Dairy products create good growth conditions for a variety of microorganisms because they are rich in many kinds of nutrients including carbohydrates (especially lactose), lipids, proteins, essential amino acids, enzymes, vitamins and minerals. Therefore, producing safe dairy products are more challenging compared to producing many other foods.
Thermal processing is the most common decontamination method to ensure food safety and to prolong shelf life by eliminating the spoilage and pathogenic microorganisms and enzymes. In recent years, use of non-thermal technologies is increasing as an alternative to the thermal processing in food industry. Ultraviolet (UV) light, which is a non-thermal technology, has recently attracted a lot attention to improvement of food safety. Compared to thermal processing, this promising technology can provide consumers with minimally processed, microbiologically safe and fresh-like products with minor effects on the nutritional and sensory properties of the product. On the other hand, this technology must not replace hygiene, good manufacturing or agricultural practice.
UV light application can also be introduced as an alternative to the use of chemicals in food industry. Besides, the use of UV light does not generate chemical residues. Additionally, it offers some technological advantages especially in developing countries in a small-scale production due to its low maintenance cost, low installation cost and low operational cost with minimal energy use. The operation and cleaning of the treatment is quite easy. In spite of its many advantages, its low penetration power restricts the area of use in food industry. Furthermore, its inactivation efficiency may be reduced or prevented because of physical features of food. At high doses, it can create negative effects on quality and some vitamins. In order to obtain effective results, applications should be made considering these situations.
UV irradiation of milk was first used in the mid-1900s for the purpose of vitamin D enrichment. Efficacy of UV light treatment has been studied in recent years and more and more research has also been carried out to evaluate the potential applications of UV light as a non-thermal alternative to thermal processing of milk. On the other hand, due to the confirmed success and convenience of thermal processing, potential processing alternatives for milk are still limited. The use of UV light must not only be considered for microbial inactivation but also for the development of novel dairy products. The UV-treated pasteurized cow’s milk was authorized as a novel food in market by European Commission. It is reported that the treatment of the pasteurized milk with UV radiation results in an increase in the vitamin D3 (cholecalciferol) concentrations by conversion of 7-dehydrocholesterol to vitamin D3.
Contamination of dairy products with microorganisms may occur at several stages of production, originating from a variety of sources during production. Although heat treatment is applied for inactivation of foodborne pathogens, dairy products especially cheese can be contaminated with undesirable microorganisms. After pasteurization process, handling of the curd, equipment, processing lines, packaging or storage rooms can result in cross-contamination with a variety of microorganisms. Even if good manufacturing practices are applied, surface applications of antimicrobial agents before packaging are commonly used to prevent spoilage and extend storage life for some dairy products. Instead of chemical preservatives, additional solution is needed to control the growth of microorganisms just before or after packaging of dairy products. Surface application of UV light after production can offer an attractive alternative method to eliminate or control the growth of post-processing contamination. Other promising uses of UV light are the disinfection of air and water used in dairy plant, and surface decontamination of food contact surfaces and packaging materials.
A lot of research is mainly focused on the application of UV light to reduce microorganisms in milk, and relatively little research focuses on the decontamination of the surfaces of solid dairy products. There is lack of information about the relation of quality and safety of dairy products. Thus, the application of UV light for various dairy products needs to be investigated in terms of both quality and safety in order to increase the use and reliability of UV light in industry. There is also need for research on various applications of UV light on dairy plant.
In this chapter, UV technology is explained in terms of its principles, inactivation mechanisms, and available UV light sources and reactors are reviewed. Then, the effects of UV light on the inactivation of microorganisms and changes in the chemical and nutritional aspects of various dairy products are discussed.
