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Lemon Myrtle (Backhousia citriodora) Oils

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Yasmina Sultanbawa at The University of Queensland
Yasmina Sultanbawa
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Lemon myrtle has been traditionally used by indigenous Australians for cooking and healing. More recently, lemon myrtle leaves are used as a dry or fresh herb in food applications and the essential oil (EO) used as a flavoring agent in food and beverages. The leaf of the lemon myrtle (Backhousia citriodora) is steam distilled to produce the EO. Lemon myrtle EO is known for its characteristic lemon flavor and the major chemical component contributing to the aroma is citral. The EO has broad spectrum antimicrobial activity and is very effective against fungi and has increased the potential of using the EO in food preservation and treatment of postharvest diseases in fruits. This chapter covers the use of lemon myrtle EO in food and agriculture applications, general usage, botanical aspects, and chemical composition.
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From Sultanbawa, Y., 2016. Lemon Myrtle (Backhousia citriodora) Oils. In: Preedy, V.R.
(Ed.), Essential Oils in Food Preservation, Flavor and Safety. Academic Press, 517–521.
ISBN: 9780124166417
Copyright © 2016 Elsevier Inc. All rights reserved.
Academic Press
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Essential Oils in Food Preservation, Flavor and Safety. http://dx.doi.org/10.1016/B978-0-12-416641-7.00059-6
Copyright © 2016 Elsevier Inc. All rights reserved.
Essential Oils in Food Preservation, Flavor and Safety, First Edition, 2016, 517-521
Chapter 59
Lemon Myrtle (Backhousia citriodora) Oils
Yasmina Sultanbawa
The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation (QAAFI), Brisbane,
QLD, Australia
INTRODUCTION
Lemon myrtle leaves are used in food applications as a fresh or dried herb, while the essential oil (EO) is used as food
flavoring because of its distinct aroma and flavor. In 1889, Joseph H. Maiden reported on the potential use of lemon myrtle
for commercial production and a German company, Schimmel & Co., was the first to identify citral as an active component
(Robbins, 2008). Citral is a major chemical component in the leaf and also the EO. Citral derives its name from Backhousia
citriodora F. Muell from where it was originally extracted and isolated, and is responsible for the characteristic lemon
flavor (Southwell et al., 2000). Lemon myrtle EO has over 90% citral, compared with the other lemon-flavored EOs, such
as citrus (3–10%), lemon grass (75%), and tropical verbena (74%) (Robbins, 2008).
Lemon myrtle has also been used in herbal teas which have been gaining popularity in western countries, with a
major market in the United States followed by Europe. Lemon myrtle teas are available as pure or blended samples and
the antioxidant properties are comparable to the black teas from Camellia sinensis (Chan et al., 2010). Lemon myrtle is
one of the most cultivated and commercially mature species in the native food industry in Australia (Clarke, 2012). This
chapter reviews the application of lemon myrtle essential oil in food and its general usage, botanical aspects, and chemical
properties (Figure 1).
BOTANICAL ASPECTS
The plant genus Backhousia is endemic to Australia and belongs to the family Myrtaceae. The most common chemotype,
B. citriodora F. Muell, is also known as lemon-scented myrtle, lemon ironwood, and sweet verbena tree. It is a large shrub
to medium-sized tree endemic to rainforest areas of coastal Queensland between Brisbane to Cairns and is a very aromatic
plant (Taylor, 1996). It is a perennial tree crop and typically planted in rows. The leaves contain about 95% citral, which
gives the characteristic lemon flavor and the flowers and seeds also have lemon flavors (Ahmed and Johnson, 2000). Horti-
cultural development has progressed through the years with the selection of clones for growth with potential for high citral
and oil capacity. There are two main commercial clones being planted: the line commonly referred to as Limpinwood shows
superior ornamental presentation, high biomass, high oil yield, and citral content; and the variety commonly referred to as
Line B or Eudlo clone is slightly lower in biomass, oil yield, and citral content (Robbins, 2008). In Australia, lemon myrtle
can be harvested all year round; however, harvesting during the monsoonal rainy periods may be restricted in Northern
Queensland. This species exists in two chemical forms: a variety characterized by an essential oil with a high content of
citral, and a variety characterized by an essential oil rich in laevo-citronellal, which is rare. The leaves contain 1.1–3.2%
oil. The citral chemotype, is the most common one used in food, cosmetics, personal care, and aromatherapy, and is grown
commercially in Queensland as well as the Lismore area of northern New South Wales (Lassak, 2012; Brophy et al., 1995).
