Phytoalexin Production in Fresh-cut Cantaloupe Melon
O. LAMIKANRA, Food Processing and Sensory Quality, USDA-ARS-Southern Regional Research Center, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124 and O. A. Richard.
Fresh-cut processing induces degradative changes associated with plant tissue senescence and a consequent decrease in shelf life relative to the unprocessed produce. As part of a defense mechanism, plant tissues frequently produce compounds such as phytoalexins that are able to inhibit the growth of microorganisms. Synthesis of these naturally occurring compounds might be slow and they could be produced at concentrations that are very low relative to other compounds present. Ultraviolet light has thus been extensively used to simulate biological stress in plants and for determining resistance mechanisms of plant tissues. Cantaloupe melon is used more than any other fruit in fresh cut processing. The objective of this study is to determine changes in volatile compounds induced by stress conditions in cantaloupe and their possible role in the sensory quality and shelf life of the fresh cut fruit. Volatile components of fresh cut cantaloupe exposed to UV light for 15 and 60 min. respectively were extracted by headspace solid-phase microextraction (SPME) and determined by gas chromatography-mass spectrometry. Several volatile ester compounds were present, of which twenty-one were identified, in control fruit slices that were not exposed to UV light. UV treatment caused significant decreases in the concentrations of aliphatic esters present in the fruit. In addition, UV treatment induced the production of phytoalexin terpenoids, cis- and trans- b-ionone, terpinyl acetate, and geranylacetone as well as b-cyclocitral and dihydroactinidiolide. These results suggest that the defense response of cantaloupe melon involves a reduction in the concentrations of aliphatic esters in the fruit, and the production of terpenoid phytoalexins. UV induced phytoalexins have been demonstrated to improve storage quality of fresh produce. The potential use of UV treatment for improving shelf life of cut cantaloupe is indicated by this study. The potential use of UV induced stress for screening cultivars of Cucumis melo L. for their resistance to microorganism growth and insect damage is also demonstrated.
Session 96, Fruit & Vegetable Products