Preservation of food by radiation
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Preservation of Food by Radiation. UV radiation Ionizing radiation - irradiation. What is radiation?. This word has a negative connotation - for most consumers it means the emission of harmful radioactivity. Radiation means exposure to radiant energy.

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Preservation of food by radiation l.jpg
Preservation of Food by Radiation

  • UV radiation

  • Ionizing radiation - irradiation

What is radiation l.jpg
What is radiation?

  • This word has a negative connotation - for most consumers it means the emission of harmful radioactivity.

  • Radiation means exposure to radiant energy.

  • Radiant energy is energy that moves at speed of light but varies in intensity with both electric and magnetic fields.

  • Ionizing radiation are rays with enough energy to strip and electron from atom (gamma rays, X-rays)

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Human and Radiation

  • We are exposed to 31 mrem per year from cosmic radiation.

  • We are exposed to 24 mrem per year of gamma radiation from food, air, water

  • We are exposed to 40 mrem per year of gamma radiation from rocks and soils

  • A dose of 100-200 rads produces nausea, vomiting and diarrhea.

  • Survival from doses >500 rads all over the body is unlikely due to depression bone marrow resulting in very low white counts.

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Principle of food preservation by radiation

To kill microorganisms, parasites andinsects

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The entire spectrum of radiation can be divided into:

  • Low frequency, long wavelength, low quantum energy of radiation 10-6 to 104 m. The effect of this radiation on microorganisms is related to their thermal effects on food.

  • High frequency, shorter wavelength, high quantum energy radiation - may excite or breakdown organic compounds and microorganisms

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The shorter radiation energy applied to food can be divided into:

  • Lower frequency, lower energy radiation - UV radiation - sufficient energy to excite.

  • Higher frequency, higher energy radiation energy - ionizing energy - capable of breaking individual molecules.

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Bactericidal effect of UV and ionizing radiation depends on: into:

  • The kind of microorganisms

  • The number of microorganisms

  • The composition of food

  • The presence or absence of oxygen

  • The physical state of food

  • The condition of microorganism

Uv radiation l.jpg
UV radiation into:

  • The most effective is radiation near 260 nm. This wavelength is strongly absorbed by purines and pyrimidines.

  • The source of UV radiation -quartz-mercury lamp or low pressure mercury lamp. These lamps emit radiation at 254 nm.

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Effectiveness of UV radiation is affected by: into:

  • Time

  • Intensity: power of the lamp, the distance of the lamp from the object, the kind and amount of interfering materials.

  • Penetration : nature of the materials; the rays only affect the outer surface of radiated foods

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Resistance of microorganisms to UV into:

  • Bacterial spores are 2-5 times more resistant than wegetative forms.

  • The yeasts are 2-5 times more resistant than bacteria.

  • The molds are 10-50 times more resistant than bacteria.

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Uv radiation doses ( into:mWsec*100) needed for 1 log cycle reduction of certain microorganisms

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Food industry uses UV for: into:

  • Treatment of water for beverages

  • Aging meats

  • Treatment of knives for slicing breads

  • Packaging of sliced bacon

  • prevention of growth of film yeast on pickles

  • killing spores on sugar crystals

  • storage and packaging of cheese

  • treatment of air used for storage or processing of foods

Food irradiation l.jpg
Food Irradiation into:

  • Permitted in 30 countries

  • 18 countries are actually irradiating food

  • Canada allows irradiation of potatoes, onions, spices, wheat and other grains, but irradiated food is not being sold here.

  • Irradiation of food is not permitted in Germany, Britain, and Scandinavian countries.

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Consumers’ reactions to food irradiation into:

  • The rejectors, 5-10 % of consumers

  • The confused consumers - 55-65% of consumers

  • The acceptors, 25-30% of consumers

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The Rejectors: into:

  • Irradiation of food is rejected because of opposition to the use nuclear energy, environ -mental concerns etc.

  • monumental effort needed to change this group

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The Confused Consumers: into:

  • They like a food free of pathogen and insects and may see irradiation as a means to achieve this, but are afraid something new and not well understood.

  • Needs a lot of credible information to address each of the concerns and carefully outline the benefits.

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The Acceptors into:

  • This group has a positive attitude but still could by groups voicing concerns

  • This groups needs messages that give risks and benefits. Data must be given that will refute or support the concerns

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Food irradiation into:

  • Who benefits

  • Is irradiation safe?

  • Does irradiation prevents foodborne illness?

  • Are radiation-resistant bacteria formed?

  • Are there any alternatives to irradiation?

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Who benefits into:

  • Consumer - elimination disease-causing organisms, extension of shelf life

  • Food marketers - reduce food spoilage

  • Nuclear industry - new justifi -cations and potential income

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Is Food Irradiation Safe? into:

  • Too much conflicting evidence as number of studie showing that food irradiation is safe is almost similar to number of studies showing adverse effect.

  • The 1980 report of the FAO/IAEA /WHO Joint Expert Committee concluded that a dose of 10 kGy presents no toxicological hazard and introduces no special nutritional or microbial problems.

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Ionizing radiation includes: into:

  • X-rays

  • alpha rays

  • beta rays

  • gamma rays

  • protons

  • neutrons

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Irradiation of foods can be into: classified as:

  • Radappertization -” radiation sterilization” - it implies high dose treatments, with the resulting product being shelf stable.

  • Radurization - “radiation pasteurization” - low dose treat- ment with the intent to extend a product’s shelf life

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Irradiation of foods can be classified as: into:

  • Radicidation - a low dose radiation pasteurization with the intent to eliminate a particular pathogen

  • Picowaved food -term used to label food treated with a low level of ionizing radiation

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Other terms used: into:

  • Disinfestation - refers to radiation treatments whose objective is to kill or inactivate insects or parasites.

  • Delayed of Ripening and Senescence - refers to radiation treatment of fruits and vegetables whose usual spoilage is overripening.

  • Sprout Inhibition - refers tp radiation treatments used to prevent or delay sprouting.

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Units into:

  • Rad is a unit of radiation dosage being an equivalent to the absorption of 100 erg per of irradiated food

  • Gray = 100 rads

  • Electronovolt is an energy gaines by an electron in moving through a potential difference of 1 volt.

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Source of ionizing radiation into:

  • Cobalt 60

  • Cesium 137

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Dose determining factors into:

  • Resistance of food - organoleptic quality

  • Resistance of microorganisms

  • Resistance of enzymes

  • Cost

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Thresholds dose for detectable off-flavors (krad) from meats irradiated at 5 C to 10 C

  • Turkey 150

  • Pork 175

  • Beef 250

  • Chicken 250

  • Lobster 250

  • Trout 450

  • Halibut 500

  • Lamb 625

  • Horse 650

  • Bear 850

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Radiation effects: Clostridium botulinum D=0.4Mrad

  • Direct effects

  • Indirect effects are due to formation of H2O2 and free radicals: *OH, *HO2. These species are products of water radiation.

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Indirect effects can be limited by: Clostridium botulinum D=0.4Mrad

  • Irradiation of frozen food

  • Irradiation in vacuum

  • Addition of radical scavengers like ascorbic acid.

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Changes in food include: Clostridium botulinum D=0.4Mrad

  • In meat-increase in pH, increase in carbonyl compounds, H2S

  • In fats - destruction of natural antioxidants, oxidation of fats

  • Loss of vitamins such as thiamine, C and B6