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Journal of Nutritional Health Sciences

Volume 1| Issue 3

Review Article Open Access

Irradiation as a non-destructive method of food preservation

M. A. K. K. P. Perera 1 * 1 Food and Water Division, Department of Government Analyst's *Corresponding author: M. A. K. K. P. Perera, Food and Water Division, Department of Government Analyst's, No. 31,

Isuru Mawatha, Pelawatta, Battaramulla, Sri Lanka; Email: kamaninamadi@yahoo.com

Citation: M. A. K. K. P. Perera (2017) Irradiation as a non-destructive method of food preservation: Nessa J Nutritional

Health Sci

Received: April 1st 2017, Accepted: May 9th 2017, Published: June 1st 2017

Copyright: © 2017 M. A. K. K. P. Perera. This is an open-access article distributed under the terms of the Creative

Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided

the original author and source are credited.

Abstract

Contamination of food with harmful bacteria can cause lethal food poisoning and spoilage. Despite substantial efforts

in avoidance of contamination, an upward trend in the number of outbreaks of foodborne illnesses caused by non-

soprengenic pathogenic bacteria are reported in many countries. Good hygienic practices can reduce the level of

contamination but most importance pathogens cannot be eliminated. Several decontamination methods exist but the

most versatile treatment among them is the processing with ionizing radiation. It may be considered as a second big

breakthrough after pasteurization. Irradiation of food is a process of exposing food to ionizing radiation such as

gamma rays emitted from the radio-isotope 60Co and 137Cs or high energy electrons or x-rays produced by machine

sources. The use of ionizing radiation to destroy harmful microorganisms in food a safe, efficient, environmentally

clean and energy efficient process. Depending on the absorbed dose of radiation, various preservative effects can be

achieved such as reduced storage losses, extended shelf-life and/or improved microbiological and parasitological

quality of foods. Irradiation is endorsed as a food safety process by independent health organization and regulatory

agencies round the world. Pasteurization or sterilization of food by irradiation can be used for all classes of food,

especially meat, poultry, spices, vegetable seasonings, dried and fresh fruits and vegetables, fish and fish products, egg

and egg products, mushrooms, herbs and spices etc. An extensive education is needed for broad public acceptance. A

strategic, multi-year, broad-scale education campaign, targeting both professional and lay audiences is necessary.

Labeling is necessary, so that people can freely choose whether to use this safe and wholesome processed food.

GC/MS, ESR, TL, PSL, DNA comet assay, DEFT/APC are reliable methods for the detection of irradiated food in

confirming compliance with regulations regarding food irradiation.

Keywords: food preservation, irradiation, decontamination, foodborne pathogens, consumer acceptance, detection.

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Journal of Nutritional Health Sciences Volume 1| Issue 3

Introduction

Food and its constant availability are among the basic human rights. Yet one person out of eight in the world population

today suffers from chronic malnourishment. Thus the problem become worse as the world's population is expected to be

double during the next thirty or forty years (van Kooij, 1981)

Foods are mainly composed of biochemical compounds which are derived from plants and animals. Carbohydrates,

proteins and fats are the major constituents of food. In addition, minor constituents such as minerals, vitamins, enzymes,

acids, antioxidants, pigments, flavors are present (Miller, 2005).

Foods can undergo various physical, chemical and biological deterioration processes. The major factors that are affected

to food spoilage or deterioration are identified as (1) growth and activities of microorganisms (bacteria, yeasts and molds),

(2) activities of food enzymes and other chemical reactions within food itself, (3) infestation by insects, rodents etc., (4)

Inappropriate temperature for a given food, (5) either the gain or loss of moisture, (6) reaction with oxygen and (7) light

(Rahman, 2007).

The vast majority of instances of food spoilage can be attributed to one of two major causes: attack by microorganisms

such as bacteria and mold, or oxidation that causes the destruction of essential biochemical compounds and/or the

destruction of plant and animal cells. As a result of these reactions, creates an adverse effect on appearance, flavor,

texture, color, consistence and/or nutritional quality of food (Miller, 2005).

Food safety is a global issue with paramount environmental and public health consequences if inadequately maintained

(Ashley et al, 2004). Contamination of foods, especially of that origin from animal with microorganisms, particularly

pathogenic non-spore forming bacteria, parasitic helminths and protozoa is an enormous public health problem suffering

all over the world (Farkas, 1998). According to the literatures, a large part of our harvested foods is loss due to various

kinds of wastage and spoilage (van Kooij, 1981).The potential for contamination is inherent at each step along the food

supply and preparation processes. That means losses take place at the post harvesting processes, storage and transportation

and it can also be happened through contaminated ingredients that are used to prepare foods such as spices, herbs, dried

vegetable seasonings, or contaminated raw materials such as meats, fish, or damaged/spoiled fruits or vegetables (Farkas,

1998; Ashley et al, 2004; Alam Khan and Abrahem, 2010).

Thus, there is a strong need to find a method to reduce or eliminate one or the other (or both) of these causative agents.

These methods should prevent the growth of bacteria, fungi and other microorganisms as well as retarding the oxidation

of fats which causes foods to turn rancid and also inhibit the enzymes processes that cause a food to rapid ripening after it

is harvested (Farkas, 1998; Ashley et al, 2004; Alam Khan and Abrahem, 2010). All the preventive processes are

collectively called as food preservation.

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Journal of Nutritional Health Sciences Volume 1| Issue 3

Microbial safety and stability as well as sensory and nutritional quality of processed foods are based on the application of

traditional or emerging preservation factors. However, preservation techniques usually accomplish safety, stability and

quality objectives by combining of more than one factor (Leister and Gorris, 1995; Lopez-Maloand Palou, 2005). The

most important factors used in food preservation to control microbial growth are high or low temperature, water activity,

pH, antimicrobials and competitive flora (Leister and Gorris, 1995; Lopez-Malo and Palou, 2005).

Food preservation has become an increasingly important component in food industry as fewer people eat foods produced

on their lands and as consumers expect to be able to purchase and consume foods that are out of season. Preservation of

food is done during the months when food is available in large quantity and therefore at low cost. Food preservation

reduces the wastage of food that means excess food which would have otherwise been wasted. Food preservation adds

variety to the food. For example, mango is a summer fruit and grows in large quantities during the month of April to

August. Different varieties of mango are grown in different parts of the country. In the absence of fresh mango in other

months of the year, canned and dehydrated mango may be made use of and also they can reach areas where the food item

is not grown then decreases dietary inadequacies of the people living in those areas. Preserved food has long shelf life.

Preservation of foods usually reduces bulk and it makes their transportation and storage easier since it requires less space.

Methods of Food Preservation

The methods those can be used as preservation of foods should totally prevent, delay or otherwise reduce food spoilage.

