Orange oil is an essential oil produced by cells within the rind of an orange fruit (Citrus sinensis fruit). In contrast to most essential oils, it is extracted as a by-product of orange juice production by centrifugation, producing a cold-pressed oil. [1] It is composed of mostly (greater than 90%) d-limonene, [2] and is often used in place of pure d-limonene. D-limonene can be extracted from the oil by distillation.
The compounds inside an orange oil vary with each different oil extraction. Composition varies as a result of regional and seasonal changes as well as the method used for extraction. Several hundred compounds have been identified with gas chromatograph- mass spectrometry. Most of the substances in the oil belong to the terpene group with limonene being the dominant one. Long chain aliphatic hydrocarbon alcohols and aldehydes like 1-octanol and octanal are second important group of substances. The presence of sinensetin, a flavone, explains the orange color. [3]
Compound | Italian Orange Oil [4] Concentration [%] | Valencia orange oil [5] Concentration [%] | Valencia orange oil [6] Concentration [%] | Valencia orange oil [7] Concentration [%] |
---|---|---|---|---|
Limonene | 93.67 | 91.4 | 95.17 | 97.0 |
α-Pinene | 0.65 | 1.4 | 0.42 | – |
Sabinene and β-Pinene | 1.00 | 0.4 | 0.24 | – |
Myrcene | 2.09 | 4.3 | 1.86 | 0.03 |
Octanal | 0.41 | – | - | – |
Linalool | 0.31 | 0.8 | 0.25 | 0.3 |
δ-3-Carene | 0.31 | – | – | – |
Decanal | 0.27 | 0.4 | 0.28 | – |
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Both California and Florida have authorized and registered d-Limonene (orange oil) as an active ingredient with the Environmental Protection Agency for the extermination of drywood termites, Formosan termites, and other structural pests. [8] [9] It is the active ingredient of the popular structural termiticide XT-2000. [10] Regarded an alternative to traditional fumigation, d-Limonene orange oil is increasing in popularity as approximately 70% of modern consumers in California prefer local structural chemical injections over traditional "tenting" or fumigation. [11]
Orange oil can be used in green pesticides for biological pest control. It can exterminate or control ants and other insects by erasing their scent- pheromone trail indicators, or dissolving their exoskeleton, [12] eliminating the infestation or disrupting re-infestation. [13] [9]
Orange oil is also known to be useful to control, but not exterminate, drywood termites ( Incisitermes), killing only those who come into direct contact with it.[ citation needed] [14] [15]
Orange oil is used as a cleaner. It is also used as an additive to certain wax finish/polish such as Howard's Feed-N-Wax Wood Polish & Conditioner.
The limonene which is the main component of the oil is a mild irritant, as it dissolves protective skin oils. Commercial use of orange oil, like that found in XT-2000 requires the use of protective gloves, according to EPA approved labeling [8] and most municipal structural pest control law such as the California Structural Pest Control Act of 2015. [16] Limonene and its oxidation products are skin irritants, and limonene-1,2-oxide (formed by aerial oxidation) is a known skin sensitizer. Most reported cases of irritation have involved long-term industrial exposure to the pure compound, e.g. during degreasing or the preparation of paints. However a study of patients presenting dermatitis showed that 3% were sensitized to limonene.
Limonene has been observed to cause cancer in male rats by reacting with major urinary protein α2u-globulin, which is not produced by female rats. There is no evidence for carcinogenicity or genotoxicity in humans. The IARC classifies d-limonene under Class 3: not classifiable as to its carcinogenicity to humans.[ citation needed]
Limonene is also flammable. [17]
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