On Modeling and Optimization for Separation, Concentration, and Purification of Saponins and Phenolic Compounds from Quinoa Hulls by Nanofiltration.

It is essential for quinoa's rapid expansion in the global market to comply with the circular economy to become a green agro-food industry. For this purpose, in this work, bioactive added-value compounds, specifically saponins and phenolic antioxidants, were extracted and purified from quinoa by-products (QbP), namely hulls, using green solvent extraction (60 wt% ethanol-water) and nanofiltration (NF). So far, research published on the implementation of NF in the treatment of QbP, or modelization and optimization of the membrane performance focusing on fouling minimization and control, is scarce. Centrifugation and microfiltration were conducted as separation-purification pretreatments before NF. A three-level factorial design was successfully applied to optimize NF membrane operation in terms of saponins and phenolic compound recovery, as well as permeate flux, comprising operating pressure and tangential velocity as key input factors. Membrane fouling, critical for stable process operation scale-up, required intensive multifactorial analysis. Optimization at 4 bar and 15 m/s permitted the recovery of up to 84.5% saponins and 84.3% phenolic compounds in the permeate stream. Moreover, NF dynamic performance modeling and optimization ensured fouling build-up minimization and maximization of membrane productivity almost ten-fold, up to a stable value as high as 175.4 L/hm2, ensuring full recovery of the membrane performance after each operating cycle, key for the technical-economic viability of the proposed process to obtain standardized purified extract products.