Characterisation of volatile aroma compounds of orange juices by three dynamic and static headspace gas chromatography techniques

Abstract

The influence of collection of volatiles by different headspace sampling techniques was compared for different orange juices, including one fresh unpasteurised, two reconstituted commercial juices and one juice freshly hand extracted in the laboratory. Dynamic headspace sampling from stirred juice samples (DH + S) and notably by purge and trap (PT) sampling gave the highest levels of analysed volatiles, but the composition of the isolated volatiles from the different types of juices varied depending on the volatiles collection method. Aroma sampling by dynamic headspace method without stirring (DH) gave results that reflected the equilibrium aroma composition as determined by static headspace better than that obtained by PT sampling. Totally, 67 aroma constituents were identified among all the orange juices. The largest amount of volatiles was isolated from the fresh commercial, unpasteurised juice, followed by the two reconstituted juices and the hand extracted juice. Limonene was the major constituent of all commercial juices comprising 72–93% of the total peak area of isolated volatiles, meanwhile its amount in the freshly hand extracted juices ranged from 25 to 62% depending on the method of isolation. Qualitatively, the aroma profiles of the freshly extracted oranges and the fresh, commercial unpasteurised juice were described by 62 and 55 aroma compounds, respectively, which included large proportions of esters and aldehydes. Only 41 and 34 aroma compounds, mainly terpenes, were identified in the reconstituted orange juices.