Lettuce may turn brown for a variety of reasons. Though it looks unappealing and the texture may change, most often, brown lettuce isn't harmful if consumed. Brown lettuce is normally considered unacceptable, especially in the culinary world, where chefs pride themselves on salads and other dishes that are full of crisp lettuce leaves. However, with a few techniques, you may be able to preserve the life of your lettuce somewhat.
Tearing and Cutting
Tearing and cutting lettuce can cause it to turn brown. Wait until you are ready to use the lettuce before tearing it. When lettuce is torn apart, the barriers between the enzymes and polyphenols break down. They are separated prior to this point and after the destruction of the barriers, they mix. The reaction causes the lettuce to turn brown, according to the professionals at The Office for Science and Society.
Substances that you add to lettuce can also cause it to brown. Once you add dressing or warm toppings, browning begins shortly afterward. Once the temperature changes -- usually for the warmer -- the walls of the enzymes and polyphenols are weakened, allowing them to mix, which causes the browning. Wait until you are ready to serve the lettuce before you add toppings. Even extra weight can damage the barriers and allow oxygen to leak in, which can spark the reaction.
Lettuce, as with any perishable, is bound to get old if not consumed in time. As the lettuce becomes decrepit, the browning in inevitable. Pay attention to the shelf life stamped on the lettuce package and try to consume it before the "use by" date. If you don't see an expiration date, try to eat the lettuce within several days of buying it so that you can eat it at its freshest.
Damaged lettuce will turn brown in some spots faster than others. The damage can occur during packaging, shipment or handling for display purposes. Lettuce, like most fruits and vegetables, is easily damaged. Handle the lettuce with care and try to select lettuce without existing brown spots when you are at the supermarket.
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