Abundant Existence of Bovine Serum Albumin Non-precipitable Tannins in Red Wines

Phenolics in red wines made from three cultivars, Muscat Bailey A (MBA), Merlot (MR), and Cabernet Sauvignon (CS), were separated into four fractions using the bovine serum albumin (BSA) precipitation method in combination with solid-phase extraction. An assay for phenolics in all fractions was carried out using the Folin-Ciocalteau (F-C) method. The average recovery of phenolics was 97.4%. Approximately 28% of total phenolics in MR and CS wines were BSA non-precipitable tannins (NP-T). It was also confirmed that approximately 50% of wine phenolics were composed of BSA-precipitable tannins (P-T) and NP-T. Wine made from MBA, the major cultivar for red wine in Japan, had a very low tannin content, and this may be a genetic characteristic of MBA. This is the first report that reveals the abundant existence of NP-T, and the whole aspect of tannins of red wines is shown with a unified quantification method.

Automated summary

Phenolics in red wines made from three cultivars were separated into four fractions, with approximately 28% of total phenolics in two cultivars being non-precipitable tannins. The major cultivar in Japan had a very low tannin content, indicating a genetic characteristic. The study revealed the abundant existence of non-precipitable tannins and showed the overall aspect of tannins in red wines with a unified quantification method.