Microwave and microwave-vacuum drying as alternatives to convective drying in barley malt processing

Barley malt is widely used in food and beverage industries. Although microwave drying can be an interesting alternative for stabilization, it has been traditionally processed by convective drying. This work studied the microwave and microwave-vacuum drying of barley malt, evaluating hydration, germination and drying. Both hydration and germination reduced the grain compression force, but without demonstrating a defined endpoint. The traditional convective drying (50–70 °C) took 540–840 min, while microwave reduced processing time in ~95%. Vacuum increased the drying rate and reduced the product temperature. Moisture profiles over processing were calculated based on the obtained effective diffusivity. The drying rate showed an intermediate moisture value when microwave radiation is optimum, which was associated with the best combination between absorption and conversion across the water molecules within the sample. The behavior parameter of Page Model suggested super-diffusion. In conclusion, microwave and microwave-vacuum technologies showed to be attractive alternatives for barley malt drying.