Optimization of the subcritical water treatment from sunflower by-product for producing protein and sugar extracts

Abstract

This study proposes the valorization of sunflower by-product (SbP) using subcritical water treatment. For this purpose, a response surface methodology in a 3× 3 Box–Behnken design was employed to study the effect of temperature (100– 150 °C), extraction time (5–25 min), and solvent-to-feed ratio (10–20 g bidistilled water/g SbP) on the water-soluble compounds. The highest amount of glucose (5.7-mg/g raw material) and xylose (13.5-mg/g raw material) was obtained at 150 °C and solvent-to-feed ratio of 15 after 25 min of extraction. The highest amount of protein (133.5-mg/g raw material) was obtained at 150 °C and solvent-to-feed ratio of 20 after 15 min of extraction. The selected temperature conditions did not promote the formation of final degradation products such as furfural and 5-hydroxymethylfurfural (HMF). The extracts obtained in this study showed simultaneous recovery of free monomeric sugars that could be used for bioenergy or biochemical, proteins that could be used for food and pharmaceutical industries and phenolic compounds that could be used for food and nutraceutical applications.