Characteristics of plants and plant extracts from five varieties of basil (Ocimum basilicum L) grown in Australia

A horticultural trial on five varieties of basil (Ocimum basilicum L.) showed differences in morphological features, growing characteristics, and yields of essential oil produced per unit area of land. Anise basil was the most productive in terms of plant biomass, while Cinnamon basil produced the most essential oil. Gas chromatographic analysis showed considerable differences in the composition of oils among varieties. Seasonal variations had a significant effect on plant growth, essential oil yield, and composition when Reunion and Anise were grown in successive years in the same soil. All varieties were susceptible to cold temperature injury caused by ground frost. Variations in oil composition due to environmental factors appear to be of the same order of magnitude as genetic factors. Data are provided on the yield, composition, and physical appearance of extracts within the same variety obtained by hydrodistillation and with CO2. The yields were highest using supercritical CO2 followed by liquid CO2 and then water. All of the CO2 extracts were quite similar in chemical composition with respect to volatile components. The hydrodistilled oil contained a larger proportion of lower boiling point hydrocarbons and oxygenated terpenes than the CO2 extracts. The sensory evaluation of hydrodistilled oil and liquid CO2 extracts obtained with a one-stage separator under defined conditions indicated that they were quite different products and they would appear to have different end uses.