Food Irradiation: quick revision, 13 bites

Three Radiation Processes, Three Dose Ranges

Dose decides the destiny.

Food irradiation is classified into **three processes** based on the radiation dose applied. **Radappertization** (30-40 kGy) destroys microorganisms for sterility. **Radicidation** (2.5-10 kGy) reduces non-spore-forming pathogens. **Radurization** (0.75-2.5 kGy) reduces spoilage organisms to extend shelf life.

Takeaway. Higher dose means stronger microbial kill; each process targets a different goal.

What Are X-rays?

Electrons smash metal, X-rays emerge.

**X-rays** are **ionizing radiations** produced by bombarding a suitable metal target with high-velocity electrons. In their behaviour, they are similar to **Gamma rays**.

Takeaway. X-rays are ionizing radiations generated by electron bombardment of a metal target.

REP Unit: Roentgen-Equivalent Physical

83 ergs per gram.

Takeaway. 1 REP equals absorption of 83 ergs per gram of matter.

RAD Unit: Radiation Absorbed Dose

100 ergs per gram.

Takeaway. 1 RAD equals 100 ergs per gram; 1 krad = 1000 rads.

GY Unit: Gray

Newer unit, 100 rads.

Takeaway. 1 Gray = 100 rads = 1 joule per kg; 1 kGy = 10^5 rads.

Radappertization: Radiation Sterilization

Destroy microbes, achieve sterility.

**Radappertization** is a radiation process that destroys microorganisms, equivalent to **commercial sterility** of heat-processed foods. Also called **radiation sterilization**, it uses a dose of **30-40 kGy** and ensures a sterile product with prolonged shelf life.

Takeaway. Radappertization uses 30-40 kGy to achieve sterility and long shelf life.

Radicidation: Pathogen Reduction

Target non-spore-forming pathogens.

**Radicidation** reduces the number of viable **non-spore-forming pathogens** that are undetectable by standard methods. It is equivalent to **pasteurization** and uses a radiation level of **2.5-10 kGy**.

Takeaway. Radicidation uses 2.5-10 kGy to reduce non-spore-forming pathogens, like pasteurization.

Radurization: Shelf-Life Extension

Minimize spoilage organisms.

**Radurization** minimizes the load of **spoilage organisms** to extend shelf life. It is considered equivalent to **pasteurization** and causes substantial reduction in viable specific spoilage microorganisms. Suitable for fresh meat, seafood, fruits, and vegetables. Dose used: **0.75-2.5 kGy**.

Takeaway. Radurization uses 0.75-2.5 kGy to reduce spoilage organisms and extend shelf life.

Undesirable Changes from Irradiation

Free radicals cause quality loss.

Irradiation can bring **undesirable changes** directly or indirectly. **Free radicals** produced during radiation cause oxidative changes: **discoloration**, **tissue softening** (due to pectin and cellulose degradation), and **rancidity** in high-fat products (from carbonyl and peroxide radicals). These can be reduced…

Takeaway. Free radicals from irradiation cause discoloration, softening, and rancidity; low temperature and no oxygen reduce these.

Permitted Uses of Food Irradiation

Many foods, many purposes.

Takeaway. Irradiation is permitted for sprout inhibition, decontamination, parasite destruction, pathogen inactivation, and shelf-life extension.

How Irradiation Kills Microbes

Direct hit and free radicals.

The **microbicidal effect** of irradiation is due to **direct interaction** of radiation with key molecules within the microbial cell, as well as the **inhibitory effect of free radicals** (H⁺, OH⁻ ions) produced by the **radiolysis of water**.

Takeaway. Irradiation kills microbes by direct damage and by free radicals from water radiolysis.

Radiation Resistance Varies by Microbe Type

Gram-negative most sensitive.

Many spoilage bacteria of seafood are **Gram-negative**, hence least resistant to irradiation. **E. coli** is highly sensitive and not useful as an indicator.

Takeaway. Gram-negative bacteria are most sensitive; spores are most resistant. Seafood spoilage bacteria are Gram-negative.

Remember the Dose Ranges

Radappertization > Radicidation > Radurization.

For exams, memorize the **dose ranges**: Radappertization (30-40 kGy), Radicidation (2.5-10 kGy), Radurization (0.75-2.5 kGy). Also remember the unit conversions: 1 Gray = 100 rads, 1 kGy = 10^5 rads.

Takeaway. Dose ranges and unit conversions are high-yield exam facts.