Measurement of total phenolic content in wine using an automatic Folin–Ciocalteu assay method

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Summary

Measuring the total phenolic content in wine is important in estimating the taste and health benefits of wine. We developed an automatic Folin–Ciocalteu (F-C) method to reduce processing times (3 min), human errors and waste volume as compared it to the manual method. The gallic acid standard responded linearly up to 5000 μg mL−1, and the wine dilution series responded linearly between four- and sixteenfold dilutions. Anthocyanins showed slower reaction rate compared with wine, gallic acid and quercetin, while ascorbic acid showed the fastest rate. Fructose and glucose at the 10% level showed approximately 8% interference in port wines, and the interference was thought to be negligible in most dry wines containing <1% sugar. Total phenolic contents ranged between 1600 and 3300 μg mL−1 by the automatic method and were approximately 20% less than those by the manual method, except in pink wines which was nearly identical. The regression analysis of the phenolic contents showed a very linear relationship between the methods (r2 = 0.97***). This automatic method was thought to be efficiently adopted in wine testing laboratories as a fast and reproducible assay.

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