Electron Beam - The Ultimate Solution for Food Safety

NON-TECHNICAL SUMMARY: Food safety is assured by heat processing. However, heat exacerbates food quality. The food industry seeks non-thermal food safety technologies. Ionizing energy non-thermally inactivates food-borne pathogens. The latest research proves a definite change in consumer attitudes toward food irradiation. It is proposed to research electricity-generated ionizing energy, electron beam (e-beam) with regard to its potential to reduce or eliminate food-borne pathogens. E-beam uses electricity to generate ionizing radiation.

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APPROACH: (1) Food safety: (i) E-beam. Single or double-sided e-beam gun will be used. Samples will be exposed to various, depending upon experiment, e-beam treatments. Samples will be transported to e-beam facility either frozen or refrigerated. Sample temperature will be adjusted overnight prior to e-beam treatment. Subsequently, samples will be transported either frozen or refrigerated to WVU Animal and Vet. Sci. Div. for laboratory analyses. (ii) Microbiological analyses. Chicken, beef, and trout samples will be inoculated with pathogens and then incubated. E-beam has limited penetration depth and dose absorbed decreases with the depth. Therefore, inoculated samples will be thin (less than 1 mm) in order to provide uniform e-beam dose distribution. Following e-beam treatment, the survivors will be enumerated and confirmed using standard methods. Survivor curves will be plotted for each pathogen and food matrix (chicken, beef, and trout), and the D-values will be calculated as an inverse reciprocal of the slope of the survivor curve. The D-value will be reported in dose units (kGy) or as time (min or sec) at dose intensity (MeV). (iii) Modeling electron penetration and microbial inactivation. Dosimeters will be inserted every 1 cm from the top to the bottom in chicken, beef, and trout samples. The absorbed dose will be read spectrophotometrically and used to plot a dose map. The dose map in conjunction with the D-values will be used to construct a microbial inactivation model.<P>
(2) Food quality: (i) Proteins and texture formation. To determine protein-protein bonds/interactions and protein structural changes in chicken, beef, and trout the following techniques will be used: (1) SDS-PAGE patterns under denaturing and non-denaturing conditions, (2) reactive (surface) and total SH groups assay, (3) protein surface hydrophobicity with 1-anilino-8-naphthal-enesulfonic acid (ANS) probe, (4) guanidine hydrochloride (G-HCl), sodium dodecyl sulfate (SDS), and beta-mercaptoethanol (beta-ME) in combination with torsional fracture shear stress to determine H bond, hydrophobic interactions, and SS bonds, respectively, (5) differential scanning calorimetry (MicroDSC) to determine protein denaturation, (6) dynamic rheology properties by Bohlin rheometer, (7) protein alpha-helicity by circular dichroism, (8) scanning electron microscopy to determine microstructure, (8) texture analyzer, torsion and punch test to determine texture properties. (ii) Lipid oxidation and flavor. To determine lipid oxidation a model food (surimi seafood gel) made with various lipid types and their concentrations will be prepared. The 2-thiobarbituric acid (TBA) assay will be used to quantify lipid oxidation. A head-space will be analyzed with GC (with SPME fiber) to determine flavor changes. (iii) Sensory evaluation. A triangle test will be designed to determine whether or not a difference exist between e-beam treated and control (no e-beam treatment) samples.

