Optimization of controlled germination conditions enhances bioactive compounds and antioxidant capacity and improves protein digestibility of Andean lupin (Lupinus mutabilis Sweet)

Germination is an effective bioprocessing strategy to enhance the nutritional and functional properties of legume seeds through metabolic activation and structural remodeling. This study optimized the controlled germination conditions of Andean lupin by evaluating germination time (24–96 h) and temperature (14–26 °C) using response surface methodology to maximize γ-aminobutyric acid (GABA), total soluble phenolic compounds (TSPC), and antioxidant capacity (ABTS+∙ and DPPH∙). Optimal conditions were identified at 96 h and 22.6 °C, achieving an overall desirability of 77.30% (P < 0.10, R2 > 0.70) and resulting in marked increases in GABA (753%), TSPC (191%), and antioxidant capacity (ABTS+∙ 10%, ORAC 37%, and DPPH∙ 112%) compared with non-germinated seeds. Temperature was the main factor governing GABA and phenolic accumulation, whereas germination time exerted a stronger influence on antioxidant capacity. Beyond bioactive enrichment, controlled germination significantly improved protein quality, as evidenced by higher levels of essential and non-essential amino acids, mainly lysine, phenylalanine, valine and tyrosine, along with a marked increase in in vitro protein digestibility (from 77.3 ± 3.7% to 88.3 ± 3.0%; P < 0.05). Overall, these findings demonstrate that optimized germination induces relevant biochemical and microstructural modifications that enhance the functional and nutritional quality of Andean lupin flour, supporting its application in functional and plant-based foods.