## 4 Discussion  
SPME has been used to quantify volatile by-products in industrial ethanol [25], volatile congeners in food-grade ethanol [23], and volatile odor-active compounds in cold-hardy wines made from Marquette and Frontenac [22] and even used to characterize street drug aromas [26; 27; 28]. Odor-active compounds in wine headspace must be extracted quickly and efficiently in order to minimize the effects of oxidation on the wine aroma profile. In this research, a SPME 50/30 \(\upmu\)m divinylbenzene (DVB)/Carboxen/polydimethylsiloxane (PDMS) coating was suitable for extraction of a wide variety of aroma volatiles including alcohols, esters, aldehydes and ketones, phenolics, and acids. Ethanol being the most prevalent in headspace did not outcompete volatile aromas for SPME sorption sites. Simultaneous sensory and chemical analyses of white wine aroma was facilitated by the use of GC-MS-O. The advantage of using olfactometry (O) simultaneously with chemical detection is the ability to focus on selected fewer aroma-causing compounds present in a very complex mixture of the wine headspace matrix. A sole focus on chemical analyses can preclude finding the aroma-defining volatile compounds in wine. Grape sugar content (\"Brix) varies depending on the species, variety, maturity (ripening), and health of the fruit [10]. Cultivars of European _Vitis vinifera_ generally accumulate sugar at a concentration of 20% or more at maturity [29]. The cold-hardy cultivars Brianna and Frontenac gris pedigree includes _V. riparia, V. labrusca, and V. vinifera_[30; 31]. Brianna, in particular, is often harvested at a lower \({}^{\circ}\)Brix to avoid \"foxy\" flavors. Sugar is added (chaptalization) to the juice to develop the 10-12% alcohol content typical of most still (non-sparkling) table wines [32]. The effects of sugar  
Figure 4: A PCA biplot of aromas from Brianna wines made from berries harvested at four different ripening stages. Wines were made from Brianna cold-hardy grapes harvested at 15.4, 17.6, 18.6, and 19.6 \({}^{\circ}\)Brix. The juice was adjusted to 20 \({}^{\circ}\)Brix for all time points prior to fermentation. Wine headspace samples were collected by SPME and analyzed with GC-MS-O. Aroma descriptors were recorded by a trained human panelist. A shift of the aroma profile from “cotton candy” to “banana” to “floral” to “butterscoth” was observed. Over 68% of the variation in harvest time is correlated with key odor-active compounds. content and ethanol concentrations on the sensory attributes of young and aged sweet wines is found elsewhere [33; 34]. However, there are few intervention options for enhancing the desired aromas. Thus, wine cold-hardy white wines produced from European/native N. American cultivars such as Brianna and Frontenac gris need to be \"farmed for flavor.\" This means that growers should consider an optimal flavor profile as a harvest parameter, in addition to the \({}^{\circ}\)Brix, pH, and TA. Grapes produce few aldehydes significant in varietal aromas. This may result from their reduction to alcohols during primary fermentation. Of the aldehydes not metabolized during primary fermentation, C-6 aldehydes appear to be the most noteworthy [35]. These aldehydes are responsible for the grassy to herbaceous odor associated with certain grape varieties or with wines made from immature grapes. They appear to be formed during crushing by the enzymatic oxidation of grape lipids [4]. Most aldehydes found in wine are created during processing or fermentation or are extracted from oak cooperative [32]. Likewise, few ketones are found in grapes. The norisoprenoid ketones (i.e., beta-damascenone, alpha-ionone, and beta-ionone) are persistent throughout fermentation [32]. The \"apple, rose, honey\" aroma of beta-damascenone [7] and low odor threshold [24] imply that it is important in the aroma of several grape varieties including \"Chardonnay\" [36] and \"Riesling\" [37].