## 4 Discussion
The \"seaweed, violet, flower, raspberry\" aroma of beta-ionone [7], along with beta-damascenone, are important in the aroma of several red grape varieties [38]. Other ketones that are generated by fungal metabolism or produced during fermentation and acetals produced during aging and distillation will not be discussed in this research. Of all the aromatic constituents of wine, esters are the most abundant. Most of these esters are found only in trace amounts and have either low volatility or non-distinct odors, and their importance to wine fragrance is often discounted. The more common esters such as acetate esters are derived from acetic acid and fused alcohols, and the ethyl esters are formed between ethanol and fatty acids or nonvolatile, fixed organic acids. The fruity aromas are important in the aroma profile of young white wines [39]; however, the esters to the aromas of red wines is less understood. Terpenes are an important group of aromatic compounds characterizing the aromas of \"flower and lavender\" (linalool), \"rose and geranium\" (geraniol), \"swet\" (nerol), \"oil, anise, mint\" (alpha-terpineol), and \"hycinth\" (hotrienol) [7]. Terpenes are responsible for the fragrance of herb-flavored wines such as vermouth and fruit-flavored wines. In addition, terpen also characterize some wine grape cultivars, most notably the \"Muscat\" and \"Riesling\" families [40]. Pyrazines are important to the characteristic varietal aromas of several cultivars [41]. Ethyl 3-mercaptoethanolpropionate is an important compound suspected to be the \"foxy\" odor of some _V. labrusca_ varieties [42]. Most thiols generate off-odors, and only a few contribute to the characteristic varietal aroma of wine grape cultivars. These are 4-mercaptoethanol-4-methylpentan-2-ol (\"floral, lemon grapreruit\") [24] and 3-mercaptoethanol-1-ol (\"grapefruit\") [43]. Both compounds are important in the varietal character of \"Sauvignon Blanc\" [43]. A key aroma important in \"Scheurebe\" is 4-mercapto-4-methylpentan-2-ol [44]. Despite the information available on volatile wine odor-active compounds and their sensory perceptions, experienced tasters are not always able to determine the grape variety (Vinifera), even when 100% of the wine is made from that cultivar [45]. A review of wine aroma in grapes is provided elsewhere [46]. The question remains if these new cold-hardy cultivars produce a distinct varietal aroma in white wines. This research adds a valuable initial report on white wine aromas from Brianna and Frontenac gris grapes. To date, the only other published research on cold-hardy wine aromas pertains to red wines [47; 48; 49; 50] and white wines [51]. Therefore, this research serves as a starting point for determining the odor-active compounds in Brianna and Frontenac gris cold-hardy wines. At this (screening) stage, using one panelist achieved the stated aims, i.e., preliminarily characterized odor active compounds. This information should be used for follow-up studies as a starting point for proper experimental design. This relatively low number of publications on cold-hardy wine varieties is significant compared with active research in Vinifera [52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62]. Results (obtained with GC-MS-O approach) from this research could be used to inform cold-hardy grape growers on \"farming for flavor.\" A shift of the aroma profile from \"fruity 1\" to \"rotten eggs, sulfury\" to \"rose 1\" was observed in wines made from Frontenac gris harvested at 19.5, 23.1, and 23.6 \"Brix, respectively (Figure 3). The must was not submitted to cold-settling and might be a major reason for the \"sulfury, rotten egg\" odors found in the research wines. In addition, a shift of the aroma profile from \"cotton candy\" to \"banana\" to \"floral\" to \"butterscotch\" was observed in wines that were made from Brianna grapes harvested at 15.4, 17.6, 18.6, and 19.6 \"Brix, respectively (Figure 4).