The Recovery of Parsley Seed Oil

Commercial recovery of essential oils folIowing steam distillation normally relies on the separation of the oil from water into a discrete phase and accumulation of the oil in traps. Observations from a local commercial process have confirmed that, while the essential oil of parsley seed adequately forms a separate phase from the water, it may separate further into floating (top) and sinking (bottom) fractions. This confirms literature reports of Akhtar et al. and Ashraf et al. In the Ashraf study, 26% of the oil sank. Although the specific gravity of the oil was close to that of water (0.995), this may not be the only reason for significant fractionation into top and bottom oils. In the Akhtar study, a recoverable amount of bottom oil separated out despite a considerably lower specific gravity (0.915) than water. Guenther quotes specific gravities of 1.043-1.110 for parsley seed oil and 0.902-1.016 for herb oil, the specific gravity increasing as seed sets and matures.

Fractionation into top and bottom oils complicates recovery--traps for both fractions must operate efficiently. The omission of either trap or incorrect operation could lead to significant losses during the recovery stage. The frequency, extent and main factors of fractionation are not well documented in the literature although a local processor suggests that the temperature of the distillate during the condensation and separation processes has a significant influence on the recovery and quality of the oil.

The work reported here was designed to determine which factors affected the fractionation to top and bottom oil, and to make suggestions on how oil recovery could be improved.

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