Q: It used to be forbidden to cut lettuce with a knife. Only tearing by hand or cutting with a plastic knife was acceptable. But now I see TV chefs regularly chopping lettuce with a regular knife. What is responsible for this change in thinking?

A: Whenever I tear lettuce, I remember a salad dressing commercial from the 1970s, where a mother tells her daughter, “Never cut the lettuce _ always gently tear it.”

I hope someone told that kid the news: There’s no reason not to cut lettuce. While people used to think that cutting lettuce leaves with a metal knife would make them brown more quickly, we now know that’s not true.

A Cook’s Illustrated report on plastic lettuce knives found that lettuce cut with a metal knife showed very faint browning on the edge after 12 days, while lettuce cut with a plastic knife browned slightly after 13 days, and hand-torn lettuce lasted 14 days. And who keeps salad around for two weeks?

What is probably responsible is that there are now more sources of information. We don’t have to depend on word of mouth (and salad-dressing commercials). I looked through books for both professional and home cooks that date back to the mid-1990s and all were already dismissing the old rule on not cutting lettuce.

— By Kathleen Purvis, MCT