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As the Pennsylvania wine industry continues to expand, a need for wine grape varieties capable of growing in the tough Northeastern United States climate, while producing consistent quality-driven wines is increasing. The Northeastern United States has always been a difficult place for European Vitis vinifera grape varieties to thrive, due to hotter and wetter conditions during the growing season. These conditions drive up fungal and disease pressure such as powdery mildew, downy mildew, and black rot, which V. vinifera has no natural immunity to. Additionally, the extreme cold during the winter season, makes the survival of V. vinifera varieties difficult, as they evolved around a Mediterranean climate. A potential aid to the Eastern United States wine industry has been the development of interspecific hybrid (Vitis ssp.) grape varietals, which are typically a cross of V. vinifera and non-Labrusca American varieties. These varieties have intended to capture the aromatic and flavor complexity and intensity characteristic of V. vinifera wines while retaining the cold tolerance, disease, and pest resistance found in American varieties. While these varieties have shown greater adaptation to the growing conditions of the Eastern United States, they have still lacked the phenolic development important to the perception of wine flavor and body as well as the aromatic intensity and complexity found in V. vinifera wines. With their lack of international renown, hybrid grapes have not gained full consumer acceptance and recognition. This study looked at adapting pre-fermentation novel maceration techniques to two white interspecific hybrids (V. ssp.), Cayuga, and Traminette, which are prevalent throughout the Eastern United States wine-growing regions. While pre-fermentation maceration techniques have been studied in white V. vinifera varieties previously, their mechanistic effects on interspecific hybrid (V. ssp.) white wine quality has not been thoroughly evaluated. Interspecific hybrid (V. ssp.) white wines have traditionally lacked aromatic and flavor complexity and intensity, while also being lower in phenolic content contributing to mouthfeel and a wine’s ability to age. Previous studies on V. vinifera white varieties have reported significant beneficial effects on phenolic content, antioxidative activity, and desirable sensory attributes of finished wines from cryogenic maceration and cold soak techniques. This study looked at three different novel maceration techniques: rapid cryogenic, slow cryogenic, and cold soak. Rapid and slow cryogenic macerations in the initial study resulted in significant increases in total phenolic content as measured by Folin-Ciocalteu analysis, as well as a significant increase in antioxidant activity as measured by DPPH radical scavenging assay. Significant increases in browning at A420 and CIE-Lab tristimulus color parameters were observed in rapid and slow cryogenic juices. However, these changes were not carried over into the finished wines, although slow cryogenic maceration did produce a slightly more yellow and darker wine compared to rapid cryogenic maceration and the control. Both freezing rates significantly increased concentrations of gallic acid, catechin, and epicatechin in finished wines compared to the control wines. Aroma profiling by HS-SPME-GC/MS analysis revealed significant increases in the concentration of terpenes and esters in the cryogenic wines compared to the control. However, the types and amounts of aroma compounds enhanced by either freezing rate were dependent on variety. The second year of the study compared rapid cryogenic maceration using dry ice to a 6 hour cold soak. All processing was conducted in a strict anaerobic environment inside of single-use pharmaceutical fermentation bags. Significant increases in total phenolic content as measured by Folin-Ciocalteu analysis, as well as a significant increase in antioxidant activity as measured by DPPH radical scavenging assay, were observed in the cryogenic wines of both varieties compared to control wines. Additionally, increases were observed in both parameters for cold soak treatment. No significant differences were observed in either variety across treatments in terms of browning at A420 and CIE-Lab tristimulus color analysis. Analysis of gallic acid, catechin, and epicatechin by reverse-phase HPLC showed a significant increase in all three phenolics in both treatments compared to the control wines. Aroma analysis by HS-SPME-GC/MS showed significant increases in terpenes of the cryogenically treated wine compared to the control. Cold soak showed significant increases in esters in both varieties compared to control. Sensory analysis for Cayuga and Traminette wines showed significant differences in certain aroma and flavor references, taste references, visual and mouthfeel references. The cryogenic maceration treatment’s ability to increase phenolic content and antioxidative content, while enhancing aromatic components compared to control wines, supports the technique’s feasibility to potentially produce more stable and quality-driven white hybrid wines. Cold soak results also show the potential to achieve similar results to the cryogenic treatments utilizing a procedure that causes less cellular disruption and is less time-consuming. Cold soak may be a more variety-specific technique and also not exhibit the same magnitude in changes that cryogenic maceration achieves. In terms of applicability and feasibility to small scale wineries, as well as increases in quality and oxidative stability, using rapid cryogenic maceration with dry ice compared to liquid nitrogen or slow freezing may be the most viable option for implementing this technique.
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|Author:||Mc Caney C 2020|
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