Effect of roasting time and method on physicochemical and functional properties of roasted maize grain (Asharo)

Grain roasting is the oldest technique and an important food processing unit operation. Roasting was performed on conditioned maize grains for the preparation of asharo. Although most parts of Ethiopia prepare tella from roasted various products using traditional methods that affect the physicochemical and functional properties of the products. The objective of this study was to investigate the Effect of roasting time and method on physicochemical and functional properties of roasted maize grain (asharo). In this study, roasting was performed using a newly designed roasting machine (MC) and Mitad (MT). A two-factor factorial experiment (2 × 3) with replication was conducted, three roasting times (30, 40, 50 min) and two roasting methods were tested. The study revealed that roasting significantly influenced the physicochemical and functional properties of maize grain. Moisture, protein, fat, fiber, carbohydrate, and energy values varied between raw and roasted grains, roasted grains were showing moisture (0.71–10.28 %), protein (8.03–8.6 %), fat (4.1–5.5 %), fiber (2.01–2.41 %), carbohydrates (72.75–83.03 %), and energy (367.62–409.2 kcal). Total phenol content increased (122.5–172.74 mg GAE/100 g), while bulk density was decreased significantly (343.8–471 kg/m³ vs. raw maize at 762.3 kg/m³). Functional properties, including water solubility index (8.68–17.71), water absorption capacity (1.52–2.12), water absorption index (5.1–6.5), and water activity (0.33–0.598), were significantly affected. Roasting time had a greater effect on these properties than the method, with protein being the only insignificant parameter (p > 0.05). The energy absorbed by the maize grain in a newly designed roaster (7205 KJ) is greater than that of the open pan roaster (5404 KJ).