Condensed tannin extraction and retention have long been a problem for cool climate grape growing and winemaking regions where Vitis interspecific hybrid cultivars are grown. Recently, the link has been made between pathogenesis-related (PR) proteins and low condensed tannin retention in red wine cultivars. At the time of this research, no agreed-upon method for grape juice and wine protein precipitation, quantification, and proteome characterization had been determined. After method

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... n, we determine with a coefficient of variation below 15 percent that the precipitation with acetone/trichloroacetic acid (TCA), solubility buffer of 6M Urea/100 mM ammonium bicarbonate, and bicinchoninic acid (BCA) protein assay for quantification to be most appropriate. For characterization, the use of shotgun-based proteomics with UPLC-ES-TIMS-TOF was used for the characterization of the proteome. Using the optimized method, seven different cultivar's juice and wine were analyzed for protein and condensed tannin. Also, condensed tannin content and proteome from Vitis interspecific hybrid cv. Chambourcin wine from 2018 and 2019 was studied more extensively with traditional and novel winemaking methods (exogenous condensed tannin additions early and late, accentuated cut edges), along with the wine and lees of micro fermentations (50 mL) with increasing levels of exogenous condensed tannin additions during fermentation (800-6400 mg/L). The addition of exogenous condensed tannin at 1-month post-press resulted in condensed tannin retention above 100 percent and the use of ACE (accentuated cut edges), a practice involving using a blender after crush to increase the skin to juice ratio, increased native condensed tannin content 2.5-fold higher than the control. Total protein does not correlate to condensed tannin concentration, but proteomic data and individual spectrum count do indicate that specific proteins may have more impact on the condensed tannin content in wines. There are many proteins (PR and other groups) that impact condensed tannin retention and is not a select handful that was previously hypothesized.