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Radiation = rays of energy; emission and propagation of energy through matter or space by electromagnetic disturbances (radio waves, visible light, microwaves ionizing radiation)Food irradiation = application of radiation, as ionizing energy, to foods ------- Radiation is the energy, Irradiation is the processMicrowave energy: long wavelength, low penetrating power in food, causes polar molecules to vibrate (heat conducted to neighbouringmolec; heat from core to outside)Ionizing radiation: Defn’ of food irradiation: treatment of food w/ ionizing radiation ; short wavelength, high penetrating power (x-rays, gamma rays, beta rays)oNo significant heat produced (cold sterilization/pasteurization)oGamma radiation from cb-60 or Cs-137 source; x-rays from machine source at </= 5MeV (megaelectron volt) ; electrons from machine source operated at </= 10MeVoGray=unit used to evaluate amount of energy absorbed by food; 1000 grays=1 kGy [most countries regulate 10 kGy or less of absorbed energy]oEnough energy to knock electron from orbit, but not enough energy to penetrate nucleus and split atoms (to become radioactive, food exposed to min 15 MeV)oChanges in food induced by ionizing radiation: direct effects(direct hit of ionizing energy upon genetic material of microbial cells; eg break bonds of DNA) ; indirect effects(ionizing energy interacts with h20 in the food; absorbed energy will dislodge electrons from water molec…..ionization energyabsorbed by food (water)ion pairs & free radicals (free radicals sanitize food & destroy MOs) ; damage to key proteins, cell membrane)oProducts formed during irradiation: Radiolytic products (benzene & derivatives… also in non-irradiated foods) ; Alkylcyclobutanones (ACBs) unique to Radiolytic products; mostly from fatty acids, o<1 kGy: inhibit sprouting of veg, kill insects, slow ripening, inactivate parasits (ex: potatoes, wheat bananas, pork, onions)o1-10 kGy:;; eliminate pathogenic bacteria, eliminate spoilage causing MOs (mould) (ex: chicken, ground beef, fruit and veg, fresh strawberries o10-50 kGy: commercially sterilizes food (ex: sterilized hospital diets, space mission foods)oRadiation pasteurization (</= 10 kGy) radurization (comparable to acid food pasteurization): kills majority of spoilage causing org; Radicidation (low acid pas): kill or inhibit disease causing org (pathogens); Radiation ster (not in CAN) >10 kGradappertization—kill or inactivate all disease/spoil causing org (comm sterilize)oMain principles: radiological safety, toxicological safety, microbiological safety, nutritional adequacy oHealth products and food branch of health Canada safety and wholesomeness; Canadian food inspection agency labelling, inspectionoD value : D10 value (kGy)… ex) for Ecoli pathogen…. D10 value=0.24; dose for 5D process …………0.24 x 5 = 1.2 (if under 10, then approved)oMost enzymes even more resistant than C. bot spores and need ~200 kGy…. use blanching or other treatments insteadoLabelling: mandatory info, international radura symbol, statement that its irradiated, if ingredient >10% must be on list