FOOD TECHNOLOGY

BNN 40304

SEMESTER 1 SESSION 2015/2016

ASSIGNMENT:

GAMMA IRRADIATION

NAME : KHAIRUL ANWAR BIN ROSLI

MATRIX ID : AN120228

LECTURER : ENGR. DR. NASRUL FIKRY BIN CHE PA

DATE OF

SUBMISSION

: 17th

NOVEMBER 2015

BACHELOR DEGREE OF CHEMICAL ENGINEERING TECHNOLOGY

(BIOTECHNOLOGY) WITH HONOUR

FACULTY OF ENGINEERING TECHNOLOGY

TABLE OF CONTENT

CONTENT PAGES

1.0 OBJECTIVE OF THE STUDY 1

2.0 LITERATURE REVIEW

2.1 Background and History of Food Irradiation 1

2.2 Irradiation 3

2.3 Gamma Irradiation 4

3.0 PRINCIPLE OF OPERATION

3.1 How Gamma Rays Works? 6

3.2 Effect of Radiation Dosage 7

3.3 Radiation Processing 9

3.4 Irradiation Equipment and Facilities 10

3.4.1 Gamma Irradiator Facility 10

3.5 Advantages and Limitation of Gamma Irradiation 13

3.6 Importance of Gamma Irradiation for Future Trend in

Food Application.

14

3.7 Foods Suitable For Irradiation 14

3.8 Application of Gamma Irradiation on Malaysian Food 15

4.0 CONCLUSION 17

REFERENCES 18

Gamma Irradiation|1

1.0 OBJECTIVE OF THE STUDY

The aims of this study are:

i. To discuss the basic principle and mechanism of Gamma Irradiation on food

processing and food preservation.

ii. To study the uses and application of Gamma Irradiation on Food.

iii. To examine the Malaysian food product that suitable to use Gamma Irradiation

technology.

2.0 LITERATURE REVIEW

2.1 Background and History of Food Irradiation

According to U.S Food and Drug Administration (2014), food irradiation refers to the

application of ionizing radiation to food which is a technology used to improve the safety and

extends the shelf life of foods by reducing or eliminating microorganisms and insects. In other

words, radiation is one of the latest methods in food preservation. Method of food radiation

has a long history of researches before it can be applied in food preservation. The technology

started when Wilhelm Conrad Röntgen successfully produced and detected electromagnetic

radiation in a wavelength range known as X-rays, followed by the discovery of radioactivity

by Henri Becquerel. Then, Paul Villard discovered the gamma radiation. More scientific

discoveries were done by scientists in ionization radiation related to food science and

microbiology. The food radiation technology continues to grow in the early 1920s when a

French scientist discovered that irradiation can be used to preserve food. The historical

milestone of food irradiation as suggested by Andres, 2011 was summarized in Table 1.

History of Food Irradiation in Malaysia is very recent. Research on food irradiation

only begins in 1974 due to the installation gamma radiation facility of Cobalt-60 at National

University of Malaysia. Since then, several studies conducted to study the effect of irradiation

on food preservation but the development are slow due to limited facilities and technology,

lack of expertise and other preservation methods can be improved with lower capital output.

In 1982, a group of researchers conduct a feasibility studies using irradiation techniques to

solve several problems associated with paddy and rice. The research and development on food

irradiation have been escalating since then and more pilot-scale study is conducted and

commercialized (Proceedings of the Workshop on The Applications of Ionizing Technology

in Food Preservation, 1985)

Gamma Irradiation|2

Table 1: Historical Milestone of Food Irradiation (E.L. Andress, Food Irradiation, 2011)

1885 → Wilhelm Conrad Röntgen a German physicist, produced and detected

electromagnetic radiation in a wavelength range known as X-rays

1886 → Henri Becquerel is a physicist who first discover radioactivity.

1900’s → Paul Villard , a French chemist and physicist, discovered gamma

radiation while studying radiation emitted from radium

1903 → Villard's radiation was named "gamma rays" by Ernest Rutherford.

1904 → Samuel Cate Prescott publishes effects of ionizing radiation on

bacteria and become the pioneer in Food Science and Microbiology.

1905 → U.S. and British patents are issued for the proposed use of killing

bacteria in food with ionizing radiation.

1940

- 1950s → U.S. government, private industries and universities conduct research

on food irradiation.

1963 → U.S. first approval of food irradiation when FDA approved its use to

control insects in wheat and wheat flour.

