Valorization of sunflower by-product usingmicrowave-assisted extraction to obtain a richprotein flour: Recovery of chlorogenic acid,phenolic content and antioxidant capacity

Abstract

The sunflower cake, which is a by-product from sunflower oil refining, is a rich source ofchlorogenic acid (CGA), a phenolic compound that must be removed from this by-productbefore its use for human consumption. This work studied the extraction of CGA from sun-flower by-product using microwave-assisted extraction (MAE) and it was divided into twosteps. The first step identified the conditions of solvent and solvent-to-feed ratio (S/F) thatmaximized the CGA extraction. The highest CGA yield was obtained using ethanol 70%, andthe S/F did not show statistical significance on the recovery of CGA. In the second stage,ethanol 70% and S/F of 10 were fixed and the effect of power (100, 200 and 300 W) andextraction time (30, 60, 90 and 120 seconds) were evaluated in the extraction of CGA. MAEprocesses were evaluated in terms of global and CGA extraction yields, total phenolic con-tent (TPC) and antioxidant capacity. The developed process allowed to recover 8.4 ± 0.1 mgCGA / g of raw material in a very short time (30 seconds). ORAC assay revealed that theextracts presented antioxidant capacity. FTIR spectra exhibited no significant differencesfor all the analyzed samples, and the SEM images showed that the sunflower by-productstructure was affected by the irradiation power. Therefore, the MAE process proved to be afast and efficient method to obtain CGA-rich extracts and a residual solid with a high con-tent of protein (26%) and essential amino acids that allows its usage in products for human nutrition.