Abstract Response surface methodology was applied to determine the optimum conditions for the Maillard reaction so that high levels of antioxidative and antimutagenic substances could be produced from defatted soybean and corn starch hydrolysates. The optimum reaction conditions predicted to produce the greatest levels of active antioxidative and antimutagenic melanoidins were 155.0 °C for 6.3 h at a pH of 12.1 and 155.5–160.4 °C for 4.60–9.70 h at pH 10.4–12.5 respectively. The range of optimum reaction conditions to maximize melanoidin production were 148–170 °C for 3.0–7.5 h at pH values between 10.2 and 13.5. These predicted values for optimum reaction conditions were in good agreement with experimental values.