1964 → FDA approves irradiation for insect disinfestation of wheat and

powder.

1965 → FDA approves irradiation to extend the shelf life and inhibit the

development of sprouts in white potatoes.

1983 → Approval to kill insects and control microorganisms in a specific list

of herbs, spices and vegetable seasonings.

1985 → FDA approves irradiation to control Trichinella spiralis in pork and

to disinfest dry enzyme preparations.

1986 → FDA approves to control and inhibit insects growth and delay

ripening of some fruits and vegetables

1990 → FDA approves irradiation to control pathogens such as Salmonella in

fresh and frozen poultry.

1997(FDA)

and 1999

(USDA)

→ Approval of irradiation to control pathogens in fresh and frozen red

meats (beef, lamb and pork).

Gamma Irradiation|3

2.2 Irradiation

Radiation is not a modern and man-made creation as we get natural radiation from sun. The

method of radiation in food started from ancient times where people used the radiation from

sun to dry and preserve food. The modern food irradiation is a method in other hand, exposing

foods either prepackaged or in bulk to very high-energy, invisible lightwaves radiation

(Andress, 2011). Irradiation processing of food involves the controlled application of energy

from ionizing radiations such as gamma rays, X-rays or electron beams that are part of the

invisible lightwaves range of the electromagnetic spectrum (refer Figure 1).

The radiation energy given to the food can cause the changes in molecules such as

breaking chemical bonds; alter properties and condition of the food such as ripening and

sprouting rate. Microorganisms also undergo alteration so it is no longer pathogenic or killed

and genetically modified to be dormant or cannot reproduce.

Figure 1: Electromagnetic Radiation Spectrum.

(Source: http://www.mpoweruk.com/images/emspectrum.gif)

There is 3 principles type of radiation sources (refer Table 2) use in food irradiation

according to the Codex Alimentarius1 (Food and Agriculture Organization, World Health

Organization, 1984).

1 Codex Alimentarius or ―Food Code‖ established by FAO and WHO to develop harmonized international food

standards to protect consumer health and promote fair practices in food trade.

Gamma Irradiation|4

Table 2: Types of Radiation Energy Use in Food Irradiation (Dosimetry for Food

Irradiation IAEA, 2002).

Types of radiation Description

(a) Gamma rays The γ rays used in food processing are obtained from large Cobalt-

60 or Caesium-137 radioisotopes sources. This type of radiation is

essentially monoenergetic, for example 60Co (most common used)

emits simultaneously two photons per disintegration with energies

of 1.17 and 1.33 MeV.

(b) Electrons beam Electrons emitted by accelerators have fairly narrow spectral

energy limits (usually less than ±10% of the nominal energy). The

energy of the electrons reaching the product is further controlled by

the bending magnets of the beam handling system, if applicable.

The range of an electron in a medium is finite (unlike that for

photons) and is closely related to its energy.

(c) Bremsstrahlung

(X-rays)

Bremsstrahlung irradiator design principles are essentially the same

as those for electron irradiators .An extended source of X rays is

achieved by distributing the primary electron beam over a target (X

ray converter) of sufficient size. In contrast to the radioisotope

sources, which emit nearly monoenergetic photons, bremsstrahlung

(X ray) sources emit photons with a broad energy spectrum.

2.3 Gamma Irradiation

Gamma radiation or gamma rays is an electromagnetic radiation of an extremely high

frequency which consists of high-energy photons denoted by the Greek letter γ. Gamma rays

are ionizing radiation that known to be biologically hazardous. Gamma ray are naturally

produced by the decay of atomic nuclei as they transition from a high energy state to a lower

state known as gamma decay, but may also be produced by other processes and sources such

as sunlight. Gamma rays typically have frequencies above 10 exahertz (or > 1019

Hz) with

energies above 100 keV and wavelengths less than 10 picometers (10−12

meter), which is less

than the diameter of an atom (refer Figure 1). This radiation commonly has energy of a few

hundred keV, and almost always less than 10 MeV.

Gamma Irradiation|5

The measure of gamma rays' ionizing ability is called the exposure2:

The coulomb per kilogram (C/kg) is the SI unit of ionizing radiation exposure, is the

amount of radiation required to create 1 coulomb of charge of each polarity in 1 kg of

matter.

The röntgen (R) is an obsolete traditional unit of exposure, represented by the amount

of radiation required to create 1 esu of charge of each polarity in 1 cm3 of dry air.

