Comparison between Folin-Ciocalteu and Prussian Blue Assays to Estimate The Total Phenolic Content of Juices and Teas Using 96-Well Microplates.

Unlabelled: Folin-Ciocalteu colorimetric assay (FC) is the most widely used assay to estimate the total phenolic content in foods, beverages, herbs and other plant extracts, but many chemical compounds may act as interfering agents, producing inaccurate estimations of the real concentration of phenolic compounds in the matrix. Based on this limitation, the objective of this study was to compare, quantitatively, the Folin-Ciocalteu and Prussian Blue (PB) assays in estimating the total phenolic content in purple grape juices (n = 20; Vitis labrusca L.) and teas (n = 25) from different botanical origins using 96-well microplates.

Characterization of conventional, biodynamic, and organic purple grape juices by chemical markers, antioxidant capacity, and instrumental taste profile.

The objectives of this study were to characterize organic, biodynamic, and conventional purple grape juices (n = 31) produced in Europe based on instrumental taste profile, antioxidant activity, and some chemical markers and to propose a multivariate statistical model to analyze their quality and try to classify the samples from the 3 different crop systems. Results were subjected to ANOVA, correlation, and regression analysis, principal component analysis (PCA), hierarchical cluster analysis (HCA), soft independent modeling of class analogy (SIMCA), and partial least-squares discriminant analysis (PLSDA). No statistical significant differences (P > 0.