Preservation of Food with Ionizing Energy

Radiation

• rays of energy

• Emission and propagation of energy through matter or space by electromagnetic disturbances

food irradiation

exposing food to radiation

Electromagnetic radiation

waves of electromagnetic field

Organized scale of electromagnetic radiation:

• radio waves

• microwaves

• visible light

• ionizing radiation

irradiation

• ionizing energy

• process of applying energy to foods

Microwave Energy (electromagnetic)

• polar molecules vibrate and are heated by intermolecular friction

• heat is conducted to neighbouring molecules

• long wavelength, low penetrating power

food irradiation

• “Treatment of food with ionizing radiation”

• short wavelength, high penetrating power

• gamma rays, x-rays, or electron beam

• no significant heat produced

Gray (Gr)

• amount of energy absorbed by the food treated with I.R.

• 1000 Grays = 1 kiloGray

ionizing

forming ions

food becomes radioactive by

being exposed to a minimum of 15 MeV of energy

Irradiation process

1. Conveyor system moves food in boxes (pallets)

2. Conveyor system moves food in boxes (pallets)

3. Absorbed dose depends on amount of time food is exposed to the irradiation source

4. Dosimeters are placed with the food to measure the dose received (in kGy)

Direct effect

• direct hit of ionizing energy upon genetic material of microbial cells

• ex. break bonds of DNA, which depend on dosage, MO, repair mechanism available

• random but extensive

Indirect effect

• Ionizing energy → absorbed by food (water) → ion pairs & free radicals- reactive

• Damage to key proteins, cell membrane

Free radicals

• don’t want excessive amount in foods

• produced in our body as part of our natural metabolism

• oxidative reactions in foods

Radiolytic Products

chemical compounds that form when food is exposed to ionizing radiation

Benzene and derivatives

• also in non-irradiated foods

• low concentrations after irradiation

Alkylcyclobutanones (ACBs)

• “unique” radiolytic products

• formed from fatty acids

• eveidence of mutagenic and genotoxity through in vitro, causing DNA strand breaks and cellular damage

• not toxic at doses found in irradiated foods

• HPFB was the central regulatory evaluator

Ways to minimize undesirable effects of food irradiation

1. frozen state - lowers production and mobility of free radicals

2. vacuum - minimize oxidative changes

3. free radical scavengers - react w the free radicals

4. lowest effective irradiation dosage, effective packaging

Radurization - Radiation Pasteurization (≤10 kGy)

kill majority of spoilage-causing organisms

Radicidation

kill or inhibit of disease-causing organisms (pathogens)

Radappertization

• kill or inactivate all disease- and spoilage-causing organisms capable of growing at storage conditions

• not allowed in Canada

4 Principles of Evaluating the safety of irradiated foods

1. Radiological Safety

2. Toxicological Safety

3. Microbiological Safety

4. Nutritional Adequacy

Radiological Safety

to control radiation dose in food

Toxicological safety

toxicological testing to avoid toxic or carcinogenic substances

Microbiological safety

Use D₁₀ Value and perform microbiological testing to ensure target MO is killed

HPFB of Health Canada

Safety and wholesomeness of irradiated foods

CFIA

labeling of irradiated foods; inspection of facilities

5D

Pasteurization

12D

Sterilization

Labelling

1. basic labelling info

2. radura symbol

3. statement that it is irradiated

4. irradiated ingredient >10% identified