1 röntgen = 2.58×10−4

C/kg

The effect of gamma and other ionizing radiation on living tissue is more closely related to

the amount of energy deposited rather than the charge. This is called the absorbed dose:

The gray (Gy) equal to units of (J/kg), is the SI unit is the amount of radiation required

to deposit 1 joule of energy in 1 kg of any kind of matter.

The rad is the deprecated CGS unit, equal to 0.01 J deposited per kg. 100 rad = 1 Gy.

The equivalent dose is the measure of the biological effect of radiation on human tissue. For

gamma rays, it is equal to the absorbed dose.

The sievert (Sv) is the SI unit of equivalent dose, which for gamma rays is numerically

equal to the gray (Gy).

The rem is the deprecated CGS unit of equivalent dose. For gamma rays it is equal to

the rad or 0.01 J of energy deposited per kg. 1 Sv = 100 rem.

2 Measuring Gamma radiation exposure (adapted from: http://www.nrc.gov/about-nrc/radiation/health-

effects/measuring-radiation.html)

Gamma Irradiation|6

3.0 PRINCIPLE OF OPERATION

Food irradiation uses the principle of exposing foods to the ionizing, the very high-energy of

invisible lightwaves radiation. The process controls the amount of radiation the food absorbs.

This method also sometimes referred as ―cold‖ process as radiation energy that applied is

converted to heat during treatment but the process normally increases the product temperature

by about 1oC only.

Gamma radiation is often used to kill living organisms, in a process called irradiation.

Applications of this include the sterilization of medical equipment (as an alternative to

autoclaves or chemical means), the removal of decay-causing bacteria from many foods and

the prevention of the sprouting of fruit and vegetables to maintain freshness and flavor.

3.1 How Gamma Rays Works?

When gamma radiation passes through biological tissues such as foods, some of the energy of

the radiation is absorbed by molecules in the food. The gamma radiation initially interacts

with food nutrients to produce similar reactive chemical intermediates that are transient and

disintegrate rapidly after exposure to ionizing radiation. The effects of irradiation are mainly

due to the indirect action of these transient chemicals rather than by the direct effect of the

radiation itself. A given amount of radiation energy absorbed by the food is called the

irradiation dose. Absorbed radiation energy excites electrons such as accelerates their

revolution in their atomic orbits in food molecules, until some of those excited electrons fly

out of their orbits, creating charged particles. This ionizing effect splits molecules.

The primary mechanism in which food irradiation can kills bacteria is through the

splitting of water molecules into hydrogen (H+), hydroxyl (OH

-) and oxygen (O

-2) radicals.

Those radicals react with and destroy or deactivate bacterial components such as DNA,

proteins and cell membranes. Radiation also capable to damage or breaking large molecules

such as DNA and enzymes. These reactions prevent bacteria from replicating destroy the

pathogen population’s growth and effectively kill germs in the food.

For example, such amount of doses of gamma radiation can be used to inactivate

pathogenic and spoilage organisms; retard or arrest decay processes; prevent premature

ripening, germination or sprouting, and rid foodstuffs of organisms harmful to plants or plant

products.

Gamma Irradiation|7

Exposing strawberry to the gamma rays of Cobalt-60.

Energy from gamma ray passing through the strawberry is enough to destroy many pathogenic bacteria and enzyme activities that cause the food to spoil.

The gamma radiation dosage given is not strong enough to change the quality, texture, flavor and taste of the strawberry.

Figure 2: Example of gamma radiation application on strawberry.

(Source: http://www.kentchemistry.com/links/Nuclear/radioisotopes.htm)

3.2 Effect of Radiation Dosage

The dose for food irradiation is the amount of radiation absorbed by the food and it is not the

same as the level of energy transmitted from the radiation sources. The dose is controlled by

the intensity of radiation and the length of time the food is exposed. In the past, the term used

was rad, short for "radiation absorbed dose," which is 100 ergs absorbed by 1 gram of matter.

The rad has been replaced by the gray (Gy). One gray is equal to 100 rads or 0.00024 Calorie

(i.e., diet calorie) per kilogram of food. (0.00024 Calorie per kilogram equals 0.0001 Calorie

per pound.) The FDA's regulations describe radiation levels in terms of the kilogray (kGy),

equal to 1000 Gy. The dose (number of kGy) permitted varies according to the type of food

and the desired action. Treatment levels are categorized by FDA as follows:

i. Low Dose Level (10 Gy to 1 kGy) – Radicidation

ii. Medium Dose Level (1 kGy – 10 kGy) – Radurization

iii. High Dose Level ( 10 kGy – 100 kGy) – Radappertization

Table 3 below shows the level of dosage approved by FDA and the application of gamma

radiation on different type of food (adapted from Kalyani and Manjula, 2014).

