan nanoparticle solution with α-pinene and a nanostructured edible coating with chitosan nanoparticles incorporated with α-pinene were evaluated in a murine model. They were supplied to mice daily for 28 days (2.5 mg/g) by an intragastric cannula (oral volume of 10 μL/bw). No toxicity or cytotoxicity was found in the studied animals based on the evaluation of liver function and erythrocyte’s structure [157].

4. Development of New Materials and Effect on Foodborne Pathogens

Gibbons et al. [158] developed ultrathin films built layer-by-layer containing a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer (Nafion), an antimicrobial enzyme (lysozyme), and chitosan. The nanocoated surface showed almost 100% inhibition against E. coli and S. aureus. The mechanism of action was based on the synergistic effect of Nafion, conventional antimicrobial agents such as lysozyme and chitosan, and, due to the chemical composition, the topography and the wetting performance of the multilayer assembly.

Recently, biodegradable coatings and films based on fruit and vegetable purees, pomace, extracts, and residues have been developed [159]. Torres-León et al. [160] elaborate and characterize biodegradable coatings and films from mango peel and antioxidant extracts of seed kernel on peaches. They found that the peaches coated with a solution of mango peel and antioxidant extract of mango seed showed less ethylene and CO₂ production (64% and 29%, respectively) than the peaches without coating, ensuring the extension of shelf life of the fruit through reduction in gas transfer.

As mentioned above, nowadays, an interdisciplinary research field such as nanotechnology has been used to benefit the agricultural field through the delivery of nutrients, natural pesticides, and herbicides [161]. Then, nanocoatings or nanofilms based on chitosan, proteins, and starch [162], among others, have been applied to preserve horticultural products. For example, Correa-Pacheco et al. [163] tested the antimicrobial activity of edible propolis–chitosan nanofilms on strawberries against E. coli, L. monocytogenes, and S. enteritidis. After 24 h, the formulations containing 10, 20, and 30% of ethanolic extract of propolis and chitosan nanoparticles showed a strong inhibitory effect on L. monocytogenes, and for the formulation containing 10% of the extract and nanoparticles, total inhibition on E. coli was observed. Moreover, the quality and antioxidant capacity of the fruit during storage were evaluated. The strawberries coated with 10% and 20% of the extract and nanoparticles showed the lowest weight loss and greatest firmness, respectively, and all propolis-containing formulations maintained the antioxidant compound and an antioxidant capacity in the fruit.

Denis-Rohr et al. [164] developed a new active agent, N-halamine, which prevents cross-contamination. The dip and spray layer-by-layer-methods were used to coat polypropylene (PP) with N-halamine containing bylayers of cross-linked polyethyleneimine (PEI) and polyacrylic acid (PAA). Antimicrobial tests show that using both methods, dip and spray layer-by-layer resulted in a 99.99% reduction against L. monocytogenes. The mechanism of action of N-halamines was the reduction of microbes by oxidizing their cellular membrane. Calvacante et al. [165] developed biodegradable coatings from fruit and vegetable residues from orange, passion fruit, watermelon, lettuce, courgette, carrot, spinach, mint, taro, cucumber, and arugula. They stated that the use of solid residue from stems, stalks, and seeds, produced on a large scale as waste, could be transformed into a value-added product. The samples, sliced or shredded, were immersed and sprayed (using a nebulizer). All samples showed a gradual weight loss. In general, the shredded samples allowed greater incorporation of the coating solution than the sliced ones. Cortez-Vega et al. [166] applied edible coatings from protein isolate of Whitemouth croaker with organo-clay montmorillonite in minimally processed papaya slices immersed in the prepared formulation. The coating was effective for 12 days in storage. Lower mass loss, lower microbial growth, and a smaller decrease in firmness, lightness, and pH were observed.

Pullulan is a biodegradable and biocompatible polysaccharide with antimicrobial properties, mainly composed of glycosidic bonds [167]. However, pullulan alone as a film does not have good mechanical properties, is highly sensitive to water, and is expensive [168]. Therefore, it has been mixed with other polymers to improve its properties. For example, Kang et al. [169] studied the effect of oat protein/pullulan and nisin-loaded oat protein/pullulan films on the shelf-life extension of strawberries. They found that bacterial growth was lower for the coated strawberries compared to the uncoated ones. After 14 storage days at 25 °C, the decay rate for the coated fruit was 20% and 30%, respectively. Priyadarshi et al. [170] developed pectin/pullulan (50/50) films loaded with grape seed extract (5%). The film containing the extract effectively delayed the bacterial growth against E. coli and L. monocytogenes and the lipid oxidation in raw and roasted peanuts.

