Impact of Steam Extraction and Maceration Duration on Wines from Frozen 'Frontenac' Must

The enology industry in North Dakota is extremely young, with less than twenty years of existence. At times throughout the development of the North Dakota viticulture and enology industries, commercial wine producers have elected to purchase or store fresh harvested grapes as frozen musts. To investigate the fermentation outcomes related to skin contact for red grapevine musts, a postfreeze fermentation experiment was conducted with fruit from 'Frontenac', one of the most widely grown red grapevines in the Upper Midwest U.S. and North Dakota. Four fermentation treatments were applied to frozen 'Frontenac' grapevine musts: steam juice extraction, rose, 1 day after inoculation (DAI) skin contact, and 9 DAI skin contact. Samples were collected daily for ten days and analyzed for fermentation progress and spectrophotometric monitoring of wine color attributes and total phenolics. The final wines were analyzed two years after bottling. Steam-extracted musts were initially darkest; however, they were lighter as final wines than the 9 DAI wines and similar to rose wines in lightness. Total phenolics were greatest for 9 DAI wines and total red pigments were lowest for steam-extracted wines. While differences between treatments were detected, the wines remained visually similar; this indicates that color extraction within the freeze-thaw processes of musts may obliterate subtly and make it difficult to produce wines of light color when stored under these conditions. Continued work with additional grapevines beyond 'Frontenac' may help fine-tune must and fermentation extraction procedures for small-scale wineries growing cold-hardy grapevines.

Automated summary

The enology industry in North Dakota is young, with less than twenty years of existence. In order to investigate the fermentation outcomes related to skin contact for red grapevine musts, a postfreeze fermentation experiment was conducted with fruit from the 'Frontenac' grapevine. Steam juice extraction, rose, 1 DAI skin contact, and 9 DAI skin contact were the four fermentation treatments applied to the musts. Differences were found between the treatments, but the wines remained visually similar, indicating that color extraction within the freeze-thaw processes of musts may affect the production of light-colored wines.