Changes of Oxalates in Banana Fruits During Ripening

Abstract

This paper describes some behavior of incorporated oxalate into pulp-homogenate.
Radioactivity of alcoholic extraction from green banana homogenate which was administrated sodium oxalate-¹⁴C gradually decreased. On the other hand, radioactivity of the extraction from yellow banana homogenate disappeared within short time.
Most of the radioactivity remained in anionic fraction and a small amount of radioactivity was found in cationic and neutral fraction. Distribution of radioactivity on silica gel chromatogram from green banana showed rapid disappearance of oxalate and corresponding increase of a acidic fraction that was eluted with 2N formic acid, while yellow banana did not show such phenomena.
Decarboxylation of oxalate by yellow banana was mainly due to subcellular particles. Relatively high activity of decarboxylation was obtained between pH 2.5 to 5.5 with optimum pH at 3.2.
Stoichiometric observation of decarboxylation of oxalate showed one volume of carbon dioxide evolution and a half of oxygen absorption. The fact indicates that the enzyme in banana pulp was oxalate oxidase (EC. 1. 2. 3. 4).