The preservation can expand the shelf life of food and can lengthen the time long enough for it to be harvested, processed,

sold and kept in the consumer's home for a reasonable length of time (Farkas, 1998). Maintaining or creating nutritional

value, texture and flavor is an important aspect of food preservation, although some methods drastically altered the

character of food being preserved, in some cases these changes have now come to be seen as desirable qualities, as with

cheese, yogurt, pickled onions etc. There are many preservation methods are available. These methods consist of thermal

and chemical processes. Out of these the most versatile treatment is the processing with ionizing radiation (Krauss et al.,

1933; Tressler et al., 1957; Dieterich et al., 1967;Arsdel et al., 1968; Caric et al., 1987; Cook and DuMont, 1991; Farkas,

1998; Susana et al., 2006; Rahman, 2007); https://en.wikipedia.org/wiki/Ethylene_oxide#Physiological_effects;

http://www.foodsafetysite.com/educators/competencies/general/foodprocessing/processing2.html;

http://wiki.zero-emissions.at/index.php?title=Sterilization_in_food_industry;

http://wiki.zero-emissions.at/index.php?title=Pasteurization_in_food_industry; http://study.com/academy/lesson/what-is-

ethylene-oxide-uses-safety-technology.html; https://en.wikipedia.org/wiki/Fermentation_in_food_processing;

http://crees.org/resources/files/forms/25.pdf;

https://en.wikipedia.org/wiki/Food_additive; https://en.wikipedia.org/wiki/Preservative (Table 1)

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Journal of Nutritional Health Sciences Volume 1| Issue 3

In this article, attention is drawn to current applications of irradiation of foods as a non-destructive method of food

preservation.

The increasing global energy crisis has led a review of the efficiency of traditional methods of food preservation in term

of energy consumption. In addition, some wildly applied methods such as chemical preservation - curing and addition of

chemical preservatives and fumigation are now being questioned in term of biological safety, economics and possible

reduction of market quality of the products (van Kooij, 1981; Alam Khan and Abrahem, 2010). While the thermal

pasteurization of liquid foods is well established and satisfactory as a decontamination treatment of such commodities, it

does not suit for solid foods, dry ingredients and fresh foods whose raw characteristics must be maintained to fulfill

specific market requirements (Farkas, 1998; Alam Khan and Abrahem, 2010). The chemical sanitizing procedures (e.g.

fumigation) have inherent problems concerning residue which pose hazards for consumers as well as for workers in food

processing factories and environmental pollution (Farkas, 1998; van Kooij, 1981). Among the physical methods studied

and evaluated as techniques for microbial control, the application of heat is generally considered as the most effective

method available since it can result in the sterilization of foods (Lopez-Malo and Palou, 2005).

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Journal of Nutritional Health Sciences Volume 1| Issue 3

Table 1: physical and chemical methods of food preservation

PHYSICAL METHODS

SMOKING –Smoking is the process of flavoring, cooking or preserving food by exposing it to smoke from burning

or smoldering materials, most often wood. Meat and fish are the most common smoked foods, though cheeses,

vegetables and ingredients used to make beverages such as whisky, smoked beer etc. Smoke adds flavor and is both

an antimicrobial and antioxidant but it does not actually penetrate far into meat or fish is insufficient alone for

preserving food; it is thus typically combined with salt-curing or drying. There are two types of smoking such as cold

smoking and hot smoking.

Cold

smoking

Smokehouse temperatures for cold smoking are typically done between 20 and

300C. In this temperature range, food take on a smoked flavor, but remain

relatively moist. Cold smoking does not cook foods. Meat should be fully

cured before cold smoking. Cold smoking can be used as a flavor enhancer for

items such as chicken breasts, beef, pork chops, salmon etc. The item is hung

first to develop a pellicle, then can be cold smoked for just enough to give

some flavor. Other important thing should keep in mind, is cold smoked foods

should be cooked before consumption.

Hot

smoking

Hot smoking exposes the foods to smoke and heat in a controlled environment.

Hot smoking can be done in a kiln or smokehouse for a short period of time. It

preserves foods in three ways: (1) Heat kills microbes; (2) chemical found in

smoke including formaldehyde and alcohol act as preservatives; and (iii) the

food dries out so there is less moist area for bacteria to grow. Like cold

smoking, the item is hung first to develop pellicle, then smoked. Although

foods that have been hot smoked are often reheated or cooked, they are

typically safe to eat without further cooking. Hams and ham hocks are fully

cooked once they are properly smoked. Hot smoking occurs within the range

of 52 to 800C. Within this temperature range, foods are fully cooked, moist,

and flavorful. If the smoker is allowed to get hotter than 850C, the foods will

shrink excessively, buckle or even split. Smoking at high temperature also

reduce yield, as both moisture and fat are cooked away.

Meat hanging inside a

smokehouse

Racks with hot

smoked pacific halibut

DRYING - Drying is a natural technique for preventing food spoilage. Leaving foods out in the sun or wind to dry

out is probably one of the earliest forms of food preservation. Evidence of the drying of meats, fish, fruits and

vegetables also go back to the earliest recorded human history. There are four types of drying method such as

dehydration, vacuum drying, spray drying and freeze drying.

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Dehydrating -

sun drying

Drying food is a slow process. It is the right combination of warmth, low

humidity and air currents (or wind speed). It can be carried out in the sun or

wind under natural environment or in an oven or a food dehydrator under

controlled environments. In drying, a warm temperature allows the

moisture to evaporate. Air currents (or wind) and low humidity accelerate

the drying process by speeding up the movement of moisture from food to

air

Vacuum

drying

Vacuum drying is a process in which drying is carried out at reduced pressure, which lowers the

heat required for rapid drying. In vacuum drying food is placed in a large container from which air

is removed. Water vapor pressure within the food is greater than that outside of it, and water

evaporates more quickly than in a normal atmosphere. It is biologically desirable since some

enzyme that cause oxidation of foods become active during normal air drying.

Spray drying

Spray drying is a method of producing a dry powder from a liquid or slurry

by rapidly drying with a hot gas. This dried powder can be easily packed

and transported. The surface area of the original food is increased many

times, making dehydration much more efficiently such as production of

milk powder from liquid milk and coffee powder from concentrated

solution of coffee. This is the preferred method of drying of many

thermally sensitive materials such as foods and pharmaceuticals.

Freeze-drying

or

lyophilization

Freeze -drying is based on the dehydration by sublimation of a frozen food.

It is convert solid directly to the gaseous phase without first melting. Due

to the absence of liquid water and the low temperature requirement, stop

most of enzymatic and microbial reactions.

Vacuum

packing

Vacuum packing is a method of packaging that removes air from the

package prior to sealing. It reduces atmospheric oxygen, limiting the

growth of aerobic bacteria or fungi, and preventing the evaporation of

volatile components. Vacuum packing is commonly used to store dry foods

over a long period of time, such as cereals, nuts, cured meats, cheese,

smoked fish, coffee and potato chips. It is also used on short term basis, to

store fresh foods such as vegetables, meats, liquids because it inhibits

bacterial growth.

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SALTING - Salting is the preservation of food with dry edible salt. It is one of the oldest

methods of preserving food. Most bacteria, fungi and other potentially pathogenic organisms

cannot survive in a highly salty environment, due to the hypertonic nature of salt. Any living

cell in such an environment will become dehydrated through osmosis and die or temporally

inactivated. Examples for salting foods are salted fish (dried fish), salted meat (bacon) and

salted vegetables (cabbage and beans)

FREEZING - Freezing is an effective form of preservation because it does not require any added preservatives and

the pathogens that cause food spoilage are killed or inactivated when temperature of food is below -9.5 0C. At this

temperature liquid converted to solid (ice) and is therefore unavailable to bacteria. But it is not effective than thermal

techniques because the pathogens which deactivated (not killed) by freezing will become active when frozen food

thaws. During freezing the time factor is critical. Base on this factor freezing can be categorized into two types such

as slow freezing and quick freezing.

Slow

freezing

The slow freezing creates larger ice crystals. They have the tendency to cause

rupture of cells and the destruction of texture in meats, fish, vegetables and fruits.

