TL;DR - How do I go about to identify the microbiological processes in a wild ferment?
I have a recipe for rose hip wine based on wild (spontaneous) fermentation, that I got from a Swedish wine/beer makers forum. The recipe is simple (I've translated and summarized it a bit to make it fit better in the Q&A forum style). I've used the recipe above five times now with good results. The wine becomes very sweet and it has a quite low alcoholic content. It has a strong character of dried fruit and rose hips.
The recipe used
- Take 2.5 liters of rose hips. Pick off bad parts but don't clean them with water or desinfect them in any way - make sure the wild microbes are kept!
- Make a syrup of 3 liters (0.66 gal) water and 1.5 kg (2.2lbs) white sugar.
- Add rose hips and syrup to a big ceramic jar with a plate as a lid (optionally use a proper fermentation lock). Let ferment like this for 3-6 months.
- Strain and age on a carboy for 3 years. The taste is terrible initially, quite okay after 1 year, good after 2, excellent after 3.
This differ from most recipes online only on a few parts. (a) this is the only recipe with wild fermentation that I've found (b) the amount of water in other recipes is rather 7-10 liters for the same amount of hips and sugar (c) the first fermentation is 3-6 months instead of the typical 1-3 weeks seen in inocculated wine making (d) other recipes typically have some acid introduced in the beginning. lemons or lemon juince and possible lactic acid.
This is similar to other recipes online in the proportion of hips to sugar, and the recommendation to age 3 years is the same.
The current ferment
This year is the first that I use a fermentation lock. I altered the recipe slightly by admitting oxygen freely the first week, stirring occasionally to get the ferment going. After that, I put the lock on.
The fermentation is slow, but carbon dioxide is released continously. A bubble every minute or so, and has now been going so for 3 weeks. The specific gravity is still very high, so there is sugars in abundance. The smell from the bubbles is a little yeasty. The smell is also a little sour, but not at all like vinager. This is the typical smell this ferment makes!
I've read online that rose hips are high in malic acid, so I guess the long aging is for malolactic fermentation to take place.
I would like to know what fermentation is currently going. Is it yeast or LAB? Could there be other carbon dioxide releasing processes of significance?
This very slow fermentation indicates to me that there might be not enough nutrition to sustain a larger yeast population. It would be nice to do some kind of before/after test if I would ad nutrition to see what effect that has.
I have pH measurements and gravity measurements currently. I consider getting other equipment for up ca $200, such as a microscope.
How does one go about to analyze the fermentation process at this hobby level?