A Bacterial Analysis of Irradiated and Non-Irradiated MeatMegan Markland

Department of Biological Sciences York College, PA

Introduction

Hypotheses

H1: The amount of bacteria will be significantly lower in irradiated beef compared to non-irradiated beef.

H2: Bacteria such as Salmonella,and E.coliwill only be found in non-irradiated meat.

Bought ground beef samples from local grocery stores

Performed 10 fold serial dilutions

Plated samples on R2A agar and incubated at 37°C for 48 hours

Performed standard plate counts

Cultured bacteria and performed EMB streak plate

Results

Methods

10 Irradiated samples

10 Non-irradiated samples

Non-irradiated

(CFU/gram)

Irradiated

(CFU/gram)

2.4×103 -

2.2×104 -

1.6×105 -

6.5×104 -

2.1×103 -

5.2×104 -

2.4×104 -

2.2×105 -

1.7×104 -

1.3×103 -

Table 1. Number of colony forming units in irradiated and non-irradiated beef samples.

Heterotrophic Plate Count

(Non-irradiated)

Heterotrophic Plate Count

(Irradiated)

•Food-borne diseases are of major concern in the health field.

•Each year 1 in 6 Americans gets sick from a food-borne illness (CDC 2011).

•Irradiation is a safe and effective treatment of food. High energy such as gamma rays or electron beams are used to destroy living bacteria and lead to the reduction of food-borne illnesses (CDC 2011).

•Successful irradiation treatment of raw meat eliminates pathogenic bacteria commonly found such as E.coli,Salmonella and Campylobacter(CDC 2011).

•In order topredict the bacteriological safety of chilled meats, accurate numbers and types of pathogenic bacteria must be obtained (Prendergast et al 2009).

•Most studies of irradiated vs. non-irradiated beef are done at slaughterhouses. This study focuses on bacteriological safety of chilled meats once it has reached the consumer.

•By comparing initial amounts of bacteria in irradiated and non-irradiated ground beef, the effectiveness of irradiation will be observed.

•This study was performed to determine whether irradiated ground beef is safer than non-irradiated ground beef from a bacteriological standpoint.

Research Questions

•Will there be a significant difference in the amount of bacteria between irradiated and non-irradiated ground beef?

•What types of bacteria will be present on either types of meat?

•Is it safer to buy irradiated or non-irradiated meat? EMB plate E.coli EMB plate Salmonella

http://www.midlandstech.edu/science/kelleherk/225/labmaterials/sel_diff_media.html

Conclusions

•The amount of bacteria was unequivocally greater in non-irradiated ground beef.

•The absence of CFU’s from irradiated ground beef shows that irradiation was successful in eliminating bacteria.

• Both Salmonella and E.coli were only found in non-irradiated meat.

•According to the Guidelines for Microbiological Quality of Ready to Eat Foods (Gilbert et al 2010), 3 of the 10 non-irradiated samples were rated acceptable. The remaining 7 samples were rated unsatisfactory.

•All 10 irradiated samples were rated satisfactory.

•In terms of bacteriological safety, irradiated meat is safer to consume than non-irradiated meat.

Bacteria Present Non-Irradiated IrradiatedE.coli 50% -

Salmonella 20% -

Table 2. Percentage of E.coli and Salmonella found in both Irradiated and non-irradiated samples.

http://www.extension.iastate.edu/foodsafety/irradiation/index.cfm?articleID=21&parent=3

http://people.uwec.edu/FLEHMEKA/trendstory.html

Literature CitedPrendergast D. Crowley K., McDowell D., Sheridan J. Survival of Escherichia coli O157:H7 and non-pathogenic E. coli on irradiated and non-irradiated beef surfaces (2009) Meat Science, 83 (3), 468-473.

Gilbert, R. J., De Louvois, J., Donovan, T., Little, C., Nye, K., Ribeiro, C. D., Richards, J.(2000). Guidelines for the microbiological quality of some ready-to-eat foods sampled at the point of sale. PHLS Advisory Committee for Food and Dairy Products. Communicabledisease and public health PHLS, 3(3), 163-167. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/11014026

Centers for Disease Control and Prevention. (2012). Estimates of foodborne illness in the United States. Retrieved from http://www.cdc.gov/foodborneburden/