Date of Graduation

12-2022

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Threlfall, Renee T.

Committee Member

Acuff, Jennifer C.

Second Committee Member

McWhirt, Amanda L.

Keywords

Enology; Fermentation; Fruit; Grapes; Wine

Abstract

Grapevines (Vitis species) are grown worldwide to produce table grapes, juice grapes, dried grapes, and wine with the United States as one of the world’s largest wine and grape producers. Though not a large contributor to the U.S. grape and wine industry, Arkansas’ industry plays an important role in the state’s agritourism and economy. Most grapes grown in Arkansas’ warm climate include native species, such as muscadines (V. rotundifolia) and hybrids (crosses of Vitis species). Two important hybrid red wine grapes grown in Arkansas are Chambourcin, grown commercially for its positive viticulture and enological quality, and Enchantment, a newer cultivar with potential in this region. Since acidity of grapes is impacted by the climate of the region, there is interest in using non-Saccharomyces yeast, such as Lachancea thermotolerans, for wine production to modify acidity and other wine attributes. Additionally, quality of grapes and wines produced in Arkansas impact consumer awareness, perception of and advancement of the local industry. Thus, the objectives of this research were to evaluate the use of non-Saccharomyces yeasts to modify acidity in wine fermentations from grapes grown in Arkansas and investigate the impact of the Arkansas Quality Wine Program on perception and quality of Arkansas wines and the Arkansas grape and wine industry. In 2020 and 2021, Arkansas grown Chambourcin and Enchantment grapes were harvested and fermented using S. cerevisiae (SC) without and with malolactic cofermentation (SC-MLF) and L. thermotolerans with a sequential inoculation of S. cerevisiae (LT-SC) without and with malolactic cofermentation (LT-SC-MLF). For Enchantment fermentations in 2021, two treatments (SC and LT-SC) were evaluated due to limited fruit. Evaluations of inoculation treatments were done on must/wine during fermentation, wine at bottling, and wine during storage. Treatments with L. thermotolerans impacted lactic acid levels of both varieties during fermentation but had a greater impact on organic acids and pH of Chambourcin than Enchantment, thus increasing potential for improved microbial and color stability. L. thermotolerans also had a greater impact on color attributes of Chambourcin wines from both years, compared to Enchantment wines. The 2020 Chambourcin wines were evaluated by sensory panels, which rated LT-SC and LT-SC-MLF wines higher than the other inoculation treatments for sourness. Although wines inoculated with L. thermotolerans were more sour, commercial wines can be adjusted at bottling to mediate sourness to increase consumer acceptability. In 2021 and 2022, an online consumer wine survey from the Arkansas Quality Wine Program (AQW) showed that consumers wanted to purchase Arkansas-made wines but were inhibited by a perceived lack of quality and desirability. An AQW wine competition was held in 2020 and 2021 with a total of 75 wines entered. Most wines submitted received high marks for gold, silver or bronze medal earnings. Competition wines with appropriate free and total sulfur dioxide levels, and lower volatile acidity, dissolved oxygen, and ethanol levels garnered higher medal earnings. Select medal-earning wines from the 2021 AQW competition were analyzed by a consumer sensory panel and for composition and color attributes. Wines that were semi-sweet to sweet were the most preferred despite higher volatile acidity levels. Through public outreach efforts in the form of virtual workshops for winemakers and wine education and tasting events, the AQW program reached nearly 1,000 individuals, both industry and non-industry from 2020 to 2022. Thus, efforts by Arkansas grape and wine producers to utilize new enological products, manage specific quality parameters in wines, and use targeted marketing strategies can increase consumer awareness of and quality of wines produced in Arkansas.

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