The sniff test is a common approach for testing produce prior to purchase, but when it comes to buying garlic, a strong aroma is a bad sign.
At the grocery store, we often give produce a sniff to size it up for freshness and flavor. Garlic is one product where a strong fragrance is a sign of questionable quality rather than potency: The main compound responsible for garlic’s aroma, allicin, is formed only after cells have been damaged during cutting or crushing. This means that a head of garlic that smells at all of garlic has likely been manhandled during transport or storage.
To demonstrate this, we put a few heads of garlic in a plastic bag and whacked at them with a rolling pin (forcefully enough to mean business, but not so much that it left visible damage). After a day in storage, they were pungent, while heads that we didn’t mistreat had no aroma at all. After a few more days, we peeled both sets, and the manhandled garlic was soft and beginning to rot in multiple places, while the carefully handled garlic was firm and unblemished.
THE BOTTOM LINE: Appearances can be deceiving, but the nose knows: Even if a head of garlic feels firm and looks good, if it smells like garlic, leave it in the bin.