USAGE AND APPLICATIONS
Lemon myrtle is an Australian native herb and is used as the dried and milled product or steam distilled to obtain lemon
myrtle essential oil (Clarke, 2012). The indigenous Australians have used lemon myrtle traditionally for cooking and
healing purposes. In Europe too, lemon myrtle is becoming popular both for use in cuisine and phytotherapy (Horn et al.,
2012). The aroma and flavor of the lemon myrtle as a dried milled leaf has been described as the aroma of lemon candy,
perfumed with some menthol notes. The flavor is strong lemon with some sweetness and cooling on the palate (Smyth
et al., 2012). Since the mid-1990s, the essential oils, foliage, flowers, and seeds of lemon myrtle have been used widely
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as ingredients in perfumes, food flavorings, herbal teas, and personal care products such as soaps, creams, shampoos, and
conditioners ( Taylor, 1996; Clarke, 2012). The antimicrobial activity of lemon myrtle has also been used in the treatment of
certain diseases such as molluscum contagiosum in children, which is a common contagious viral disease affecting children
globally, a 10% (v/v) solution of lemon myrtle EO as a topical application has shown a reduction of greater than 90% in
the number of lesions in children (Burke et al., 2004). Lemon myrtle EO has also been effective in inhibiting methicillin-
resistant Staphylococcus aureus, which has been identified as a multidrug-resistant bacterium (Chao et al., 2008) and also
shown very good antifungal activity, indicating the potential of using this EO as an antiseptic (Wilkinson et al., 2003).
USAGE AND APPLICATIONS IN FOOD SCIENCE
For essential oil production from B. citriodora, specialized machines cut the stems and leaves into smaller particle sizes.
The cut leaves are placed in stainless steel bins and then steam distilled to obtain the essential oil, which predominantly con-
tains citral (3,7-dimethyl-2-7-octadienal) with two main isomeric aldehydes: neral and geranial. The essential oil is stored
in stainless steel or glass containers and not in plastic as the EO is very corrosive to this material (Robbins, 2008). Lemon
myrtle is used as a dried herb, flavoring agent, and herbal tea in Australia and is approved in the European Union under
the novel food category. Food products to be approved under this category must be excluded from potential health risks
and thorough testing of these plants and their parts in food preparations is a prerequisite (Horn et al., 2012). The chemical
composition of the lemon myrtle EO is given in Table 1 (Hayes and Markovic, 2002; Southwell et al., 2000; Brophy et al.,
1995), the physical properties assessed were relative density (0.888–0.910), refractive index (1.4853–1.4909), and optical
rotation (−1.5° to + 0.4°) (Southwell et al., 2000).
ANTIMICROBIAL PROPERTIES
The antimicrobial activity of B. citriodora EO is believed to be directly related to the high citral content (Lis-Balchin
et al., 1998); however, the importance of other minor components such as linalool, citronellal, and β-myrcene in combina-
tion with citral for enhanced antimicrobial activity has also been reported. A study by Sultanbawa et al. (2009) revealed
complete inhibition of Escherichia coli at 0.313% and S. aureus at 0.156% when evaluated against lemon myrtle EO;
however, the levels of citral alone required to completely inhibit E. coli and S. aureus were 2.5% and 0.625%, respectively.
The higher levels of citral on its own, compared with lemon myrtle EO suggests an enhanced antibacterial activity with
the EO possibly due to synergies between the major and minor chemical components. A study on four lemon myrtle EOs
with citral contents between 93% and 98% were evaluated for antibacterial and antifungal activity against 21 organisms.
This study in general reported that antimicrobial activity of lemon myrtle EO was greater than citral alone. In addition,
the EO was an effective antibacterial agent and an excellent antifungal agent. This indicates the potential of using lemon
FIGURE 1 Lemon myrtle shrubs (picture kindly provided by Australian Rainforest Products).
