Semester of Graduation

Spring

Degree

Master of Science (MS)

Department

School of Nutrition and Food Science

Document Type

Thesis

Abstract

Cantaloupe ranks among the most widely consumed fruits in the United States. Frequently, cantaloupes are treated with chemical antimicrobials during the manufacturing process. We evaluated the possibility of replacing it with natural compounds such as curcumin. Curcumin possesses antimicrobial properties, but its direct application is limited due to chemical instability. Oil in water nanoemulsion effectively incorporates curcumin, facilitating its antimicrobial use. The study aimed to evaluate the efficacy of nanoemulsions containing CUR (Cur-NE) in reducing pathogenic loads. Two nanoemulsions, 1CUR and 2CUR, were produced by mixing 0.05 g and 0.10 g CUR separately (w/w) with medium-chain-triglycerides oil (3%), polysorbate 80 (2%), and polyethylene-glycol (10%). The optimum levels of polysorbate 80, and polyethylene-glycol for the Cur-NE were determined by the spread plate method. The Cur-NE were produced by agitating at 800 rpm for 30-minutes, homogenizing at 18,000 rpm for 5 minutes using a high-pressure homogenizer and applying a 15-minute ultrasound treatment (175W). The viscosity and droplet size (DS) of the Cur-NE were assessed. The antibacterial effects of Cur-NEs were assessed using Listeria innocua B-33016 and Escherichia coli ATCC25922. In each experiment, 50µL of the bacteria inoculum separately was applied to a 4 cm2 area of fresh-cut-cantaloupe, and 5 mL of each Cur-NE was separately applied by immersion to the inoculated cantaloupe surface. Controls included untreated uninoculated cantaloupes (Control-1), inoculated untreated (Control-2), and cantaloupes treated with distilled water (Control-3). The cantaloupes were refrigerated and subsequently sampled on days 1, 3, 6, 9, and 12 to assess L. innocua and E. coli counts. The rind surface was analyzed using Scanning electron microscopy (SEM). The viscosity of 1CUR and 2CUR was 0.0030±0.0001Pa·s and 0.0027±0.0006Pa·s, and droplet size of 122.47 ± 3.06 nm and 137.67 ± 1.36 nm, respectively. Notably, on day 6, 2CUR showed significantly lower (p2 values (2.50±1.00 log CFU/cm2) for L.innocua than controls, while no significant differences were observed in log CFU/cm2 values between Control-1 and 1CUR-treated samples. For E. coli, 2CUR demonstrated significantly lower (p2 values on day 6 (1.55±0.40 log CFU/cm2), day 9 (1.91±0.36 log CFU/cm2), and day 12 (0.72±0.26 log CFU/cm2) than controls. In contrast, 1CUR showed significantly lower (p2 values only on day 6 (1.25±0.51 log CFU/cm2) compared to Control-2 and Control-3. SEM at days 6, 9, and 12 showed markedly reduced surrogate load on 1CUR and 2CUR treated samples than controls. These findings demonstrate the effectiveness of the developed low-concentration Cur-NE, particularly 2CUR, in significantly reducing L.innocua and E. coli on cantaloupe surface.

Date

4-4-2024

Committee Chair

Subramaniam, Sathivel

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