Identification of key aroma compounds from bitter orange (Citrus aurantium L.) products: essential oil and macerate-distillate extract

The volatile compounds of bitter orange (Citrus aurantium L.) products, essential oil (EO) and the heart cut (HC) of the distillate were detected and quantified using gas chromatography (GC) coupled with a mass spectrometer and flame ion- ization detector. The flavour compounds were characterized using GC-olfactometry by nine trained panellists by the fre- quency of detection method. In total, 53 molecules were detected in the EO and 40 in the HC. The EO was characterized by 19 major odour compounds (frequency of detection from 6/9 to 9/9) with different aromatic notes among which a-pinene (floral), octanal (green), limonene (citrus), linalool (floral), a-terpineol (indeterminate: 'ND', green), linalyl acetate (floral), (E,E) or (E,Z)-2,4-decadienal (frying), dodecanal (ND), caryophyllene (green) and an unknown compound (I T =1678, plastic note). The HC presented a complex mixture of several molecules in low concentrations, which characterize the bitter orange flavour. The HC was characterized by seven high FD odour compounds, three of them (myrcene, a-phellandrene, and limonene) with citrus and mint aromatic notes, and the other four ((Z)-linalool oxide, a-terpinolene, linalool and neral) with floral notes. The comparison of these two products brought to light that the overall process of maceration/distillation could induce the loss of 15 strong odours previously found in simple essential oil and characterized by plastic and metal notes. These results show that macerating-distilling bitter orange peels and EO makes it possible to select the most pleasant odour compounds while eliminating some off-odours present in the EO. This is the first time that the characterization of odour-active compounds has been carried out on bitter orange products. This valuable information could help for further investigation on process/product optimization. Copyright © 2011 John Wiley & Sons, Ltd. Several studies detail the composition of the volatile part of bitter orange oil. The percentage content of monoterpene hydrocarbons varies from 97.3% to 97.8%, while sesquiterpene hydrocarbons have a percentage of about 0.2%. Oxygenated compounds have a percentage between 1.8% and 2.2%. Esters are the main oxygenated class. Their content ranges from 0.8% to 1.4%, carbonyl compounds from 0.35% to 0.63% and alcohols from 0.33% to 0.46%. The main component of bitter orange es- sential oil (EO) is limonene, its content being more than 93%. Among the minor monoterpene hydrocarbons, only myrcene al- ways exceeds 1%. Its content ranges from 1.7% to 1.8%, and b- pinene has a percentage of about 1%. Linalyl acetate is the main oxygenated compound and it represents the major part of the esters. Linalool is the main alcohol and octanal and decanal the main carbonyl compounds. (4-13)