Fast and Simultaneous Determination of Antioxidant Activity, Total Phenols and Bitterness of Red Wines by a Multichannel Amperometric Electronic Tongue
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An electronic tongue based on a flow injection system equipped with a multichannel amperometric detector was used to determine the antioxidant activity, total phenols and bitter taste of red wines. The detector composed of four glassy carbon electrodes, arranged in a square configuration, where two parallel electrodes (poised at E1=+400 and E2=+800 mV) were followed by other two electrodes (poised at E3=+800 and E4=−400 mV). This configuration allowed to gain information on the content of the antioxidants activity (E1) and total phenols (E2 and E3). E1/E2 was used to express the proportion of strong vs. weak antioxidants. E3/E4 was used to express an index of reversibility. Finally, the ratio E2/E3 was used to control the system. Overall, the four electrodes led to seven variables, which provided a characteristic pattern profile. The eleven variables in total were analyzed by principal component analysis (PCA) to determine, the antioxidant activity, total phenol content and bitterness value of red wine samples. The results of antioxidant activity were correlated with the Folin Ciocalteu index (R2=0.94). Bitterness was correlated with the descriptors of the e-tongue (R2=0.81). Overall, the analysis with the proposed electronic tongue is simple (only a dilution is required), fast (the analysis takes less than 20 seconds per sample), objective (precision within 5 %, expressed as RSD%) and cheap compared to classical sensory analysis.