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American Journal of Food Technology
Year: 2011  |  Volume: 6  |  Issue: 3  |  Page No.: 215 - 225

Influence of Developmental Stage on Activities of Polyphenol Oxidase, Internal Characteristics and Colour of Lettuce cv. Grand Rapids

B. Chutichudet, P. Chutichudet and S. Kaewsit    

Abstract: An analyzing study to evaluate the relationship between Polyphenol Oxidase (PPO) activity, internal qualities and degree of browning was conducted on lettuce var. Grand Rapids in order to understand the basis changes relating to the appearance of leaf browning and some quality characteristics. For PPO activity, Factorial experiment in completely randomized design was arranged with two factors: developmental stage (Factor A) at four levels (28, 42, 59 and 73 days after planting, DAP) with three different parts of plant (Factor B) (stem, leaf and root), while Completely Randomized Design (CRD) was applied for studying the internal qualities and browning appearance in leaves at 28, 42, 59 and 73 DAP. The experiment was carried out during May-July, 2009, with four replications, ten plants per replication. The results showed that each developmental stage and the various sections of the plant affected PPO activity. The leaf section of the plant particularly affected PPO, especially at 73 DAP. In addition, at the more mature stages of the leaf, more phenolic substance, ascorbic acid content and pH value were apparent, while quinone content decreased at advancing leaf age. In addition, as the plants reached an older stage, the leaf colour in terms of L* and b* decreased. Thus, the appropriate harvest for lettuce var. Grand Rapids should be at 59 DAP in order to face fewer incidence of browning and maintain good quality.

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