Food Toxicology
                                                                                                                            Learning Objectives
                                                                                                          • Define food irradiation.
                                                                                                          • Explore the background of ionizing radiation and its 
                                                                                                            application to food.
                                           Food Irradiation                                               • Describe the various food irradiation processes.
                                                                                                          • List the benefits of food irradiation.
                                                                                                          • List the food safety, food quality, 
                                               Food Toxicology                                              and non-food concerns of 
                                     Instructor: Gregory Möller, Ph.D.                                      food irradiation.
                                              University of Idaho                                         • Explore the consumer opinions 
                                                                                                            of food irradiation.
                                                                                                          • Explore the current food uses 
                                                                                                            and future of food irradiation.
                                                                                                         2
                                                                               Food Toxicology                                                                    Food Toxicology
                                             Food Irradiation                                                                 Ionizing Radiation
                       • Food irradiation is the exposure of food products to                             • Ionizing radiation is from X-rays or radioactive decay
                         ionizing radiation to destroy microorganisms, insects,                              – Alpha particles, beta particles, gamma rays
                         and parasites that cause disease and spoilage                                    • Can cause chemicals reactions and alterations of 
                       • Compare to non-ionizing radiation                                                  chemicals in tissues
                          – Cooking - IR                                                                     – Can be toxic or fatal to humans in high dose
                          – Microwave ovens                                                               • Much of the reactivity in 
                                                                                                            organisms is with water.
                                                                                                          • Produces: 
                                                                                                                                        -
                                                                                                             – Superoxide radical (O2•) 
                                                                                                                Hydroxyl radical (HO•)
                                                                                                                Hydroperoxyl radical (HOO•)
                                                                                                                and hydrogen peroxide.
                      3                                                                                  4
                                                                               Food Toxicology                                                                    Food Toxicology
                                           Ionizing Radiation                                                                Radioactive Decay
                       • Recall “oxidative stress” from free radicals                  Manahan           • The decrease in the amount 
                          – Endpoints: lipid peroxidation, DNA strand breaks, enzyme                        of any radioactive material 
                             inactivation, covalent binding to nucleic acids, covalent                      with the passage of time, 
                             binding to proteins.
                       • Direct ionization of organic molecules can yield                                   due to the spontaneous 
                         carbonium ions CH3+                                                                emission from the atomic 
                          – Can alkylate DNA.                                                               nuclei of either alpha or beta 
                       • Example: Radon, a noble gas                                                        particles, often accompanied 
                         that emits alpha particles                                                         by gamma radiation.
                          – Results from the decay of U and 
                             Ra in naturally occurring minerals.                                            60           60          -
                          – Accumulates in basements of                                                        Co → Ni + e + νe
                             some homes
                              • Presents the most risk of any                                             NC-DRP
                      5         element to humans.                                                       6
                                                                                                                                                                                         •1
                                                                                       Food Toxicology                                                                            Food Toxicology
                                     Cobalt-60 Radioactive Decay                                                                              Alpha Particle
                               Co60            Half-life                                                            • A positively charged particle ejected spontaneously 
                            27                5.24 years                                                               from the nuclei of some radioactive elements. 
                               0.31 MeV β                                                                               – Low penetrating power and a short range. 
                                                   28Ni60*                                                          • The most energetic alpha particle will generally fail to 
                                                                                                                       penetrate the dead layers of cells covering the skin. 
                                        1.17 MeV γ                                                                  • Alphas are hazardous when 
                                                                                                                       an alpha-emitting isotope is 
                                                   28Ni60*                                                             inside the body.
                                         1.33 MeV γ
                                                   28Ni60
                        7                                                                                          8 NC-DRP
                                                                                       Food Toxicology                                                                            Food Toxicology
                                                   Beta Particle                                                                               Gamma Ray
                         • A charged particle emitted from a nucleus during                                         • High-energy, short wavelength, electromagnetic 
                            radioactive decay.                                                NC-DRP                   radiation (photon; a packet of energy) emitted from 
                             – Mass equal to 1/1837 that of a proton.                                                  the nucleus. 
                             – A negatively charged beta particle is identical to an                                    – Gamma radiation frequently accompanies alpha and beta 
                               electron; a positively charged beta particle is called a                                   emissions and always accompanies fission. 
                               positron.                                                                                – Ionizing radiation.
                         • Large amounts of beta                                                                    • Gamma rays are very penetrating 
                            radiation may cause skin 
                            burns, and beta emitters                                                                   and are best stopped or shielded 
                            are harmful if they enter                                                                  by dense materials, such as 
                            the body.                                                                                  lead or uranium. 
                         • Beta particles may be                                                                    • Gamma rays are similar to 
                            stopped by thin sheets                                                                     X-rays: no mass or charge.