Quick

freezing

In order to deal with above problem the technique of quick freezing has been

developed. In this method a food is cooled to or below its freezing point as

quickly as possible and forms smaller ice crystals, less tendency to change the

texture of the food

FERMENTATION - Fermentation in food processing is the process of converting

carbohydrates to alcohol or organic acids using microorganisms such as yeast or bacteria

under anaerobic conditions. The term fermentation sometimes refers especially to the

chemical conversion of sugars into ethanol, producing alcoholic drinks such as wine, beer

and cider. However, similar processes take place in the leavening of bread (CO2 produced by

yeast activity) and in the preservation of sour foods with the production of lactic acid, such

as sauerkraut and yogurt. Other widely consumed fermented foods include vinegar, olives

and cheese. Food fermentation serves five main purposes: to enrich the diet through

development of a diversity of flavors, aromas and textures in food substrates; to preserve

substantial amounts of food through lactic acid, alcohol, acetic acid and alkaline

fermentations; to enrich food substrates with protein, essential amino acids and vitamins; to

eliminate antinutrients; and to reduce cooking time and the associated use of fuel.

Fermented foods:

Bean-based - soya sauce, soya bean paste

Grain-based - beer, bread, sake, rice wine, malt whisky, grain whisky, idli, dosa, vodka

Vegetable-based - mixed pickle, sauerkraut, Indian pickle

Beer and bread, two

major uses of

fermentation in food

Fermented soya bean

food

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Fruit-based - wine, vinegar, cider, perry, brandy, pickling, chocolate

Honey-based - mead, methrglin

Dairy-based - cheese, cultured milk products such as yogurt

Fish-based - fish sauce, shrimp paste

Meat-based - salami, saucisson

Tea-based - pu-erh tea, kombucha

Batter made from rice

and lentil (Vigna

mungo) prepared and

fermented for

baking idlis and dosa

Cheeses

THERMAL TREATMENT -Heating food is an effective way to preserving it, because the great majority of

pathogens are killed at temperatures close to the boiling point of water. The most common types of heat treatment

processes are pasteurization and sterilization.

Pasteurization

Pasteurization is a controlled heating process used to eliminate any

dangerous pathogens that may present in milk, fruit-based drink, some

meat products etc. to make food safe to eat and helped to reduce

transmission of diseases such as typhoid fever, tuberculosis, scarlet fever,

polio and dysentery. However, pasteurized foods are safe; it can be re-

contaminated unless it is not properly handled. For example, all pasteurized

foods must be refrigerated. The pasteurization inactivates most viable

vegetative form of microorganisms but not heat resistant spores. In

pasteurization, generally a heating temperature below 1000C is applied.

High-Temperature-Short-Time Treatment (HTST) pasteurization -

This process uses higher heat for less time to kill pathogen bacteria (e.g. for

milk - 720C or 1610F for 15 seconds).

Low-Temperature-Long-Time Treatment (LTLT) pasteurization -

This process uses lower heat for a longer time (e.g. for milk - 630C or

1450F for 30 minutes).

The temperatures and times depend on the type of food and the final results

one want to achieve such as retaining food nutrients, color texture and

flavor. There are three main types of pasteurization processes such as flash,

steam and irradiation.

Flash pasteurization - Involves a high temperature and short time

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treatment (e.g. for pourable liquid - juices are heated for 3 to 15 seconds).

After heating, the product is cooled (about 40C) and packaged (e.g. boxes

and pouches) and as it allows extended unrefrigerated storage while

providing a safe product.

Steam pasteurization - The methods commonly uses to control or reduce

microorganisms in beef. This system passes freshly-slaughtered beef that

are already inspected, washed and trimmed, through a chamber that

exposes the beef to pressurized stem (88 to 930C or 190 to 2000F) for about

6 to 8 seconds and cooled with a cold-water spray. This process has proven

to be successful in reducing pathogenic bacteria such as E.coli O157:H7,

Salmonella and Listeria without the use of any chemicals.

Irradiation pasteurization - Foods, such as poultry, red meat, spices and

fruits and vegetables are subjected to small amounts of gamma rays. This

process effectively controls vegetative bacteria and parasites foodborne

pathogens and increases the storage time of foods.

Sterilization

Sterilization is a controlled heating process used to completely eliminate

all living microorganisms including thermo resistant spores in milk and

other food. It is used to treat all types of food products. It can be achieved

by physical methods such as moist heat, dry heat, irradiation or chemical

methods.

Ultra-High Temperature (UHT) sterilization - It has a heat treatment of

over 1000C during very short times (e.g. about 1400C for a few seconds), it

is especially applicable to low viscous liquid products (milk, juices, cream,

wine, salad dressing), foods with discrete particles (baby foods, tomato

products, fruits and vegetable juices, soup) and larger particles (stews). The

basis of UHT is the sterilization of food before packaging, then filing into

pre-sterilized containers in a sterile atmosphere. There are two principal

methods of UHT treatment such as direct heating (injection and infusion)

and indirect heating.

Sterilization with moist heat - In this method, temperatures generally

ranging from 110 to 1300C with sterilizing times being from 20 to 40

minutes (e.g. canned foods - at about 1210C for 20 minutes). Higher

temperatures and shorter times may have similar effects (e.g. 1340C for 3

minutes) and lower temperatures and shorter times can also be applied (e.g.

with acid fruit juices, jam or desserts - heating to 80 - 1000C for 10

minutes).

Autoclaver

Injection and infusion

for direct heating in

UHT treatment

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Sterilization with dry heat - In this method, longer exposure times (e.g.

up to 2 hours) and higher temperatures (e.g. 160 - 1800C) are required than

moist heat for killing bacteria end-spores.

Sterilization by ionizing radiation - X ray, gamma radiation is used to

sterilize food and other compact materials.

CHEMICAL MEHTODS

CHEMICAL ADDITIVES - Food additives are substances added to food to preserve flavor or enhance its taste,

appearance or other qualities. Some additives have been used for centuries; for example, preserving food by pickling

(with vinegar), and using sulfur dioxide (for wine). The chemical additives which are used to prevent or inhibit

spoilage of food due to fungi, bacteria and other microorganisms are called as antimicrobial preservatives; and which

are used to inhibit the oxidation of food constituents are known as antioxidants (e.g. oxygen absorber).

Preservatives

Antimicrobial preservatives - These prevent degradation of food by microbial growth. Common

antimicrobial preservatives are sodium benzoate, benzoic acid (used in acidic foods such as jams,

salad dressing, juices, pickles, carbonated drinks, soya sauce); calcium and sodium propionate and

propionic acid (for baked goods); and calcium, sodium, potassium sorbates and sorbic acid (used in

cheese, wine, baked goods); and sodium and potassium sulfite and sulfur dioxide (used in fruits);

nitrate and nitrite (used in meat).

Antioxidants - The oxidation process spoils most food, especially those with high fat content. Fats

quickly turn rancid when exposed to oxygen. Antioxidants prevent or inhibit the oxidation process.

The most common antioxidant additives are ascorbic acid (vitamin C) and calcium and sodium

ascorbates (used in oils, cheese and chips). Other antioxidants include the phenol derivatives such as

butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) (used in food packaging);

gallic acid and sodium gallate (used as oxygen scavenger) and sodium and potassium sulfite and

sulfur dioxide (used in beverages, wine).

