Valorisation of quinoa scarification residues: impact of desaponification methods on functional and emulsifying properties

Abstract

BACKGROUND: Quinoa is widely recognised for the high biological value of its proteins. However, its outer layer contains saponins, an antinutrient that must be removed for consumption. The process of dry desaponification of grains is known as scarification and produces a residual powder that is usually discarded. RESULTS: The quinoa scarification residue (QSR) contained 5 g kg−1 of saponins. Thus, washing with water, homogenisationassisted washing (HQSR) and sonication-assisted washing (SQSR) methods were evaluated. The assisted washing methods used 50% less water, although all of them reduced the residual saponin content (∼0.5 g kg−1 ) and significantly concentrated the protein content of the samples (∼270–290 g kg−1 ), compared to the control sample (∼210 g kg−1 ). The electrophoretic profile in sodium dodecyl sulfate–polyacrylamide gel electrophoresis showed the presence of the structural protein chenopodin, with its acidic (30–40 kDa) and basic (20–25 kDa) subunits, as well as protein macromolecules higher than 100 kDa. Fragmented particles were also observed in the HQSR and SQSR samples using low-vacuum scanning electron microscopy, although the latter also presented porous structures. Both a decrease in oil/water interfacial tension – mainly in HQSR (19.22 mN m−1 ) − and a significant increase in interfacial viscosity in SQSR (1.5 E−5 Pa s) were observed. Emulsions formulated with the sonicated sample showed greater stability against coalescence, creaming and sedimentation processes. CONCLUSION: Ultrasound-assisted desaponification proved to be efficient, improving the functional characteristics of this residue and opening new possibilities for its use in food systems.