Gamma Irradiation|8

Table 3: Level dosage of Gamma Radiation and the Application

Type of dosage Dosage (kGy) Application Examples of food

Low Dose

(Radicidation)

0.05 – 0.15 Inhibition of sprouting Potatoes, onions, garlic, root ginger,

yam

0.15 – 0.50 Insect disinfestations and parasite

disinfection

Cereals, fresh and dried fruits, dried fish

and meat, fresh pork

0.25 – 1.0 Delay of physiological processes such

as ripening and browning Fresh fruits and vegetables.

Medium Dosage

(Radurization)

1.0 – 3.0 Extension of shelf-life Fresh fish, strawberries, mushrooms

1.0 – 7.0 Elimination of spoilage and pathogenic

microorganisms

Fresh and frozen seafood, raw or frozen

poultry and meat

2.0 – 7.0 Improving technological properties of

food

Grapes (increasing juice yield),

dehydrated vegetables (reduced cooking

time)

High Dosage

(Radappertization)

10 – 50 Decontamination of certain food

additives

Spices, enzyme preparations, natural

gum and ingredients

30 – 50 Industrial sterilization (in combination

with mild heat)

Meat, poultry, seafood, prepared foods,

sterilized hospital diets.

Gamma Irradiation|9

3.3 Radiation Processing

There are several processes that are referred to as Food Irradiation. The aim of each process is

to kill or inhibit the growth of unwanted living organisms or to affect the product morphology

in a beneficial way that will extend shelf-life. Each process has an optimal dose of ionizing

energy (radiation) dependent on the desired effect. Some of the major processes are:

i. Pathogen Reduction

Irradiation is used to efficiently eliminate pathogenic organisms including

bacteria and parasites. For example;

a) Irradiating ground beef to make it safe from E. coli O157:H7.

ii. Sterilization

Irradiation is used at a very high dose to eliminate all organisms so that

refrigeration is not required (shelf stable). For example;

a) Certain foods are sterilized for NASA astronauts and for immune-

deficiency patient.

iii. Sanitation

Irradiation is widely used to reduce organisms for spices, herbs and other dried

vegetable substances. For example;

a) Spice blends that are added to meat for hot dogs and other ready to eat

products that may not be cooked again.

iv. Shelf – life Extension

On certain fruits and tubers, irradiation delays ripening and/or sprouting. For

example;

a) Irradiating berries to reduce mold.

b) Irradiating fresh fruits to extend their market reach.

c) Irradiating potatoes, onions and garlic to impair cell division and hence

allow them to go through the off season without sprouting.

v. Disinfestation

Irradiation is used to stop reproduction of both storage and quarantine insect

pests. For example;

a) Irradiating foreign produced mangoes to eliminate the seed weevil,

which is a quarantined pest, for import to the US.

b) Irradiating papaya is to eliminate fruit flies, which are quarantined

pests, for import from Hawaii or foreign countries into the US

mainland.

Gamma Irradiation|10

3.4 Irradiation Equipment and Facilities

Food is irradiated in ―irradiators‖ that use electron beams or gamma rays or x-rays as their

source of ionizing energy (radiation). Irradiators are designed to enable the irradiation of the

food products to the desired dose and dose uniformity, without exposing workers or members

of the public to radiation and without any effect on the environment. All commercial

irradiators have four primary components:

i. A source of radiation.

ii. A method of product conveyance.

iii. ―Shields‖ to prevent exposure of personnel.

iv. The environment to radiation and safety systems.

Ionizing radiation is penetrating energy and thus, products are usually irradiated after

they are fully packaged. The choice of which irradiator is most cost effective for a particular

product depends on the type of product, how it is packaged, the product dose, dose uniformity

requirements and, most important, logistics.

3.4.1 Gamma Irradiator Facility

Gamma rays are emitted spontaneously through the radioactive decay of Co-60 and Cs-137.

