Purification and deodorizing activity against methyl mercaptan of polyphenol oxidase from lettuce (Lactuca sativa L.)

Abstract

Polyphenol oxidase (PPO) from lettuce was isolated to determine the effect of its involvement in deodorizing activity by measuring the reduction in the amount of methyl mercaptan. The enzyme and deodorizing activities of PPO from lettuce were evaluated using different substrates, temperatures, and pH levels. The molecular weight of purified PPO from lettuce was estimated to be 56 kDa. The PPO and deodorizing activities were highest at the pH range of 6.0 at 20 A degrees C and 5.0 at 10 A degrees C, respectively. The deodorizing and PPO activities were greater for ortho-diphenols than monophenols and polyphenol. Especially, (+)-catechin, one of ortho-diphenols was shown in 100% PPO activity, and chlorogenic acid and caffeic acid eliminated a methylmercaptan odor up to 95%. The deodorizing activity was highest in Cu2+ solution, but ascorbic acid and sodium hydrosulfite inhibited deodorizing activity. These basic data will provide an optimum manufacturing condition for commercial products using lettuce extracts.