Millions of people worldwide are undernourished and affected by “hidden hunger”, which is caused by a lack of essential minerals and micronutrients. Food items need to contain enough nutrients, whether processed or unprocessed, so that these nutrients can be significant contributors to food and nutrition security [1,2]. The majority of consumers view food safety as being of the utmost importance [3]. On the other hand, they are increasingly aware of nutrient uptake and seek to consume more foods that will benefit their health, well-being, and nutritional status. The increased consumption of fruit- and vegetable-based products has been motivated by the potential health benefits based on the significant amounts of vitamins, nutrients, and bioactive compounds contained in these products [4]. Several fruit- and vegetable-based products are preferred in their fresh state. However, they have a high perishability and a short shelf life. This limits the amount of time for which they are available and safe for consumption. Processing techniques can increase food choices while increasing the length of time before a food product becomes unfit for consumption. In the manufacture of processed foods, the use of preservation strategies is unavoidable in suppressing microbial or enzymatic and nonenzymatic spoilage, and therefore achieve an extended shelf life [5].

Thermal processing has historically been one of the most extensively used and approved methods to prevent foodborne illnesses and ensure food safety through the inactivation of spoilage enzymes and the destruction of microbial contaminants (pathogenic and spoilage) in foods and beverages [6]. The intensity of the heat treatment is dependent on the combination of temperature and treatment duration. From a microbiological perspective, intense heat treatment is preferable, but the employment of excessively high temperatures during prolonged times (severe heat treatments) can have deleterious consequences on the flavor, taste, and nutritive quality. Hence, a food product may be free of contaminants, comply with food safety standards, and still be nutritionally poor [7]. For instance, severe heat treatments degrade several heat-labile vitamins (e.g., vitamins A and C, and thiamin) and decrease the biological value (BV) of proteins by denaturing them and reducing their digestibility and bioavailability. The significance of nutrient degradation on nutrition security is determined by the eating habits and consumption frequency of a certain kind of food in the diet. Loss of nutritional value is thus more significant when there is a decrease in nutrients in nutritionally-rich and highly consumed food items that are sources of nutrients for a large share of the population than in foods that are either consumed in low quantities or have low nutritional contents [8,9].

Novel food processing methods are under investigation to address the loss of nutritional value due to thermal preservation [10]. Food processors and scientists have been exploring more effective low-temperature technologies that enable high-quality retention to deliver safe food products with acceptable organoleptic and rich nutritional profiles [7]. Nonthermal processing methods have been employed and among these, ultraviolet irradiation holds great promise as a food preservation technique for pathogen reduction and to minimize nutritional losses observed in heat-processed foods [11,12]. Ultraviolet radiation is divided into four categories in terms of wavelength range: UV-A (315–400 nm), UV-B (280–315 nm), UV-C (200–280 nm), and vacuum-UV (100–200 nm) [13]. The UV-C range possesses great antimicrobial effectiveness, which makes it useful for ensuring the microbial safety of foods. The genetic material (DNA or RNA) of microbes strongly absorbs UV photons within the UV-C range, with a wavelength around 260–265 nm corresponding to maximal UV absorption [14]. The preferred alternative pasteurization and shelf life extension method for beverages for the past two decades has been UV-C radiation at 253.7 nm [15]. UV-C irradiation causes damage to the nucleic acids of microorganisms, mainly due to the formation of dimers of pyrimidine bases between adjacent pyrimidines in a DNA strand, which prevents microbial replication and ultimately leads to cell death [16,17].

UV-C is a nontoxic and noninvasive method with numerous advantages that include the absence of chemical residues, it produces no waste, is cost-effective (low installation and maintenance cost), simple to implement, eco-friendly, has low energy consumption, minimal impact on nutritional quality and organoleptic parameters, and good consumer perception [11,15,18,19]. The primary drawback of this technology is the poor penetration depth of UV-C, which limits its antibacterial efficacy [20]. The microbial inactivation efficiency of UV-C is dependent on several factors like the UV-C dose (UV-C fluence), uniformity of UV-C dose distribution, UV-C sensitivity of the target microbial cells, the ability of the microorganisms to repair UV-induced damage, the physicochemical properties of the treated product (e.g., viscosity, density, soluble and suspended solids), and the optical properties of foods (e.g., transparency, absorption coefficient, scattering) [16,21,22,23]. This poses difficulties in the design of UV-C food treatment devices and for laboratory tests (experiments) that must guarantee a defined and consistent UV-C delivery while ensuring that all of the food surfaces are exposed to the UV-C illumination [22]. 

