Valorization of sunflower by-product using microwave-assisted extraction to obtain a rich protein 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 of chlorogenic acid (CGA), a phenolic compound that must be removed from this by-product before its use for human consumption. This work studied the extraction of CGA from sunflower by-product using microwave-assisted extraction (MAE) and it was divided into two steps. The first step identified the conditions of solvent and solvent-to-feed ratio (S/F) that maximized the CGA extraction. The highest CGA yield was obtained using ethanol 70%, and the 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) and extraction time (30, 60, 90 and 120 seconds) were evaluated in the extraction of CGA. MAE processes were evaluated in terms of global and CGA extraction yields, total phenolic content (TPC) and antioxidant capacity. The developed process allowed to recover 8.4 ± 0.1 mg CGA / g of raw material in a very short time (30 seconds). ORAC assay revealed that the extracts presented antioxidant capacity. FTIR spectra exhibited no significant differences for all the analyzed samples, and the SEM images showed that the sunflower by-product structure was affected by the irradiation power. Therefore, the MAE process proved to be a fast and efficient method to obtain CGA-rich extracts and a residual solid with a high content of protein (26%) and essential amino acids that allows its usage in products for human nutrition.