Here at Gadoi we firmly believe in the power of information and training, because we know that a well-informed and knowledgeable user can more easily appreciate quality products. Essential oils are products of exceptional interest and potential. However, their highly concentrated nature and their relative novelty (compared to other products derived from aromatic plants), plus the unfortunate proliferation of incomplete, superficial, incorrect or fraudulent publications on the Internet or in printed form means that one needs to stay informed and updated. In this section we intend to offer various resources and opportunities for information and training.

Below you’ll find: a list of residential courses and of on-line courses available now, all held by Marco Valussi; a section of insights on the topic of essential oils; one section on selected sources of information on the web; and finally a selection of useful texts.


Residential courses

Gadoi, in collaboration with the Associazione OfficinaLessinia, organizes training courses at various levels, from open days at the production site, to observe and collaborate in the harvesting operations and in the distillation processes, to professional courses for professionals (herbalists, pharmacists, aromatherapists, nurses, doctors, etc.).

An overview of the courses scheduled for the beginning of 2017 is available in the Depliant Gadoi Courses, and further details with respect to schedules and prices can be viewed in the Calendario Corsi Gadoi.

The list of coming-soon courses includes:

  • 29th-30th April 2017: Seminar on essential oils, topical applications and dermatology.
    Duration: 1 weekend (14 hours)
  • 13-14 maggio: Seminar on ancient aromatic materials, balsams, resins and spices
    Duration: 1 weekend (14 hours)
  • 27-28 maggio: Seminar on infectious diseases and essential oils
    Duration: 1 weekend (14 hours)
  • 17-18 giugno: Seminar on Mediterranean fragrances: focus on Lamiaceae
    Duration: 1 weekend (14 hours)
  • giugno-luglio: Theoretical and practical seminar on distillation
    Duration: 3 weekends (42 hours)

In addition to these professional courses, Gadoi also organizes theoretical and practical weekends in which you can work directly in the production chain, helping us to collect the plants to be distilled and collaborating in the distillation, the essential oil collection and separation.
On all days there will be moments of theoretical study both in class and during operations. 
Since these events depend on the availability of plant material and the weather, we will post the exact dates in a few weeks.

For more information contact us at

 Other courses

Dr. Marco Valussi participates as a lecturer to courses and seminars organized by other organizations/firms. Here are some of the events:

  • 2nd-5th of March: presentation on local and controlled supply chains at the Fippo Forum, at Massa Marittima
  • 17th-19th of March: a theoretical and practical seminar on distillation at Maribor, Slovenia (Seminario professionale distillazione)
  • 3rd-6th of August: presentation on the market for high quality essential oils at the AIA Conference, in New Brunswick, NJ, USA
  • 14th-16th of August: workshops on fermented essential oils at the “Ancient Alchemy” workshop with Ann Harman, at Bozarth Mansion, Spokane, WA, USA (Contact:; Register at Botannicals)
  • 5th-9th of September: workshop on chemistry and steam distillation at the “Chemistry for the Distiller” workshop with Ann Harman, at Bozarth Mansion, Spokane, WA, USA (Contact:; Register at Botannicals)

On-line courses

To meet the needs of foreign users or those who cannot afford to attend to our residential courses, we are planning to publish on-line courses. As soon as they become available they will be listed in this space

At the moment there is an online introductory course to essential oil research held by Marco Valussi for SISTE, available here

For those who can follow a course taught in English, here is an excellent series of on-line videos on the chemistry of essential oils, filmed during the lectures of the chemist Robert Pappas (in English).

For more information contact us at



1. What is an essential oil?

Definitions, in the case of essential oils, are useful and important because they can help a person who might not be familiar with the subject to orient herself in the maze of the many pieces of information that can be found in print or on the internet, ti distinguish between the other “aromatic” products on the market, and also to delimit a meaningful discussion and research field. The definition I prefer is the following:/span>

An essential oil is the hydrophobic product of the steam distillation of aromatic plants, or, but only in the special case of Citrus peels, the hydrophobic product of cold pressing.   Usually the term refers to products obtained from a single drug (whereby by drug we mean an organ or tissue of a single species of plant).