FUMIGATION - Fumigation is one of the quickest and most effective ways to eliminate pests from processes food,

wood, large building and sometimes homes. The fumigation also use in quarantine. A substance that is used to

fumigation is called as fumigant. A fumigant is a pesticide that is a gas or forms a gas, when applied. In a high

enough concentration, a fumigant can kill insects and other pests. Fumigants may be odorless and usually cannot be

seen.

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Toxic gas

fumigation

Ethylene oxide (C2H4O), methyl bromide (CH3Br) and phosphine (PH3) are most

commonly used fumigants in the food industry.

Ethylene oxide (C2H4O) - It is a cyclic ether; a colorless and flammable gas at

room temperature with a faintly sweet odor. It is used to remove bacteria and

moulds from food products. The disinfectant effect of ethylene oxide is similar to

that of heat sterilization, but because of limited penetration, it affects only the

surface. This process can take up to 12 hours due its slow action upon

microorganisms, and lengthy processing and aeration time. The gas ethylene oxide

kills microbes through a reaction known as alkylation. This is a process whereby a

hydrogen atom is replaced by an alkyl group. Ethylene oxide is a sterilant,

meaning it is something that kills every living microbe, including bacterial spores

on an inanimate object or surface. It can be used to sterilize equipment that is heat-

sensitive.

Methyl bromide (CH3Br) - Methyl bromide is a colorless gas. At normal

concentrations, it is odorless, tasteless and has no irritating qualities to indicate its

presence. However, at concentrations higher than those used in fumigation it gives

off a sickly sweet odor. It is toxic to all stages of insect life. The gas is 3.3 times

heavier than air and tends to stratify, settling out the low places. Fans are needed

to ensure thorough mixing of gas with air. With fans, methyl bromide penetrates

most commodities very well.

Methyl bromide is used to control pests in processed food or feed. It is strictly for

the treatment of raw or processed commodities and some nonfood products. There

are several materials that should not be exposed to methyl bromide such as iodized

salt, full fat soya flour, Items that may contain reactive sulfur compounds (e.g.

some soap powder, some baking soda), sponge rubber, foam rubber (cushions and

mattresses), Leather goods, woolens, paper (writing paper cured by the sulfide

process, photographic materials used in dark rooms and cinder blocks.

Phosphine (PH3) - Phosphine is used to fumigate raw agricultural commodities

such as grains, seeds, cotton, wool and tobacco. Also it uses to treat animal feeds

and feed ingredients, processed foods and nonfood items. The fumigation process

is carried out in boxcars, containers, ships and other transport vehicles, bins, mills,

food processing plants and warehouses.

There are two main types of phosphine fumigants: aluminium phosphide and

magnesium phosphide. These "metal phosphides" are formulated as solids that

react with moisture in the air to produce "hydrogen phosphide" (phosphine gas).

Phosphine also comes as a bottled product (phosphine dissolved in liquid carbon

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dioxide). Phosphine gas is colorless and highly toxic to all stages of insect and

animal life. It has a distinct garlic or carbide odor that is readily detectable at

levels below worker protection limits (0.3 ppm). The odor is due to an impurity

rather than phosphine gas itself. Aluminium phosphide is the main form used to

treat agricultural commodities. Magnesium phosphide is more reactive than

aluminium phosphide. It is preferred when rapid release is desired and treatment is

performed at lower temperature and humidities.

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Journal of Nutritional Health Sciences Volume 1| Issue 3

Due to these reasons and keeping mind the universality of the food spoilage, arising a need to develop emerging

technologies those can be used to achieve almost all the objectives of food preservation (Lopez-Malo and Palou, 2005

Alam Khan and Abrahem, 2010;). This is where food irradiation and other alternatives come into the picture (Farkas,

1998; Alam Khan and Abrahem, 2010). The pasteurization or sterilization of food by irradiation is a technology useful for

all classes of food as well as this method can be used for preventing foodborne illness, preservation, control of insects,

delaying sprouting and ripening and sterilization of food of both liquid and solid by using different approved doses

(Acheson and steele, 2001; Akram and Kwon, 2010) (Figure 1).

Figure 1: Uses of ionizing radiation in food preservation

Irradiation of Food

The process of irradiation involves exposing the food to ionizing radiation so that a prescribed quantity is absorbed. These

ionizing radiation either gamma rays from the nuclides 60Co or 137Cs or x-ray generated from machine sources operated at

or below an energy level of 5MeV or electron beams generated from machine sources operated at an energy level of 10

MeV ((van Kooij, 1981; CAC/RCP 19-1979; WHO, 1994; Farkas, 1998; Acheson and Steele, 2001; CAC/CX-STAD 106-

1983, Rev.1, 2003; Alam Khan and Abrahem, 2010). These types of radiation are chosen because: they produce the

desired food preservative effects; they do not induce radioactivity to foods or packaging materials; and they are available

in quantities and at costs that allow commercial use of the irradiation process (Beaker, 1983; Farkas, 2004; Alam Khan

and Abrahem, 2010).

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Journal of Nutritional Health Sciences Volume 1| Issue 3

Because the irradiation does not heat the treated material, the food keeps its freshness (fruits, fish, vegetable) and its

physical state (frozen or dried commodities) as before the radiation treatment (van Kooij, 1981). Irradiation leads to the

destruction of pathogenic non-spore forming foodborne bacteria and parasitic organisms such as trichina. As a result of

this, consumers protect from microorganisms-related diseases such as salmonellosis, hemorrhagic, diarrhoea caused by

Escherichia coli or gastroenteritis from Vibrio vulnificus (Thayer et al., 1996). This destruction is mainly based on the

principle that ionizing radiation causes very effective disruption of DNA molecules in the nuclei of the cells rendering

them inactivated (Diehl, 1995; WHO, 1994). Therefore microorganisms, insect gametes and plant meristems are

prevented from their reproduction, which consequently results in various preservative effects as a function of the absorbed

radiation dose (Table 2), while chemical and other radiation induced changes are minimal (Thayer, 1990).

Table2: Dosage of radiation of various application of food irradiation (Alam Khan and Abrahem, 2010)

Preservative Effects and Types of Application Dose Requirements

(kGy)

Killing and sterilizing insects (disinfestations of food) 0.2 - 0.8

Prevention of reproduction of foodborne parasites 0.1 - 3.0

Decreasing after-ripening and delaying senescence of some fruit and

vegetables; extension of shelf-life of food by reducing of microbial

populations

0.5 - 5.0

Elimination of viable non-spore forming pathogenic micro-organisms

(other than viruses) in fresh and frozen food 1.0 - 7.0

Reduction or elimination of microbial population in dry food ingredients 3.0 - 10.0

An important reason for the relatively high sensitivity of the DNA to the radiation is the fact that DNA molecules are

much larger than other molecular structures inside the cell. The damage is either direct caused by reactive oxygen-

centered radicals (.*OH) originating from the radiolysis of water or indirect. In the case of indirect, the damage to the

nucleic acids occurs when radiation ionizes an adjacent molecule, which in turn reacts with the genetic material. In view

of the fact that water is a major component of most foods and microbes, it is often the adjacent molecule that ends up

producing a lethal product (Grecz et al., 1983; Alam Khan and Abrahem, 2010). The very reactive hydroxyl radical (.*OH)

and are known to interfere with the bonds between nucleic acids within a single strand or between opposite strands. The

survival of a microorganism, after having sufficient ionizing radiation as gamma or electron beam depends upon its

enzymatic DNA repair system, the number of copies of given gene within the DNA and the given radiation dose (Molins,

2001; Akram and Kwon,

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2010).Although biological systems have a capacity to repair both single stranded and double stranded breaks of DNA

backbone, the damage occurring from irradiation is random and extensive. Therefore, recovery

processes in bacteria after their radiation damage are unlikely to occur (Razskazovskiy et al., 2003; Alam Khan and

Abrahem, 2010). The differences of the sensitivity to radiation among microorganisms are related to the differences in

their chemical and physical structure and their ability to recover from the radiation injuries (Alam Khan and Abrahem,

2010). The amount of radiation required to controlling the microorganisms in food, therefore, depending on resistance of

the strand and the number of organisms present (Alam Khan and Abrahem, 2010). In addition to the their inherent

abilities, several environmental factors such as composition of the medium, moisture content, temperature during

radiation, presence or absence of oxygen and others, significantly influence their radiation resistance, particularly in

vegetative cells (Ashley et al, 2004).

