Abstract
Phenolic compounds are currently the most investigated class of functional components in quinoa. However, great variability in their content emerged, because of differences in sample intrinsic and extrinsic characteristics; processing-induced factors; as well as extraction procedures applied. This study aimed to optimize phenolic compound extraction conditions in black quinoa seeds by Response Surface Methodology. An ultrasound-assisted extraction was performed with two different mixtures; and the effect of time; temperature; and sample-to-solvent ratio on total phenolic content (TPC) was investigated. Data were fitted to a second-order polynomial model. Multiple regression analysis and analysis of variance were used to determine the fitness of the model and optimal conditions for TPC. Three-dimensional surface plots were generated from the mathematical models. TPC at optimal conditions was 280.25 ± 3.94 mg of Gallic Acid Equivalent (GAE) 100 g−1 dm upon extraction with aqueous methanol/acetone, and 236.37 ± 5.26 mg GAE 100 g−1 dm with aqueous ethanol mixture. The phenolic profile of extracts obtained at optimal conditions was also investigated by HPLC. The two extracting procedures did not show different specificities for phenolic compounds but differed in the extraction yield.
Highlights
Phenolic compounds (PCs) have increasingly become an emerging field of interest in food science and nutrition because of the beneficial effects on human health, associated with their dietary intake
Response Surface Methodology (RSM) was used to identify the optimal conditions for phenolic compound extraction from black quinoa seeds
Extraction time, extraction temperature and sample-to-solvent ratio were set as independent variables, and total phenolic content (TPC) was set as a response
Summary
Phenolic compounds (PCs) have increasingly become an emerging field of interest in food science and nutrition because of the beneficial effects on human health, associated with their dietary intake. These molecules act as antioxidants by preventing transition metal-mediated formation of hydroxyl free radicals, and by scavenging reactive species of oxygen, nitrogen and chlorine [1]. An up-to-date systematic review of the literature showed that spectrophotometric assays have been mainly applied to PC determination in quinoa [4]. Studies on TPC determination in quinoa lack optimization of extraction conditions, which is pivotal to obtain accurate data on TPC. Optimization of extraction conditions is crucial to obtain reliable data
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