Thermally induced protein modifications in mealworm: Gastrointestinal digestibility and derived bioactive peptides with antioxidants and ACE/DPP-IV inhibitory activities.

Sustainable protein sources from edible insects are gaining attention as alternatives to conventional proteins, yet comprehensive understanding of thermal processing effects on insect protein structure-function relationships remains limited. This study systematically characterized mealworm (Tenebrio molitor) protein across three developmental stages (larval, pupal, adult) and examined thermal-induced conformational changes in pupal-stage proteins subjected to controlled heating (50 °C, 90 °C, 130 °C, 170 °C for 60 min) using Fourier transform infrared spectroscopy (FTIR), SDS-PAGE, and size exclusion chromatography coupled with gastrointestinal digestion models. Pupal-stage proteins exhibited highest protein content (54.38 %) and distinct molecular weight profiles (10-200 kDa). FTIR analysis revealed systematic thermal-induced structural transitions: native α-helix (15.87 %) transformed to β-sheet aggregates (59.22 % at 90 °C) and β-turn conformations (12.25 % at 170 °C). These conformational changes directly influenced gastrointestinal digestibility, with moderate heating (90 °C) achieving optimal protein hydrolysis (49.36 %) and enhanced small bioactive peptide generation. Temperature-dependent bioactivity patterns emerged: 90 °C preserved thermolabile DPP-IV inhibitory activity (antidiabetic) with improved digestibility, while extreme heating (170 °C) enhanced antioxidant capacity and ACE inhibition (antihypertensive) through protein aggregation. Molecular weight analysis confirmed selective peptide generation, with 90 °C producing predominantly small bioactive fragments (<500 Da) versus larger aggregated complexes at 170 °C (500-3000 Da). This study establishes that controlled thermal processing enables precision bioactivity tailoring-moderate heating (90 °C) optimizes thermolabile enzyme inhibition for diabetes management, while extreme heating (170 °C) maximizes antioxidant enhancement for cardiovascular health-providing a paradigm shift from traditional processing to targeted functional ingredient development through temperature-controlled protein structural modifications.