Co-60 are the most used radioactive in gamma facility. Co-60 decays with a half-life of 5.3

years (every 5.3 years the amount of Co-60 will half in value). Cs-137 is very rarely used as a

gamma ray source although it has a longer half-life of 30.1 years. However, Cs-137 emits

gamma rays that are approximately half the energy of those emitted by Co-60. Under normal

conditions, Cesium also occurs as an anion in a chemically stable ionic salt. Thus, the metallic

form of Co-60 has higher gamma ray energies for large irradiation facilities.

Food irradiation using Cobalt-60 is are the most preferred compared to Cs-137 due to

the deeper penetration that enables controlling treatment of entire industrial pallets or totes,

reducing the need for material handling. Radioactive material must be monitored and

carefully stored to shield workers and the environment from its gamma rays. During operation

this is achieved by substantial concrete shields. The example of commercial gamma irradiator

is shown in Figure 3.

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Figure 3: Gamma Irradiator Device Model JS9600 (Registered by the International

Atomic Energy Agency with serial number IR-185.)

(Source: https://upload.wikimedia.org/wikipedia/su/1/15/Commercial_gamma_irradiator.jpg)

Gamma Irradiation Device Model JS9600 – Registered by the International Atomic Energy

Agency with serial number IR-185 (Adapted from GAMMA-PAK STERILIZATION &

TRD. INC.) consists of:

1. Process Control (Control Room)

- In the Gamma Irradiation Facility, powerful and reliable computer system

(Programmable Logic Control) is important for irradiation process. Each phase of

irradiation process is controlled in a very sensitive mode. Irradiator turns off

automatically and gives audio and visual alarms when unexpected situation

occurred.

2. Product Transportation System

- The products are placed inside the aluminum tote boxes on the conveyor system

and sent to the irradiation room. The product boxes are moved around the gamma

radiation source by pneumatic pistons. After treated with radiation the products

automatically taken out by conveyor and stored at the irradiated product area.

3. Source and Source Rack

- Source rack contains of a stainless steel frame that has specific dimensions and

rectangular intermediate components. The source pencils that are 45 cm long and

with a diameter of 0.81 cm located on each module. Metallic formed Co-60 slugs

used as gamma source are placed in these source pencils. Source pencils are double

encapsulated in stainless steel tubes and both ends are formed in a leakage proof

Gamma Irradiation|12

method. The source pencils must protect their leakage proof characteristics for 20

years. Unstable Co-60 isotopes is gained from the stable Co-59 atom by adding a

neutron into its nucleus through neutron bombardment in the nuclear reactors. Co-

60 isotope discharges one beta and two gamma rays with energy levels of 1.17

MeV and 1.33 MeV and transformed to stable Ni-60 atom.

4. Irradiation Cell (Biological Shield)

- This is the shielded room in which the irradiation process. Operating the Irradiation

Facility, the Co-60 source rack is taken out of the water pool and placed among the

boxes full of products. The protective concrete barriers are called biological shield.

The thickness of the biological shield depends on the activity of the employed

cobalt source and it was designed to meet the requirements of the International

Radiation Protection Regulations. The personnel and product entry doors of the

irradiation cell can be accessed after a maze for protection purposes.

5. Source Storage Pool

- In order to turn the irradiation process off in the Irradiator, Co-60 source panels is

immerse into a pool full of water with 6-meter depth. Co-60 source continues

emitting gamma radiation inside the water. On the other hand the water mass within

3.2 meters thick from the upper part of the source rack avoids the gamma lights to

reach in the irradiation cell so that the personnel can enter to the irradiation cell

without being exposed to the gamma rays and carry out the maintenance and repair

works safely.

6. Product Storage Area

- The gamma irradiation facility consists of two product storage which is

unprocessed products storage area and processed products storage area. The

products received are taken to the unprocessed products storage area and after they

are prepared for irradiation process loaded to the conveyor. After the irradiation

process the treated products are taken to the processed products storage area for

loading to the vehicles.

Gamma Irradiation|13

3.5 Advantages and Limitation of Gamma Irradiation

The use of Gamma Irradiation on food is a big issue that created a hot debate. The term of

―radiation‖ usually indicate the potential harm and hazard. There may many advantages

beyond safety and some disadvantages to be consider such as:

The Advantages

Reduce the occurrence of food-borne disease by destroying pathogenic organisms

without affecting the sensory quality the food.

Reduce spoilage of foodstuffs by retarding or arresting decay processes and destroying

spoilage organisms.

Reduce loss of foodstuffs by inhibit or slowing ripening, germination or sprouting.

Get rid of organisms that harmful to plant or plant products (phyto-sanitary treatment).

