Cold pressed orange oils contain predominantly d-limonene (approximately 95%) and various other lower concentration monoterpenes, sesquiterpenes, sinensals plus 3 key aliphatic aldehydes: hexanal, octanal. and decanal. The aldol self-condensation products or "dimers" for each aldehyde have been postulated as being present at low concentrations in the oil. However, to date only the hexanal dimer has been previously reported. In this paper, cold pressed Valencia orange oil was fractionally distilled/folded and analyzed by GC and high resolution GC-MS to detect these compounds on 2 different capillary column phases. Subsequently the hexanal, octanal, and decanal self-aldol condensation products, 2-butyl-2-octenal, 2-hexyl-2-decenal, and 2-octyl-2-dodecenal, respectively, were detected in the folded oil. These predominantly trans configuration isomeric compounds were synthesized, to confirm them as being present in nature and evaluated organoleptically by a panel of evaluators. To further confirm the mechanism of their formation, the enriched oil was made into a simple beverage to show the effect on the formation of these aldol compounds under acidic conditions. Finally aliphatic aldehydes from hexanal to undecanal were reacted together in various combinatorial pairs to give an additional 33 self and mixed aldol condensation products, some of which were also detected in the folded oil. PRACTICAL APPLICATION This paper discloses the structural elucidation and synthesis of 8 novel aldol condensation products found at trace concentrations in citrus and leading to a further 31 mass spectrally determined aldol products. Sensory evaluations and application of some of these components were demonstrated in a model citrus beverage.

中文翻译：

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巴伦西亚橙油中醛醇缩合物的天然存在

冷榨橙油主要含有 d-柠檬烯（约 95%）和各种其他浓度较低的单萜、倍半萜、香茅以及 3 种关键脂肪醛：己醛、辛醛。和十进制。已经假定每种醛的羟醛自缩合产物或“二聚体”以低浓度存在于油中。然而，迄今为止，之前仅报道了己醛二聚体。在本文中，对冷压瓦伦西亚橙油进行分馏/折叠，并通过 GC 和高分辨率 GC-MS 进行分析，以在 2 个不同的毛细管柱固定相上检测这些化合物。随后，在折叠油中分别检测到己醛、辛醛和癸醛自醛醇缩合物、2-丁基-2-辛醛、2-己基-2-癸烯和2-辛基-2-十二烯醛。合成了这些主要为反式构型的异构化合物，以确认它们存在于自然界中，并由一组评估者进行感官评估。为了进一步证实它们的形成机制，将富集油制成一种简单的饮料，以显示在酸性条件下对这些醛醇化合物形成的影响。最后，从己醛到十一醛的脂肪醛以各种组合对一起反应，得到另外 33 种自身和混合的醛醇缩合产物，其中一些也在折叠油中检测到。实际应用 本文公开了在柑橘中发现的痕量浓度的 8 种新型羟醛缩合产物的结构解析和合成，并进一步得到了 31 种质谱测定的羟醛缩合产物。