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myrtle EO as a surface disinfectant and as a natural preservative in the food industry (Wilkinson et al., 2003). The shelf-
life of barramundi fillets was extended when treated with both the oregano and a mix of oregano and lemon myrtle EO
compared with the controls. Based on microbiological data, the shelf-life of barramundi fillets during vacuum storage was
10–12 days. Dipping in antimicrobial solutions of 0.1% (v/w) of oregano and a mixture of 0.05% oregano (v/w) + lemon
myrtle 0.025% (v/w) extended the shelf-life of the fish fillets by an additional 4 days. This study also indicates the potential
of reducing the concentration of essential oils used by developing blends that have synergies (Sultanbawa et al., 2012).
One of the challenges of using EO as natural preservatives is the strong flavor it can impart to the food, and if the concen-
tration can be reduced by blending then it becomes more attractive to use as a natural antimicrobial in food applications.
The effectiveness of lemon myrtle against postharvest fungal diseases in nectarines has been reported. The essential oils,
lemon myrtle (B. citriodora), cinnamon bark (Cinnamomum zeylanicum), oregano (Origanum vulgare), thyme oil ( Thymus
vulgaris), clove bud (Eugenia caryophyllata), valerian (Valeriana officinalis), and Australian tea tree oil (Melaleuca
alternifolia) in controlling brown rot caused by the fungus Monilinia fructicola in nectarines was evaluated. This study
revealed lemon myrtle essential oil as the most potent fumigant to control the mycelium growth and spore germination
(Lazar-Baker et al., 2011).
Clostridium perfringens is the causative agent of necrotic enteritis in poultry. Economic production of poultry meat
with intensive growing techniques is threatened by bacteria showing multiple resistances to antibiotics compounded by the
restriction in the European Union of in-feed use of antibiotic growth promoters. This has resulted in the increase of necrotic
enteritis and the search for natural alternatives to reduce gut colonization of C. perfringens. Use of four essential oils, lemon
myrtle (B. citriodora), eucalyptus oil (Eucalyptus citriodora), lemon tea tree oil (Leptospermum petersonii), tea tree oil
(M. alternifolia), and other secondary plant metabolites have indicated that the fermentative activity of C. perfringens is
inhibited by all essential oils tested with the most effective being lemon myrtle with a minimum inhibitory concentration of
0.05%. This indicates the possibility of using lemon myrtle EO as a feed additive in poultry to control the gut colonization
of this pathogen (Zrustova et al., 2006).
FLAVORING AGENT
Lemon myrtle EO in Australia is used as a source of lemon flavoring in the food and beverage industries. A study of the
sensory properties of lemon myrtle EO assessed the main contributing compounds to the lemon and sweet aromas of lemon
myrtle to be neral and geranial, citronellal, and linalool (Forbes-Smith and Paton, 2002). Lemon myrtle EO is used as a
lemon flavor replacement in milk-based products, such as cheesecake or ice cream to prevent curdling associated with the
acidity of lemon fruits (Horn et al., 2012). However, like other essential oils lemon myrtle is sensitive to light and oxygen
and this can affect the shelf-life and limits its application in the food industry (Buchaillot et al., 2009). To stabilize the EO,
encapsulation by spray drying to powder form has been reported by The Vien et al. (2008). In this study, the optimized
microencapsulated blend contained 18% of the essential oil. The benefit of such powders is the solubility in aqueous phase
which is an advantage when used as a flavoring agent in food applications. These encapsulated flavors can also be used in
shortbread, pasta, and macadamia and vegetable oils (Horn et al., 2012). Lemon myrtle has been used as a herb in speciality
TABLE 1 Chemical Composition of the Essential Oil of Lemon Myrtle
Component Percentage
β-Myrcene 0.1–0.7
6-methyl-5-Hepten-2-one 0.1–2.5
(±)Linalool 0.3–1.0
Citronellal 0.1–0.9
Iso-neral (Cis-iso citral) 0.6–2.7
Iso-geranial (Trans-iso citral) 1.0–4.2
Neral (citral A) 32.0–40.9
Geranial (citral B) 46.1–60.7
Trans-geraniol 0.4–0.7
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cheeses in Australia; these cheeses are semihard, vacuum packed, and are matured for less than 3 months. This market is
growing as the consumer is looking for new flavors (Agboola and Radovanovic-Tesic, 2002).
