Food Irradiation

FOOD IRRADIATION ADVANCED NUTRITION

HFS 4352

Mohd Razif Shahril, PhD

School of Nutrition & Dietetics

Faculty of Medicine and Health Sciences

Universiti Sultan Zainal Abidin

Originally prepared by:

LAILA RUWAIDA BINTI MOHD ZAINUDDIN

Definition

• Radiation: the emission and propagation of

energy through matter or space by

electromagnetic disturbances called photons.

• Irradiation: the process of applying radiation to

matter.

• Food irradiation: application of irradiation as

ionizing energy to foods.

Why irradiate food

1. Prevention of foodborne illness • effectively eliminates microbes; Salmonella and E. Coli

2. Preservation • Destroy/ inactivate organisms that cause spoilage and

decomposition.

3. Control of insects • Destroys insects e.g imported fruits.

4. Delay of sprouting and ripening • Lengthen the longevity of products e.g: potatoes.

5. Sterilization • Useful for patients in the hospital especially with impaired

immunity.

Sources of radiation used in food

irradiation 1. Gamma Rays are emitted from radioactive forms of the

element cobalt (Co60) or of the element cesium (Cs137). Gamma radiation is used routinely to sterilize medical, dental and household products and is also used for the treatment of cancer.

2. X-rays are produced by reflecting a high energy stream of electrons off a target substance (usually one of the heavy metals) into food. X-rays are also widely used in medicine and industry to produce images of internal structures.

3. Electron beam (or e-beam) is similar to x-rays and is a stream of high-energy electrons propelled from an electron accelerator into food.

Dose and dose rate

• Ionizing energy processes create enough of an

absorbed dose to destroy microbes.

• Unit of absorbed dose in food is kGy (kilograys).

• Dose can be divided into three categories:

1. Radicidation

2. Radurization

3. Raddapperization

Dose and dose rate

•“Low” doses <1 kGy (Radicidation)

Controls insects in grains and fruits

Inhibit sprouting in tubers

Delay the ripening of some fruits/vegetables

Reduce the problems of parasites in products of

animal origin. (e.g: Trichinella spiralis in pork)

Dose and dose rate

“Medium” dose (1~10 kGy) (Radurization)

Control Salmonella, Shigella, Campylobacter,

Yersinia, Listeria and E.coli in meat poultry and fish.

Delay mold growth on strawberries and other fruits

“High” dose (>than 10kGy) (Radapperization)

Kill microorganisms and insects in spices

Commercially sterilize foods, destroying all

microorganisms of public health concern (i.e, special

diets for people with weakened immune systems)

Does the food become radioactive?

• To make the food become radioactive, it will

require a lot of energy; 15MeV.

• Foods are actually naturally radioactive.

• Due to natural presence of Ca, P, K, and S

elements in the food.

• Fresh foods vs irradiated foods?

• The longer the storage time of irradiated food,

more natural radioisotopes have time to undergo

decay.

Effects of irradiation on microorganisms

• Indirect effects: Due to formation of the free radicals during radiolysis of water

molecules.

Free radicals are highly reactive - form stable products.

Combine with one another or oxygen molecules – oxidizing agents.

Can damage bacterial cell components.

Unstable free radicals react with bacterial cell membranes to change or damage their structure- bacterial death.

Effects of irradiation on microorganisms

Direct effects Ionizing radiation kills microbes by damaging biomolecules of

their cells.

Incoming photon hit electrons in the atoms of microbes or food molecules.

During the collision, photon’s energy is transferred to the electron changing the photon’s direction.

Electron free to collide with neighboring electron.

This cause chemical bonds breakage

interrupts normal cell metabolism and division.

Effect of food irradiation on food quality

• The food molecules are made of water, lipids,

proteins, carbohydrates and vitamins.

• Radiation energy generates a degradative reaction when it interacts with food → radiolysis.

• Products of radiolysis is known as radiolytic products.

• Irradiation cause changes to food molecules

particularly at high doses.

• Sterilization levels causes nutrient loss and

desirables effects. E.g: ???

How does irradiation effect food quality?

• Food water

• Radiolysis of water molecules produce hydroxyl

radicals.

• Highly reactive species that can cause

characteristics associated with food spoilage

e.g: off-flavour and off-odors.

• To minimize this effects:

• Apply lowest effective irradiation dose

• Irradiate at lower temperature

• Choose appropriate packaging in terms of moisture

and oxygen barrier properties.


• Food Lipids

• Absence of oxygen leads to cleavage of interatomic bonds

• Producing compounds e.g. CO2, alkanes, alkenes and aldehydes

• Presence of oxygen, lipids are highly vulnerable to oxidation by free radicals, a process that yields peroxide, carbonyl compounds and alcohols

• Rancidity – high unsaturated fatty acid

• To minimize effects: • Vacuum packaged and low temperature used during

irradiation

• Adding lipid-soluble antioxidants and use lowest irradiation dose


• Food proteins

• Proteins are not significantly degraded at low

doses of irradiation.

• Does not inactivate enzymes involved in food

deterioration.

• Most enzymes survives higher doses

• Biological value of protein remain high

• Availability of essential amino acids is not

compromised.


• Food Carbohydrates

• Large CHO molecules (polysaccharides) are

broken down by irradiation.

• Depolymerization reduces gelling and functional

properties such as starches and gums

• Protection by other food constituents

• Effect on simple sugar is negligible.


• Food vitamins

• Have varying degrees on sensitivity

• Some shows sensitivity at higher dose, e.g:

Vitamin A, C, E and B1

• Sensitivity is apparent in food packaged under

air.

Does radiation create unique radiolytic

products • Radiolytic products are unstable atoms or molecules derived from substances naturally present in foods treated by ionizing energy.

• A free radical is one such type of radiolytic products.

• Formed as result of irradiation, might cause cancer.

• Radiolytic products produced from radiation is just the same as other radiolytic products from conventional processing methods.

• Concentration is much more lower.

Regulation of Irradiated food

• Considered as a food additive by the FDA

• For approval for any irradiated food, FDA requires

the foods labeled with statement:

• Treated by ionizing energy/treated by irradiation

• International symbol of irradiation, Radura

• Labeling requirement apply only to foods sold in

stores

• No labeling requirement if minor ingredients in

other foods and restaurant foods.

Foods have been approved for irradiation

• FDA has approved a variety of foods for

irradiation in USA including:

• Beef and pork.

• Poultry

• Mollusk shellfish

• Shell eggs

• Fresh fruits and vegetables.

• Lettuce and spinach

• Spices and seasonings.

• Seeds for sprouting

Conclusion

• Consumer are gaining knowledge about the

benefits of food irradiation and its potential to

reduce the risk of foodborne disease but the

process is not a replacement for proper food

handling practices.

• Irradiation like other prevention methods,

however measures have to be taken to prevent

foodborne illness.

Challenge Question

• Suppose you work at a poultry processing plant, and the

boss wants to irradiate the chicken meat, which he knows

is on average 30% contaminated, to eliminate Salmonella

sp. The plant produces both fresh (refrigerated) and

frozen chicken meat and chicken meat products. Here is

your conversation with him;

Boss : Let’s use as low a dose as possible

You : But the approval is for 1.5 to 3.0 kGy

Boss : Just because its approved, we don’t have to

go that high. Give it 1.0kGy of treatment

You : (What should your response be?)

THANK YOU

Health & Medicine

Food Irradiation