When an onion is cut a chemical reaction generates propanthial S-oxide . This makes up the LF enzyme and is responsible for causing tears . Comment: The " acid " in onions, which you can see when they are sliced open ( or not ), comes from acetic acid that forms on your skin as it reacts with oxygen to form But a spokesman said no decision had yet been made on whether they would commercialise their tear-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 .