What we get at the end of the distillation process are two materials, essential oils and aromatic waters, also called hydrosols and hydrolats. These latter, famous and widely used up to the mid 700’s were then forgotten, apart from the classic ones like orange flower water or rose water, while essential oils rose to greater fame. For some years now, however, aromatic waters are coming back to the forefront.
But what are they? According to the French Pharmacopoeia, an hydrolat is “a distilled water charged, by the distillation, of volatile active ingredients contained in the plants.”
If you remember the vapor steam distillation method you will remember in all cases a mixed steam of water and essential oil enters the condenser, where it loses heat, cools down until it returns to liquid and is then gathered in a Florentine flask.
At this point we have all the odorous, volatile and non water-soluble molecules in the layer over (or in a few cases below) the water. Not all the odorous and volatile molecules are, however, insoluble in water, some are only partially so, while others are completely soluble in water. These molecules will therefore not found in the essential oil, but will remain in solution in the distilled water at a concentration that is usually very low (rarely more than 1%) but sufficient to perfume the water and to exert certain effects. How and how much it this water will be scented will naturally depend on the plant from which it derives, just like the essential oil, but the chemical composition will always be different from that of the essential oil. Given that the hydrolats contain the water-soluble fraction of the volatile component of the aromatic plants, and since the molecules that dissolve well in the water are those especially rich in oxygenated compounds, the hydrolats will be particularly rich in alcohols and carboxylic acids, weak acids which are absent from EOs, while hydrocarbons, molecules composed solely of carbon and hydrogen and therefore not soluble in water, will only be in essential oil. The aromatic water will be so the more aromatic and charged the more the plant contains oxygenated compounds, while it will be rather poor in aroma when the plant contains almost only hydrocarbons. To experience this difference is enough to smell the aromatic water of a plant rich in oxygenated compounds such as Thyme, Rosemary, Sage, etc. and compare it to that derived from the distillation of a conifer like Pine.
What we do not consider aromatic waters
Unlike the definition in French Pharmacopoeia, there are also unacceptable (to me) aromatic water definitions. In some cases, these so-called aromatic waters are produced by solubilizing an OE in water by means of magnesium tritiation and subsequent filtration. In other cases, essential oils, sometimes in addition to synthetic fragrances, are dissolved in a solution of water and ethanol.
Hydrolat production varies greatly from one country to another and from one distillation plant to another. In larger, commercial distillation plants, the material is usually distilled in a closed and controlled environment and therefore it is difficult for the hydrolats to be contaminated. But when the plant is small and in the open, hydrolats can easily be contaminated due to poor hygienic conditions of the plant or due to contact with the atmosphere. Unlike EOs, which are a substrate extremely refractory for the growth of bacterial or fungal colonies, hydrolats, being mainly water with a small amount of volatile compounds, are almost ideal substrates. Of course a contaminated hydrolat can be safely restored by the bottling process if it is preceded by pasteurization or micro-filtration.
Again in this case the non-contamination safety lasts until the bottle is opened, after which the hydrolat can again be contaminated. Another way to ensure the purity of the product would be to add a food preservative, although this may not please certain users. Of course the risk is relative, it is the same risk that we may have to drink mineral water in the bottle after a while we have opened it.
However, this risk must not be minimized. In fact, several bacterial cultures, in particular Cryptosporidium and Giardia, have been found in bottled mineral waters; This could be a problem in patients with immunocompromised or children. This applies to oral use, while there are no problems with topical use. But how can we know if we are buying a contaminated product? We have to ask ourselves and our supplier the following questions: • Does the hydrolat contain preservatives?
If it does not:
- Has it been produced in a a food-grade lab, following HACCP specs?
- If not, has it been tested for bacterial contamination? and are the results available?
- Where has the product been bottled (at the manufacturer’s or later in the distribution chain)?
- If the hydrolat was produced by the subject who offers it, how was it stored? How was it protected from contamination?
- If the supplier suggests oral use, is he or the manufacturer authorized to prepare food?
It is hard to think of hydrolats toxicity, since they are highly diluted derivatives of plants which are mostly permitted for free consumption; to reach a toxic dose it would be necessary to drink several liters of the substance. Only the hydrolats of frankly toxic plants, such as Acorus calamus, should be looked at with distrust. It is also necessary to pay attention to hydrolats produced from plants that cause allergy problems, such as Lippia citriodora.
First of all, it should be remembered that there are not many scientific data supporting the hydrolats activity, and that their use is mainly justified using data from hydrolats of rose, orange, rosemary and few others that have a tradition of use; from infusions of the same plants (though different from the hydrolats, some inferences are justified); and on the inferences based on the chemical composition, and on the general lack of toxicity.
Having said that, according to various authors, the carboxylic acids present in hydrolats are very calming elements and are ideal for treating the skin, as they preserves its acidity. Also the presence of a fraction of mono- and sesquiterpene alcohols is interesting for possible hydrolats applications when it is necessary to act with great delicacy with antiseptic and anti-inflammatory agents. Some hydrolats can be very useful in a limited range of problems, especially dermatologic ones. For example, Rose, Chamomile, Lavender, Immortelle, Neroli and a few others are excellent dermatological applications for every type of inflammation, in some cases better than the same EOs.
They can be cosmetic agents used to control excessive sebum production or to reduce acne inflammation. Some are ideal for eye injuries and inflammation of the conjunctiva and are, from this point of view, better than infusions because most of the plant particles are eliminated. Other uses include cases of irritation or bruising in breastfeeding mothers, or vulvar irritations.
Given the absence of toxicity, it is possible to use them in place of the essential oils in the nebulizers in order to scent the air of a room without running the risk of exaggerating with the doses, and with the added bonus of nebulizing also water, useful in case of very dry air or respiratory problems. They can also be used as a simple and uncomplicated scent method or as refreshed sprays. In the last few years, aromatic waters have come back to the forefront of fashion in the field of aromatization of foods and beverages. Always due to their lack of toxicity and the delicacy of aroma, they are ideal to spice at the last minute on the dishes before serving them or as delicate marinade. In the cocktail range they can be replaced with the aqueous phase, added to increase the aromatic profile without altering the flavor.
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