SAFETY OF LEMON MYRTLE ESSENTIAL OILS
Lemon myrtle essential oil has a high content of the aldehyde, citral (>90%), which is known to be a potential skin sensitizer;
however, the risk is relatively low (Pengelly, 2003). A study by Hayes and Markovic (2002), where an in vitro toxicity test
was performed based on the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H- tetrazolium,
or MTT, carried out cytotoxicity assay. This test revealed that products containing 1% lemon myrtle oil were found to be
low in toxicity and could potentially be used in the formulation of topical antimicrobial products. There is a lemon myrtle
EO standard for Australia, AS 4941 published in 2001, that is under revision to reflect the current commercial quality of the
oil. Three aldehydes: caprylic aldehyde, pelargonic aldehyde, and caprinic aldehyde, that are not present in lemon myrtle
essential oil, have been found in some of the lemon myrtle oils in the global market. In order to protect the Australian lemon
myrtle EO and also to prevent adulteration the Australian standard is currently under revision. These three aldehydes must
not be present in lemon myrtle EO and the range for geraniol is recommended to be amended to 0.6–2.5% (Lassak, 2012).
SUMMARY POINTS
l Leaves of lemon myrtle (Backhousia citriodora) are steam distilled for the production of the essential oil.
l Citral is the major chemical component contributing to the lemon flavor of the essential oil.
l Lemon myrtle EO is used in the food and beverage industry globally as a flavoring agent.
l It has broad spectrum antimicrobial activity and has the potential to be used as a natural food preservative.
l Antifungal activity enables the application in postharvest disease management.
l The characteristic lemon flavor in the EO can be used as a flavor in a wide range of food and beverage products.
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... Because of toxicity investigations, topical use at less than 1% in a formulation is recommended [45]. There have been a host of industry production and use-related publications extolling the value and benefits of lemon myrtle and its essential oil [60,[78][79][80][81][82][83][84][85][86][87][88][89][90]. ...
Backhousia citriodora F. Muell. (Lemon Myrtle), an Unrivaled Source of Citral
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Lemon oils are amongst the highest volume and most frequently traded of the flavour and fragrance essential oils. Citronellal and citral are considered the key components responsible for the lemon note with citral (neral + geranial) preferred. Of the myriad of sources of citral, the Australian myrtaceous tree, Backhousia citriodora, is considered superior. This review examines the history, natural occurrence, the cultivation, the taxonomy, the chemistry, the biological activity, the toxicology, standardisation and the commercialisation of Backhousia citriodora especially in relation to its essential oil.
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... Lemon myrtle belongs to the Myrtaceae family, and it is endemic to the subtropical rainforests of coastal Queensland and New South Wales, Australia. Lemon myrtle is used as a dried herb, flavoring agent, and herbal tea in Australia and has been approved in the European Union under the novel food category and used in herbal teas (Sultanbawa, 2016). Once the valuable essential oil is extracted, solid biomass is generated as a residue which are usually thrown away as waste or combusted directly to produce heat for the required applications. ...
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... geranial (46.1-60.7%) and trans-geraniol (0.4-0.7%) (Sultanbawa, 2016b). Brophy and Boland (1991) reported that the yield of EO from AM varies from 1.3 to 2.0% and AM EO had two different chemotypes depending upon the content of anethole and methyl chavicol. ...
