What is the primary mechanism by which irradiation kills microorganisms?

• A. Direct damage to DNA and cellular components.
• B. Heating the product to high temperatures.
• C. Adding chemical preservatives.
• D. Increasing moisture content.

Answer: (A)

Irradiation kills microorganisms mainly by causing damage to DNA and other vital cellular components through ionizing energy. The radiation can directly ionize DNA and proteins, creating breaks in DNA strands and disrupted cellular functions. It also interacts with water inside the cell, producing reactive free radicals (like hydroxyl radicals) that go on to damage DNA, membranes, and enzymes. This combination of direct and indirect damage prevents replication and essential metabolism, leading to cell death. This is a non-thermal method, so heating isn’t how irradiation works; chemical preservatives or changing moisture levels affect microbes through different mechanisms, not the primary action of irradiation itself.