Evaluation of a Comprehensive Red Wine Phenolics Assay Using a Microplate Reader

Abstract

A 96-well microplate reader was found to be an efficient and cost-effective tool for assaying red wines using an existing comprehensive red wine phenolics assay. This instrument increases the throughput three-fold while also reducing the time required to complete the assay. A traditional UV-vis capable spectrophotometer was used as the reference method to validate the procedure for the analysis of tannin, iron-reactive phenolics, anthocyanin, large polymeric pigment, and small polymeric pigment. The iron-reactive phenolics and anthocyanin steps were completely scaled down to microplate volume. The tannin and polymeric pigment measurements required two initial steps in microfuge tubes before transfer to the microplate. The 40 wine samples representing four different wine types were assayed and compared using the two different instruments. The average instrumental differences between microplate and spectrophotometer ranged from 1 to 6% for tannin, 1 to 5% for iron-reactive phenolics, <1 to 4% for anthocyanin, and 0.50 to 6.66% for large and small polymeric pigments. The largest discrepancies were seen in the large polymeric pigment measurements, where the greatest difference was 6.66% for the 2003 Merlot samples.