Department of Food ScienceTopic ON

Application of gamma radiation technology for enhancement of shelf life of food

Submited by;- Presented by:- Dr .S.S. Shukla Kuldeep Sharma Roll no. 6460

B.Sc. 4th year

COLLEGE OF AGRICULTURE JAWAHARLAL NEHRU KRISHI VISHWA VIDYALAYA JABALPUR (M.P.)

In 1903 Rutherford demonstrated that, if the applied magnetic field were strong enough, the alpha radiation itself could also be deflected and behave as if positively charged. At almost the same time , however it was found that :

The portion of the alpha radiation was highly penetrating and was undeflected in even the strongest magnetic field. The component was termed as gamma radiation.

Gamma Radiation

Gamma rays are emitted by radioisotopes such as Cobalt-60 and Caesium-137 while electrons and X-rays are generated by machines using electricity.

Radiation processing of food is one of the latest methods developed for food preservation

Alongside traditional methods of processing and preserving food, the technology of food irradiation is gaining more and more attention around the world. In at least 39 countries, their health and safety authorities have approved irradiation of more than 40 different foods. These approvals include spices, grains, chicken, fruits, and vegetables. Twenty-nine of these countries were using food irradiation as a process for commercial purposes as of 1995.

Relative penetration power of alpha, beta and gamma radiation

How irradiation worksIrradiation works by disrupting the biological

processes that lead to decay. In their interaction with water and other molecules, that make up food and living organisms, radiation energy is absorbed by the molecules they contact.

The product of ionization may be electrically charged (ions) or neutral (free radicals). These then further react to cause change known as radiolysis.

The water is ionised by radiation. Electrons are expelled from water molecules and break the chemical bond. The products then recombines to form hydrogen, Hydrogen peroxide, hydrogen radical (H),hydroxyl radicals and hydroperoxyl radicals(H2O )

The radicles are short lived ( less than 10-5s) but they are sufficient to destroy bacterial cell.

How do we irradiate foodRadiation processing of food is carried out

inside an irradiation chamber shielded by 1.5 - 1.8 m thick concrete walls. Food either pre-packed or in-bulk placed in suitable containers is sent into the irradiation chamber with the help of an automatic conveyor.

The conveyor goes through a concrete wall labyrinth, which prevents radiation from reaching the work area and operator room.

When the facility is not in use the radiation source is stored under 6 m deep water. The water shield does not allow radiation to escape in to the irradiation chamber, thus permitting free access to personnel to carry out plant maintenance.

• For treating food, the source is brought to the irradiation position above the water level after activation of all safety devices.

• The goods in aluminium carriers or tote boxes are mechanically positioned around the source rack and are turned round their own axis, so that contents are irradiated on both the sides.

• The absorbed dose is determined by the residence time of the carrier or tote box in irradiation position.

• Absorbed dose is checked by placing dosimeters at various positions in a tote box or carrier

Effect on microorganisms

The reactive ions produced by irradiating foods, injure or destroy micro-organism by changing the structure of cell membrane and effecting metabolic enzyme activity.

More important effect on DNA and RNA molecules in the cell nuclei.

The sensitivity of micro organism to radiation is expressed as the D10 value ( the dose of radiation that reduces microbial population to 10% of its initial value)

Viruses are very resistant to irradiation and are unlikely to be affected by the dose levels used in commercial processing

 

Organism Approximate lethal dose (kGy)Insects 0.22 to 0.93 Viruses 10 teo 40 Yeasts (fermentative) 4 to 9 Yeasts (film) 3.7 to 18 Molds (with spores 1.3 to 11Bacteria (cells of pathogens):  

      Mycobacterium tuberculosis         Staphylococcus aureus         Cornybacterium diphtheriae         Salmonella spp.

1.41.4 to 7.0

4.23.7 to 4.8

* Adapted from Frazier, W.C., and Westhoff, D.C. 1988. Chapter 10. Preservation by radiation. In Food Microbiology (Fourth edition). McGraw-Hill. New York, NY.

Approximate Killing Doses of Ionizing Radiation for micro organisms (kGy)

Effect on foodsInduced radioactivity:At recommended doses Cobalt -60 and

cesium 137 have insufficient emission energies to induce radioactivity.