Learn more here

2. How is it produced?

Distillation, according to the Treccani Dictionary, is an:

industrial and laboratory operation that has the purpose of (…) to separate liquids of different volatility, and which is carried out by boiling the liquid and condensing the resulting vapors by means of a heat exchanger

So, in general terms, distillation is a method for separating two liquids by taking advantage of their boiling points difference, or their difference in volatility. In this way it is possible to obtain a greater percentage of one of the two liquids in the condensed product. A classic example is the production of Brandy or Cognac from wine. Wine can be modeled as an ethanol-water mixture, a mono-phasic one because water and ethanol are miscible. This comparison is not, however, perfectly fitting to our case, for two main reasons: first, unlike wine, essential oil and water are two immiscible liquids (or, better, liquids which are very little miscible) and do not therefore form a mono-phasic mixture, rather a biphasic mixture, which behaves in a different way with respect to the boiling temperature; second, while distilling aromatic plants we don’t have in the still a mixture of water and essential oil, but rather a load of plant material, immersed in water or invested by a steam flow. The problem is thus divided into two separate ones: first, extracting aromatic molecules from the plant matrix so that they can mix with water or steam, and second, describing the behavior of a two-phase mixture once in distillation.

Learn more here

3. Is there a right and a wrong way to distill?

This question is absolutely justified, but to be able to respond accurately you must first understand that the rightness or wrongness of a distillation depends on the result you want to achieve, on the product that we expect at the end of the process. What is wrong for those who do distills to obtain an essential oil may be the best for those who distill to obtain aromatic waters. 

Learn more here

4. Cold expression of Citrus fruits rinds

Learn more here

5. What’s in an essential oil?

Essential oils are obtained by distillation (apart from the particular case of citrus peels), and the output will be a set of volatile (otherwise they wouldn’t be volatilized during the distillation) and lipophilic (otherwise we would find them in the aromatic water) molecules. But what are these molecules?

The answer may surprise you: in most cases essential oils are dominated by a single chemical class, that of terpenoids, a very broad class of molecules (at this time more than 40,000 structures are known) produced by plants (and by animals, including human beings

Learn more here

6. Why do plants produce essential oils?

So far we’ve spoken of the essential oils as the result of a process that humans put in place to obtain a useful product, but we must not forget that we can get this product only because the plant itself has synthesized these molecules internally. It is therefore quite natural to ask why, or for what purpose, the plant has spent time and energy to synthesize them.

To understand the role they play is useful to point out some important data:

1. not all plants produce essences, and so it is obvious that essences are not absolutely necessary to all plants

2. plants that produce essences belong to botanical families that are very different and taxonomically far apart

3. essences are contained in various tissues or specific secretory cell types, from external ones (glandular hairs of many Mediterranean plants), to the internal ones (secretory cells in the wood, roots and bark, the secretory sacs of eucalyptus, or the secretory channels of Umbelliferæ such as anise and fennel), in addition to the epidermal cells found on Rose and Jasmine petals

Learn more here

7. What is an aromatic water?

The aromatic waters, famous and widely used until the mid 1700, much more than essential oils, have later on finished by the wayside, apart from the classics like Orange flower water or Rose water. For some years now, however, aromatic waters are again in great vogue.

But what are they? According to the French Pharmacopoeia a hydrolat (another name, along with “hydrosol”, for aromatic water) is a “distilled water charged, by means of distillation, of active volatile principles contained in the plant”.

An aromatic water is therefore one of the two products of the distillation of aromatic plants. If you remember the steam distillation method, in all cases a mixed steam of water and essential oils enters the condenser, where it loses heat, it’s cooled down to a liquid phase and its collected in the Florentine flask. At this point all odorous molecules, volatile and not soluble in water, will stratify above (or in a few cases below) water. Not all volatile and odorous molecules are, however, insoluble in water; some are completely soluble in water, and others are only partially so. These molecules then they will not be found in the essential oil, but will remain in solution in distilled water, at a concentration of usually very low (rarely more than 1%) but sufficient for perfuming the water and to exert some effects.

Learn more here

8. What other aromatic materials exist in the market?

Essential oils are probably the most famous and used aromatic materials in the world, but they are not the only ones present on the market. It useful to describe what other materials are because they can still be interesting for applications in perfumery, and because knowing their existence allows one not to be fooled into buying a product that is not what it says it is.
Aromatic materials different from essential oils are basically aromatic extracts obtained by subjecting the plant material to the action of an organic solvent. To give an example, a hydroalcoholic tincture of an aromatic plant is, from a certain point of view, an aromatic material. Indeed scented tinctures are one of the basic materials of natural perfumery.

