When an onion is cut a chemical reaction involving propanthial S - oxide . This makes up the entire enzyme and is responsible for preventing tears . farmers used irradiating ions to reduced the toxicity of this enzyme . But a spokesman said no decision had yet been made on whether they would commercialise their acid - free onions .
When an onion is cut a chemical reaction generates propanthial S-oxide . This makes up the LF enzyme and is responsible for causing tears . Scientists used irradiating ions to reduced the level of this enzyme . But a spokesman said no decision had yet been made on whether they would commercialise their tear-free onions .