Provide minimal further processing for food that is not intended to be cooked such as

salad.

Irradiation serve as alternative treatments for fresh fruits and vegetables that capable of

reducing bacterial populations by only 90 to 99 percent as traditional treatment such as

Chemical preservation (e.g: washing, chlorination, warm water dips) that not effective.

Can be used to treat heat sensitive food product as irradiation is non-thermal food

preservation, can maintain freshness and physical states of the food.

Packaged and frozen food may also be treated.

Help people with immune deficiencies to be able to have safe foods to eat

The Disadvantages and Limitation

Irradiated food can be more expensive, due to the initial costs of a food irradiation

facility. A typical commercial facility cost about $3 to $5 million to be build.

Psychological and acceptance issues due to the safety concern of induction of

radioactive on food.

Insufficient or incorrect amounts of radiation could lead to mutations among microbial

strains, creating more dangerous bacteria and long-term use of irradiation will cause

bacteria and microbes to adapt, becoming resistant to the radiation and harder to kill.

Radiolytic products are formed by the radiation breaking molecular bonds in water,

leaving free radicals that in turn either recombine into water or react with other

chemicals that change in the taste, odor, color or texture of food.

Gamma Irradiation|14

Macronutrients (proteins, fats and carbohydrates) and minerals (iron, phosphorous and

calcium) are substantially unaffected by radiation doses at approved levels but not at

higher dosage. In addition, some vitamins, particularly thiamine, undergo an

appreciable reduction when exposed to radiation.

3.6 Importance of Gamma Irradiation for Future Trend in Food Application.

The interest in the irradiation process of food in Malaysia is growing persistently due to high

number of food loss from infestation, contamination, and spoilage caused by bacteria, fungi

and pest. According to Food and Agriculture Organization (2005), it is estimated about 25 to

50% of all food product is lost due to bacteria, fungi and pest worldwide. In addition, due to

environmental concern, restricted regulations or complete prohibition on the use of a number

of chemical fumigants for insect and microbial control in food, irradiation is an effective

alternative to protect food against insect damage and reducing the dependence on chemical

pesticides. Malaysia’s climate which categorized as equatorial, being hot and humid

throughout the years also contributes to the food lost due to organism infestation and spoilage.

Thus, irradiation of food using gamma rays is an effective alternative to protect food against

insect damage and reducing the dependence on chemical pesticides.

The increasing need also due to the rising concerns over food-borne diseases and

growing international trade in food products that must meet strict import standards of quality

and quarantine, all areas in which food irradiation has demonstrated practical benefits when

integrated within an established system for the safe handling and distribution of food.

Malaysia is among the food producers country that involves actively in food trades which

import food product from other country and export food to others. Thus, gamma radiation

processing offers an alternative for other preservation treatments and solves all the problems

of post-harvest, packaging and distribution of foods, but it also can play an important role in

cutting losses and control foodborne diseases. Gamma Irradiation also important for food

quarantine treatment against major insects species and food diseases. For tubers and roots,

sprouting is the major cause of losses. Thus, there is a concern to find alternative methods to

preserve the tubers and roots instead the use of chemicals. Irradiation serves a better technique

to inhabit the sprouting. It is also applied to the physiological process such as browning and

ripening of fruits and wilted of vegetables (WHO, 1988).

Gamma Irradiation|15

3.7 Foods Suitable For Irradiation

The main types of food that have been classified as safe to irradiate are meat, seafood, fruit,

vegetables, herbs and spices. The EU authorized list of irradiated foods currently only

contains dried aromatic herbs, spices and vegetable seasonings, although the EU Scientific

Committee for Food has issued favorable opinions on a number of other food types. However,

other type of food can undergo gamma irradiation treatment after the food being frozen or

packaged.

3.8 Application of Gamma Irradiation on Malaysian Food

Malaysia aim to increase food production, supply and decrease the loss due to infestation,

spoilage and diseases. However, the problem of storage, transportation and quality is of

utmost importance. Food irradiation is a positive alternative method that has been proven to

be safe and versatile. It will find a place among the traditional food and food raw material,

ingredient and packaging material.

