Variation in Concentration and Composition of California Sauvignon Tannin

In order to develop an improved understanding of the extent to which tannin chemistry can vary within a single variety, samples form 38 blocks (three replicates) of Cabernet Sauvignon sourced from regions of California ranging from the southern San Joaquin Valley through Sonoma were studied. Blocks represented variation in allocation grade as assessed by the cooperating winery, and growing climate. Tannin information was collected from exhaustive extracts of isolated skin and seed tissue as well as from a partial extraction system designed to investigate the potential impact of physiological integrity of tannin extraction. Extracted tannins were purified by solid phase extraction and analyzed by acid-catalyzed cleavage in the presence of excess phloroglucinol which provided information on subunit composition and average degree of polymerization. In addition, purified tanning extracts were analyzed by gel permeation chromatography (GPC), which provided information on tannin size distribution and flavan-3-ol amount. For berry samples, berry weight varied from 0.72-1.36 gm/berry and 1.3-1.8 seeds/berry with no observed geographical relationship. For exhaustive seed extracts, the tannin average molecular mass at 50%, as determined by GPC, varied form 2331-3646 molecular mass units, with no concentration ranging from 1.2-3.1 mg/gm berry weight for tannin, an d0.07-0.36 mg/gm berry weight for flavan-3-ol monomers. For exhaustive skin extracts, (-)-epigallocatechin subunits comprised 34-48 mol % of total extension subunits. The proportion of skin tannin in the partial extraction system varied from 36-86% suggesting a large potential variation in the wine skin tannin contribution. Overall, the results from this study indicate that across regions a large impact on fruit tannin concentration and compostion.