QUANTITATIVE ANALYSIS OF ALDEHYDES, ESTERS, ALCOHOLS AND ACIDS FROM CITRUS OILS

ABSTRACT Actual amounts of octanal, decanal, dodecanal, tetradecanal, geranial and neral in various coldpressed citrus oils were determined by quantitatively preparing and analyzing the 2,4‐dinitrophenylhydrazone derivatives. These major and other minor carbonyl components in citrus oils were separated and isolated using a combination of column and thin‐layer chromatography of the derivatives. Differences in aldehyde composition include nearly equal amounts of octanal and decanal in Valencia orange oil and significantly less decanal than octanal in Pineapple, Hamlin and Temple orange oil. Tangerine oil has nearly equal amounts of octanal and decanal, but lesser quantities than the orange oils. Valencia essence oil, manufactured commercially by decantation from the aqueous essence phase recovered during juice evaporation, contained almost twice as much decanal as octanal. Coldpressed oils generally showed higher aldehyde/ester ratios than essence oils. The higher ester contents of the essence oils accounted for a more juice‐like aroma of the latter. Quantitative chemical analyses of total aldehydes, esters, alcohols and acids of eight types of citrus oils were performed. These analyses illustrated basic compositional differences in the oxygenated components of orange, mandarin, grapefruit and essence oils.