## 1 Introduction  
The grape berry undergoes significant changes during ripening, including acid catabolism and the accumulation of sugar, anthocyanins, flavor and aroma compounds [1]. Brix measurements correspond to the percent total soluble solids (TSS), i.e., sugar, in a given weight of grape juice. Sugar content increases throughout berry ripening and is often monitored as a function of maturity. Flavor and aroma compounds are complex. Although frequently subjected to sensory analysis, flavor and aroma compounds have limited objective measures specifically identifying the chemical and aroma links. Wines from Albillo and Muscat grape varieties (_V. vinifera_) have been shown to exhibit more \"fruity\" aromas and less \"vegetal\" and \"floral\" aromas at higher Brix during harvest [2]. Isobutyl methoxyppyrazine, C6 alcohols, and hexyl acetate were shown to decrease in wine as Cabernet Sauvignon (_V. vinifera_) grape maturity developed [3]. The research by [PERSON] et al. [3] also demonstrated how higher sugar levels led to higher levels of volatile esters, dimethyl sulfide, and glycerol. Many studies have investigated the aroma profile of wines [4; 5; 6; 7], with only a few that are focused on cold hardy grapes _V. labrusca_[8] or hybrids of _V. vinifera_, _V. labrusca_, and _V. riparia_[9; 10]. In addition to TSS, pH and titratable acidity of the grapes is monitored before harvest. Some varieties of wine have a distinct varietal aroma, and these can be attributed to a few compounds. Examples include 2-methoxy-3-isobutyl pyrazine (a green bell pepper aroma) reported in Sauvignon blanc [11] or 4-vinylguaiacol (spicy, clove aromas) found in Gewurztraminer [12]. Some varieties such as Chardonnay or Seyval do not have characteristic aromas originating from one or two specific compounds [13; 14]. Understanding the volatile organic compounds (VOCs) that can contribute to the overall aroma profile of wine is important in making high quality, aromatic wines. Use of solid-phase microextraction (SPME) and GC-MS is common for characterization of VOCs and other compounds in wine [15; 16] and food grade alcohols [17; 18]. VOC partitioning into headspace is suppressed with increasing concentration of ethanol in wine samples; ethanol influenced matrix-VOC partitioning more than glucose levels [19], possibly affecting SPME extraction efficiency of flavor and aroma compounds. SPME is an equilibrium extraction method and if extraction conditions such as extraction temperature, agitation, sampling time can be controlled in the laboratory quantitation using SPME is possible [20]. A previously developed method, optimizing the efficiency of SPME [21], is used in this research. Aroma dilution analysis (ADA) is helpful in determining the major contributor to the aroma profile of the wine. ADA has been used to evaluate aroma character of Pinot norig grapes [7], Carmenere red wine [22], and Grenache rose wines [23]. It is difficult to dilute extracts while using SPME, so an ADA approach using successive sample dilutions of wine has been demonstrated [24]. Use of SPME in place of ADA has an advantage of speed due to eliminating sample preparation steps. Perceived aroma is not only based on its chemical concentration. Another consideration is the odor detection threshold of a compound (ODT), or the lowest concentration (mass/volume) needed for detection by a human nose [25]. It is critical to recognize that any odor threshold found is valid only at the conditions the test was run. For example, the odor compound will have a different threshold in water, air, and wine and is influenced by environmental conditions during the test. Odor activity value (OAV) is the ratio of the concentration of a compound to its odor detection threshold (ODT), and has been previously discussed [26; 27; 28; 29]. It is important to recognize that for the same compound, odor threshold and taste threshold usually have very different values.