In

Table 4. Effect of different compounds/antimicrobials polymer-based for controlling different foodborne pathogens.

Antimicrobials	Polymer/Carrier	Target Microorganisms	Effect	Refs.
Enzymes
Lactoperoxidase system (0.1, 0.5, 1%), H2O2 (0.2, 0.4, 0.8 mM), KSCN (1, 2, 4 mM).	Alginate	E. coli, L. innocua, and P. fluorescens	Growth of all tested bacteria prevented for a 6 h period.	[171]
Enterocin 416K1 (1280 IU/mL).	Chitosan	L. monocytogenes	Anti-listerial activity for most combinations.	[172]
Nisin or pediocin	Corn starch	L. monocytogenes and Clostridium perfringens	Active films against these two bacteria. The halloysite retained antimicrobial activity when comparing to films without nanofiller addition.	[173]
Bacteriophages
vB_EcoMH2W	Chitosan	E. coli O157:H7	Chitosan-based edible coating can stabilize phage vB_EcoMH2W without significant loss in lytic activity of phage over a period of one week.	[174]
Listeria bacteriophage P100 and silver nanoparticles	Alginate	L. monocytogenes	Antimicrobial activity of the alginate–silver coating was achieved with an alginate concentration of 1%. Adding phage P100 (109 PFU mL−1) into the alginate–silver coating led to a synergic effect that resulted in a 5-log reduction in L. monocytogenes.	[175]
Bacteriophages (EC4 and φ135) and cinnamaldehyde (CNMA)	Sodium alginate	S. enteritidis and E. coli	A combination of both phages with the higher concentration of CNMA resulted in a synergic antimicrobial effect against E. coli and a facilitative effect against Salmonella.	[176]
Myoviridae bacteriophages (T-even type), DT1 to DT6	Whey protein concentrate (WPC) matrix	E. coli O157:H7 and STEC strains	The six-phage cocktail added into WPC films was highly stable, effectively released from films, and proved highly effective as a biocontrol.	[177]
Nisin and organic acids
Citric, lactic, malic, and tartaric acids (0.9, 1.8, 2.6) in combination with nisin (205 IU g −1of protein).	Soy protein	L. monocytogenes, E. coli O157:H7, and S. Gaminara	Malic acid (2.6%) was the most effective acid into soy protein films for controlling these bacteria.	[178]
Nisin-EDTA	Gelatin	E. coli	1 and 3 logarithmic cycles of the films with 5%, 10%, and 20% of the compound (nisin/Na-EDTA) distributed in the polymer matrix, respectively.	[179]
Malic, citric, lactic, formic, ascorbic, fumaric, acetic acids (1.5–3%), and Nisin 50 IU/mL, pH 6.2.	Whey protein	L. monocytogenes	Nisin (50 IUmL−1) improved the antilisterial effects of lactic, citric, and malic acids.	[180]
Acetic acid (2%), lactic acid (2%), levulinic acid (2%), and 10 ppm of allyl isothiocyanate.	Chitosan	Cocktail of four Salmonella strains	The three-acid solution without chitosan reduced the populations of Salmonella by 6.0, 3.6, and 5.3 log CFU mL−1.	[107]
Essential oils
Carvacrol (10 g L−1) and pomegranate peel extract (PPE, 10 g L−1).	Chitosan	E. coli and S. aureus	Except for PPE-incorporated film, all exhibited antibacterial activity	[181]
Rosemary essential oil (REO, 0.5, 1.0, and 1.5%).	Chitosan	L. monocytogenes, P. putida, S. agalactiae, L. lactis, and E. coli	Higher antibacterial activity	[182]
Clove oil (CO, 0.05% v/v) and/or ethylenediaminetetraacetate (E, 10 mM).	Chitosan	E. coli and S. aureus	All coating solutions exhibited moderate to strong antimicrobial activity	[183]
Essential oils and functional extracts (FE) (50, 100, 250, 500, 750, and 1000 mg L−1).	Chitosan	S. Typhimurium, E. coli O157:H7, S. aureus, B. cereus, and L. monocytogenes	Antimicrobial activity against most strains tested	[184]
