what causes brown color on lettuce?
How to Keep Iceberg Lettuce From Getting Brown. Iceberg lettuce provides crunch to burgers and sandwiches. It's also suitable for salad when combined with other lettuce varieties and vegetables. The lettuce leaves begin browning soon after harvest or purchase if not stored properly. Browning occurs from spoilage. Reddish-brown discolorations, called rust, occur when there is too much moisture on the lettuce head. Managing the moisture level during storage prevents both spoilage and rust. Coring the lettuce helps prevent browning.