Concentrated Lemon Oil

#### Lemon Oil, concentrated. Expressed **Lemon**** ****Oil**** **consists of more than 90% hydrocarbons (mainly d-limonene) which have but little flavor value, and whose insolubility in alcohol is a nuisance in flavor compounding, etc. By careful vacuum distillation, most of the terpene fractions of **Lemon**** ****Oil**** **can be removed. This method of concentration leads to the so-called two-fold, five-fold, ten-fold, etc. **Lemon**** ****Oils**. However, these concentrates present certain drawbacks: The waxes and high-boiling sesquiterpenes have been concentrated with the remaining oil, and have made it dark and not clearly soluble in all proportions in alcohol. The terpenes have carried over some oxygenated compounds (important flavor and perfume principles of the oil) and a certain loss of aroma must be expected. A five-fold lemon oil does not yield 5 times the flavor of a natural oil. The residual concentrate has been exposed to considerable heat during the last part of the distillation (concentration process). The delicate aldehydes in lemon oil may suffer during this kind of treatment. A more advanced method of concentrating citrus oils is a combination of vacuum distillation and alcohol-washing. The principle is that an “absolute” lemon oil is prepared. This “absolute” is subsequently “cut back” with selected fractions from the vacuum distillation in order to produce a wax-free, sesquiterpeneless, partially monoterpeneless oil, possessing the freshness from the purified and selected monoterpenes and the solubility of other essential oils. It has, furthermore, an attractive, yellow color, not more intense than the color of the natural oil. **Example**: 120 kilos of a selected Cyprus or Californian cold-expressed **Lemon Oil **is submitted to vacuum distillation in an all-glass still at 0.1 to 0.3 mm Hg.-pressure. At this vacuum, either infra-red lamps or a hot-water glass coil heat exchanger will produce sufficient heat to start distillation. The temperature in the pot (distillation flask) will remain below 40° C. and, at the top of a four-foot column (6 inches diameter and packed with half-inch glass raschig rings), the distillation temperature will be 21 to 28° C. An acetone—C02—trap will secure the ballast-type vacuum pump with a freeze of minus 90°C. The first 10% of the distilling oil is “broken” into one-kilo fractions. 75% of the oil is distilled off, leaving 30 kilos in the pot and almost 90 kilos of distillate (lemon terpenes). The 30 kilos are transferred to a smaller glass still, and 10 kilos (of monoterpenes) are distilled off under similar conditions although the pressure is now 0.05 to 0.15 mm. Hg. at the receiver. The remaining oil, about 20 kilos, is then extracted with a mixture of 70 parts by weight of ethyl alcohol and 30 parts by weight of distilled water. Three to four extractions, using respectively 40 kilos, 30 kilos, 20 kilos and 10 kilos of alcohol- water mixture at room temperature, will usually prove sufficient to exhaust all the oxygenated materials from the concentrated lemon oil. Some manufacturers use a 60% alcohol or even more diluted. More than four extractions are then required. Lemon oil contains little or no solid waxes, and the alcohol-insoluble part is a viscous, orange-yellow liquid. It can be vacuum distilled to yield certain useful fractions, but it is of little or no flavor value. When distilling lemon sesquiterpenes even at very reduced pressure, care should be taken that the “skin temperature” (the inner surface temperature of the flask) does not exceed 110°C. Viscous liquids tend to “burn” during distillations at elevated temperature because of the slow circulation and heat exchange in the liquid. The alcoholic solutions from the above mentioned extractions are mixed, and the alcohol is cautiously evaporated. Vacuum is applied during the last part of the evaporation. It will be necessary to interrupt the distillation when oil separates from the water or weak alcohol in the pot. The two layers are then distilled separately in order to avoid loss by water-distillation of the oxygenated compounds (azeotropic distillation of a binary/ ternary mixture). The oil layer, freed from alcohol and water, is dried with anhydrous sodium sulfate and weighed. The “cutback operation” is then carried out with fractions from the first distillation according to the flavor needs of the company. It is possible to establish a standard prescription for this oil-concentration if the oil to be used is adequately flavor-checked prior to the above processing. The sesquiterpene fraction, insoluble in 70% alcohol, is an excellent material for the compounding of artificial citrus oils. A faster but less delicate method involves no alcohol-extraction. The Lemon Oil is vacuum distilled all the way and may be transferred to a smaller still at the end of distillation (the last 20% of the oil). If the pot temperature (the maximum temperature to which the oil is exposed) can be kept below 80° C. through sufficient vacuum, cautious heating and careful distillation, the oxygenated components of the oil will not suffer severely. However, the high- boiling residue (2 ½ to 4 ½ percent of the oil) will act as a strong “fixative”, and will retain small but important amounts of flavor components. It should be mentioned that trace amounts of very important flavor ingredients are found in the lowest boiling fractions; these components are thus hidden or lost in the first terpene fractions. Accordingly, these fractions should be comparatively small (one-half to one percent of the oil, each fraction). A skillful “cut-back” process may reproduce the natural aroma of the oil with a minimum amount of monoterpenes. See also **Lemon**** ****Oil,**** ****Terpeneless**** **and **Sesquiterpeneless**. **Concentrated**** ****Lemon**** ****Oils**** **are used extensively in flavor work where a high amount of unstable and insoluble terpenes may cause trouble: Carbonated beverages (terpenes tend to form an oil- ring in the neck of the bottle), sherbet ice flavors (terpene peroxide formation and rancidity), etc. The **Concentrated Lemon Oils **are particularly superior to the sesquiterpeneless-terpeneless oils when used in soft drinks since the former will have the fresh notes from the monoterpenes which are so characteristic of lemon peel. A six-fold, alcohol- washed, concentrated lemon oil is soluble in alcohol in the proportions usually needed. A plain 6-fold concentrated lemon oil is not.