Noel G Porter

Chemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides.

The major components of commercial New Zealand essential oils of Leptospermum scoparium (manuka) and Kunzea ericoides (kanuka) are identified. In the manuka oil, monoterpenes are present at low levels (< or = 3%). Sesquiterpene hydrocarbons are predominant (> or = 60%) and include groups possessing cubebene/copaene, elemene, gurjunene/aromadendrene, farnesene/ caryophyllene, selinene, calamenene and cadinene skeletons. Oxygenated sesquiterpenes and triketones are present (< or = 30%). The antimicrobial activity of the manuka oil was associated with a fraction containing three major and three trace triketones, two of the latter were previously unreported. Kanuka oil was characterized by high levels of alpha-pinene (> 50%) and lower levels (< 10%) of viridiflorol and viridiflorene. GC-MS and GC-FID detector responses to the same components were noticeably different for some major components, including the triketones. Non-commercial manuka oils from different sites differed widely in composition and could be separated into four groups by the presence and levels of distinctive components. The density and refractive index of manuka and kanuka oils were closely correlated with the total sesquiterpene levels. The density of the commercial manuka oil was closely correlated with the level of the triketones. Simple density measurements enabled discrimination between the commercial oil and oils from other sites, and prediction of antimicrobial activity.

Investigation of isothiocyanate yield from flowering and non-flowering tissues of wasabi grown in a flooded system

Wasabi (Japanese horseradish) is used extensively in Japanese cuisine because of its characteristic flavour. The plant is grown as a perennial crop in New Zealand. The rhizomes are the most sought after part of wasabi although other parts of the plants are pungent. In this study the yields of individual and total isothiocyanates (ITCs) were measured in the four main parts of the plant: root, rhizome, petiole and leaves in mature, flowering and non-flowering, 18-month-old plants. The plants were grown without fertilizer in beds flooded with river water. The total ITC and individual contents of allyl, 3-butenyl, 4-pentenyl and 5-hexenyl ITC in the roots and rhizomes of the flowering plants were all significantly higher (P<0.001) than in the comparable non-flowering plant parts. The level of total ITC in the epidermis and cortex of rhizomes of the flowering plants was 3144 mg/kg fresh weight basis compared to 1773 mg/kg in the non-flowering tissue. The total ITC contained in the vascular and pith tissue was 2234 mg/kg fresh weight for the flowering plants compared to 1388 mg/kg fresh weight for the non-flowering plants. Such differences between the ITC profiles in the flowering and non-flowering tissue of wasabi plants suggest there will be differences in the overall aroma profiles when the material is made into a processed product. The magnitude of such differences suggest the flowering state of wasabi plants could be important in crop management for optimal processing quality.

Effect of Temperature on the Relative Densities of Essential Oils and Water

ABSTRACT The densities of essential oils from traditional herb and New Zealand native species were measured over the temperature range 20°-60°C. The density of all oils decreased as temperatures increased. There was some variation between oils in the temperature coefficients of the change in density. The density differentials between oil and water and their temperature coefficients varied markedly between the different oils. A preliminary separation coefficient is used to indicate the effect of oil density and condensate water viscosity on oil separation at different temperatures. Separation of less dense oils with small differentials (fennel) would benefit more from increased temperatures than less dense oils with large differentials (coriander). It is necessary to use both density and viscosity data to determine if temperature control of a separator will be required to obtain efficient separation of an oil from the condensate stream.

Evaluation of variability in single plants of Boronia megastigma using plant and chemical criteria

Abstract A seedling population of Boronia megastigma (Nees) plants was established to explore the extent and degree of variation in plant and chemical characteristics and to select plants of superior performance in the production of aromatic concretes for commercial use. Obvious variations between selected individual plants were found in plant habit, growth vigour, flower yield, ease of flower removal for harvesting, concrete yield, β‐Ionone and monoterpene content, and the proportion of “volatile” components in the concrete. Selection of elite plants on the basis of so many different criteria is difficult. Quality indices were calculated by incorporating the criteria for each plant into a single value that could be used to rank the plants on plant, chemical, or combined criteria. Ranking using plant and chemical indices gave very different results. Ranking using a quality index that incorporates all criteria offers the opportunity to apply differing weights to individual characteristics. Examples of weig...

Essential Oil of Eucalyptus olida L. Johnson et K. Hill 1: Variability of Yield and Composition in Foliage from a Seedling Population

Abstract Pet. Ether (65°-69°C) extracts of Eucalyptus olida L. Johnson et K. Hill leaves and stems from 3-5 year old trees in a trial planting generally contained very high levels (>91% of oil yield) of methyl cinnamate (MC). Some trees had low (0%) or variable levels (0-21%) of MC, highlighting the need to explore selection of proven clones for plantation-scale production of MC. Leaf age and time of harvesting affected MC levels and yields, and also oil yields, which peaked in younger leaves in mid summer. In general, higher MC yields were more closely related to high yields of oil in the foliage rather than high levels of MC in the oil.