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  • Jul 2022
  • J FOOD SAFETY
Oil‐in‐water nanoemulsions were formulated using sunflower oil mixed with each of the essential oils of Tasmannia lanceolata (Tasmanian pepper leaf [TPL]), Backhousia citriodora (lemon myrtle [LM]) and Syzygium anisatum (anise myrtle [AM]) and stabilized with Tween 80 using ultrasonication. An oil‐surfactant ratio of 3:1 was found to produce the lowest emulsion droplet sizes of 96.6 nm for LM, 122.2 nm for AM and 131.8 nm for TPL. Increase in surfactant concentration above 10r resulted in larger droplet sizes, 165.8–2,647.2 nm for LM (radius, r = .82), 153.7–2,573.5 nm for AM (r = .93) and 157.4–2,621.6 nm for TPL (r = .83). Sonication for 3 min produced smaller droplet size; however, sonication for 9 min resulted in increase of droplet size by 1.48, 1.43 and 1.47 times for oils of LM (r = .82), AM (r = .93) and TPL (r = .83), respectively. A positive correlation was found between sonication amplitude (20–50%) and droplet size for nanoemulsions of LM (r = .93), AM (r = .98) and TPL (r = .95). TPL and LM nanoemulsions showed broad‐ spectrum antimicrobial activities against yeasts and bacteria. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) against weak‐acid resistant yeasts were between 0.001–0.003 and 0.002–0.007 mg/ml for nanoemulsion of TPL and between 0.003–0.014 mg/ml and 0.005–0.027 for nanoemulsion of LM, respectively. The stability and antimicrobial activity of TPL and LM essential oil nanoemulsions confirm their potential for application as food preservatives especially in beverage products that are commonly spoiled by weak‐acid resistant yeasts. Nanoemulsions formulated from the of essential oils of Tasmannia lanceolata, Backhousia citriodora and Syzygium anisatum have strong antimicrobial activity against bacteria and fungi.
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Antimicrobial and antioxidant AIE chitosan-based films incorporating a Pickering emulsion of lemon myrtle (Backhousia citriodora) essential oil
Article
  • Jul 2022
  • FOOD HYDROCOLLOID
Films based on chitosan (CS) and Lemon Myrtle (Backhousia citriodora) essential oil (LEO) were prepared that exhibited novel dose-dependent fluorescent patterns owing to aggregation-induced emission (AIE) effects. Specifically, chitosan-coated alkali lignin ([email protected]) colloid particles were obtained by a facile one-pot ultrasonication, and were used to prepare LEO-loaded Pickering emulsions ([email protected]). Different amounts of [email protected] were incorporated into CS-based film-forming solutions. The composite ([email protected]) films contained LEO/CS (w/w) ratios around 0%, 5.9%, 14.8%, 29.6% and 59.2% after solution casting. The microstructures, optical properties, water affinity, mechanical attributes, fluorescent characteristics, as well as antimicrobial and antioxidant efficacies of [email protected] films were assessed for multifunctional food packaging. 0.5% (w/v) of [email protected] particles (pH ∼4.3 to 4.6) enabled stabilization of [email protected] (φ = 0.4) for at least 35 days. Adding [email protected] with appropriate LEO/CS (w/w) ratios modified the properties of the composite films. The [email protected] film (with LEO/CS (w/w) around 29.6%) was the most promising candidate for multifunctional packaging considering its optimal optical properties, resistance to moisture and mechanical stress, characteristic fluorescent attributes along with antimicrobial and antioxidant activities.
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Anti-Yeast Synergistic Effects and Mode of Action of Australian Native Plant Essential Oils
Article
Full-text available
  • Nov 2021
Yeasts are the most common group of microorganisms responsible for spoilage of soft drinks and fruit juices due to their ability to withstand juice acidity and pasteurization temperatures and resist the action of weak-acid preservatives. Food industries are interested in the application of natural antimicrobial compounds as an alternative solution to the spoilage problem. This study attempts to investigate the effectiveness of three Australian native plant essential oils (EOs) Tasmanian pepper leaf (TPL), lemon myrtle (LM) and anise myrtle (AM) against weak-acid resistant yeasts, to identify their major bioactive compounds and to elucidate their anti-yeast mode of action. The minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC) and minimum bactericidal concentration (MBC) were assessed for EOs against weak-acid resistant yeasts (Candida albicans, Candida krusei, Dekkera anomala, Dekkera bruxellensis, Rhodotorula mucilaginosa, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Zygosaccharomyces bailii and Zygosaccharomyces rouxii) and bacteria (Staphylococcus aureus and Escherichia coli). The EOs showed anti-yeast and antibacterial activity at concentrations ranging from 0.03–0.07 mg/mL and 0.22–0.42 mg/mL for TPL and 0.07–0.31 mg/mL and 0.83–1.67 mg/mL for LM, respectively. The EOs main bioactive compounds were identified as polygodial in TPL, citral (neral and geranial) in LM and anethole in AM. No changes in the MICs of the EOs were observed in the sorbitol osmotic protection assay but were found to be increased in the ergosterol binding assay after the addition of exogenous ergosterol. Damaging of the yeast cell membrane, channel formation, cell organelles and ion leakage could be identified as the mode of action of TPL and LM EOs. The studied Australian native plant EOs showed potential as natural antimicrobials that could be used in the beverage and food industry against the spoilage causing yeasts.
