Abstract

Polyphenol oxidase (PPO) has been shown to be responsible for browning reactions and discolouration in many fruit and vegetable products. Crude polyphenol oxidase (PPO) of ripe and unripe plantain (Musa paradisiaca cultivars – Agbagba, Cardaba and plantain hybrid) was isolated and some of the characteristics of the PPO extracts investigated. The activity of the enzyme was evaluated using spectrophotomeric method. Plantain PPO (ripe and unripe) catalyzes oxidation of both various substrates with catechol being the most readily oxidized substrate. The optimum pH of the enzyme was between pH 6 and 7 for the three cultivars. Thermal inactivation data showed that activity of the enzyme was lost after heating for 15 and 4 min at 50 and 80°C, respectively. Browning reactions of plantain PPO were inhibited by sodium metabisulphite (0.1%), ascorbic acid (0.2%), malic acid (1.0%) and the least sodium chloride (>1.0%) which is similar to banana PPO. Plantain polyphenol oxidase was active towards catechol but not with cresol.

Key words: plantain (Musa paradisiaca) cultivars, polyphenol oxidase, catechol, enzyme activity