Production of Fermentable Sugars and a High Protein Meal by Dilute Acid Hydrolysis of Soybean Meal at High Temperatures

Abstract

The objective was to produce fermentable sugars with low levels of fermentation inhibitors and a high-protein meal, with acceptable color, by treating defatted soybean meal with dilute sulphuric acid at temperatures between 105 and 135 oC and durations up to 45 min. The conditions that maximized the amount of protein were 120 °C, 0.5% H2SO4, and 45 min, which increased protein from 48.1% to 58.6% d.b. The highest amount of fermentable sugars (32.2% d.b.), without regard for the protein content, was for the treatment at 135 °C, 2% H2SO4, and 45 min; such treatment generated relatively low 5-HMF and furfural levels (0.0018 g/L and 0.32 g/L, respectively), and 0.87 g/L, of acetic acid. The treatment at 120 °C, 1.5% H2SO4, and 30 min had the best balance between a high concentration of fermentable sugars (21.3% d.b.) in the liquid fraction and crude protein (52.1% d.b.) in the solid fraction without a significant change in the original color of the solid fraction.