Optimization of Thermal-Alkaline Treatment Combined with Solid-State Fermentation for Enhanced Production of Bioactive Protein Hydrolysates from Corn Germ Meal

Corn germ meal contains high-quality protein with the potential of producing bioactive peptides. This study aimed to improve the peptide yield and bioactivity of protein hydrolysates from corn germ meal via thermal-alkaline treatment and solid-state fermentation. Corn germ meal was subjected to thermal-alkaline treatment, and the processing conditions were screened. The material obtained under the optimal conditions was then used for solid-state fermentation. The optimal conditions for thermal-alkaline treatment were 100 meshes, a treatment temperature of 100 °C, an alkali concentration of 1.3%, a treatment duration of 30 min, and a water addition of 120%. The protein digestibility of corn germ meal under optimal conditions improved by 86.28%. The combined treatment of thermal-alkaline treatment and solid-state fermentation significantly altered the chemical composition and structural characteristics of corn germ meal, thereby influencing the solubility and hydrolyzability of its proteins. This approach effectively increased the protein yield (≤37.89%) and peptide yield in protein hydrolysates (≤26.01%) of corn germ meal, consequently enhancing the antioxidant activity and angiotensin I-converting enzyme (ACE) inhibitory activity of protein hydrolysates. Furthermore, the treatment altered amino acid composition in the meal material and effectively degraded anti-nutritional factors such as phytic acid and tannin and improved the comprehensive utilization of corn germ meal.