A lettuce knife is a knife which is designed to cut lettuce without causing the lettuce to brown, yellow, or wilt. These special knives have serrated blades and they are typically made from plastic, which will not react with the lettuce to stimulate browning. Since browned lettuce is deemed aesthetically unpleasing, a lettuce knife can help keep a salad looking crisp and fresh without forcing cooks to tear lettuce by hand. The use of a knife also reduces the need to handle lettuce directly, reducing the risk of food borne illness.
Two things distinguish a lettuce knife from other knives. The first is the plastic blade. As you may have noticed when you cut lettuce with a metal knife, the metal reacts with the lettuce, creating unsightly brown, slightly wilted edges. Plastic does not stimulate a reaction, and the serrated edge of the knife cuts crisply through lettuce without tearing it. By using a lettuce knife, you can break lettuce up into manageable chunks without having to handle it; in addition to being a boon for food safety, this is also helpful when you are cooking for a crowd..
Lettuce knives are not one trick ponies. They can also be used on tomatoes and other soft vegetables, along with cakes and soft breads. Many people like using serrated blades on cakes in particular because they reduce torn, ragged edges, and a lettuce knife is ideal for this purpose. The blade of the knife is also strong enough to use as a cake server, for people who like to minimize dishes.
Many kitchen supply stores sell lettuce knives. These kitchen utensils are fairly basic, and your options are generally limited to different color choices and types of handles. The plastic material makes most lettuce knives dishwasher safe, although you may want to double-check on this when you buy a lettuce knife. In addition, you may want to consider getting a sheath, since the edge can deliver a nasty nick, although it certainly can't cause mortal damage.
While a lettuce knife will certainly reduce the risk of passing food borne illness to food consumers, it doesn't eliminate it. You should always wash your hands before handling food, and lettuce should be washed before use, along with other greens. You can either run lettuce under cool running water and shake it out, or you can wash lettuce in a salad spinner. Make sure to keep people with colds and coughs out of the kitchen as well.