Depending on the type of solvent used and the processes involved, we will obtain different materials. Normally these processes are used when the plant material cannot be extracted otherwise, for example because it contains “fragile” molecules, i.e. that suffer too much from a high temperature, or that cannot stay for too long in contact with water, or for high-quality and high-cost vegetable materials in which the non-volatile compounds are very important for the smell of the product (as in the case of Roses).

Let’s briefly see the main products and processes here


Continuing Education

Botanical Databases

  • Medicinal Plant Names Services. An incredibly useful database maintained by The Royal Botanical Gardens at Kew, which solves many of the ambiguities related to the scientific and popular names of medicinal plants, and allows you to search directly in PubMed using scientific name and all the synonyms of the plant, thus reducing the risk of neglecting some published paper.
  • The Plant List. Another database maintained by The Royal Botanical Gardens at Kew, this time dedicated to resolving the ambiguities of scientific nomenclature for all vascular plants and Briophytes.
  • USDA Taxonomy. Although not as complete as The Plant List, this database uses a different systematic approach, and can be useful for crosschecking the data
  • Eur+Med PlantBase. Site specifically dedicated to European and Mediterranean Plant. Useful when we are looking for plants of these areas.
  • Database Kew. The full list of online resources of the famous botanical gardens

Biomedicine articles Database

NB: academic databases allow you to filter your search by publication type, age, gender, etc. and provide the opportunity to use standardized language (MeSH) to improve research. oThey contain almost only published material and are transparent re: the journals they index

  • PubMed – Free Access Platform to MedLine, the online database of the NLM (National Library of Medicine), 22 millions of citations of biomedical and biology articles since1946. PubMed is composed at 90% of MedLine items, at 8% of articles from PubMed Central and at 2% of articles not yet indexed in MedLine
  • PMC – PubMed Central: the repository of free scientific articles and books from NLM and NCBI
  • Cochrane Database – A database of systematic reviews and meta-analyses from the Cochrane Institute
  • ClinicalTrials – registry and database of published and in-publishing clinical studies, as well as trials still running
  • ToxNet – A database of databases of toxicology


Other useful websites

  • BoDDDatabase of skin reactions to plants and derivates
  • IFRA – Website of the International Fragrance Association
  • Google Scholar Subsection of the famous search engine, which carries out his searched only on credible sources. Not selective enough, but useful for content that may be missed in a PubMed
  • Cropwatch – Excellent site on aromatic materials, their environmental sustainability and the risks to human beings
  • Research Gate – Social network for researchers, useful for exchanging opinions and to request information and papers
  • Academia – Same as Research Gate
  • AGORA (Aromatherapy Global Online Research Archives) –  Non commercial articles on essential oils and aromatherapy
  • Aromamedical –   Another non commercial and independent website
  • Robert Tisserand’s blog, always interesting and up-to-date (blog)


Scientific or professional journals

  • Flavour and Fragrance Journal. Amongst the most important scientific journals for the world of aromas and fragrances. Although it doesn’t cover exclusively essential oils, it undoubtedly one of the most  important resources in this field.
  • Journal of Essential Oil Research.  Possibly the most  famous and important scientific journal in the world of essential oil, ranging from analytical techniques, composition analysis, biological activities and toxicology..
  • International Journal of Clinical Aromatherapy.  UK-based professional journal for aromatherapists, with a special focus on research and clinical applications.
  • The International Journal of Professional Holistic Aromatherapy.US-based professional journal for aromatherapists, with special emphasis on professional development and continuing education.
  • PLOS One. The most important open-access, multidisciplinary medical journal.
  • The British Medical Journal (BMJ).  One of the oldest, famous and respected medical journal in the world
  • New England Journal of Medicine (NEJM).One of the most famous and respected medical journal in the world



  • Great interview to Robert Tisserand on the importance of research in aromatherapy.
  • An article by Robert Tisserand on the dangers in using undiluted, or wrongly diluted, essential oils on the skin

Facebook pages


  • Circle H Institute: website of the colleague and friend Ann Harman, dedicated to hydrosol research
  • PhytoChemia’s Blog: website of a specialized Canada-based laboratory for essential oils analyses, and adulteration verification
  • Jim Duke’s DB: phytochemistry database
  • ChEBI: a dictionary of molecules with biological activity, specialized in “small” molecules”


This post is also available in: Italian