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CURRENT TRENDS IN PROCESSING: PRESERVATION OF FOOD WITH IONIZING ENERGY CHAPTER 21 Describe chemical and nutrient changes irradiation causes in food products Analyze advantages and disadvantages of food irradiation as a preservation method Compare reduced oxygen packaging with other packaging an TERMINOLOGY Radiation is the energy Irradiation is the process! Electromagnetic spectrum ( of radiation) Organized scale of electromagnetic radiation: radio waves, visible light, microwaves, ionizing radiation Frequency, wavelength, energy value (penetrating power) LOW WAVE LENGTH, LOW ENERGY Bacteria and viruses Penetrates skin Microwave ovens Visible ( sunburn due to short penetrating waves) ELECTROMAGNETIC ENERGY: MICROWAVE ENERGY (LONG WAVELENGTHS – LOW PENETRATION) In food- cause polar molecules to vibrate Heat created by intermolecular FRICTION Heat then conducted to neighboring molecules Microwaves are absorbed up to a depth of 5 to 7.5 cm ( 1 to 1.5 inches) Microwaves pass through PAPER, PLASTIC, GLASS Reflected by metals Attracted to fat, water and sugars Cooks unevenly so needs rotated, stirred or rearranged during cooking MICROWAVE OVENS https://www.youtube.com/watch?v=XZzdNjm1JzU invention https://www.youtube.com/ watch?v=4h1ESUz2H3E ELECTROMAGNETIC ENERGY: IONIZING RADIATION ( SHORT WAVELENGTHS- HIG PENETRATING POWER) Ionizing radiation means: A. GAMMA radiation from Cobalt-60 or Cesium-137 source B. X-RAY from machine source operated at <10 MeV ( Mega electron volts)- voltages used on food C. ELECTRONS from machine source operated as < 10 MeV (stream of electrons accelerated to a 99.9% the speed of light) FOOD IRRADIATION “GRAY” Amount of energy absorbed by the food treated with irradiation 1 GRAY (Gy) = 1 joule of energy per kg of food 1000 Gy= 1kilogray or 1kGy Most countries regulate 10 kGy or less of absorbed energy DOES IRRADIATION INDUCE RADIOACTIVITY IN FOODS? Irradiation uses ionizing energy Enough energy to change atoms by “knocking” an electron from the outer orbit which forms ions (ionizing energy) Knock out- breaks the dna from the bacteria Not enough energy to penetrate the nucleus and split atoms ( this would cause radioactivity) Food can never become radioactive from irradiation USING APPROVED ENERGY SOURCES. DOES IRRADIATION INDUCE RADIOACTIVITY IN FOODS? To become radioactive, food would need to be exposed to a minimum of 15 MeV of energy Energy output: colbalt 60, cesium 137, and e-beam accel.- carefully regulated Maximum energy uotputs of 5 or 10 MeV Too low to induce radioactivity in foods THE FOOD IRRADIATION PROCESS 1. Conveyor system moves prepackaged food in boxes (pallets) 2. Food is carried into a chamber with irradiation source (eg cobalt 60) 3. Absorbed dose depends on amount of time food is exposed to the irradiation source. Dosimeters are placed with the food to measure The dose received (in kGy) PRESERVATION EFFECT 1. Direct effect Direct hit of ionizing energy upon genetic material of microbial cells Eg. Break bonds of DNA OF BACTERIA IN THE FOOD DEPENDS ON DOSE, MICROORGANISM, REPAIR MECHANISM AVAILABLE….. RANDOM, EXTENSIVE DAMAGE May cause development of resistant bacteria and microorganisms If radiation is not hitting on the same place in the dna, then the molecules is less likely to mutate BASIS FOR FOOD PRESERVATION BY IONIZING RADIATION 2. Indirect effect Ionizing energy interacts with water in the food Absorbed energy will dislodge electrons from water molecules Ionizing energy absorbed by food (water) ion pairs and free radicals-reactive Damage to key proteins and cell membranes “free-radicals” normal aging process when cells die FREE RADICALS ….