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PROGRESS: 2002/10 TO 2007/09 <BR>
OUTPUTS: Inactivation kinetics of a food-borne pathogen, Escherichia coli O157:H7 has been established in various food products subjected to electron beam (e-beam). Inactivation kinetics of food-borne pathogens is expressed as a D-value. The D-value determines the e-beam dose (kGy) required to inactivate (kill) 1-log (90%) of a target microorganism. We determined D-value for E. coli in the most representative meat products, ground beef, chicken breast meat, and fish fillets. Depending on the conditions in a food product and the type of a food product, it takes between 0.22-0.64 kGy of e-beam to inactivate 1-log (equivalent of 90%) of the initial microbial population of E. coli. Our laboratory has also established inactivation kinetics for another very common food-borne pathogen, Salmonella in tomatoes. Since tomatoes are naturally acidic foods, our studies determined D-value for Salmonella in tomatoes as a function of pH. The D-value for Salmonella in tomatoes ranged between 1.07-1.50 kGy depending on the pH. <BR>
PARTICIPANTS: Graduate students: Jennifer L. Black (MS student) Leah Levanduski (MS student) Deborah James (MS student) Visiting Professor: Dr. Priya R. Chalise (Department of Electronic and Electrical Engineering, Loughborough University, the U.K.) Research collaborators: Dr. Eiki Hotta, Department of Energy Sciences, Tokyo Institute of Technology, Japan Dr. Kristen E. Matak, Division of Animal and Nutritional Sciences, West Virginia University <BR>
TARGET AUDIENCES: food scientists and technologists, regulatory agencies, food industry and academia <BR>
PROJECT MODIFICATIONS: We added a new aspect of compact electron beam that was developed by Dr. Hotta's laboratory in Japan. This new e-beam device has a great potential to be integrated with a microwave oven. This new device would be targeted at increased food safety at a house hold level in a non-thermal fashion. Therefore, it this new device would be applicable to fresh food products such as fresh greeen vegetables. This modification was added in a response to the recent outbreaks implicating E. coli O157:H& in leafy greens.
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IMPACT: 2002/10 TO 2007/09<BR>
Escherichia coli O157:H7 is commonly associated with food products, especially ground meat products. However, more recently E. coli O157:H7 has also been implicated in outbreaks associated with fresh green vegetables that resulted in confirmed deaths. E-beam effectively inactivates this pathogen. Our studies demonstrated that the D-value for E. coli varies depending on a food product. Not only does the D-value differ for various food products, but it also changes depending of the water activity, ionic strength, and temperature of a food product during e-beam processing. In our studies we demonstrated that lowering water activity and ionic stress suppress growth of E. coli; however, at the same time E. coli becomes more radio-resistant to e-beam and survives e-beam processing better (i.e., higher D-value). Our food science laboratory was also the first one to demonstrate that E. coli has a capability to develop an significantly increased resistance to e-beam if the microorganism is repetitively exposed to e-beam at sublethal doses. This phenomenon is similar to the increased microbial resistance to various antibiotics. Salmonella has been recently implicated in several outbreaks in fresh tomatoes that resulted in numerous law suits. Fresh food products such as tomatoes of fresh green vegetables simply cannot be thermally processed. However, as evidenced by recent outbreaks involving E. coli and Salmonella, these food products should also be considered vehicles for pathogen transmission. Therefore, in order to maintain high food safety/security standards for the fresh food products (especially "ready-to-eat" ot RTE), non-thermal processing should be developed and implemented. As demonstrated in our studies, e-beam efficiently inactivates common food-borne pathogens such as E. coli and Salmonella in a non-thermal fashion; and therefore, the quality attributes of the processed food products are not affected by heat. Research in my laboratory at WVU with food-borne pathogens and e-beam has led me to believe that a key to further increase microbial safety of our food supply is the development of a non-thermal device at the end of the food distribution chain - the household level, immediately preceding consumption of the food. My belief was confirmed by the recently publicized outbreaks implicating fresh vegetables (spinach, lettuce) and peanut butter contaminated by E. coli and Salmonella, respectively; which resulted in confirmed deaths. Therefore, I initiated research collaboration with a plasma physicist specializing in compact e-beam linear accelerators, Dr. Eiki Hotta from the Department of Energy Sciences (Tokyo Institute of Technology, Japan) and an electrical engineer specializing in design of e-beam linear accelerators, Dr. Priya Raj Chalise from the Department of Electronic and Electrical Engineering (Loughborough University, the U.K.). Under my leadership we submitted a proposal to the USDA-NRI for the 2008 funding cycle. The long-term aim of the submitted proposal was to develop a compact e-beam device integrated with a microwave oven for the purpose of increased microbial food safety at a household and food service level.