Radiation rays of energy emission and propagation of

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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 process Microwave energy: long wavelength, low penetrating power  in food, causes polar molecules to vibrate (heat conducted to neighbouring molec; 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 ) o No significant heat produced (cold sterilization/pasteurization) o Gamma radiation from cb-60 or Cs-137 source; x-rays from machine source at </= 5 MeV ( megaelectron volt ) ; electrons from machine source operated at </= 10MeV o Gray=unit used to evaluate amount of energy absorbed by food; 1000 grays=1 kGy [ most countries regulate 10 kGy or less of absorbed energy] o Enough 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) o Changes 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 energyabsorbed by food (water)ion pairs & free radicals (free radicals sanitize food & destroy MOs) ; damage to key proteins, cell membrane) o Products 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) o 1-10 kGy:;; eliminate pathogenic bacteria, eliminate spoilage causing MOs (mould) (ex: chicken, ground beef, fruit and veg, fresh strawberries o 10-50 kGy: commercially sterilizes food (ex: sterilized hospital diets, space mission foods) o Radiation 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 kG radappertization —kill or inactivate all disease/spoil causing org (comm sterilize) o Main principles: radiological safety, toxicological safety, microbiological safety, nutritional adequacy o Health products and food branch of health Canada  safety and wholesomeness; Canadian food inspection agency  labelling, inspection o D value : D 10 value (kGy)… ex) for Ecoli pathogen…. D 10 value=0.24; dose for 5D process …………0.24 x 5 = 1.2 (if under 10, then approved) o Most enzymes even more resistant than C. bot spores and need ~200 kGy…. use blanching or other treatments instead o Labelling: mandatory info, international radura symbol , statement that its irradiated, if ingredient >10% must be on list

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