POST-PROCESS INHIBITION OF LISTERIA MONOCYTOGENES ON READY-TO-EAT POULTRY PRODUCTS USING UV RADIATION TECHNOLOGY

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0224612
• Project Start Date: Oct 1, 2010
• Project End Date: Sep 30, 2012
• Program Code: [(N/A)]- (N/A)

Recipient Organization
AUBURN UNIVERSITY
108 M. WHITE SMITH HALL
AUBURN,AL 36849

Performing Department
Poultry Science

Non Technical Summary
Several factors affect the growth of Listeria monocytogenes (LM) in ready-to-eat (RTE) meat and poultry products including temperature, pH, water activity and microbial competition. In comparison to other pathogenic organisms, LM can grow at very low water activity. Therefore, ready-to-eat meat products could be excellent environments for this organism. The ability of LM to grow at low temperatures, low water activity, and a wide pH range, while most competing organisms cannot, allows for easy survival and proliferation of this organism on RTE products. Most cases of listeriosis are sporadic. However, recently there have been more outbreaks associated with products such as deli meats and frankfurters. Recalls are costly to the food industry because of product loss and loss of customer confidence in certain products and processors involved in the recalls. Contamination of RTE products with LM usually occurs as a result of handling of meat products following cooking and during repackaging. For example, after cooking, casings are removed from RTE meat items such as hot dogs and deli meats are sliced prior to packaging. This coupled with the long shelf life of such RTE meat and poultry products and the ability of LM to grow under refrigerated conditions makes it a pathogen of public health concern. Due to these above mentioned concerns and the potential of developing new technologies to control foodborne pathogens, in this proposal UV radiations will be evaluated to inhibit/ eliminate LM on RTE meat and poultry products. The first phase of this proposal will be to evaluate the efficacy of UV radiations to reduce populations of LM in laboratory media and meat extract and develop D-values. D-values will help in providing information about the susceptibility of this pathogen to UV radiations and set parameter (time and intensity combinations) for the second phase. In the second phase of this study, the efficacy of UV radiation to reduce LM on surfaces of RTE meat and poultry products will be evaluated. Results from this study will be used to develop future studies on the mechanism by which the bacteria are inhibited/ reduced and the impact of prior exposure of LM to other environmental stressors like low temperatures and pH on the microbicidal effects of UV radiation in addition to impact on quality parameters of poultry products.

Animal Health Component

50%

Research Effort Categories

Basic

10%

Applied

50%

Developmental

40%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
712	4099	1103	100%

Knowledge Area
712 - Protect Food from Contamination by Pathogenic Microorganisms, Parasites, and Naturally Occurring Toxins;

Subject Of Investigation
4099 - Microorganisms, general/other;

Field Of Science
1103 - Other microbiology;

Keywords

uv radiation

listeria monocytogenes

ready-to-eat meats

Goals / Objectives
The overall goal of this proposed study is to determine the efficacy of UV light against Listeria monocytogenes in food systems. In order to validate the overall goal of this study researchers hypothesize that exposure of food systems to UV light will reduce surviving populations of Listeria monocytogenes. To accomplish the overall goal of this project the specific objectives of our proposed study are: 1. Determine the D-values of Listeria Monocytogenes strains (grown at 35 and 4 C) in peptone water and meat extract. LM strains will be inoculated into laboratory media and meat extract and exposed to UV for varying times to determine 90% reduction in bacterial populations. 2. To evaluate the disinfecting efficiency of high and low intensities of UV on log and stationary phase Listeria Monocytogenes grown at two different temperatures. LM will be grown and harvested at log and stationary phases, exposed to low and high intensities by varying the distance from the UV source, and survival populations will be determined in laboratory media and meat extract. 3. Determine the efficacy of UV light against Listeria monocytogenes in Ready-To-Eat poultry products. LM inoculated RTE poultry products will be exposed to predetermined time and UV intensity combinations as optimized by objective 1 and 2; survival populations will be enumerated to evaluate efficacy in food systems. Expected Outcomes: The results from this study can show possible reductions in the survival populations of Listeria monocytogenes in laboratory media, meat extract, and on RTE poultry products. Also, results will be able to demonstrate an ideal time of exposure to UV and intensity of UV combination to attain maximum reductions of the pathogen without adversely affecting quality parameters such as oxidation and color of the products.

