In intact tissues, the enzyme is located in the cytoplasm while their substrates are located in the vacuoles (Chazarra, Garcia- Carmona, & Cabanes, 1999). Damaging lettuce tissue by cutting results in the mixing of the enzyme and substrates, and exposures to oxygen leading to the browning reaction (Degl'Innocenti, Guidi, Pardossi, & Tognoni, 2005). Saltveit (2000) suggested that altered phenol metabolism was involved in browning of lettuce leaf tissue. Polyphenols are produced by a complex set of interrelated