Semester of Graduation

Fall 2021

Degree

Master of Science (MS)

Department

Nutrition and Food Science

Document Type

Thesis

Abstract

Listeria monocytogenes is one of the main foodborne pathogens found in cantaloupes causing a severe infection called Listeriosis that in many cases can be fatal. Turmeric extract is a potential antimicrobial agent in reducing the pathogenicity of microorganisms through its mechanisms of action that inhibit them. Therefore, this study aimed to determine antilisterial and antimicrobial activity of the turmeric extracts against Listeria innocua NRRLB-33016 on the cantaloupe surface (Cucumis melo variety “Hale best”). A pulsed ultrasonic-assisted method was used to obtain turmeric extract. A total of three concentrations of turmeric extract (TR1 5.5 mg/mL, TR2 3 mg/mL, TR3 2 mg/mL) were selected for this study. Three controls were employed, water (W), L. innocua (C), and uninoculated-untreated (U).

The antimicrobial effect of mixtures against L. innocua on the surface of cantaloupes stored for 12 days at a temperature of 4°C was evaluated. Cantaloupes were grown and harvested at the Louisiana State University AgCenter Botanic Gardens. Then transported to the Food Engineering Laboratory at the LSU Wilson building.

All cantaloupes were marked on the surface with three circumferences containing 20 cm² each. The designated area was inoculated by spreading on the surface of the cantaloupe 100 µL of Listeria inoculum resulting in 5.24 log CFU of L. innocua per cm2. Cantaloupes were individually dipped for 10 min in 250 mL of treatments TR1, TR2, TR3, or distilled water (W). Listeria innocua, aerobic bacteria, yeast, and mold were enumerated on days 1,3,6,9, and 12. Texture and color of cantaloupes were analyzed on the same days. The total phenol content, pH, density, and color were determined on day 1 for the turmeric extract mixtures used in the treatments. Data from experiments were statistically analyzed (p≤0.05).

The application of TR1, TR2, and TR3 treatments on day one significantly reduced L. innocua on the cantaloupes by 1.20, 0.83, and 0.66 logs CFU/cm2, respectively. Turmeric extract applications significantly reduced aerobic bacteria and yeast and mold with a maximum reduction of 1.05 and 1.17 log CFU/cm2, respectively. For texture and color, values within the same treatment across storage times were not significantly different.

This study demonstrated that turmeric extract could reduce L. innocua, aerobic bacteria, and yeast and mold count on the surface of cantaloupes. Our results indicate that 5.5 mg/mL turmeric extract was the most effective antimicrobial treatment tested on whole cantaloupe surfaces and did not affect the texture or color of this fruit.

Committee Chair

Sathivel, Subramanian

Available for download on Friday, November 17, 2028

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