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Backhousia citriodora F. Muell. (Lemon Myrtle), an Unrivalled Source of Citral
Article
Full-text available
  • Jul 2021
Lemon oils are amongst the highest volume and most frequently traded of the flavor and fragrance essential oils. Citronellal and citral are considered the key components responsible for the lemon note with citral (neral + geranial) preferred. Of the myriad of sources of citral, the Australian myrtaceous tree, Lemon Myrtle, Backhousia citriodora F. Muell. (Myrtaceae), is considered superior. This review examines the history, the natural occurrence, the cultivation, the taxonomy, the chemistry, the biological activity, the toxicology, the standardisation and the commercialisation of Backhousia citriodora especially in relation to its essential oil.
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Molecular diagnostics of Lemon Myrtle (Backhousia citriodora versus Leptospermum citratum)
Article
Full-text available
  • May 2012
‘Lemon Myrtle’ is becoming increasingly popular in Europe both for use in cuisine and phytotherapy. However, this common name covers two completely different species, Backhousia citriodora F. Muell. and Leptospermum citratum Challinor, Cheel & A.R.Penfold. These species differ with respect to secondary compounds and even can cause, if mixed up and applied in high dose, toxic effects. We describe how the two species can be discriminated microscopically making use of differences in the morphology of leaf pavement cells and the relative size of palisade parenchyma. Based on the large subunit of ribulose-1,5-bisphosphate carboxylase oxygenase (rbcL) as molecular marker, the phylogenetic position of the two species within the Myrtaceae could be clarified. This sequence information was used to develop a simple assay to discriminate the two species even in dried and highly fragmented mixtures as typically occurring in commercial samples. This assay utilises the occurrence of single-nucleotide exchanges between those species that produce different fragments when the rbcL amplificates are restricted with Sac II.
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Backhousia citriodora F. Muell. (Myrtaceae), A Superior Source of Citral
Article
Full-text available
  • Nov 2000
Leaf from the citral chemical variety of lemon myrtle, Backhousia citriodora, was examined for volatile constituents by GC and GC/MS analysis of both steam volatile oils and solvent extracts. Identified constituents present at more than 0.1 per cent on average in the oil were found to be myrcene (0.1-0.7%), 6-methyl-5-hepten-2-one (0.1-2.5%), linalool (0.3-1.0%), citronellal (0.1-0.9%), iso-neral (0.6-2.7), iso-geranial (1.0-4.2%), neral (32.0-40.9%) and geranial (46.1-60.7%). Physical constants were found to fall within the ranges of 0.888-0.910 for relative density, 1.4853-1.4909 for refractive index, -1.5°-+0.4° for optical rotation and 0.8-2.3 volumes for solubility in 70% ethanol. Comparison of chemical and physical data with those of other citral-rich commercial oils showed that B. citriodora was richer in citral than both lemongrass (Cymhopogon flexuosus and C. citratus) and Litsea cuheba. Micro-extraction of fresh leaf with absolute ethanol gave volatile extracts with higher proportions of citral and lower proportions of cogeners iso-neral and iso-geranial than steam distillation suggesting partial double bond migration during the distillation process. No significant variation in citral content was observed between flash growth and mature leaf or between fresh and dried leaf.
