## 4 Discussion and Conclusions
Similar VOCs detected were (from Table 2) compound numbers **12**, **16**, **19**, **21**, **22**, **24**, **27**, **37**, **39**, **44**, **46**, **49**, and **50**. The optimized headspace SPME method yielded more compounds detected when compared to PDMS stir bar coated sample preparation method. In a previous study of commercial Frontenac wines, using a trained panel, aroma descriptors of the most impactful characters were black currant, cherry, and cooked vegetable [37]. These aromas correspond to methoxymethylbutanethiol or mercaptomethylpentanone (black currant) [35], and acrolein, butylrophenore, or cyclohexyl cinnamate (cherry) [38]. Other significant aromas in the sensory study included black berry, jammy, cooked vegetable, fresh green, cedar, floral, geranium, tamari, and earthy [37]. There is no consensus on the mechanism for explaining olfactory perception. Mixtures of odorants, even at concentrations below the detection thresholds, act in a synergistic manner [39]. This might be the key to understanding wine aroma, where hundreds of compounds are present. A limitation to this study is the small sample size. Only one five-gallon vinicitation could be completed per treatment (22\({}^{\circ}\) Brix and 24\({}^{\circ}\) Brix) because only 12 vines were available. PCA analysis, in this study, only accounted for 48% of the variance between vinicitations and is more reflective of the analytical method. More replications, repeated over several years would yield more data to draw direct conclusions about the aroma of Frontenac and Marquette wines. The olfactometry portions of this study allows for a single panelist at a time. The use of more panelists, \(n>10\), could help account for variation within wine consumers due to age, sex, recognition and detection thresholds, etc. This research adds to the growing body of knowledge about lesser-known wines from cold-hardy grapes grown in Midwest U.S. states. More research is needed to understand the aroma potential of these new cold-hardy grapes to produce quality wines that can stand on the same stage as traditional Old World wines. New cold-hardy grape cultivars that are complex hybrids of _Vitis vinifera_ and native _Vitis riparia_ have created a cold climate wine industry in North America. Frontenac and Marquette are vigorous, disease resistant and can grow sustainably in regions with low winter temperatures [30]. While there is significant information available for the aroma of _V. vinifera_ wines, very little is known about the aroma profile of wines from cold-hardy grapes. Research is warranted to identify potential signature aromas in these new hybrid varieties as this information can advance viticultural practices, improve marketing and bolster the local economies of cold climate vineyards and wineries. The following are available online at [[http://www.mdpi.com/2297-8739/5/1/20/s1](http://www.mdpi.com/2297-8739/5/1/20/s1)]([http://www.mdpi.com/2297-8739/5/1/20/s1](http://www.mdpi.com/2297-8739/5/1/20/s1)). This study was funded by the USDA's Specialty Crops Research Initiative Program of the National Institute for Food and Agriculture, Project #2011-5118130850. [PERSON] and [PERSON] conceived and designed the experiments; [PERSON] and [PERSON] performed the experiments; [PERSON] analyzed the data; [PERSON], [PERSON] and [PERSON] contributed reagents/materials/analysis tools; and [PERSON], [PERSON], [PERSON], and [PERSON] wrote the paper. The authors declare no conflict of interest. The funding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.