Carbonic Maceration in Norton (2017)

This study examines the impact of different winemaking styles on resulting Norton wine. Norton grapes were harvested over two days, and on the first day whole cluster, undamaged grapes were placed into a CO2-purged stainless steel tank with dry 71B yeast on the bottom (this yeast promotes ester formation) while on the second day grapes were destemmed and crushed into multiple T bins. This carbonic maceration tank was gassed with carbon dioxide daily throughout the maceration (approximately 17 days) and held at 65°F. The grapes were then pressed on November 6, and the press fraction was separated, inoculated, and fermented to dryness. The other treatment was punched down twice per day in T Bin throughout fermentation, and the T bins were inoculated with a mix of Lalvin C and Clos yeasts. The T Bins were pressed off on November 3. The carbonic maceration wine has higher alcohol, pH, and VA, with lower TA and lactic acid. The carbonic maceration wine has higher color and phenolic parameters, except for catechin. In sensory analysis, 58% of judges were able to correctly distinguish the wines, suggesting that the wines were significantly different (p<0.01). People who were able to distinguish the wines tended to prefer the carbonic maceration wine. There was a strong trend for the carbonic maceration wine to have higher Body than the traditional fermentation wine. There was a slight tendency for the carbonic maceration wine to have higher Ester Intensity. More studies should be performed on carbonic maceration in Norton and other non-vinifera grape varieties. Additionally, more studies should examine the evolution of aroma and flavor of these wines over time, and how this impacts overall consumer preference.

Read Full Report (PDF)

Enhancing Color Stability of Norton with Different Enological Fermentation Tannin (2017)

This study examines the impact of adding different kinds of exogenous tannin prior to fermentation in Norton grape must. Norton grapes were harvested on the same day and destemmed into four T bins. The T bins then received the following treatments: 1) No tannin addition (control), 2) Tan Color (Enartis) addition at 180g/ton followed by Pro Tinto addition (150g/ton) partway through fermentation (mostly condensed tannins), 3) FT Rouge (ScottLabs) addition at 60g/hL (hydrolysable tannin), and 4) a series of BSG product additions: UVA V-Tan at 30g/hL, Premium Limousin at 15g/hL, and Premium Color at 15g/hL (mix of condensed and hydrolysable tannins). All other treatments between wines were equal. After approximately two weeks, wine was pressed off. The BSG wine and the FT Rouge wine had slightly slower fermentations. Wines had slightly differing alcohol contents (slightly higher when using condensed tannin, and slightly lower when using hydrolysable tannin), but otherwise no major chemistry differences were seen. No color differences can be seen. The addition of these products may have slightly lowered caftaric acid and increased epicatechin and gallic acid, and these increases were more correlated to products containing condensed tannin. No major tannin or anthocyanin differences could be seen. For the descriptive analysis, there were no strong trends for the descriptors used in this study. There were slight trends for the control to have lower Fruit Intensity, Astringency, and Body. The wines made with BSG products tended to have higher Fruit Intensity, Overall Aromatic Intensity (along with FT Rouge in this regard), Bitterness, Astringency, and Body. The Pro Tinto/Tan Color and FT Rouge treatments were relatively similar and often fell in-between the Control and BSG products, except for FT Rouge with Overall Aromatic Intensity (where it was higher) and for Pro Tinto/Tan Color with Herbaceous/Green quality. In general, there was a preference for the wine produced with BSG products; however, judges thought that the wines were all fairly similar. In the future, more studies should be performed with these products on different grape varieties.

Read Full Report (PDF)