The benefits of irradiation also include the fact that it causes only minimal temperature raise in the product and can be

applied through packaging materials as a terminal treatment, thus it eliminates the re-contamination or re-infestation of

product (Alam Khan and Abrahem, 2010). Radiation caninactivate organisms in food that are in the frozen state without

thawing them up (Farkas, 1998).

In fact, heating, drying, and cooking may cause higher nutritional losses. In addition to that certain carcinogenic aromatic

and heterocyclic compounds produced during the thermal treatment of food at high temperature were not identified in

food after irradiation (Becker, 1983; Alam Khan and Abrahem, 2010). According to Miller (2005), macro-nutrients such

as carbohydrates, proteins and lipids and micro-nutrients mainly water-soluble and fat-soluble vitamins are not

significantly affected by irradiation below 10 kGy radiation doses. However, with higher radiation doses (above 10 kGy),

structural properties of the fibrous carbohydrates can be degraded, and lipids in the presence of oxygen, can become lipid

hydro peroxides. This oxidation product can cause undesirable odours and flavours (rancidity). It is known that the

unsaturated fatty acids are more prone to develop rancidity (Miller, 2005; Alam Khan and Abrahem, 2010). Lipid

oxidation can be significantly reduced by freezing and/or removing of oxygen prior to irradiation (Miller, 2005; Alam

Khan and Abrahem, 2010). The micronutrient thiamine (e.g. pork) is relatively high sensitive to the effect of radiation

(Alam Khan and Abrahem, 2010). Minerals have been shown to remain stable (Diehl, 1995). In addition to nutritional and

sensory values, the wholesomeness (lack of mutagenicity, teragenicity and toxicity) of irradiated foods has been studied

extensively (Thayer, 1990). Long-term animal feeding studies have demonstrated that radiation-pasteurized or -sterilized

foods are safe and nutritious also for humans (Thayer et al., 1996). Toxicological and nutritional studies have confirmed

the safety of foods irradiated at doses below 10 kGy (Thayer, 1990; Smith and Pillai, 2004).

Based on a review of scientific evidence, various agencies from round the world such as World Health Organization

(WHO), the European Parliament, US Food and Drug Administration (US-FDA) and the US Department of Agriculture

(USAD)

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have made recommendations regarding the safety of irradiated food consumption and the wholesomeness of them (van

Kooij, 1981; Kader, 1986; Ashley et al, 2004). During the past decade several steps were taken by the Joint

FAO/IAEA Division or developed in close co-operation with the WHO, the Organization for Economic Co-operation and

Development and the Joint FAO/WHO Food Standard Programme, to promote international acceptance of irradiated food

(van Kooij, 1981; WHO-TR, 1981; Ashley et al, 2004). To aid harmonization of national laws the Codex Alimentanus

Commission has adopted a recommended international general standard for irradiated foods (CAC/RS 106-1979 and

CAC/RCP 19-1979).The 1980 Joint FAO/IAEA/WHO Expert Committees concluded that the irradiation of any food up

to an average dose of 10 kGy causes no toxicological hazard (WHO-TR, 1981; Kader, 1986; WHO, 1994).

However, irradiated foods are not widely available yet; approval for irradiation of food was given by US FDA since the

early 1990s. For meats, separate approval is required both from the FDA and USDA (Table 3).American astronauts have

eaten irradiated foods to prevent food-related sicknesses in space since the early 1970s. Patients with weakened immune

systems (e.g. AIDS patients) are fed irradiated foods to reduce the chance of life-treating infection (WHO, 1994). In

addition, irradiation is widely used to sterilize a variety of medical and household products, such as joint implants, band-

aid, baby pacifiers, cosmetic ingredients, wine and bottle corks and food packaging materials (Thayer et al., 1996; Farkas,

1998).United State Food and Drug Administration (FDA) approved irradiation of pork, fruits, vegetables, spices and herbs

in 1986 and poultry in 1990 (WHO, 1994). During the 1990 scientists improved irradiation methods to destroy toxins and

bacteria, especially Escherichia coli, Salmonella, Shigella and Campylobacter in food (Farkas, 1998).

Table 3: FDA and USAD approval for food irradiation

(https://uw-food-irradiation.engr.wisc.edu/Facts.html; Lewis et al., 2002)

Approval Food Purpose

1963 Wheat flour Control of mold

1964 White potatoes Inhibit sprouting

1986 Pork Kill Trichina parasites

1986 Fruit and vegetables Insect control and Increase shelf life

1986 Herbs and spices Sterilization

1990 - FDA

1992 - USDA Poultry Bacterial pathogen reduction

1997 - FDA

1999 - USDA Meat - beef and lamb Bacterial pathogen reduction

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Food irradiation is now being commonly used in many countries, as people are becoming more aware of the role of food

irradiation in regards to food safety and product shelf-life extension. Labeling is necessary, so that people can freely

choose whether to use this safe and wholesome processed food (Akram and Kwon, 2010). Countries in North America,

Europe, Asia, Africa and Middle East accepted irradiation (WHO, 1994). The radura (Figure 2) is the international food

packaging symbol for irradiation (WHO, 1994; CAC/CX-STAN-001, Rev 2, 1999).

Figure 2: International food packaging symbol (radura) for irradiation

Foods Suitable for Irradiation

Food which are used for radiation decontamination are poultry meat, egg products, red meat, fishery products, spices,

mushrooms and other dry ingredients.

POULTRY

Pathogenic microorganisms such as Campylobacter, Salmonella and Escherichia coli 0157:H7 are normally found in the

intestinal tracts of food-producing animals. Raw meats and poultry products can become contaminated with these

pathogens during slaughtering and processing (Mead et al., 1999; Lewis et al., 2002). According to Lewis et al. (2002),

the irradiation doses of 1.0 and 1.8 kGy were sufficient to eliminating bacteria in the boneless, chicken breasts fillets.

They also carried out investigation on the effect of radiation at 1.0 to 1.8 kGy on the overall color of the products. Results

for the color determination are showed that irradiation of 1.0 and 1.8 kGy had no effect on color when compared to the

non-irradiated control (Lewis et al., 2002; Javanmarda et al., 2006). Recommended doses for radiation processing of

frozen poultry are 3-5 kGy and 1.5-2.5 kGy for chilled poultry (Lewis et al., 2002).