(CONT) FR are not unique to “irradiated foods” Also produced within our bodies and other living tissues As part of normal metabolism Oxidative reactions in foods ( unsaturated fats) Mechanisms (chemical and enzymatic) within human body for inactivation of free radicals Antioxidants/supplements prevent free radicals from forming in the body which delays cell death CHANGES DURING FOOD IRRADIATION? Radiolytic products Benzene and derivatives Also in non-irradiated foods Low concentrations after irradiation Alkylcyclobutanones (ACBs) “unique” radiolytic products Most from fatty acids Toxic doses found in irradiated foods?......not known yet WAYS TO MINIMIZE UNDESIRABLE EFFECTS/ CHANGES OF FOOD IRRADIATION Frozen state Lower production and mobility of free radicals Vacuum Minimize oxidative changes Free radical scavengers React with the free radicals ( affinity for Free Radicals) Vitamins E , C *** Irradiation is not heating the food…..There is no friction TYPICAL NON-FOOD APPLICATIONS OF IRRADIATION Band aids Diaper wipes Pet treats Wound cares Cosmetics 50% of all medical devices Baby bottles Animal vaccines Computer chips Contact lenses/ cleaning solutions TYPICAL FOOD APPLICATIONS (INTERNATIONAL) DOSE <1 kGy Radurization 1-10 kGy Radicidation 10-50 kGy Radappertization Purpose • • • • • Inhibit vegetable sprouting Kill insects and larva Slow ripening Eleviate parasites Eliminate spoilage causing microorganisms Eleminate pathogenic bacteria (salmonella, E.coli0157:H7 KILLS PATHOGENS Commercially sterilizes food Examples Potatoes Wheat Bananas Pork Chicken, ground beef, fruit and vegetables, fresh strawberries Sterilizes hospital diets, Space mission foods SHELF LIFE EXTENSIONS OF STRAWBERRIES RESISTANCE/ DESTRUCTION OF MICROORGANISMS BY IONIZING ENERGY Concept of Decimal reduction Time ( D-Value) in thermal processing- also applies to radiation D10 value = Dose (kGy) of ionizing energy needed for a 90% decrease ( 1 log reduction) of microorganism population REQUIRED IRRADIATION DOSE (KILOGRAYS) FOR A 5D OR 12D PROCESS Pathogen D10 values (kGy) Dose for a 5D process Dose for a 12D process E. Coli 0157:H7 0.24 1.2 2.9 Listeria Monocytogenes 0.45 2.2 5.4 Salmonella 0.5 3.0 7.2 C. Botulinum spores 3.56 18 >.40 0.45 x 5D= * Not optimal for C. Botulinum, but okay for other pathogens .045 x 12D= RESISTANCE OF ENZYMES TO IONIZING ENERGY Most food enzymes are even more resistant than C. botulinum spores Will need nearly 200kGy! Can we use irradiation to inactivate enzymes? Not the best…. But may need to blanch before irradiating IRRADIATED FOOD- LABELING The Food and Drug Administration (FDA) establishes regulations for labeling of irradiated foods. Labels must contain the words "Treated with Radiation" or "Treated by Irradiation" and display the irradiation logo, the Radura. The petals represent the food, the central circle the radiation source, and the broken circle illustrates the rays from the energy source Retail Foods FDA requires labeling of packaged, irradiated food sold at retail stores. Irradiated, whole foods sold in bulk, such as fruits and vegetables, also must display the label. No label is required for food products that contain irradiated ingredients, such as spices, as long as the entire product has not been irradiated. Wholesale Foods Irradiated foods sold at the wholesale level also must be labeled. However, both the shipping container and the invoice or bill of lading must display the statement, "Do not irradiate again." FDA has not evaluated products that have been irradiated more than once. Restaurant Foods FDA does not require labeling of irradiated food served in restaurants. WHAT APPLICATIONS ARE CURRENTLY APPROVED IN THE UNITED STATES ( SEE TEXT) Decontamination ( microbial, parasite control) of Pork Fresha dnfrozen poultry Poultry feed Fresh and frozen red meat Shell eggs Animal feed, pet feed, spices Vegetable seasoning (dried) Sterilization of Meat, frozen packaged- for NASA space missions only