Introduction

Food irradiation is a technique in which food is exposed to controlled levels of ionizing radiation to preserve it by sterilizing, disinfecting, or disinfesting the product. This method is considered highly effective in destroying food-borne pathogens, making it a preferable alternative to heat or chemical preservation. This process, often referred to as “cold pasteurization,” kills harmful bacteria and pests without the need for heat.

What is Food Irradiation?

Food irradiation involves exposing food to ionizing radiation, which can kill harmful bacteria, pests, or parasites, and preserve the food’s freshness. Unlike heat, which changes the structure and quality of food, irradiation achieves sterilization without altering the food’s flavor, texture, or nutritional value. This makes it a valuable method for enhancing food safety while maintaining product quality.

Mode of Action

Food irradiation works by causing direct or indirect damage to the cell structure of microorganisms, insects, and parasites:

• Direct Action: Ionizing radiation can impair key cell functions or components, such as DNA, leading to cell death.
• Indirect Action: Ionizing radiation creates free radicals (from water molecules) that damage DNA and other vital components of cells.

Depending on the radiation dose:

• High doses can kill microbes and insects.
• Low doses can delay ripening in fruits by destroying enzymes responsible for the process and inhibit the reproduction of microbes and insects.

Radiation in Food Preservation

Ionizing radiation, capable of removing electrons from atoms and molecules, is used in food irradiation. It converts atoms and molecules into ions, disrupting biological processes in bacteria, pests, and parasites. Importantly, irradiation doses for food processing are insufficient to make food radioactive, as the radiation cannot penetrate the food’s nuclei.

There are three approved types of ionizing radiation used in food irradiation:

1. Electron Beams: High-energy streams of electrons generated from machine sources. These penetrate food to a limited depth (about 1.5 inches) and are effective for certain foods but not for bulky items or packed cartons.
2. X-rays: Generated from machine sources, X-rays have better penetration and can irradiate larger, bulkier items. Like electron beams, they can be switched on or off as needed.
3. Gamma Rays: These rays are emitted from radioisotopes such as Cobalt-60 (Co-60) or Cesium-137 (Ce-137). Gamma rays have deep penetration and are often used for bulk food processing. However, unlike electron beams and X-rays, they cannot be turned on or off at will, and their operation is continuous, requiring shielding when not in use.

Units of Irradiation

The amount of radiation absorbed by food during processing is called the radiation dose, measured in gray (Gy). One gray is equivalent to the absorption of one joule of energy per kilogram of food.

• 1 Gy (Gray) = 100 rad
• 1 Kilogray (kGy) = 1000 Gy

Health and safety authorities have established that food irradiation is safe at doses up to 10 kGy. The process does not make food radioactive, and the food remains safe for consumption even at higher doses, similar to heat treatment.

Food Items Approved for Irradiation in India

India has approved irradiation for specific food items under the Prevention of Food Adulteration (PFA) Rules (1955) and Food Safety and Standards Authority of India (FSSAI) Regulations (2011). Here are some examples:

Advantages of Food Irradiation

1. Non-impact on food quality: Unlike heat, irradiation does not significantly affect the texture, flavor, taste, or nutritional content of food.
2. Effective preservation: It helps increase shelf-life without refrigeration, as it effectively kills or sterilizes pathogens and pests.
3. No radioactivity: Food remains safe and does not become radioactive, eliminating concerns about harmful residues.
4. Environmentally friendly: The process requires no chemicals, making it a more sustainable alternative.
5. Improved food safety: Effective at controlling pathogens and pests, which helps prevent foodborne illnesses.

Disadvantages of Food Irradiation

1. Limited application: Not all food items are suitable for irradiation, and only those listed in government regulations can undergo the process.
2. Does not eliminate toxins: It cannot destroy pre-existing toxins or pesticides in food.
3. Requires testing: Each food type must undergo specific testing in a laboratory before irradiation can be applied.
4. Cannot salvage spoiled food: Irradiation cannot make spoiled or low-quality food look or taste better. It works on fresh food with the aim of preservation.