MUSHROOMS

Mushrooms are fleshly fungi, being used as food and medicinal purposes by human since time immemorial. However,

their short shelf-life and high initial microbial load are major problems regarding their easy distribution and self-

consumption. Mushrooms have a short-life due to post-harvest changes such as softening and browning process, stalk

elongation and cap opening (Patterson, 1990). Extended shelf life is a key factor for producers to develop the market over

great distances (Akram and Kwon, 2010). The irradiation of mushrooms can be a safe and cost effective method to

increase shelf-life as well as to ensure hygienic and sensory quality (Akram and Kwon, 2010). Different studies exhibited

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great effect of irradiation at all dose levels on reducing microbial counts. The qualitative and quantitative changes in the

microflora of mushrooms by irradiation contribute to overall increase in the shelf life of fresh mushrooms without

changing the original appetence (Akram and Kwon, 2010). The recommended dose for extending the shelf life of fresh

mushroom in different countries is 1 - 3 kGy, while the recommended dose regarding the decontamination of dried

mushrooms used as seasonings is 10 - 50 kGy (ICGGI, 1999; Akram and Kwon, 2010). Irradiation of mushrooms at 0.06 -

0.5 kGy has been shown the inhibition of cap opening and stalk elongation, the reduction of surface molds and darkening

of the gills and the maintaining of the fresh appearance of mushrooms (Kader, 1986).

EGG PRODUCTS

Sensory and functional properties of eggs are relatively radiation sensitive. The Salmonella count in naturally

contaminated eggs are very low do not normally exceed 10 – 100 colony forming units (CFU)/mL) (Farkas, 1998). A

minimal dose of 0.5 kGy would be enough to eliminate Salmonella from the surface of whole eggs and a dose of 1.5 kGy

would be sufficient to eliminate the organism from whole shell eggs and liquid whole eggs without significant adverse

effects on the egg quality (Serrano et al., 1997). According to Ley et al. (1962), irradiation of 4 - 5 kGy does not affect the

quality of frozen whole egg or of food prepared with egg product. Salmonella are the principal microorganism in dried

egg products (ICMFS, 1980). The dosage 6 kGy is enough for radicidation of dried egg albumen without changing their

functional and organoleptic properties. However, irradiation under aerobic condition gives off-flavour (Farkas, 1998).

Irradiation of 2 kGy would result in 2 - 3 log-cycles reduction of Salmonella without changing sensory quality of the

product (Farkas, 1998). Irradiation of sensitive product in oxygen-free packaging would minimize oxidation; improve

flavour retention (Lebovics et al., 1994).

RED MEATS

Escherichia coli O157:H7 has been considering as leading causative agent in under-cooked hamburgers (Lee, 1994).

Organic acid spray proposed for sanitation can reduce entire pathogens but has limited efficiency particularly in

controlling E. coli O157:H7 (Brackett et al., 1994; Cutter and Siracus, 1994).Thus, irradiation of prepackaged meat

products such as ground beef, minced meat and hamburgers may help in controlling meat borne pathogens and parasites

(Cutter and Siracus, 1994). Pathogenic microorganisms and parasites in meat products which are commonly consumed

raw (e.g. filet american) are of particular importance. A dose as low as 1 kGy was effective in reducing Salmonella up to

approximately 2 log-cycles in 'filet americain" and Campylobacter jejuni and Y. enterocolitica more than4 log-cycles

(Kampelmacher, 1984).

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Relatively high doses, 4 to 6 kGy are required to kill foodborne parasites. Significant sensory changes would be induced

at these dose levels in raw foods which carry the parasites (Urbain, 1978). Gamma irradiation of Trichinella spiralis

infected pork with a dose of 0.15 - 0.30 kGy made the parasites sexually sterile and blocked the maturation of ingested

larvae in the hosts gut (Sivinski, 1985). The use of irradiation to control Trichinella spiralis in porkat a minimum dose f

0.3 kGy and not to exceed 1.0 kGy was approved by the US FDA (FDA, 1985).

FISHERY PRODUCTS

Crustaceans and molluscs originating from polluted environments, frequently harbour pathogenic microorganisms and

pose a public health hazard (Farkas, 1998). Radiation microbiology studies with fishery products indicated that irradiation

doses up to 4 kGy to control pathogens could be useful with frozen fishery products such as shrimps, prawns

(Nouchpramoul, 1985; Ito et al., 1989). D10 -values of Salmonella serovariants in artificially contaminated shrimps in

Thailand were found to range from 0.3 to 0.5 kGy for refrigerated samples and from 0.4 to 0.6 kGy for frozen samples

(Nouchpramoul, 1985). Vibrio parahaemolyticus has been considered as the leading causative agent of bacterial

gastroenteritis from eating fishery product in South-East Asia. Sixty percent of fresh fish obtained from local markets in

Bombay, India and eighty five percent of fresh or frozen shrimp in Thailand was reported as being contaminated with this

organism (Lewis, 1983; Nouchpramoul, 1985). A dose as low as 1 kGy is sufficient to eliminate Vibrio parahaemolyticus

in frozen sea-foods (Lewis, 1983).The maximum permissible dose of ionizing radiation for raw shrimps is approximately

9 kGy (Coleby and Shewan, 1965). A radiation dose of 1 kGy is sufficient to eliminate Vibrio vulnificus in oysters

(Mallett et al., 1991).

SPICES AND OTHER DRIED INGREDIENTS

A major concern of food processors is to assure that the microbial load in ingredients and processing aids does not

contribute to spoilage of food and does not diminish its microbial safety (Farkas, 1998). The radiation decontamination of

spices, herbs, enzyme preparation and other dried ingredients with doses of 3 - 10 kGy proved to be a reliable method for

improving microbiological safety of such products (Farkas, 1988). The black pepper is one of the most contaminated

spices. Spices often originate in developing countries where harvest and storage conditions are inadequately controlled

with respect to food hygiene are more prone to contaminate with micro-organisms and insects. Thus, they may have been

exposed to a high level of natural contamination by mesophylic, sporogenic and asporgenic bacteria, hyphomycetes and

fecal coli forms (Khan and Abrahem, 2010). Most spices are dried in the open air and can be contaminated by air and soil

borne bacteria, fungi and insects. Microorganisms adversely effect to public health such as Salmonella, Escherichia coli,

Clostridium perfringens, Bacillus cereuc and toxigenic moulds can also be present (Khan and Abrahem, 2010).

Contaminated dry plant ingredients cause serious problems to food processers. Therefore, they fumigate spices and other

dry plant ingredient with methyl bromide to eliminate insects or with ethylene oxide to remove bacteria and moulds

(Loaharanu, 1994). These chemicals cause serious damage to environment as well as public health. Many commercial

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food processers are currently interested in the use of ionizing radiation to decontamination of spices, herbs and dried

vegetable seasonings. It is more effective against bacteria than the thermal treatment and does not leave chemical residues

in food products (Loaharanu, 1994; Thayer et al., 1996). There is no change in the composition of volatile oils between

thermally treated and irradiated black pepper samples. Gamma irradiation at the dose of 10 kGy (toxicologically and

nutritionally confirmed maximum safe does) can eliminate microbial in spices without causing any significant

organoleptic or chemical alterations (Khan and Abrahem, 2010). Irradiation treatment of ginger, turmeric, cayenne

pepper, onion and garlic powder at the dose of 30 kGy did not change their seasoning capacity (Lescano et al., 1991).