Lime and thyme essential oil	Chitosan—beeswax	Escherichia coli DH5α	In vitro experiments showed the best coatings were those of chitosan (1%), beeswax (0.1%), and lime essential oil (0.1%), since no growth of E. coli DH5α took place.	[185]
Oregano oil (0, 15.7, 25.9, 36.1 mg mL−1)	Pectin	E. coli O157:H7, S. choleraesuis, S. aureus, and L. monocytogenes.	Pectin-OEO film was effective against E. coli O157:H7, S. aureus, and L. monocytogenes. All concentrations with pectin showed inhibition of violacein production and total coliforms, yeast, and molds.	[186]
Geraniol (Ger) and α-terpilenol (Ter)	Ethylene–vinyl alcohol copolymer (EVOH)	E. coli, S. enterica, and L. monocytogenes	The incorporation of Ger and Ter inhibited the growth of the three bacteria. (EVOH/Ter).	[187]
Thyme extract-loaded nanoliposomes	Whey protein isolate	S. aureus and E. coli	The possible antimicrobial activity of the films containing TE-loaded nanoliposomes against S. aureus and E. coli decreased in comparison to the free TE-incorporated films.	[188]
ZnONPs and rosemary essential oil	Zein nanofibers with κ-carrageenan (Z/KC/ZnONPs/RE)	S. aureus and E. coli	The Z/KC/ZnONPs/RE sample showed inhibition activity against S. aureus (18.5 mm) and E. coli (14.7 mm).	[189]
Rosemary and Aloe vera oil	Cellulose acetate	E. coli and B. subtilis	The antimicrobial activity against E. coli and B. subtilis increased as rosemary and A. vera oil percentage increased in cellulose acetate membranes.	[190]
Plant extracts
Grape seed extract (1%), nisin (10,000 IU/g), and EDTA (0.16%).	Soy protein	L. monocytogenes, E. coli O157:H7, and S. Typhimurium	Film incorporated with the combined GSE, nisin, and EDTA demonstrated the greatest inhibitory activity against L. monocytogenes, E. coli O157:H7, and S. Typhimurium.	[191]
Honeysuckle flower extract (5, 10, 20, and 30%	Chitosan	E. coli	The film-forming solution of chitosan with 30% HFE exhibited the best antimicrobial effect.	[192]
Grapefruit seed extract	Poly(lactide) (PLA)/poly(butylene adipate-co-terephthalate)	L. monocytogenes and E. coli	Antibacterial activity against L. monocytogenes, but only bacteriostatic activity against E. coli.	[193]
Allyl isothiocyanate	Halloysite nanotubes (HNTs) coated with sodium polyacrylate (PA)	S. aureus and E. coli	The activity was pronounced against E. coli at 100 μg mL−1 with concentrations of 25 μg mL−1 and 200 μg mL−1, reducing the viable cell population by 41% and 96%, respectively.	[194]
Allyl isothiocyanate (AIT) and nisin	Chitosan	Salmonella	The chitosan + 60 AIT coating reduced populations of native bacteria on cantaloupes to ca. 2 log10 CFU cm−2 during the first 6 days, and populations remained unchanged through day 14 at 10 °C.	[195]
Allyl isothiocyanate	Polylactic acid and sugar beet pulp	Salmonella Stanley	The films (8.16 μL of AIT per cm2 of surface area) inhibited the growth of Salmonella during 24 h of incubation at 22 °C, while the populations of Salmonella in controls increased from ca. 4 to over 8 log CFU mL−1, indicating a minimum inactivation of 4 log CFU mL−1 on films in comparison to the growth on controls.	[196]
Allyl isothiocyanate (AIT), nisin, 2%, acetic acid, 2% lactic acid, and 2% levulinic acid	Chitosan	Cocktail of three Salmonella strains	The addition of nisin to the chitosan-AIT coating synergistically increased the antibacterial effect.	[197]
Chitosan
Chitosan (1, 3, and 5%).	Yam starch 4% and chitosan	S. enteritidis	The chitosan-treated film caused a reduction of 1–2 log cycles, the pure chitosan presented a reduction of 4–6 log cycles.	[198]