The principle behind UV-C light’s germicidal action is based on its ability to damage the DNA or RNA of microorganisms such as bacteria, viruses, and fungi through interaction between the UV photons and the genetic material of these microorganisms [21]. When UV-C light penetrates the cell wall of a microorganism, it is absorbed by the DNA or RNA inside the cell. This disrupts the genetic material, which can lead to the formation of new bonds or the breakage of existing ones. This alteration results in photodimerization, where two adjacent bases in the DNA/RNA sequence bind together. This genetic damage disrupts the affected cells’ ability to replicate, rendering them unable to cause infection or pose a threat [24].

The mechanism of UV-C germicidal action involves several factors including the light intensity, exposure time, and the type of microorganism being targeted, which can vary depending on the specific application [21,25]. Furthermore, the germicidal effectiveness of UV-C light as a disinfectant is based on the dose–response relationship, microbial susceptibility, and the optical properties of the food matrices or treated surfaces [26,27]. In Figure 1, the main factors that affect the success of UV-C processing are presented as well as a general representation of the reactor chamber.

It is important to note that these factors are interconnected and should be considered collectively during the design and implementation of UV-C treatment processes for developing shelf-stable food. Higher intensity levels of UV-C radiation generally lead to better microbial inactivation [28]. However, the duration of UV-C exposure should be carefully selected to achieve microbial reduction without compromising food composition and quality [29,30]. Furthermore, the choice of the UV-C wavelength should be based on the target microorganisms and the food product [24]. The material of the product’s container can affect UV-C treatment, with transparent materials allowing for better penetration; the depth of the liquid and flow rate through the UV-C system should be considered for uniform exposure [31,32]. At the same time, suspended solids can reduce the effectiveness of UV-C treatment [25,33]. The pH and turbidity of the liquid also impact treatment efficiency, and maintaining optimal ranges enhances the effectiveness of UV-C treatment [25]. From the understanding of these principles, UV-C light technology has been used effectively not only for disinfection and sterilization in various applications such as healthcare settings and water treatment, but also in the food industry and more recently as a neutralizing agent of the infectivity of SARS-CoV-2 [22,34,35,36,37,38]. Some factors that influence UV-C efficacy are described below.

The dose-response relationship of UV-C light germicidal action follows a pattern where the effectiveness of killing microorganisms increases with higher doses or intensities of UV-C light [39,40]. At lower doses, the light exposure may not be sufficient to cause significant damage to the microorganisms, allowing some of them to survive or repair the damage [12,40,41]. As the dose of UV-C light increases, the likelihood of DNA and RNA damage also increases, leading to a higher rate of microorganism inactivation [42].

It is important to note that there is an optimal range of UV-C light intensity for germicidal action. The sensitivity of microbes to UV light varies depending on the wavelength [21]. However, the strong absorption of ultraviolet light by water at wavelengths below 230 nm is a limiting factor for the germicidal effect. Beyond this wavelength, increasing the dose may not significantly enhance the killing efficacy and may even result in diminishing returns. Additionally, excessively high doses of UV-C light can harm human health and damage materials or surfaces [37,43]. In this sense, it is crucial to use UV-C light within safe and recommended exposure limits to balance its germicidal efficacy with potential risks.

The susceptibility of microorganisms to UV-C light varies depending on their structure and genetic makeup [33]. UV susceptibility of microorganisms can differ considerably due to differences in cellular elements like cell wall thickness, composition, nucleic acid structure, type of proteins within the cell, photoproducts, the physiological condition of the microbe, and the cell’s capacity for repairing damage caused by ultraviolet radiation [19]. However, it is worth mentioning that the effectiveness of UV-C light as a microbial inactivation method depends on other factors including the food matrix [44], exposure time, distance from the UV-C source, and the presence of any physical barriers or shadows that may shield microorganisms from direct UV-C exposure [42]. Different microorganisms have varying levels of sensitivity to UV-C-induced DNA/RNA damage. In this sense, viruses with RNA genomes are more susceptible to UV-C light than viruses with DNA genomes [45]. Another important factor is the cell wall structure. Microorganisms with more robust and resistant cell walls may be more resistant to germicidal UV-C light. Viruses and fungi, on the other hand, may be more susceptible to UV-C light due to their fragile cell walls. Gram-negative bacteria, in general, are more sensitive to UV-C light than Gram-positive bacteria due to their thinner cell walls [46]. The efficacy of UV-C microbial inactivation greatly depends on the treated food. Opaque and turbid nonsolid food matrices are more challenging to treat compared to transparent food substrates. This is because the turbidity and presence of suspended solids in nontransparent liquids confer protection to microorganisms by scattering or absorbing the radiation before it reaches them [44].

