IF YOU COULD TASTE A CLOVE of garlic without cutting or crushing it or biting in, it wouldn’t taste like much at all. Only when the cells are broken and their contents interact do the heat and aroma form. That happens instantly and then continues, more and more slowly, as the substances, mostly sulfur compounds, change and new ones form. That’s why dehydrated garlic, such as garlic powder, tastes so different from fresh (and is rarely if ever a plus). The same thing occurs with other allium species. Onions themselves, when sliced, turn unpleasant in half an hour or less, and then they get worse. They’re responsible for the characteristic smell of a bad sandwich shop. Chives, shallots, and garlic hold up better.