Polyamide 6/66 chitosan (1, 2, 2.5, and 3% w/v).	Plastic films chitosan films chitosan solution	S. typhimurium and S. aureus	Antimicrobial activity was lessened when chitosan was combined with the plastic matrix.	[199]
Chitosan (1%)/poly(vinyl alcohol)/pectin (1, 1.5, and 2 g) ternary film.	-	E. coli, S. aureus, B. subtilis, Pseudomonas, and C. albicans	Antimicrobial activity of the film against pathogenic bacteria.	[200]
Chitosan nanoparticles (0.1, 0.5, 1, 5, 10, and 30% (v/v)).	Cellulose films	E. coli	A maximum E. coli inhibition of 85% was achieved at 5% (v/v) by doping chitosan nanoparticles into the cellulose films.	[201]
Nanoemulsions
Cinnamaldehyde 1.5%.	Pectin/papaya puree films	E. coli, S. enterica, L. monocytogenes, and S. aureus	Cinnamaldehyde provided antimicrobial properties against all bacteria tested. L. monocytogenes and S. aureus were more susceptible.	[202]
Gold nanoparticles (2.5 and 5% v/v).	Quinoa starch (4%)	E. coli and S. aureus	The active biofilms (2.5% gold nanoparticles) exhibited strong antibacterial activity against foodborne pathogens with inhibition percentages of 99% against E. coli and 98% against S. aureus.	[203]
Ag@AgCl/ZnO nanocomposites	Pectin	S. aureus	Nanocomposites with excellent photocatalytic antibacterial activity.	[204]
Silver nanoparticles (AgNPs)	Biopolymer pullulan	E. coli O157:H7, L. monocytogenes, S. Typhimurium, S. aureus, and B. cereus	Nanocomposite films, especially pullulan/AgNPs and pullulan/pectin/AgNPs films exhibited good antimicrobial activity against them.	[205]
Copper montmorillonite modified (MtCu2+) antimicrobial nanocomposites	Cellulose acetate (CA)	E. coli	Antimicrobial effect was observed for nanocomposites films, obtaining a 98% reduction against E. coli.	[206]
Montmorillonite −copper oxide (MMT-CuO) nanocomposites	Chitosan	E. coli, P. aeruginosa, B. aureus, and B. cereus	CSG3MMT-CuO90 films showed more intense antibacterial activity against S. aureus and B. cereus than E. coli and P. aeruginosa.	[207]
Silver nanoparticles	Pectin–laponite	E. coli and S. aureus	Coated bionanocomposite exhibited a strong antimicrobial activity against the E. coli and S. aureus.	[208]
Silver nanoparticles (AgNps)	Polymer matrix (thiol-acrylato)	E. coli, P. aeruginosa, S. aureus, and B. cereus	Antimicrobial results show that photochemically prepared nanocomposites considerably increase the antimicrobial activity on Gram-negative bacteria compared to Gram-positive bacteria.	[209]
Zinc oxide nanoparticles (ZnO-N; 0%, 1.5%, 3%, and 4.5%)	Buckwheat starch (BS)	L. monocytogenes	The BS/ZnO-N films reduced this bacterium in a range of 2.96–3.74 log CFU mL−1.	[210]
Others
Ag+, Cu2+, Zn2+, Mn2+, or Fe2+ (120 µg mL−1).	Chitosan	E. coli, S. Sholeraesuis, and S. aureus	Antibacterial activity was enhanced by the metal ions loaded, except for Fe2+. Especially for chitosan nanoparticles loaded Cu2+, the MIC and MBC against E. coli, S. Sholeraesuis, and S. aureus were 21–42 times lower than that of Cu2+, respectively.	[211]
Chlorine dioxide (ClO2) microcapsule	Polylactic acid (PLA)	E. coli and S. aureus	Addition of ClO2 microcapsules at a concentration of 20% imparted PLA films with excellent antimicrobial properties, with a growth inhibition of E. coli and S. aureus by 4.95 log CFU mL−1, and the antibacterial rate was 99%.	[212]
Chlorine dioxide microcapsule	Polylactic acid film	Foodborne pathogens	Cross-sections of the antimicrobial film showed that the film was covered with voids due to deliberate release of chlorine dioxide gas during the packaging process.	[213]

