Effects of Microwave Electromagnetic Radiation on Milk Microbiology and Physicochemical Properties

Conventional thermal treatments for milk processing in small and medium-sized enterprises (SMEs) often fail to fully meet Colombian food quality and safety regulations, particularly in microbial inactivation and nutrient preservation. In response, non-conventional thermal treatments, such as microwave heating, offer a promising alternative due to their ability to generate efficient volumetric heating and reduce processing times compared to traditional methods. This study evaluated the effects of microwave electromagnetic radiation on the microbiology and physicochemical properties of milk under different exposure times and power levels. In phase 1, a randomized experimental design was applied using a 1500 W microwave at 2450 MHz to treat 100 ml milk aliquots for different exposure times (0 to 50 seconds). In phase 2, a pilot-scale continuous flow system with an 18-liter capacity was developed, operating at 700 W and 1000 W with exposure times of 10, 15, and 20 seconds. Microbiological and physicochemical analyses demonstrated that treatment at 1000 W for 20 seconds met the standards of Decree 616 of 2006 and the Pasteurized Milk Ordinance (PMO), achieving significant microbial reduction without altering physicochemical properties such as fat, protein, and total solids content. In contrast, treatments at 700 W were ineffective for microbial inactivation, indicating the importance of using higher power levels. Additionally, the continuous flow system improved heat distribution, making the process more homogeneous and efficient. These findings suggest that the use of microwaves in continuous flow systems is a viable alternative for improving the microbiological quality of milk, optimizing its processing in SMEs through an efficient method with minimal impact on the final product composition while maintaining regulatory compliance.