Date of Graduation

8-2022

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Renee T. Threlfall

Committee Member

Amanda L. McWhirt

Second Committee Member

Ya-Jane Wang

Keywords

Food Science, Gas Chromatography, Horticulture, Volatile

Abstract

Arkansas has a climate and geography that allows for the production of unique horticultural crops, including hops (Humulus lupulus L.), blackberries (Rubus subgenus Rubus), and muscadine grapes (Vitis rotundifolia). These crops not only have potential for growers in Arkansas but have unique flavor and aroma attributes that impact marketability. Volatile compounds present in many different agricultural plants are the primary source of biologically-derived aromas and flavors. Therefore, the volatile and other quality attributes of hops, blackberries, and muscadine grapes were evaluated at the University of Arkansas (UA System) Division of Agriculture. The quality, volatile, and sensory attributes of four hops cultivars (Cascade, Cashmere, Crystal, and Zeus) grown at the UA System Division of Agriculture Fruit Research Station in Clarksville, AR were evaluated in 2020 and 2021. In general, cultivar impacted individual and total alpha and beta acids levels with total alpha and beta levels as follows; ‘Cascade’ (6.0-9.2% and 5.7-9.1%, respectively), ‘Cashmere’ (4.9-6.9% and 5.5-8.5%. respectively), ‘Crystal’ (2.9-3.6% and 7.5-10.1%, respectively), and ‘Zeus’ (4.6-5.7% and 4.1-4.8%, respectively). In both 2020 and 2021, ‘Crystal’ had the highest volatile concentration (6,278 and 8,106 µg/kg, respectively) followed by ‘Cashmere’ (6,668 and 5,434 µg/kg, respectively) and ‘Cascade’ (5,829 and 4,132 µg/kg, respectively) with ‘Zeus’ (3,230 and 2,072 µg/kg, respectively) containing the lowest concentration. In both years, the five volatile aroma compounds with the highest levels found in Arkansas-grown hops were beta-pinene (monoterpene with herbal and pine aromas), beta-myrcene (spicy monoterpene), caryophyllene (sesquiterpene with woody aromas), beta-Selinene (herbal sesquiterpene with celery notes), and humulene (spicy/woody sesquiterpene). In both years, the descriptive sensory panelists (n=5-7) could differentiate between cultivars for aged cheese, overall citrus complex, lemon, overall green herb complex, and overall pepper complex with overall impact as the highest rated attribute (5-7 on a 15-point scale). Since blackberry quality can vary during a harvest season, blackberries grown at the UA System Fruit Research Station were harvested on three harvest dates (early, middle, late) in 2020 (four cultivars) and 2021 (three cultivars). In general, cultivars differed for berry weight (5-13 g), soluble solids (9-13%), pH (3.3-4.2), titratable acidity (0.4-1.0%), and solids/titratable acidity ratio (9.8-31.0), but harvest date impact varied by cultivar and year. ‘Sweet-Ark® Ponca’ late harvest date in 2021 had the lowest concentration of volatile compounds (1,370 µg/kg), and ‘Sweet-Ark Ponca’ middle harvest date in 2020 had the highest (4,693 µg/kg). In 2021, six seeded and ten seeded and seedless muscadines genotypes (cultivars and breeding selections) were harvested in Arkansas and North Carolina, respectively. Muscadine grape soluble solids ranged from 14-19 %, pH ranged from 3.0-3.9, titratable acidity ranged from 0.25-1.14 %, soluble solids/titratable acidity ratio ranged from 16-70. Volatile compound levels (2,151-5,746 µg/kg) were impacted by genotype, and in the 16 cultivars harvested in both locations, there were 181-198 volatile aroma compounds identified across nine compound classes including 52 esters, 38 monoterpenes, 31 sesquiterpenes, 29 alcohols, 27 aldehydes, 16 ketones, four lactones, two aromatic hydrocarbons, and two epoxides. The three muscadine genotypes with the highest concentrations of volatiles were AM-154 (5,745 µg/kg), ‘Lane’ (5,285 µg/kg), and ‘Hall’ (5,107 µg/kg), while the three muscadine genotypes with the lowest concentration of volatiles were AM-77 (2,151 µg/kg), JB 06-30-2-20 (2,367 µg/kg), and AM-148 (2,468 µg/kg). Data generated from this project provided information on volatile and other quality attributes of hops, blackberries, and muscadine grapes that can be used to support the future growth of these industries.

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