NOTICE: Hard copies of the Australian New Crops Newsletter are available from the publisher, Dr Rob Fletcher. Details of availability are included in the
Advice on Publications Available.Luigino Doimo
Summary of PhD thesis
Submitted May 1998
The University of Queensland Gatton College
Essential oil production from a purpose-bred Australian geranium (Pelargonium hybrid) growing at Perseverance Creek in Queensland, Australia, was investigated with a view to determining its suitability as a new crop product.
Climatic, agronomic and environmental factors were monitored. Growth studies indicated geraniums were well adapted to the site and its environment. Soils from the site were low in pH but suitable for geranium growing. The plants were not affected by low nitrogen, low boron or marginal sulphur levels in the soil.
The effect of cutting the geranium plants at various heights was significant in terms of oil yield whereas the effects of pre-drying the leaves or packing the still at differing densities were not.
Studies of the harvested leaves found the oil was concentrated in the youngest leaves, near the growing tip. Mechanical harvesters would need to trim the geranium plant to maximumise oil yield.
Geranium essential oils were extracted from leaf material collected in a series of experiments over time, designed to investigate the effects of seasonal conditions on oil yield and composition. Analysis of essential oils was by gas chromatography, gas chromatography with mass spectrometry using non-polar BPX-5 and chiral (-cyclodextrin columns.
Queensland-grown geranium oil contained citronellol (28.9%), citronellyl formate (14.2%), geraniol (10.2%), 6,9-guaiadiene (6.8%), isomenthone (6.7%), geranyl formate (5.7%), linalool (3.7%), germacrene D (2.2%), geranyl tiglate (1.6%), geranyl propanoate (1.2%), furopelargone B (1.2%), cis-rose oxide (1.1%), b-bourbonene (1.1%), b-caryophyllene (1.1%), phenyl ethyl tiglate (0.8%) and citronellyl tiglate (0.8%).
It is therefore of the 'Bourbon' type and is similar to Chinese geranium oil.
This oil is therefore considered a valuable and extremely desirable product. The concentrations of most compounds detected in the Queensland-grown oil varied with season.
The ratio of the concentrations of the two important alcohols, citronellol and geranoil (the citronellol:geraniol ratio, C:G) was found to be a sensitive indicator of compositional changes in the oil.
Changes in C:G were linked to variablility in the prevailing weather conditions and have been proposed as an indicator of physiological stress experienced by the plants.
Distillation studies of geranium using copper, stainless steel, mild steel, aluminium or borax glass-lined vessels indicated that the resulting oil yields were not affected by the nature of the material lining the distillation vessel.
However, the aroma of the resulting oil was affected, with the product from copper, stainless steel or glass-lined vessels having a more pleasant aroma than that of the oil extracted using an aluminium-lined vessel.
In terms of oil quality, oils extracted using copper, stainless steel or glass-lined vessels were significantly higher in linalool and 2-phenyl ethyl tiglate and significantly lower in geranial than oils extracted using mild steel or aluminium-lined vessels.
The most variability in component levels was evident amongst the water soluble compounds, such as the aldehydes and some sesquiterpenes.
Hydro-distilled geranium oils contained a wide range of esters. GC-MS identified these esters emerging as a series, with citronellyl esters eluting regularly before neryl and geranyl esters. Iso-esters (comprising 1.2% of the oil) were of the (n-1)-substituted type and they eluted before their straight chain namesakes. Successive ester series were spaced 90-120 retention index units apart.
Australian-grown geranium oil was high in esters (comprising 30% of the oil) with the most prevalent being formates (19.7%) and tiglates (3.9%). It was low in acetates (0.8%).
The new concepts of chiral excess (CE) and total excess (TE) were developed to allow the chirality of geranium essential oils to be expressed as a single number so that 18 commercial geranium oils from a wide range of geographical origins and 24 geranium oils collected over several seasons from the Queensland study site, were able to be distinguished.
Australian geranium oils had high TE values. TE values were able to differentiate oils from different growing areas. TE values in oil from Australian-selected geranium varied with season, being higher in August than it was in April or November.
In terms of the new crop potential of Queensland-grown geranium, the production, harvesting and extraction of the crop and the quality characterisation of the essential oil are now sufficiently well documented to indicate that geranium warrants carefully controlled commercialisation.
Any claims made by authors in the Australian New Crops Newsletter are presented by the Editors in good faith. Readers would be wise to critically examine the circumstances associated with any claims to determine the applicability of such claims to their specific set of circumstances. This material can be reproduced, with the provision that the source and the author (or editors, if applicable) are acknowledged and the use is for information or educational purposes. Contact with the original author is probably wise since the material may require updating or amendment if used in other publications. Material sourced from the Australian New Crops Newsletter cannot be used out of context or for commercial purposes not related to its original purpose in the newsletter
Contact: Dr Rob Fletcher, School of Land and Food, The University of Queensland Gatton College, 4345; Telephone: 07 5460 1311 or 07 5460 1301; Facsimile: 07 5460 1112; International facsimile: 61 7 5460 1112; Email:
r.fletcher@mailbox.uq.edu.au[
New Crops Home Page] [New Crops Program] [Australian New Crops Newsletter] [New Crops Publications] [Order Form] [People] [Crop Profiles] [Other Resources]originally created by:
GK; latest update 6 June 1999 by: RF