FRESH FRUITS AND VEGETABLES

Fresh fruits and vegetables are highly sensitive to various stresses such as those induced by - wounding, bruising or other

types of physical damage; exposure to higher or lower than the optimum temperature for each commodity; water loss;

exposure to oxygen and/or carbon dioxide levels beyond the concentration which are tolerated by each commodity

(Kader, 1986). During the irradiation free radicals are formed. These free radicals react with various food constituents and

may damage the cells. Since fresh fruits and vegetables contain eighty to ninety percent water and twenty percent of their

intercellular spaces contain oxygen, the most common free radicals are those formed from water and oxygen (Kader,

1986; Grecz et al., 1983). The formation of free radicals can be reduced by irradiating in nitrogen atmosphere and then

reduce possible injuries to the plant tissue (Kader, 1986). The effects of ionizing radiation at various doses on fresh fruits

and vegetables are shown in Table 4.

Table 4: Effects of ionizing radiation on fresh fruits and vegetables (Kader, 1986)

Dose (kGy) Observed Effects

0.05 - 0.15 Sprout inhibition in tuber, bulb and root vegetables; inhibition of growth in

asparagus and mushrooms

0.15 - 0.75 Insect disinfestations

0.25- 0.50 Delayed ripening of some tropical fruits such as banana, mango and papaya

> 1.75 Control of postharvest disease

1.00 - 3.00 Accelerated softening; development of off-flavours in some commodities

>3.00 Excessive softening; abnormal ripening; incidence of some physiological

disorders; impaired flavour

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A large number of insects can be carried by fresh fruits and vegetables. Many of these insects (e.g. fruit flies) can

seriously effect to the trade among countries. Therefore, effective insect-disinfestations treatments (quarantine treatments)

which are not harmful to the consumer, the workers or the commodity are essential for allowing unrestricted distribution

of fresh fruit and vegetables (Kader, 1986). The currently approved quarantine treatments include certification of insect-

free areas and use of chemicals (methyl bromide, phosphine, and hydrogen cyanide), cold treatments, heat treatments and

some combination of these treatments. These methods are usable on a limited number of commodities due to phytotoxic

effects on others (Kader, 1986). Cold treatments can be used on commodities like apple, pear, grape, orange, kiwifruit,

and pomegranate; they are not usable for highly perishable commodities like strawberry, apricot, cherry or for chilling-

sensitive commodities like grapefruit, lemon, avocado, papaya, mango, tomato, and pepper. Thus, search continues for

alternative treatments. The possible use of ionizing radiation for insect disinfestations is one of the most promising

applications (Moy, 1985). Dosage below 1 kGy is an effective insect-disinfestations process against various fruit flies,

mango seed weevil, navel orange worm and other insect spices of quarantine significance in marketing fresh fruits and

vegetables. Most insect are sterilized at doses of 0.05 - 0.75 kGy. In general, eggs are the most sensitive to ionizing

radiation, followed by larvae, then pupae (Kader, 1986). The relative tolerance of fresh fruits and vegetables is shown in

Table 5. The position of the fruits and vegetables in this classification can be varied according to production area, season

and handling procedures (Moy, 1985).

Table 5: Relative Tolerance of fresh fruits and Vegetables to ionizing radiation stress at doses < 1 kGy (Kader, 1986)

Relative Tolerance Commodities

High Apple, cherry, date, guava, mango, papaya, peach, rambutan, raspberry,

strawberry, tomato, longan, muskmelon, nectarine, tamarilio

Moderate Apricot, banana, grapefruit, orange, cherimoya, fig, kumquat, loquat, lychee,

passion fruit, pear, pineapple, plum, tangelo, tangerine

Low Avocado, cucumber, grape, green bean, lemon, lime, olive, pepper, sapodilla,

soursop, summer squash, leafy vegetables, broccoli, cauliflower

The effectiveness of radiation as a fungicidal and/or fungi static treatment depends on the pathogen, its stage of growth

and the number of viable fungal cells on or within the tissue. Generally, a minimum dose of 1.75 kGy is required for

effective inhibition of post-harvest fungi (Kader, 1986).

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Consumer Acceptance of Irradiated Food

Food irradiation is being promoted as a simple process that can be used to effectively and significantly reduce foodborne

illnesses around the world (Ashley et al., 2004). Despite the obvious benefits of the application of gamma-radiation on

food this technology remains vastly underestimated in the food industry. The hindering factors in the way of commercial

implementation of food irradiation process are politics and consumer advocacy (Khan and Abrahem, 2010). The use of

any treatment as a commercial food process depends on its acceptance by consumers. The attitudes of the consumer

toward food irradiation vary according to country, national traditions and political climate and the major concerns of

consumer included safety, nutrition, detection, labeling of irradiated foods (Broad, 1991). There are fears that the process

would be used to up-grade low-quality products (Khan and Abrahem, 2010). The people who oppose to food irradiation

are carried out picketing, making inflammatory demands and pressuring legislation (Satin, 1993). In a joint International

Organization of Consumers Unions (IOCU)/ International Consultative Group on Food Irradiation (ICGFI) seminar on

food irradiation and consumers, a number of recommendations were agreed on the areas including application, trade,

environmental implications, regulation and enforcement, consumer acceptance and labeling (IAEA, 1993). It has not been

widely accepted and adopted yet, is often linked to the fear and confusion about radiation itself and the lack of

understanding of the process. Providing science-based information on food irradiation leads to positive consumer attitude

(Fox, 2002). Increasing the acceptance of consumers reflect the level of awareness and quality of information provided.

This is emphasized the importance of educating the public on the technology and the benefits of irradiation (Nayga et al.,

2004). The key issue with the consumers is the labeling of irradiated foods that means informative labeling. The labeling

to provide identification is not sufficient. The information that describes the purpose of the treatment promotes consumer

acceptance, e.g. instead of "irradiated chicken", the words "treated by irradiation to control Salmonella and other food-

borne bacteria" (Pszczola, 1993; CAC/CX-STAN 106-1983, Rev 1, 2013; CAC/CX-STAN-001, Rev 2, 1999). Another

group of people proposed the labeling statements "cold pasteurization" and "electronic pasteurization" instead of

"irradiated foods" that is misleading the consumers (Ashley et al., 2004). Some people claim, based on false or poor

understanding of this process, that it can make food radioactive or can produce some very dangerous substances.

However, researches over many decades have proven that food irradiation is as safe as other common food preservation

techniques. Various authentic studies have concluded that food irradiation can be considered as radiologically,

microbiologically and toxicologically safe type of technology (Ehlermann, 2005). To promote the world-wide

introduction of food irradiation, it is necessary to develop national legislation and regulatory procedures that will enhance

confidence among trading nations that foods, irradiated in one country and offered for sale in another, have been subjected

to commonly acceptable standards of wholesomeness, hygienic practice and irradiation treatment control. To aid

harmonization of national laws the Codex Alimentanus Commission has been adopted a recommended international

general standards for irradiated foods (CAC, CAC/RS 106-1979, CAC/RCP 19-1979; CAC/CX-STAN 106-1983, Rev.1,

2013).

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Detection Methods for Irradiated Foods

Irradiation is used in food to eliminate pathogenic and spoilage microorganisms. However, irradiation is not fully

accepted by all consumers (Broad, 1991). Also food irradiation is approved in some countries but only on specific

products (Ashley et al., 2004). There is a need for methods to identify irradiated foods to check compliance with existing

regulations; to give consumers the opportunity to choose; and facilitate international trade of foods. Simple and reliable

methods are required to identify irradiated foodstuffs as different countries have different legislative requirements for

irradiated foods (Delincee, 1991). The irradiation detection methods in foods can be classified in three basic groups such

as chemical, physical and biological methods. The methods have different degrees of development such that some are

already approved and some are in the research phase (Delincee, 1991). The general methods for detection of irradiated

foods were adopted by the 24th session of the Codex Alimentarius Commission in 2001 and revised by its 26th session in

2003 are shown in Table 6.

