A protein precipitation method was used to measure the tannin concentration of 1325 commercial red wines made from Vitis vinifera cultivars: Cabernet Sauvignon, Merlot, Pinot noir, Syrah, Zinfandel, and several blends. Samples were taken from the United States (California, Oregon, Washington), Australia, and France. The concentration of tannins ranged from 30 to 1895 mg/L catechin equivalents (CE) among all wines measured, with a mean concentration of 544 mg/L CE and a standard deviation of 293. Within a single variety the variation in the concentration of tannins was larger than an order of magnitude and in two varieties (Cabernet Sauvignon and Pinot noir) the variation was 32-fold. Because of the wide variation in concentration range, there was overlap among the different populations. However, differences were found (p < 0.05) among the varieties at the population mean value: Cabernet Sauvignon (672 mg/L CE) ≥ Zinfandel (652 mg/L CE) > Merlot (559 mg/L CE) > Syrah (455 mg/L CE) > Pinot noir (348 mg/L CE). Pinot noir and Syrah wines from different states were compared and revealed that the tannin concentration in Oregon and California Pinot noir wines were not statistically different, while California Syrah was higher in tannin than both Washington State wines and those from several states in Australia.
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