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Horticultural development of Australian native edible plants
Article
Full-text available
  • Aug 2000
The Australian native edible plant industry is rapidly expanding. We provide a review of the horticultural research that has been carried out on the top 14 commercially significant Australian native edible plants; Acacia spp. Miller (wattle), Acronychia acidula F.Muell. (lemon aspen), Backhousia citriodora F.Muell. (lemon myrtle), Eremocitrus glauca (Lindl.) Burkill (desert lime) and Microcitrus spp. Swingle (native lime), Hibiscus heterophyllus Vent. and Hibiscus sabdariffa L. (rosella), Kunzea pomifera F.Muell. (muntries), Podocarpus elatus R.Br. ex Endl. (Illawarra plum), Prostanthera spp. La Billardiere (native mint), Santalum acuminatum R.Br. (quandong), Solanum centrale Black (bush tomato), Syzygium leuhmannii F.Muell. (riberry), Tasmannia spp. R.Br. (native pepper), Terminalia ferdinandiana (= T. latipes Benth. subsp. psilocarpa Pedley) (kakadu plum) and Tetragonia tetragonioides (Pallas) Kuntze (warrigal greens). The research on most of these species has focused on propagation, breeding, cultivation, nutritional value and the isolation of natural products. On none of the species has research been completed in all these areas, and three species have no research published on them. We describe horticultural research on two other commercial species, Backhousia anisata Vickery (aniseed myrtle) and Davidsonia pruriens F.Muell. var. pruriens and var. jerseyana (Davidson’s plum), and one species with commercial potential, Pringlea antiscorbutica R.Br. ex Hook.f. (kerguelen cabbage). We identify areas that require further research and issues of concern, such as indigenous intellectual property rights and environmental implications.
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Leaf Oils of the Genus Backhousia (Myrtaceae)
Article
  • May 1995
The leaf oils of eight described and one undescribed species of Backhousia were examined by GC and GC/MS. The major components of the five suspected chemotypes of B. angustifolia F. Muell. were 1,8-cineole, (E)-β-ocimene, angustifolenone, angustifolionol, dehydroangustione and angustione. B. anisata Vickery was found to exist in two chemotypes in whch the major compound was either (E)-anethole or methyl chavicol. The oil from B. bancroftii F. M. Bailey & F. Muell., which varied quantitatively between trees, contained octyl acetate (0.3–61.7%), dodecyl acetate (0.2–21.0%), dodecanol (trace-22.9%), decyl acetate (0.5–39.0%), decanol (0.1–17.4%), 2,4,6-trimethoxy-3- methylacetophenone (trace-23.0%) and a novel compound, bancroftinone (6-hydroxy-2,4-dimethoxy-3-methylacetophenone) (trace-90.0%) as its major constituents. B. citriodora F. Muell. was found to exist as two chemotypes in which either citral or citronellal predominated. The major constituents of B. hughesii C. T. White were β-bisabolene (1.0–44.0%) and an unidentified sesquiterpene hydrocarbon (8.0–54.0%). B. kingii Guymer gave an oil which contained α-pinene (24.0–49.0%), limonene (7.0–24.0%) and 1,8-cineole (10.0–17.0%) as the principal constituents. Four chemotypes of B. myrtifolia Hooker & Harvey were found in which the major components were methyl eugenol, (E)-methyl isoeugenol, elemicin and (E)-isoelemicin. B. sciadophora F. Muell. gave an oil with α-pinene (44.0–55.0%), β-pinene (2.4–8.0%), limonene (6.5–12.7%) and linalool (2.8–6.7%) as its major components. The principal components of Backhousia sp. (Didcot P.I. Forster PIF12671) were α-pinene (11.0%), β-pinene (5.3%), β-caryophyllene (12.0%), dodecyl acetate (8.1%) and dodecanol (8.2%).
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Lexicon for the Sensory Description of Australian Native Plant Foods and Ingredients
Article
  • Dec 2012
Understanding and describing “Australian flavor” has proved to be a challenge for marketers of native foods because of the diversity of unique flavor signatures exhibited. Descriptive analysis techniques were applied, using a panel of 11 experienced judges, to define and articulate the sensory properties of 18 key commercial Australian native plant foods and ingredients including fruits, herbs and spices. Quantitative descriptive data were transformed into concise and accurate verbal descriptions for each of the species. The sensory language developed during the vocabulary development panel sessions was combined, categorized and ordered to develop a sensory lexicon specific for the genre. The language developed to describe the foods and ingredients was diverse and distinctly Australian including aromas such as musk, rosella, citrus and spiced tea to eucalypt, bush scrub, fresh beetroot and wheat biscuit. This work provides a clear, useful means of characterizing and accurately describing the flavors of Australian native plant foods and ingredients. This information has been communicated to the native food industry, chefs, formulators, food technologists and flavor experts, and provides knowledge that will assist the wider food industry to successfully develop flavor blends and produce food products from native food ingredients. It is anticipated that extension of this information to both the local and international food markets will stimulate a renewed interest in Australian native ingredients and open new market opportunities for the industry. The data developed by this research have also formed the basis of quality control targets for emerging native foods and ingredients.