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Table 6: General methods for the detection of irradiated foods (CAC/CX - STAN 231 - 2001, Rev. 2003)

Provision Commodity Method Principle

Detection of

irradiated

food

Food containing fat (raw chicken, pork, beef,

avocado, mango, papaya, cheese, eggs and foods

containing eggs)

EN

1784:1996

Gas chromatographic analysis of

hydrocarbons

Food containing fat (raw chicken, pork and liquid

whole egg)

EN

1785:1996

Gas chromatographic/

spectrophotometric analysis of 2-

alkylcyclobutanones

Food containing bone (Poultry, meat, fish) EN

1786:1996

Electron Spin Resonance (ERS)

spectroscopy

Food containing cellulose (pistachio nut shells and

paprika powder )

EN

1787:2000

Electron Spin Resonance (ERS)

spectroscopy

Food containing silicate minerals (herbs, spices,

their mixture and shrimps)

EN

1788:2001 Thermo-luminescence

Food containing silicate minerals (herbs, spices

and seasonings, crustacean and shellfish)

EN 13751:

2002 Photo-stimulated luminescence

Food containing crystalline sugar (dried mango

and dried fig)

EN 13708:

2001

Electron Spin Resonance (ERS)

spectroscopy

Herbs, spices, and raw minced meat

EN

13783:2001

NMKL

137 (2002)

Direct Epifluorescent Filter

Technique/ Aerobic Plate Count

(DEFT/APC) (screening method)

Food containing DNA (frozen chicken and pork) EN 13784:

2001

Micro-gel electrophoresis - DNA

comet assay (screening method)

Gas chromatographic analysis of hydrocarbons - Irradiated lipids are cleaved in the alpha and beta C-C bond forming

Cn-1 and Cn-2 alkanes, alkenes and alka-polyenes. Although hydrocarbons are also formed by heat, the radiolytic

hydrocarbons have a unique pattern of distribution. This method involves the isolation of fat, separation of hydrocarbon

fraction by adsorption chromatography (florisil) and characterization of hydrocarbons is performed using gas

chromatography with a flame ionization detector or a mass spectrometer. This method is applicable to all irradiated foods

contain lipids even though they are present at low concentrations (EN 1784, 1996).

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Gas chromatographic/ spectrophotometric analysis of 2-alkylcyclobutanones - Cyclobutanones are thought to be

radiation specific. The detection involves Soxhlet extraction of homogenized sample with hexane, florisil

chromatography, followed by gas chromatography/ mass spectrometer (EN 1785, 1996).

Electron Spin Resonance (ERS) spectroscopy - The method detects radiation-specific radicals produced upon

irradiation of food. Free radicals are usually transient species. However, in rigid and dry matrices their lifetime extends.

Unpaired electrons in free radicals are negatively charged that possesses an intrinsic and magnetic moment. The energy

difference between the two electron spin states is called Zeeman splitting. When an external magnetic field is applied to a

magnetic particle it attempts to align with the field and some electron try to flip. However, they need energy to overcome

the transition (Zeeman splitting). When an electromagnetic wave is applied to the electron and its frequency is equal to the

electron spin frequency (induced by external magnetic field), resonance condition is achieved and flipping occurs. The

flipping causes energy from the electromagnetic wave to be absorbed. The ESR equipment detects this absorption and

draws a curve. This technique is non-destructive, very sensitive, specific and combines simplicity with rapid

measurement. The two most significant drawbacks of ESR spectroscopy are the cost of the spectrometer and the special

technical skills required to operate it (EN 1786, 1996; EN 1787, 2000; EN 13708, 2001).

Luminescence - When ionizing radiation interacts with an insulating crystal lattice (silicate mineral in food sample), net

redistribution of electronic charge takes place. Electrons are stripped from the outer shells of atoms and though most

return immediately, proportion escape and become trapped at 'meta-stable' sites within the lattice. In order to release these

trapped electrons, more energy is required. When the necessary energy is applied, these electrons return from the excited

state to the electronic ground state by losing part of their excess energy as a photon. This phenomenon is called

luminescence. The emission of trapped energy as light may be induced.

Thermally - Thermo-luminescence (TL) - The TL apparatus consist of a metal planchet on which a disk with sample

powder is heated by high frequency current. The TL chamber is tightly closed and can be evacuated and flushed with inert

gas before measurement. The TL glow is measured by a photomultiplier tube. The second TL measurement of the same

sample after exposure to a known dose of radiation is necessary. Salt may also serve as a TL-sensitive irradiation

indicator. This method mostly enables an unequivocal classification of irradiated and un-irradiated samples. The TL

technique is laborious, since the minerals have to be prepared free of organic material. There is a small amount of mineral

product on food surface; there is natural TL of some materials; stringent quality assurance procedures are necessary. The

equipment is costly and a radiation source is needed (EN 1788:2001).

Micro-gel electrophoresis - DNA comet assay (screening method) - DNA is a large molecule and easy target for

ionizing radiation. Upon irradiation DNA molecules suffer denaturation, base modification and fragmentation either by

single or double-bond strand breaks. These changes in DNA can be used to identify irradiated foods. DNA comet assay

detects fragmentation of DNA using the micro-gel electrophoresis of single cells or nuclei. These are embedded in

agarose on microscope slides, lyses for disruption of membranes using detergent and electrophoreses at a set voltage.

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DNA fragments will stretch or migrate out of the cells forming a tail in the direction of the anode. Irradiated cells will

show considerably larger comets (more fragmentation) than un-irradiated cells, which will appear nearly circular. The

DNA comet assay is a relatively simple and rapid screening test that makes use of low-cost equipments and can be used in

all foods containing DNA. However, this method is not radiation specific because there are other treatments that also

induce DNA fragmentation. Suspicious sample may need to be confirmed by an officially validated method (EN 13784:

2001).

Conclusions

Irradiation of food has been proved as a safe and effective process in controlling microbial contamination without adverse

side effects and chemical residues that can be used to improve the integrity and safety of our food supply. Scientific

research has also determined that food irradiation does not make food 'radioactive' at low and medium doses (up to 10

kGy doses - maximum dosage used for most commercial applications). Scientists have also studied the creation of

radiolytic products, including 'free radicals', by food irradiation. There is broad agreement among renowned researchers,

health organization and agencies that radiolytic products formed during irradiation pose no danger to humans. An

extensive review of science related to microbiological safety indicates that irradiation is an effective solution to the

problem of microbial contamination. Under good manufacturing practices assuring proper handling of product, irradiation

eliminates harmful bacteria that can cause lethal food poisoning and spoilage. Irradiation is endorsed as a food safety

process by independent health organization and regulatory agencies round the world. Food irradiation is now being

commonly used in many countries, as people are becoming more aware of food safety and products shelf-life extension.

An extensive education is needed for broad public acceptance. A strategic, multi-year, broad-scale education campaign,

targeting both professional and by audiences is necessary. Labeling is necessary, so that people can freely choose whether

to use this safe and wholesome processed food. Reliable methods for the detection of irradiation food (food irradiation)

are now available and are effective in confirming compliance with regulations regarding food irradiation.

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