What particles must be reaching you nose if smell onions on a BBQ?

When you smell onions on a BBQ, particles of volatile compounds released by the onions are reaching your nose. These compounds are produced when the onions are heated, and they travel through the air until they reach your olfactory receptors, located in the back of your nose. These receptors bind to the compounds and send signals to your brain, which allows you to perceive the smell of onions.

The main volatile compounds responsible for the smell of onions include:

- Sulphur compounds, such as allyl sulphide, methyl sulphide, and dimethyl sulphide.

-Allicin, a compound that is formed when onions are cut or damaged.

-Pyruvic acid, a compound that is produced when onions are cooked.

These compounds are all released into the air when onions are heated, and they can travel significant distances. This is why you can often smell onions being cooked even if you are not in the same room as the BBQ.

In addition to the compounds listed above, onions also release other volatile compounds that can contribute to their overall smell. These compounds include:

- Alcohols, such as ethanol and propanol.

-Esters, such as ethyl acetate and methyl butyrate.

-Aldehydes, such as acetaldehyde and propanal.

The combination of these volatile compounds creates the unique and characteristic smell of onions.