Raw produce has frequently been identified as the source of bacterial pathogens that can cause human illnesses, including listeriosis and salmonellosis. Microbial pathogens may attach and form biofilms on raw fruit surfaces and can be difficult to remove. A cavitation process (formation of bubbles in water) was studied for its effectiveness for removal and inactivation of Listeria monocytogenes and Salmonella Newport from the surfaces of fresh Roma tomatoes and cantaloupes.
Individual fruit were separately inoculated with each pathogen, then submerged in a water tank and treated with a bubble flow through an air stone using one airflow rate (0 – 14 liters/min.) for up to 60 sec. As air flow increased, pathogen reduction increased up to 1.2 log CFU/fruit greater than with water alone (no bubbles). Additional pathogen reduction in the tank water (organisms detached from the fruit) was observed with the bubble treatments. Therefore, these bubble streams can be used to enhance the detachment of bacteria from fruit surfaces and to inactivate a proportion of these detached microorganisms.
Additionally, recoveries of Salmonella from inoculated Roma tomatoes and cantaloupe were determined for treatment water that contained 50 or 150 ppm sodium hypochlorite. The combination of cavitation and chlorine resulted in greater efficacy of inactivating the pathogen in treatment water, but not in removing this organism from the fruit surfaces. The physical force of a bubble stream on raw produce can effectively reduce and inactivate surface bacteria, and has the potential to reduce antimicrobial chemical and water use in post-harvest packing operations. / Master of Science in Life Sciences / Every year, one in six Americans will have been affected by a foodborne illness, many of which are caused by bacteria found on the surface of fresh fruits and vegetables. Most of these bacteria are removed with the help of a water wash with or without chlorine added. Nevertheless, microorganisms, including bacterial pathogens, may attach and form biofilms on raw fruit surfaces and can be difficult to remove. For this research, a cavitation process (formation of bubbles in water) was studied for its effectiveness for removal and inactivation of <i>Listeria monocytogenes</i> and <i>Salmonella</i> Newport from the surfaces of fresh Roma tomatoes and cantaloupes.
Individual fruit were separately spiked with each pathogen, then submerged in a water tank and treated with a bubble flow through an air stone using one airflow rate (up to 14 liters air per minute) for 30 or 60 seconds. As air flow increased, the number of bacteria was reduced by up to 94% more bacteria per fruit than when using water alone (no bubbles). Additional bacteria reduction in the tank water (organisms detached from the fruit) was observed with the bubble treatments. Therefore, these bubble streams can be used to enhance the detachment of bacteria from fruit surfaces and to kill or injure some of these detached microorganisms.
Additionally, recoveries of <i>Salmonella</i> from inoculated Roma tomatoes and cantaloupe were determined for treatment water that contained 50 or 150 parts per million sodium hypochlorite (chlorine solution). The combination of cavitation bubbles and chlorine showed a greater ability for inactivating these bacteria in the tank water, but not in removing this organism from the fruit surfaces. The physical force of a bubble stream on raw produce can effectively reduce and inactivate surface bacteria, and this process could reduce the amount of water or chemicals used to process fresh fruits and vegetables, while ensuring that these foods will not cause people to get sick upon eating.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/74995 |
| Date | 10 February 2017 |
| Creators | Lee, Joshua Jungho |
| Contributors | Food Science and Technology, Eifert, Joseph D., Strawn, Laura K., Jung, Sunghwan |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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