                        9 of metal or plastic.                                                                     10
                                                                                                                       NC-DRP
                                                                                       Food Toxicology                                                                            Food Toxicology
                                        Electromagnetic Spectrum                                                                  Measurements of Radiation
                                                   Visible                                                          • One gray (Gy) is the absorption of one joule of 
                                                0.4       0.7
                                                                                                                       radiation energy by one kilogram of matter
                                             UV               IR                                                    • 1 Gy = 1 J/kg  
                                                                             Wavelength, μm                             – Gray (Gy) = 100 rads
                           -6   -5   -4   -3   -2   -1             2    3    4    5    6    7    8                      – rad is older unit
                         10   10   10   10   10   10    1101010 10 10 10 10 10
                                                                                                                            •"radiation absorbed dose". 
                                                                                                                    • Kilogray (kGy) = 1000 Gy
                          γ-Rays            Ultraviolet     Thermal IR                 Radio
                                   X-Rays           Near, Mid IR       Microwave
                        11                                                                                         12
                                                                                                                                                                                                          •2
                                                            Food Toxicology                                               Food Toxicology
                                   Lethal Doses                                                 Food Irradiation
                 • Vegetative bacteria - 0.5-10 kGy                             • Radiation energy applied to food; does not induce 
                 • Bacterial spores - 10-50 kGy                                   radioactivity
                 • People and animals - 0.005 - 0.01 kGy                        • Uses γ radiation (ionizing radiation from Co60 or Cs137
                 • Insects - 0.1-1.0 kGy                                          decay), X-rays (high energy photon from accelerated 
                                                                                   -                                     -  -
                                                                                  e colliding with W metal), or accelerated e (e beams 
                                                                                  from accelerators) 
                                                                                • Passes through food w/o 
                                                                                  generating intense heat
                                                                                • Will disrupt some cellular 
                                                                                  processes (i.e. DNA)
                                                                                   – Sprouting, microorganisms, etc.
                 13                                                             14
                                                            Food Toxicology                                               Food Toxicology
                                      Historical                                                    Historical
                 • 1895 - X-rays discovered                                     • Cost and scarcity of radiation sources reduced 
                 • 1896 - suggested use in food preservation                      industry interest
                 • 1903 - process patented by US and France                     • Adverse sensory attribute were a problem
                    – Destruction of Trichinella in pork                        • Military research continued 
                                                                                   – Stable field rations
                        Röntgen
                 15    Radiograph                                               16
                                                            Food Toxicology                                               Food Toxicology
                                      Historical                                                    Historical
                 • 1962 - Army research facility in Massachusetts               • 1958 - FDA ruled irradiation sources as food additives 
                 • Demonstrated meat shelf-life in years w/o                    • Part of Food Additives Amendment
                   refrigeration                                                • Delayed commercialization
                 • Performed many safety studies                                • Industry lost interest
                    – Basis for much toxicology data                            • Late 1960s - FDA approved 
                                                                                  irradiation of potatoes 
                                                                                  (sprout inhibition) 
                                                                                  and grains 
                                                                                  (reduce insect infestation)
                 17                                                             18
                                                                                                                                           •3
                                                             Food Toxicology                                                 Food Toxicology
                                      Historical                                    Food Irradiation Processes: Categories
                  • 1965 - Surgeon General announced irradiated foods             • Rad-urization
                    were safe and wholesome                                       • Rad-icidation
                  • NASA adopted for space program                                • Rad-apperization
                  • 1991 - First US commercial irradiation plant
                    – Vindicator of Florida,  Inc.                                • Based on radiation dose
                               NASA
                 19                                                              20
                                                             Food Toxicology                                                 Food Toxicology
                               Radiation Processes                                   Strawberries, 1 KGy, 25 Days @ 3 ºC
                  • Radurization: (0.75-2.5 kGy) 
                  • Inhibit sprouting, delay ripening, insect disinfestations 
                    and shelf-life extension
                  • Mimics pasteurization
                 21                                                              22
                                                             Food Toxicology                                                 Food Toxicology
                               Radiation Processes                                             Radiation Processes
                  • Radicidation: (2.5-10 kGy)                                    • Radapperization: (10-50 kGy) 
                  • Eliminate spoilage microorganisms and non-spore-              • Reduction of microorganisms to the point of 
                    forming pathogens                                               sterility
                  • Problem - food will not spoil but still may contain             –12D process for C. botulinum (30-45 kGy)
                    some pathogens                                                     • 12 log cycle spore reduction: 99.9999999999%
                                                                                  • Not approved for general use 
                                                                                    on food
                                                                                  • Diets for immuno-deficient
                                                                                  • Military and NASA operations
                       Listeria
                 23 monocytogenes                                                24
                                                                                                                                              •4