Date of Graduation

5-2022

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Renee Threlfall

Committee Member

Luke Howard

Second Committee Member

Amanda McWhirt

Keywords

blackberry, postharvest, robotic, sensory, volatiles

Abstract

Fresh-market blackberries (Rubus subgenus Rubus) are sold worldwide and have attributes that appeal to consumers. The delicate-nature of the fruit requires hand harvesting, and minimal handling of the fruit postharvest. Objectives of this research on Arkansas fresh-market blackberries was to 1) identify the unique attributes 2) determine the best handling practices to increase postharvest quality, and 3) evaluate the potential of soft robotic gripper for harvesting. For the first objective, blackberry genotypes were harvested from the University of Arkansas System (UA System) Division of Agriculture Fruit Research Station in Clarksville, AR. Nineteen genotypes were harvested in 2020, eight genotypes were harvested in 2021. Physical and compositional attributes, and volatiles were evaluated and descriptive sensory attributes of six genotypes each year were evaluated. For both years, berries were 6-15 g, 24-44 mm long, 21-26 mm wide, 2-13 N firm, 9-15% soluble solids, 3.0-4.2 pH, 0.4-1.4% titratable acidity, and 8.2-32.2 soluble solids/titratable acidity ratio. ‘Sweet-Ark® Ponca’ had highest soluble solids in both years (14-15%). There were 159 volatile aroma compounds identified in Arkansas blackberry genotypes in 2020 and 103 in 2021, mainly monoterpenes, esters, aldehydes, and alcohols. In both years, five impactful volatiles, ethyl butanoate (fruity), linalool (floral), ethyl 2-methylbutanoate (fruity), 2-hexenal (green), and geraniol (sweet) were identified. For descriptive sensory attributes in 2020, the genotypes differed in fruity aroma, green/unripe aromatics, and sour basic tastes. In 2021, the genotypes differed in overall intensity of aromatics and basic tastes. For objective 2 in 2020 and 2021, cultivar, harvest method, and acclimation temperature were examined to increase postharvest quality. Physical and composition attributes were evaluated at harvest and marketability attributes were evaluated after postharvest storage for 21 days at 2 °C on four cultivars harvested using two harvest methods and two acclimation treatments. For both years berries were within commercially acceptable ranges. Cultivar impacted marketability attributes. Overall, there were no clear trends on marketability degradation of the blackberries. For objective 2 in 2020 and 2021, evaluations were done to develop a prototype of a soft-robotic gripper to harvest fresh-market blackberries. In 2020, a custom-made force sensing apparatus (sensors) was developed to determine the force (N) to harvest. Then in 2021, this data was used to create a soft robotic gripper prototype (gripper) for harvesting blackberries. In both years, physical and compositional attributes were evaluated at harvest, and marketability attributes were evaluated after postharvest storage for 21 days at 2 °C of four Arkansas-grown cultivars. The force used by the thumb and middle finger (0.77 N and 0.37 N, respectively) were greatest for harvesting blackberries. A prototype of a 3-prong soft robotic gripper was designed using results from the force sensing apparatus. The forces applied to grab, stabilize, and harvest blackberries with the sensors or gripper did not cause excessive marketability damage to the blackberries at harvest or after 21 days at 2 °C postharvest storage. This project identified unique flavor attributes, determined the best handling practices to increase postharvest quality, and evaluated the potential for a soft robotic gripper for harvesting.

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