Effects of One-Pass Microwave Drying on Rice’s Utilization in the Brewing Process.

Rice is utilized as an adjunct grain by the beer manufacturing industry. Before utilization, the rice has to be dried to a desired moisture content. The drying process employed may have an impact on the rice’s physicochemical properties which influence the rice’s performance in the brewing process. This study focused on investigating the impact of microwave drying on rice’s physicochemical properties and utilization in the brewing process. Rough rice samples at an initial moisture content of 19.7% wet basis were exposed to microwave dryer set to deliver 525 kJ/kg of energy in a single drying pass. The effects of the single-pass continuous drying on the dried rice amylose content, protein content, and specific gravity (°Plato, fermentable sugar content) of the wort were determined. The results were compared with samples dried using natural air at 25°C and 56% relative humidity (RH), and two-pass heated-air drying at 45°C and 60°C with RH set at 20%. There was a statistical difference in measured rice amylose and protein contents (p= 0.042) of microwave dried samples compared to the natural air-dried samples. However, these attributes were significantly different from those of samples dried at a higher temperature of 60°C and RH of 20%. There was a significant difference (p=0.0197) in the initial gravity content of all-malt samples and the rice adjunct samples as expected, but there was no significant difference between the rice adjunct samples. Overall, the studied drying methods could create variation in the rice’s physicochemical properties, but no measurable differences were observed among the wort’s initial gravity contents. This study analyzed the effect of microwave drying on rice processing and subsequent use in the brewing process and determined that it was most comparable to natural air drying, but results in a greater head rice yield resulting in a larger profit for rice farmers and processors