Malaysian Standard was developed by the Working Group on Food Irradiation under the

authority of the Food and Agricultural Industry Standards Committee. MS 1265 consists of

the following parts, among the Malaysian food product that include under the general title

Code of good irradiation practice:

Part 2: Bulb and tuber crops for sprout inhibition

Part 3: Fresh fruits and vegetables for insect disinfestations and as quarantine treatment

Part 4: Cereal grains for insect disinfestations

Part 5: Dried fish and dried salted fish for insect disinfestations

Part 6: Bananas, mangoes and papayas for shelf-life extension

Part 7: Fish, frog legs and shrimps for the control of micro flora

Part 8: Prepackaged meat and poultry for the control of pathogens and/or to extend shelf-life

Part 9: Spices, herbs and vegetable seasonings for the control of pathogens and micro flora

Part 10: Dried meat and dried salted meat of animal origin for insect disinfestations, control

molds and reduction of pathogenic microorganisms

Gamma Irradiation|16

Papayas Fruit Irradiation for Shelf-Life Extension

This Malaysian Standard describes the code of good irradiation practice for the following

fresh tropical fruits such as papaya (Carica papaya L.). The purpose of irradiation of papaya

fruits is to extend the normal shelf-life by delaying their ripening and for the reduction of

microorganisms spoilage or insect disinfestation.

Papayas are climacteric fruits and should be harvested during the hard mature greenish

state. Papaya to be irradiated should be freshly harvested, clean and free of any physical

damages or physiological condition, and without microbial spoilage or insect infestation. The

fruits should be harvested at the suitable maturity stage and before starting their climacteric

changes. The irradiation is applied for the purpose of delaying papaya ripening so that the

papaya ripened upon arrival at their destination markets.

After harvested, the fruits undergo fungal control where the irradiation treatment to

control fungi requires doses might be phytotoxic. In order to control spoilage due to fungi by

irradiation treatment, these fruits are to be given a pre-irradiation treatment with hot water.

For example, papayas are pre-irradiated for 20 min at 49oC or 10 min at 50

oC. Approved

chemical fungicide may be added in the water to maximize the fungi control.

The fruits are separately wrapped in clean white paper and packed in fibre board or

wooden containers with wood wool as a packing material. Hot-water treated fruits should be

dried well before wrapping and packing in containers. The container size may vary depending

on the range of the fruit size. Irradiation can be performed in the package.

Absorbed doses in the range of 750 Gy to 1000 Gy given to papayas in the pre-

climacteric state are effective. Absorbed dose above 1500 Gy may cause changes in physical

characteristics, such as scalding of the skin. Irradiated papayas have acceptable sensory

characteristics. Papayas given a combination heat-radiation treatment, for example 20 min in

49 water for disease control and 750 to 1000 Gy, are satisfactory and ship well. This

irradiation process will ensure that the papaya will have extended shelf life and delayed in

ripening and only be ripened upon arrival at the destination.

Gamma Irradiation|17

4.0 Conclusion

Food irradiation technology has exceptional advantages over conventional methods of

preservation such as chemical, freezing, canning, dehydration, salting and others. This process

not contributes to the loss of nutrient content, flavour, odour, texture, and freshness.

Compared to chemical fumigants, the method of irradiation is more effective and does not

leave hazardous toxic residues in food. The World Health Organization (WHO) (1987)

summarizes advantages of the irradiation technique over conventional food processing

methods including:

1. Foods can undergo treatment even after packaging.

2. Irradiation treatment permits the conservation of foods in the fresh condition.

3. Perishable foods can be kept longer without noticeable quality loss.

4. The cost of irradiation and the low energy requirements compare favorably with

conventional food processing methods. Irradiation treatment up to the recommended

dose leaves no residue; changes in nutritional value such as loss of some vitamin.

5. Foods processed under recommended conditions for irradiation do not become

radioactive, a fact that many people do not understand.

Previous technology of post-harvest practices and inadequate storage and preservation

facilities includes adverse climatic conditions cause tremendous losses in agricultural, marine

and food products. Thus, food irradiation technology potentially serves as an effective method

for minimizing these losses and increasing their availability, and increase imports and exports

trades.

Food irradiation technology safely preserves food and controls pathogens. Irradiation has

been researched more than any other food process. It has come a long way since the

pioneering days of early 1900’s. Important UN agencies such as the World Health

Organization and the Food and Agriculture Organization now recognize irradiation as another

important method of controlling pathogens and food spoilage. Food irradiation is also

regulated and endorsed as safe by agencies as the FDA, USDA and WHO. Concerns will

always remain, but if following best management practices and standard operating procedures

we can gain the benefits of the technology with minimal consequences.

Gamma Irradiation|18

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