The science of vinegar. Part 2. Seasonal summer vinegars and accelerated prototyping.

Alcohol is often obtained by the action of yeast fermentation solution with a high sugar content (juice, syrup, etc.). But some ingredients contain too little sugar for self-fermentation. In this case, we can use distilled alcohol (usually from 5 to 9 percent ethanol by volume) to produce alcoholic mixtures.
This article describes how this idea can be used to create vinegars, juices and teas. The most important thing is that this method is much faster than the traditional one, especially with the use of accelerated aeration, with the help of simple and affordable tools.
As part of the research on new flavors, we wanted to experiment with fresh seasonal ingredients, but didn't want to wait too long for the results. We found that the aerator allows you to make a portion of vinegar for 3-6 days. We used six 1.5-litre-per-minute pumps to run six experiments at the same time. It is also possible to use a splitter that divides the air flow from the pump into several aerators, and save on equipment. It should, however, be remembered that in this case the volume of air on each specific aerator will be much less and fermentation will be slower.
It should be taken into account not only that the smaller the diameter of the bubbles produced by the aerator, the more oxygen the liquid will be saturated, but also that the deeper the container, the longer the bubbles float and the more oxygen will dissolve. And the more oxygen dissolved in the liquid and available acetic acid bacteria, the faster the process]
Acetic bacteria and acidic fluids.
In each batch of vinegar we add 20% of the finished vinegar (by volume). It can be both homemade and purchased - unpasteurized. This is done in order to introduce a dose of acetic bacteria and create acidic conditions for the life of these bacteria. When possible, we use vinegar with appropriate flavors. For example, we added celery vinegar made earlier to the fresh batch. When there are no suitable ones, we use high-quality Apple cider vinegar, which can be called our lifeline.
Alcohol and sources of flavors.
We wanted to learn as much as possible when testing the basic ingredients and flavors, so we investigated the use of vinegar fermentation to fermented liquids, juices with alcohol, as well as other ingredients with a bright taste and low juiciness. In theory, alcohol in vinegar fermentation can be of any origin, so we experimented with adding alcohol directly in the liquid, which lacked natural sugars for fermentation, followed by fermentation with acetic acid bacteria. In our experience, the starting alcohol content of 5-9% gives a fairly versatile vinegar, ideal for flavor additives rather than, for example, for marinating.
Guilt.
We also experimented with more traditional fermentation processes of sweet ingredients. We made wine from beetroot, strawberry and elderberry, using as the basis of the book Boulton et al's Principles and Practices of Winemaking and elegant site Jonathan Master Vinocalc to calculate the amount of sugar needed to achieve the proportion of ethanol in 5-9% by the end of fermentation. 13% sugar by weight will give us 7% ethanol if we ferment before " dry " (leaving no sugar in the liquid), which falls exactly in the middle of the range and therefore becomes our goal. In the case of elderberry, this meant insisting on it 13 percent sugar syrup (slightly acidified with citric acid, in order to lower the starting pH and stabilize the fermentation). Neither strawberry nor beet juice has a sufficient level of sweetness: both are at level 8 brix, and not 13-so we cheated, divided the portions of the juice in half, evaporated one half of each juice twice, and then mixed everything back, thus increasing the sweetness of drinks and keeping the fresh taste of the products. We then supplied each of the fruit juices champagne yeast and Packed them in containers with seal for fermentation to dryness.
While elderberry and strawberry wines were fermented successfully, the surface of beet wine bloomed mold (read “yeast”), known as a mycoderm or “wine flower”, which led to the unwanted release of ethyl acetate, similar in smell to nail Polish. Although we managed to remove the mold from the surface and move the wine to a new sterile container, it soon reappeared and we had to stop trying. Perhaps we had problems with acidity – insufficient acid content/too high pH can lead to all sorts of unwanted microbial activity, and although we tried to compensate for the natural alkalinity of beet juice with tartaric acid, such precautions were not enough. Or maybe we're just unlucky. In any case, watch carefully for beet wine, if you still decided to do it.
One of our readers sent us a comment in which she described the method of obtaining beet flavor in fermented liquids without the formation of a mycoderm. She used whole peeled beets, which insisted on a simple base for Kombucha (Kombucha mushroom), thus obtaining a pink sparkling drink with a clear beet flavor. Theoretically, this technique could be applied to the production of vinegar without a mycoderm that violates the fermentation process, for example, to insist on beet neutral non-fermented vinegar base (something like 73% water, 20% live Apple vinegar and 7% ethanol), before starting aeration. ]

Nicodemia on beet vinegar
Juices.
Some of the flavors that we hoped to capture in vinegar come from plants that are low in sugar. Instead of making wine, we used the above system of accelerated prototyping, squeezing the juice and adding a strong distillate to achieve an overall level of ethanol of 6-7%. We squeezed the juices from celery, rhubarb, white and green asparagus and left them to ferment in a system with aquarium aerators.

Teas.
Other flavors and aromas from the Nordic region, which we were particularly interested in, did not allow to squeeze the juice. Liquorice in the form of candy is incredibly popular in Denmark, but the dry and woody texture of licorice roots makes them very difficult to process. Spruce needles have a bright and multi-layered flavor, but also give in to the usual methods. In both cases, as well as with other bright herbs, squeezing juice is not an option, because they contain too little water. So instead of juices, we made carefully brewed "teas", punching the ingredients in a Thermomix into paste/dust and heating in a mixture with water to 60 degrees for two hours. So we got a bright, but not bitter tincture. After receiving tea, we approached them as juices - added ethanol, vinegar and aerated.