Radiolytic products: Ions and radicles produced during irradiation are capable of reacting with component of food to produce radiolytic product

Nutritional and Sensory value

Potential Applications of Gamma Radiation Sterilisation ( or radappertisation)

It is possible to sterilize meat and other product, the dose required exceed the current limit of 10 kGy. A dose of 48 kGy is needed for 12 D reduction of Cl. butulinum. High dose make the product organoleptically un acceptable.

Reduction of pathogens (radicidation)Food poisoning bacteria such as salmonella typhimurium are less resistant to radiation than Cl. Botulinum ,and doses of 3-10 kGy are sufficient for destruction.

Prolonging shelf life (or radurisation)Relatively low doses are needed to destroy yeast, moulds and non-spore forming bacteria. This process is used to increase shelf life by an overall reduction of vegetative cells.

Control of ripeningfruits and vegetables can be irradiated to extend their shelf life about 2-3 time when stored at 100CThe ripening and maturation of fruits are arrested by inhibition of hormone production and interupting the biochemical process of cell division.

DisinfestationsGrain and tropical fruits may be infested with insect and larvae, they reduces export potential . A low dose below 1 kGy is effective for disifestation

Inhibition of Sprouting:The technology is effective in inhibiting sprouting of potatoes, A dose of about 150 Gy has been recommended. Similar doses are also effective in preventing sprouting of onian and garlic.

Radiation processing is a cold process and therefore, unlike heat, it can be used on agricultural commodities without changing their fresh-like character

Radiation processing dose not alter significantly nutritional value, flavour, texture and appearance of food

Radiation using Cobalt-60 cannot induce any radioactivity in food and does not leave any harmful or toxic radioactive residues on foods as is the case with chemical fumigants

Due to the highly penetrating nature of the radiation energy, it is a very effective method

Prepackaged foods can be treated for hygienization and improving shelf-life

The radiation processing facilities are environment friendly and are safe to workers and public around

THE BENEFITS AND LIMITATIONS OF RADIATION PROCESSING OF FOOD

BENEFITS

Limitations

•Radiation processing is a need based technology and cannot be applied to all kinds of foods

•Radiation processing cannot make a bad or spoiled food look good

•It cannot destroy already present pesticides and toxins in foods

•Amenability of a particular food commodity to radiation processing has to be tested in a laboratory

•Only those foods for which specific benefits are achieved by applying appropriate doses, and those duly permitted under the Prevention of Food Adulteration Act (PFA) Rules, 1955, can be processed by radiation.

Radiation processed food cannot be recognized by sight, smell, taste or touch. Codex Alimentarius Commission has endorsed a green irradiation logo.

RADIATION PROCESSED FOODS IN MARKET PLACE

  Sr.No. Country Food Commodities

1 Argentina Spices, onion

2 Bangladesh Onion, dry fish, pulses

3 Belgium Spices, dehydrated vegetables, deep frozen foods

4 Brazil Spices5 Canada Spices6 Chile Dehydrated vegetables, onion, potato, seafood

7 China Spices and vegetable seasonings, Chinese sausage, garlic, apple, potato, onion, dehydrated vegetables, sauces, rice, tomatoes, beef

8 France Spices, vegetable seasonings, herbs, poultry (frozen boneless chicken, dried fruits, frozen frog legs, shrimp, cereals, strawberries, dry fruits)

9 Hungary Spices, herbs

10 Indonesia Spices, rice, dry fish, mungbean

11 Israel Poultry

12 Japan Potato

13 Korea Republic Spices, garlic powder, dry - mushrooms, fish & meat

14 Netherlands Spices, frozen products, poultry, dehydrated vegetables, egg powder

15 Norway Spices

16 Poland Onion, potato

17 South Africa Spices, shelf-stable foods, fruits, potato, cereals

18 Thailand Spices, fermented pork sausages, enzymes, onion, rice

19 UK Spices

20 USA Spices, poultry, fruits, vegetables

21 Vietnam Onion

22 Yugoslavia Spices

Radiation processed food

Thank You