Project Methods
A panel of 10 UV bulbs (254nm) is hung in a metal framed box with sides made of plexi-glass covered. Listeria monocytogenes serotypes 3a, 4b and 4c will be used in this study. A loop of frozen bacterial culture will be inoculated in brain heart infusion broth for 24h and incubated at 35C. Before using the cultures for any experiment, the cultures will be grown in fresh BHI tubes for two generations. Growth curves of individual serotypes will be obtained at 35 and 4C to determine the log and stationary phase. Bacterial suspensions of each serotype will be prepared separately by centrifuging 20 mL BHI tubes with bacteria for 10 min at 5000 x g, the supernatant will be decanted. The pellet will be resuspended in peptone water (PW), centrifuged again. Bacterial count of the suspension will be enumerated by serially diluting and spread plating 1 mL of suspension. Preparation and inoculation of meat extract (ME): Ground chicken breast meat will be added to PW (1:1) and homogenized for 1 min. The final supernatant will be sterilized and collected in a sterile flask and stored at 4C. Bacterial pellet obtained as stated above will be resuspended with ME. Bacterial count will be enumerated by spread plating. Bacterial suspensions (10mL) in ME and PW at log and stationary phase grown at 35 and 4C will be placed in separate 10cm diameter sterile petri dishes for irradiation. All suspensions will be exposed to UV light of 254 nm at various intensities for 10,30,50,70,90 and 110s. Intensities will be changed by adjusting the height of the UV lamps in the chamber. After exposure for the set period; 1 mL of the exposed suspension will be serially diluted in 9 mL PW and spiral plated. Both sets will be incubated for 24h at 35C and colonies counted. Cooked grilled chicken breast (CB), fully cooked chicken sausage(CS), chicken breast breaded patties (BP) will be used for this experiment. LM 3a,4b and 4c cultures grown at stationary phase will be inoculated on the products at high and low concentration. Bacteria will be introduced on both surfaces of CB and BP. LM in BHI broth will be inoculated on one side of the sample and allowed to set for 3 min. The sample will then be over turned and the same process repeated. 0.01 mL of inoculum will be spread on the surface of CS. After inoculation, samples will be transferred to whirlpak bags and sealed. CB and BP will be placed in the freezer and sausages in refrigerator. For the high concentration of bacteria, samples will be directly inoculated with stationary phase cells. Lower concentrations of bacteria will be made by serially diluting the stationary phase culture. After 12h under storage conditions, samples will be exposed to UV at high and low intensities for 30,60,90,120,150, and 180s. Midway through each exposure time, the product will be overturned to ascertain that the product gets subjected to UV evenly. After UV exposure, individual sample will be placed aseptically into a whirlpak bag and a 1:9 dilution will be pulsified for 1 min. Serial dilutions using peptone water will be spread-plated on MOX. Colonies will be counted after an incubation period of 35 C for 24 h and reported as log CFU/ g of product.

Progress 10/01/10 to 09/30/12

Outputs
OUTPUTS: With the growing negative public reaction over chemicals added to foods, and the flavor and quality deteriorating in both thermal and non-thermal processing, UV light in food processing maybe a promising application for the food industry. As a physical preservation method, UV irradiation has a positive consumer image. The US Food and Drug Administration (FDA) and US Department of Agriculture (USDA) have concluded that the use of UV irradiation is safe. And in 2000, the FDA approved UV-light as alternative treatment to thermal pasteurization of fresh juice products with a performance criterion of 5-log10 reduction in the number of target pathogen (FDA, 2000). The germicidal effects of UV radiation have been known since the 1800s. It is an established technology for water treatment, air disinfection and surface decontamination. Though, the germicidal use of UV in food is restricted due to the fact that UV acts only on transparent liquids literatures shows that UV can be used on the surface of food. This demonstrates that UV light has the potential to reduce bacterial contamination on food surfaces and therefore has the potential to be used as post lethality treatment to control L. monocytogenes and other pathogens of concern. PARTICIPANTS: 1. deepika Suresh a MS student has worked on this project. 2. Dr. Manpreet Singh (Co-PI) has worked on this project. TARGET AUDIENCES: The target audiences are poultry and meat processing plants. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
1. Populations of L. monocytogenes were significantly reduced (p<0.05) after 10 and 30 s of exposure and further significant (p<0.05) reductions were observed at 50, 70, 90, and 110 s when compared to the 10 and 30 s exposure times irrespective of the growth phase and UV light intensities. Irrespective of the UV light intensity and exposure times, significantly higher (p<0.05) reductions were observed in the log phase cells as compared to the stationary phase cells. 2. On bologna, 150 s of UV exposure resulted in significant reductions (p<0.05) irrespective of the intensities. Moreover, irrespective of temperature, intensity, and exposure times, significantly higher (p<0.05) reductions were observed in the log phase cells as compared to the stationary phase cells in the laboratory media as well as on bologna. 3. Higher (p<0.05) reductions were observed in the log phase as compared to the stationary phase cells. Significant differences (p<0.05) were observed in the L, a, b values at different storage temperature and exposure time over 8 weeks of storage. However, UV did not affect the lipid oxidation of bologna irrespective of the storage temperatures and time.

Publications

• Abstracts have been submitted to the International Poultry Expo and the International Association for Food Protection 2013 annual meetings.

Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: Activities: Experiments have been performed in the last year to gain knowledge about the behavior of Listeria monocytogenes strains when exposed to UV radiation. Studies have been completed to determine growth behaviors of Listeria monocytogenes at various incubation temperatures and their resistance development to UV radiation. PARTICIPANTS: 1. Deepika Suresh - Graduate Student (MS) has been working on this project for the past year and conducting experiment and making adequate progress. She has submitted an abstract to present at the international association of food protection meeting. 2. Michelle Hayden - Research Associate has been assisting Deepika in conducting the experiments. 3. Manpreet Singh (Co-PI) - Designing experiments and providing guidance to the graduate student on analytical procedires of the experiments. 4. Donald E. Conner (PI) - Developed protocols for UV radiation exposures and growth models for L. monocytogenes strains. Training: Graduate student and research associate are being trained to conduct experiments independently and working with L. monocytogenes cultures. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
To date based on the experiments that have been conducted in the past year have suggested that Listeria monocytogenes has shown to adapt well to colder (4C) environments however, with a much slower growth rate as compared to the 37C. Initial experiments on exposing L. monocytogenes to UV radiation during the loag and stationary phase of growth show difference in their susceptibities. The bacteria a very sensitive to UV radiation while in their log phase as compared to stationary phase.

Publications

• No publications reported this period