, some examples of coating formulations and films amended with various antimicrobials for controlling foodborne are given.

5. Overall Mechanisms of Action of the Postharvest Technologies on Foodborne Pathogens

A great diversity of mechanisms of action have been reported on foodborne bacteria development as a result of the application of chemical, physical, and natural products treatments.

For example, the mechanisms of action of the electrolyzed water affects the permeability of their cell walls, allowing a disarrangement and leakage of their intracellular components [56].

For organic acids, they can include direct pH reduction in the substrate or growth medium due to an increase in proton concentration, depression of the internal cellular pH by ionization of the undissociated acid molecule, and disruption of substrate transport by alteration of cell membrane permeability [214].

As for plant-derived compounds, the main mechanisms can include changes in cell morphology, disruption of cytoplasmic membranes, disruption of outer membranes in Gram-negative bacteria, changes in membrane properties, disruption of membrane potential, disruption of intracellular pH homeostasis, disruption of intracellular Ca²⁺ homeostasis, disruption of cellular respiration, complex reaction mechanism, inhibition of particular enzymes, inhibition of cell division, changes in transcriptome, changes in proteome, and changes in toxin production [144,215,216,217,218,219].

To date, information about the mechanisms of action of coatings is limited to the study of each particular component of the formulation.

For example, an area of active research to control food spoilage and pathogenic organisms has been the incorporation of enzymes into packaging films. The main enzymes used for preparing edible films and coatings are lysozyme and nisin; however, lactoperoxidase and enterocin 416K1 have been used, too [220,221]. Lysozyme is an enzyme that is naturally present in avian eggs and mammalian milk and is GRAS for direct addition to foods. It is reported that it hydrolyzes the β-1, 4-glycosidic bond between the N-acetylmuranimic acid and the N-acetyl-d glucosamine of peptidoglycan, which is the major component of Gram-positive bacteria cell walls [221,222,223,224,225,226]. The nisin is a small, heat-stable antimicrobial peptide produced by Lactococcus lactis subsp. lactis and has shown antimicrobial activity mainly against Gram-positive bacteria, but it has also been tested against Gram-negative bacteria using Ethylenediaminetetraacetic acid (EDTA). This is a membrane-active peptide that destroys the integrity of the cytoplasmic membrane via the formation of membrane channels. In doing so, these peptides alter membrane permeability and, therefore, cause leakage of low-molecular-mass metabolites or dissipate the proton motive force, thereby inhibiting energy production and biosynthesis of proteins or nucleic acids [227].

As for chitosan compound, its antimicrobial activity will depend on several factors, such as the kind of chitosan (deacetylation degree, molecular weight) used, the pH of the medium, the temperature, the presence of several food components, etc. [228,229]. Its mode of action includes several responses from the affected microorganisms. Among them, the morphology and ultrastructure of the chitosan-treated microorganism showed that the electrostatic interaction between chitosan and the microorganism resulted in dramatic alterations in the structure of the plasma membrane, which, according to Bautista-Baños et al. [230], became locally detached from the cell wall, giving rise to vacuole-like structures underneath the wall and hence generating ions and water efflux that provoked decreases in the internal bacteria pressure; therefore, the integrity of organelles can be seriously disrupted leading in many cases to lysis of the cell. Other mechanisms mentioned in the literature are the interaction of diffused hydrolysis products with microbial DNA, which leads to the inhibition of the mRNA and protein synthesis and the chelation of metals, spore elements, and essential nutrients [231,232].

6. Conclusions and Outlook

The horticultural industry needs to satisfy the strong demands of a growing and increasingly health-conscious population for fresh fruit and vegetables; however, the presence of foodborne pathogens is still a serious concern.

Currently, the application of chemical methods has been significantly limited in many countries due to the possible formation of carcinogenic byproducts such as trihalomethanes during the disinfection process. As for others, such as the ozone, although it is considered to be an environmentally friendly disinfectant with superior effectiveness as an oxidant and biocide, its application in air is not as common as water due to the concern surrounding its toxicity. In addition, compared to other treatments, it requires higher capital investment and operating costs.

Thus, to date, new approaches have been proposed, such as edible active coating formulations enhanced with antimicrobials. Today, these coatings represent a novel technology that provides the protective function enhanced with new ingredients integrated into the formulations that render this antimicrobial function.

The incorporation of these antimicrobial compounds into edible active coatings should extend the shelf-life of fruit and vegetables. On this line, some plant extracts and essential oils are GRAS substances, so their application as components of coating formulations would not represent a regulatory problem; however, their practical application in the food industry is still a challenge, because they are expensive compared to synthetic fungicides. In addition, the most important factor is to control the release of the active substance, as it is desirable for the antimicrobial coating to have a long effectiveness against a broad spectrum of bacteria.

Recent studies have shown that the use of nanotechnology with micro and nanocapsules holds great promise in this area. Nevertheless, developing these new technologies will require a multidisciplinary team composed, among others, of material engineers, microbiologists, toxicologists, and food scientists. The analysis of their effects on the environment and consumers are certainly subjects to be studied in the future. In addition, the new materials to be considered in the coating formulations must meet the requirements necessary to satisfy consumer and industry demands in order to preserve and extend the quality and shelf-life of fruit and vegetables, reducing the risk of foodborne illnesses.

Additional limitations of most technological applications in the industry are the scale-up costs, investment in equipment installation, and processing.