Degree

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

Document Type

Dissertation

Abstract

The overall goal of this study was to design and build an experimental refrigerated chamber-type spray chilling system to evaluate its spray characteristics, and the effectiveness of spray chilled peroxyacetic acid (PAA) in reducing bacteria on cantaloupe rind surfaces during refrigerated storage. The first part of this study focused on designing and building an experimental refrigerated chamber-type spray chilling system. The system consists of the following components: air compressor, air pressure regulator, gas rotameter, refrigerated circulating bath, copper coil (heat exchanger), inline dial thermometer, peristaltic pump equipped with a digital modular drive control, a refrigerated chamber fitted with an electronic temperature controller, and a two-fluid type nozzle. The refrigerated circulating bath with a programmable controller integrated with the spray system was used to maintain the ethylene glycol-water bath for producing the desired air temperature (4°C). An electronic temperature controller for the refrigerated chamber was designed. A Love 16C series microprocessor temperature controller was used to keep the temperature inside the chamber at the setpoint temperature (4°C) within +0.5°C. Phase-Doppler Particle Anemometry, a light-scattering technique, was used to measure the spray droplets' diameter and velocity. The two-fluid type atomizer in the spray chilling system produced an average droplet size and droplet velocity at 170 mm downstream along the centerline of 10.97±0.47 µm and 9.73±0.05 m/s, respectively. In the second part of the study, chilled PAA and chilled water produced by the spray chilling system were evaluated for effectiveness on the surrogates Listeria innocua NRRL B-33016 and Escherichia coli ATCC 25922 loads on the surface of cantaloupes under laboratory and field conditions. In addition, cantaloupes were evaluated for the effect of chilled PAA and chilled water on the quality of the cantaloupes during refrigerated storage. Chilled PAA reduced L. innocua under laboratory and field conditions, respectively. Chilled PAA reduced E. coli significantly (P ≤ 0.05) higher than chilled water during the refrigerated storage. Both chilled PAA and chilled water maintained the cantaloupe quality during storage. The study demonstrated that spray chilled PAA (4°C) could reduce pathogenic bacteria (Listeria and E. coli) on cantaloupe rind surfaces while maintaining the quality of cantaloupes.

Date

7-5-2022

Committee Chair

Sathivel, Subramaniam

Available for download on Wednesday, June 27, 2029

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