The Key, or More Correctly, the pH-Hydrosols
When I started testing the pH of the waters, I had no idea why I was doing it. I was given a meter by my brother. L'aromatherapie Exactemente listed the pH values for a few hydrosols, and I was curious. Also, it was the only "scientific" test I could conduct in my kitchen.
I knew that distilled water has a 7.0 pH, and I already knew hydrosols were just not "just water" as some would have it. They have aroma and flavour, unlike distilled water, so at the very least these were substances comparable to herbal tea. What the tests showed is that hydrosols are nothing like water or even herbal teas and although waters are distilled, not one has a 7.0 pH-far from it. I was excited!
If we look at the pH of a few other common substances, we can see that the acid nature of hydrosols, while not immediately apparent, is very important. Compare the pH valuses of various hydrosols (pages 69-72) to the substances listed in the table on the next page.
Lemon juice is highly acidic, as is vinegar, and we can taste and feel this acidity in the mouth and in the way our body reacts. Rock rose hydrosol is as acidic as some vinegars, but we do not taste or feel the acidity in the same way at all.
Tomato juice is too acidic for some people's taste and sugar is often added to tomato sauces and juice to reduce the acid effects. Elder flower, German chamomile, neroli, fennel, and several other hydrosols have a pH value equivalent to that of tomato juice-4.0-but we find no acidity in their flavours; on the contrary, they seem quite sweet.
This does not however, change the fact that they are acid by nature, and this is an important consideration in how, why, and when we use them. Only peppermint and linden blossom hydrosols have a pH close to that of our own saliva, which is very near neutral.
pH Table of a Few Comparative Substances
I compared my first hydrosol pH tests with those of Franchomme and Penoel, and the measurements didn't all jibe. Some were spot-on, but for others there was a huge difference between their figure and mine. To much difference to be right, I thought. So I started testing every batch soon after it arrived but without developing a clear picture of what the data meant.
Really, I just wondered why my numbers were so different from the only reference numbers I could find. Interestingly, my tests were usually pretty close to each other; that is, geranium was always in the 4.7 to 4.9 pH range, different from the 3.3 pH in Franchomme and Penoel but relatively stable within my own tests. Other glaring differences were green myrtle, 3.95 pH versus my reading of 5.8; rosemary cineole, 3.7 versus 4,2 pH; and oregano, 5.2 versus 4.2 pH.
However some hydrosols, specifically neroli, or orange blossom, were quite variable in my own tests, ranging from as low as 4.0 pH to as high as 5.5pH. The hydrosols came from several different countries and sources, and at the time, I put the differences down to those variables. I now believe that some of the neroli waters contained preservatives, probably alcohol.
Ethanol, or 95 percent ethyl alcohol, has a 6.9 to 7.o pH; distilled water also has a pH of 7.0 and is considered neutral. No hydrosol has a Ph in the alkaline range above 7.0; they are all acid-either slightly, like lavender ( lavandula angustifolia, 5.7 pH), or very like rock rose (cistus ladaniferus 2.9 pH), According to data the pH range of authentic essential oils is around 5.0 pH, with a maximum of 5.8 pH.
I have never tested individual oils but must assume that there are distinct ranges for each oil, as there are for each hydrosol. Balz and others go on to say that the acidic nature of oils contributes to their antibacterial properties, as an acid environment inhibits the growth of bacteria and can even kill some bacteria.
When we are dealing with the huge range of pH values in hydrosols, we can see the importance of using this knowledge in judging appropriate therapeutic applications. We can also see that they must work.
For the most part I tested each bottle of hydrosol only once, usually on or shortly after receipt. Then I decided to test the bay that had bloomed-bingo! The pH was way off, infinitely more alkaline than the original reading. I ran the hydrosol through a paper filter, and although the pH dropped by 0.15, the reading was still nowhere near where it should be.
It was clear that a change in pH can be triggered by the appearance of bacteria. ( Okay, so maybe this would have been obvious to a chemistry student, but to me it was ..... Eureka!). After numerous tests of this kind, I would suggest that as soon as a change in Ph is noticed, one should suspect that the hydrosol has become contaminated in some way, I now test each bottle of hydrosol every three to four weeks.
Hydrosols are really remarkably stable for natural, preservative-free products, including beer (Budweiser's shelf life is 110 days0, have a much shorter shelf-life then hydrosols. Regardless of our former thinking, if we want to embrace this new aromatherapy, that is the first bite of the cookie to digest. They don't last forever, but they are not totally unstable!
Contamination can happen in may ways, from non sterile bottles, shipping and transport conditions, formation of condensation inside the bottles, plant matter or residue from the distillation stage, heat and light damage, just smelling the bottle directly under your nose, and so forth. Even aerial contamination during the bottling stage could undo all the precautions and sterilizing techniques you may employ; it's not common, but it's certainly possible.
Reference; Hydrosols; The Next Aromatherapy: Suzanne Catty
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