Changes in Sugars, Enzymic Activities and Acid Phosphatase Isoenzyme Profiles of Bananas Ripened in Air or Stored in 2.5% O2 with and without Ethylene

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Abstract
This study investigates the effect of 2.5% O2, both alone and in combination with ethylene, on respiration, sugar accumulation and activities of pectin methylesterase and acid phosphatase during ripening of bananas (Musa paradisiaca sapientum). In addition, the changes in the phosphatase isoenzyme profiles are also analyzed. Low oxygen diminished respiration and slowed down the accumulation of sugars and development of the yellow color. Furthermore, low O2 prevented the rise in acid phosphatase activities and this suppression was not reversed by the inclusion of 100 microliters per liter ethylene in 2.5% O2 atmosphere. Gel electrophoresis of both the soluble and particulate cell-free fractions under nondenaturing conditions revealed the presence of 8 and 9 isoenzymes in the soluble and particulate fractions, respectively. Low O2 suppressed the appearance of all isoenzymes, and the addition of 500 microliters per liter ethylene to the low oxygen atmosphere did not reverse this effect. Similarly, the decline in pectin methylesterase that was observed in air-ripened fruits was prevented by 2.5% O2 alone and in combination with 500 microliters per liter ethylene.