Desenvolvimento de aparato experimental para redução da carga microbiana do leite por meio da radiação UV-C

Abstract

The dairy industry uses pasteurization to reduce microorganisms in milk, but the high temperature can alter its sensory and technological characteristics. Therefore, research is being conducted to replace heat treatment with other technologies, such as ultraviolet (UV) irradiation. The main challenge of this non-thermal treatment is the low light penetration in foods with an optical density higher than that of water, such as milk. This work aimed to design an experimental apparatus that uses UV-C light to reduce the microbial load of milk. The experimental apparatus was designed inspired by equipment observed in the literature, simulating its conditions of use. The consolidated experimental apparatus presented two main regions: the UV-C application region, composed of a lamp surrounded by a helical duct, and the process control and milk recirculation region. To define the treatments to be applied, tests were carried out using sterile milk inoculated with Escherichia coli (ATCC 25922, 10⁶ CFU/mL) and subjected to UV-C doses of 13.45 (T1), 29.02 (T2) and 66.53 kJ/m² (T3). Based on the tests, raw milk from a dairy industry in Ceará (Brazil) was treated under the most effective conditions for microbial reduction (T1 and T2). The samples were evaluated for physicochemical parameters (pH, acidity, color, viscosity, density, and cryoscopy), microbial counts (mesophilic bacteria, Staphylococcus spp., Enterobacteria, E. coli), and structural changes using FTIR. Both UV-C treatments reduced the microbial groups: taphylococcus spp. (~4 log), mesophilic bacteria, enterobacteria (~2 log) and E. coli (~3 log), with T2 achieving greater reductions in mesophilic and enterobacteria. T1 provided a balance between efficiency in microbial reduction and shorter exposure time. Overall, the physicochemical changes were minimal, remaining within regulatory standards. The experimental apparatus demonstrated potential for large-scale expansion in dairy processing.