Microstructural and functional transformations induced by germination and digestion in Lupinus angustifolius L

Germination is a used bioprocess to improve the nutritional quality and functionality of legumes; however, there is little information on how it alters the structural, functional, and digestive properties of Lupinus angustifolius, a species of interest in food innovation due to its high protein content. This study evaluated the effect of germination time (0, 3, 5, and 7 days) on the structural composition, morphology, and digestibility of Lupinus angustifolius flours. Germination decreased lipid content from 24.9 % to 12.1 %, while protein increased from 25 % to 29.2 %, and fiber from 9.9 % to 13.4 %. Starch fractions also changed, with resistant starch increasing from 0.02 % to 0.24 % and rapidly digestible starch from 0.86 % to 1.55 %. Histological and spectroscopic analyses revealed progressive tissue disorganization, hydrolysis of conglutins, and modifications in protein secondary structure components, specifically a shift from α-helices to β-sheets, along with changes in starch crystallinity. These microstructural transformations reduced flour viscosity (peak viscosity from 48.4 to 26.8 cP) and protein thermal stability (ΔH from 1.20 to 0.47 J/g). After simulated gastrointestinal digestion, confocal microscopy analysis showed a highly fragmented and porous matrix in germinated flours, with fragments corresponding to digestion-resistant peptides, which may hold biological interest and high potential for application in novel food development. Germination significantly modified the biochemical, functional, and structural properties of lupin flours, enhancing their nutritional profile, digestibility, and bioactive potential. These findings highlight the value of germination as a bioprocess to optimize the use and application of this seed in the development of novel foods with potential health benefits.