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Relationship between Bioactivity and Chemical Composition of Commercial Essential Oils
Article
  • Mar 1998
  • FLAVOUR FRAG J
In order to establish the value of the use of biological activities as accessory criteria (in conjunction with gas chromatography, but in the absence of enantiomeric analysis) for establishing the authenticity of essential oils, the biological activities of 105 commercial essential oils were investigated against 25 species of bacteria, 20 strains of Listeria monocytogenes, and three filamentous fungi; their antioxidant action was also determined and all the results were related to the actual chemical composition of the oils as determined by gas chromatography. The results showed some relationship between the major components and some bioactivities. There was a negative correlation between 1,8-cineole content and antifungal activity. There was, however, great variability between the biological action of different samples of individual oils and groups of oils under the same general name, e.g. lavender, eucalyptus or chamomile, which was reflected in differences in chemical composition, The results suggest that, although the biological activities are not all related to the main components, any significant blending, rectification and adulteration of commercial oils can be monitored by their biological activities. The use of essential oils named simply as ‘chamomile’ or ‘eucalyptus’, or any commercial oil which has been adulterated, cannot be justifiably used in treating medical conditions unless it can be shown that the action is non-specific and independent of the chemical composition. © 1998 John Wiley & Sons, Ltd.
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Inhibition of methicillin‐resistant Staphylococcus aureus (MRSA) by essential oils
Article
  • Nov 2008
  • FLAVOUR FRAG J
Ninety-one essential oils, each distilled from a single plant source, and 64 blended essential oils obtained from a commercial source were screened using the disc diffusion assay for inhibitory activity against methicillin-resistant Staphylococcus aureus (MRSA). Of the 91 single essential oils, 78 exhibited zones of inhibition against MRSA, with lemongrass, lemon myrtle, mountain savory, cinnamon and melissa essential oils having the highest levels of inhibition. Of 64 blended essential oils, 52 exhibited inhibitory activity against MRSA, with R.C. (a combination of myrtle, Eucalyptus globulus, Eucalyptus australiana, Eucalyptus radiata, marjoram, pine, cypress, lavender, spruce, peppermint and Eucalyptus citriodora oils), Motivation (a combination of Roman chamomile, ylang ylang, spruce and lavender oils) and Longevity (a combination of frankincense, clove, orange and thyme oils) blended essential oils having the highest inhibitory activity. These results indicate that essential oils alone and in combination can inhibit MRSA in vitro. Application of these results may include the potential use of essential oils as an alternative therapy for various diseases sustained by S. aureus MRSA. Copyright © 2008 John Wiley & Sons, Ltd.
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Influence of Australian Native Herbs on the Maturation of Vacuum-packed Cheese
Article
  • Nov 2002
  • LWT-FOOD SCI TECHNOL
The composition, microbiology and biochemistry of semi-hard cheeses flavoured with native mint, lemon myrtle and bush tomato (BT) were compared with unflavoured (control) cheese during a 90-day period of maturation. Moisture, protein and salt levels of all cheeses were similar and did not change during maturation. However, the fat content of control cheese was significantly higher than that of the flavoured cheeses while the pH of cheese flavoured with BT was consistently lower throughout maturation. Total viable organisms, Lactobacillus and Lactococcus counts were between 106 and 107 colony forming units (cfu)/g cheese for all cheeses. Yeast and mould count was <102 cfu/g cheese throughout the maturation of all cheeses except in the cheese flavoured with BT which was >103 cfu/g cheese. Biochemical indices of proteolysis and lipolysis increased with the extent of maturation in all cheeses but were most pronounced in the BT-flavoured cheese. The capillary electrophoretic profile of this cheese also indicated a more extensive hydrolysis of both α s- and β -caseins. The microbiological quality of BT appeared to have exerted a very significant influence on cheese properties.
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