Citrus nobilis Lour. var. microcarpa Hassk. - Rutaceae - Pontianak orange
Type of Siam (Thailand) orange cultivated in West Kalimantan (Indonesia; Tebas region, Pontianak), with thin and smooth, shiny and sticky skin (difficult to detach from the fruit pulp). Pontianak oranges have a sweet taste.
„Isolation of the volatile fraction from the peel of Pontianak orange (Citrus nobilis var. Lour. microcarpa Hassk.) by a careful solvent extraction/vacuum distillation process followed by application of an aroma extract dilution analysis (AEDA) revealed 32 odour-active compounds in the flavour dilution (FD)-factor range of 4–2048, 26 of which could be identified. On the basis of high FD-factors, (R)/(S)-linalool, myrcene, (R)-limonene, and 1,8-cineole were characterised as the most potent odorants, followed by octanal, (E,E)-2,4-decadienal, nerol, (E)-2-dodecenal, geraniol, and (E,E)-2,4-nonadienal. In addition, one odorant resembling the characteristic sulphurous, resinous aroma of the Pontianak peel oil was detected with a quite high FD-factor of 128. By mass spectrometry followed by synthesis, 1-phenylethanethiol exhibiting an intense sulphurous, resinous smell at the very low odour threshold of 0.005 ng/L in air, was found to be responsible for the odour impression detected in the extract. 1-Phenylethanethiol occurring as a mixture of the (R)-(76%) and the (S)-enantiomer (24%) has previously not been reported as odorant in foods. Application of static headspace aroma dilution analysis (SHA) on Pontianak peel revealed the green, grassy smelling odour-active compounds hexanal and (Z)-3-hexenal as further important odorants in the headspace above the peels.“
[Fischer, Anja, Willi Grab, and Peter Schieberle. „Characterisation of the most odour-active compounds in a peel oil extract from Pontianak oranges (Citrus nobilis var. Lour. microcarpa Hassk.).“ European Food Research and Technology 227.3 (2008): 735-744]
„The aroma-active compounds of Pontianak orange peel oil (Citrus nobilis Lour. var. microcarpa Hassk.) were characterized by using gas chromatography−olfactometry (GC−O) and aroma extract dilution analysis (AEDA) techniques. Forty-one compounds were found to be aroma-active, which were mainly dominated by saturated and unsaturated aldehydes. The flavor dilution (FD) factor was within the range of 2−2048, and compounds having the highest FD factor were α-pinene, β-pinene, linalool, and 2-methoxy-3-(2-methylpropyl) pyrazine, including a few unknown compounds. On the basis of GC−O results, odor activity value (OAV) and relative flavor activity (RFA) were determined for aroma model reconstitution. These resembled the original aroma of the peel oil for the green, fatty, fresh, peely, floral, and tarry attributes, with the model solution derived from OAV being the closest to Pontianak oil. Omission tests were carried out to verify the significance of (Z)-5-dodecenal and 1-phenylethyl mercaptan as key compounds in the aroma of Pontianak orange peel oil.“
[Dharmawan, Jorry, et al. „Evaluation of aroma-active compounds in Pontianak orange peel oil (Citrus nobilis Lour. Var. microcarpa Hassk.) by gas chromatography− olfactometry, aroma reconstitution, and omission test.“ Journal of agricultural and food chemistry 57.1 (2008): 239-244]