The optical properties of surfaces refer to how they interact with light. These properties can include the reflection, absorption, transmission, and scattering of light [21,32]. When it comes to UV-C light, the optical properties of surfaces that host microorganisms can affect the effectiveness of UV-C light. For example, surfaces that are rough or uneven may scatter UV-C light, potentially reducing the intensity of UV-C radiation in a particular direction [32], and if they are porous, UV-C light can be absorbed. Reflective surfaces can also scatter and absorb UV-C light [22,37]. When compared to smooth surfaces, some of these surfaces require roughly two orders of magnitude greater UV-C doses to adequately inactivate microorganisms [37,47]. Normally, light transmission refers to the passage of UV-C light through materials. Materials like certain types of glass can allow UV-C light to pass through with minimal attenuation, while others may block or attenuate UV-C light, reducing its transmission [31,32].

The recent consumer demands for safe food with high-quality nutritional (e.g., vitamins, protein) and sensory (mainly color, flavor, and texture) attributes have challenged the scientific community and the food industry to develop and implement nonthermal technologies to process/manufacture foods while minimizing the changes to these attributes [48,49,50]. In this sense, UV-C light has been a promising technology for improving food safety and reducing the risk of foodborne illnesses in the food industry [21,33]. In the last decades, the food industry has used this versatile tool for surface decontamination, air and water treatment, to prevent the spread of microorganisms, and ensure food safety and preservation.

UV-C light is used to purify air in food processing facilities. UV-C lamps can be installed in air handling units to sterilize the air as it circulates through the facility, reducing the risk of airborne contamination [35]. Air disinfection can be accomplished by irradiating only the upper parts of the room or by irradiating the entire air, either in an empty room or using an air conditioner [51]. UV-C light is also used to disinfect surfaces following routine cleaning procedures in food processing facilities including food preparation areas, packaging areas, and equipment. UV-C light can effectively kill bacteria, viruses, and other microorganisms that may contaminate surfaces and cause foodborne illness [35,52,53]. Low-pressure mercury lamps are ideal for controlling surface microorganisms in the food industry, since 90% of the emitted light is at a 253.7 nm wavelength [54].

UV-C light can be used to sanitize water used in food processing and production as well as help prevent the growth of harmful bacteria and other microorganisms in municipal water supply systems [53,55]. Additionally, UV-C light has been used to extend the shelf life of fresh, minimally processed, and liquid foods by reducing the microbial load and helping to prevent spoilage [12,56,57,58,59,60].

While UV-C light technology is commonly used for its antimicrobial properties in the food industry, there is also research indicating that it can be used to improve and/or preserve the nutritional properties of fruit and vegetables [33,60,61,62,63]. When exposed to UV-C light, certain compounds in foods can be activated or transformed, resulting in the production of bioactive compounds that may have health benefits [64,65,66]. Bhat and Stamminger (2014) reported that exposure to UV-C light has been shown to increase the levels of phenolic compounds and antioxidant activity in strawberry juice [48]. In the same way, UV-C light exposure has been shown to increase the levels of certain phytochemicals in plant produce [67].

Győrfi et al. (2011) identified the capacity of UV-C light to increase the production of vitamin D in mushrooms. When exposed to UV-C light, the ergosterol in mushrooms is converted to vitamin D2, increasing the vitamin D content [68]. Overall, UV-C light can be a useful tool for producing bioactive compounds in foods, which can enhance their nutritional value and potential health benefits. However, it is important to carefully evaluate the safety and efficacy of these compounds before incorporating them into food products.