It used to be forbidden to cut lettuce with a knife. It had to be torn. Now I see TV chefs regularly chopping lettuce with a knife. What gives?
There's no reason not to cut lettuce. People used to think it would make it turn brown more quickly but we now know that's not true.
A Cook's Illustrated report found 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. Who keeps salad around for two weeks?
The change in thinking is probably due to nothing more than we have more sources of information now. We don't have to depend on word of mouth. I looked through books for both professional and home cooks that date back to the mid 1990s and all were already dismissing the never-cut-your-lettuce-with-a-knife edict.
Kathleen Purvis, MCT