Chemical and nutrient content of corn (Zea mays) before and after being flame roasted

Samples were collected before and after corn (Zea mays L) was flame roasted on several farms in southwestern Ontario. Seven sources of corn were sampled during one field trip and three during another. After passing through a propane flame, the roasted corn was cooled to ambient temperature within ∼ 15 min. All samples were ground (1 mm screen) and analysed. The true metabolisable energy, corrected to zero N balance (TMEn), true available amino acids (TAAA) and true DM digestibility were determined on the first collection of samples using adult White Leghorn cocks. The temperature of the corn as it left the roasting unit ranged from 110 to 140°C. The dry matter content was higher (P < 0.05) and the 100‐kernel weight and mould count were lower (P < 0.01 and P < 0.05, respectively) for the roasted than for the non‐roasted corn. Among the seven sources the N content of the roasted corn was higher (P < 0.05) than that of the non‐roasted corn; among the other three sources the N content was similar. The zearalenone and free ergosterol contents were lower in the roasted than in the non‐roasted corn, though the differences were not significant (P > 0.05). Roasting had little or no effect on TMEn, TAAA and true dry matter digestibilities or on the carbohydrate and fibre fractions of the corn samples. These and other reported data indicate that flame roasting of corn is an effective procedure for the removal of moulds without affecting the nutrient content and bioavailability of the roasted material.