Volatile Acids of Citrus Unshu and Citrus Natsudaidai

Existence of benzoate, acetate and other fatty acids

Abstract

The ether extractS of steam distillate (distilled under acidifying with tartaric acid) of natural orange juices showed the similar pattern to benzoic acid in UV spectrum. The distillates were subjected to silica-gel column chromatography followed by gas chromatography.
Benzoic acid and acetic acid were identified by means of UV, IR and mixed melting methods. Contents of benzoic acid in Citrus Unshu and Citrus Natsudaidai peel were about 0.04 and 0.006% of fresh weight, respectively. From the results that recovery of the acids increased by treatment of alkali hydrolysis, it was suggested that they exist in the form of esters of high boiling substances. Existence of formic acid, isobutyric acid and n-butyric acid were tentatively identified by threshold volume of silicagel column and gas chromatography. The acids may contribute to off-flavor of concentrated juices of Citrus Unshu and Citrus Natsudaidai.