Temperature profiles within milk after heating in a continuous-flow tubular microwave system operating at 915 MHz

Milk with different fat contents (0, 1, 2, 4%, and chocolate milk) were heated in a specially designed continuous-flow microwave applicator operating at 915 MHz. The nominal power was 5 kW and the flow rates were 2.0 and 3.0 L/min to attain laminar flow. Temperature profiles at the exit of the applicator were measured. The results showed that the average increases in temperature were similar to one another, being 42 degreesC at 2.0 L/ min and 29 degreesC at 3.0 L/min. Differences between the lowest and highest temperatures were 3.7 and 3.0 degreesC, respectively. The temperature profiles illustrated that slightly higher temperatures were achieved within segments flowing close to the center of the tube.