Succession and Why We NEVER Continuous Brew
This entry was posted on February 29, 2016.
A Common Problem :
My Kombucha tastes like vinegar.
My kombucha ferments so fast I can't control it.
Time and time again, it is because they were trying the continuous brew method. Sometimes they only continuous brewed for a few weeks before noticing a dip in quality. When they attempted to revert to batch brewing with the same culture, they discovered they had fundamentally changed the culture and could not get it back to its former glory. Here is our educated assumption of what is happening....
Succession is the observed process of change in the species structure of an ecological community over time. Many multi-species ferments are successive in their microbial activity meaning that in the beginning of the fermentation process, a certain species or set of species is active. As their activity changes the composition of the substrate (making it more acidic, for example), the conditions become unfavorable to those first pioneering species. They grow sluggish and eventually halt their activity while the new conditions they created are prime real estate for the next wave of species to succeed. And this can happen several times throughout a fermentation process.
The succession process in fermentation is highly studied and documented in sauerkraut. In the beginning of sauerkraut fermentation, Leuconostoc mesenteroides is the pioneering species that gets going first. As this bacteria proliferates and its acid-producing activity lowers the pH in the crock, the conditions become intolerable for it. It’s kind of like if you keep setting up more and more kombucha brews in your kitchen, eventually it will become so overwhelmingly acidic smelling in there you won’t be able to go in without a respirator. (Believe me, we know). So, once Leuconostoc mesenteroides has chopped its nose off despite its face, other species in the crock that love lower pH conditions, like Lactobacillus plantarum and Luteimonas cucumeris, wake up and shine! They get active digesting stuff, transforming stuff, creating their own styles of acids that then lower the pH even more. They have their time in the limelight and then the conditions become intolerable to them (again by their own activity!) and they stagnate. But those low low pH conditions are perfect for the next round of fermenting bacteria to set up shop and Lactobacillus brevis begin their heyday creating their own signature acids.
With each wave of microbial activity, a new set of compounds is created and it is the layering of these compounds in succession that creates the complex health attributes and delicious characteristics of finely made sauerkraut. One would not throw a cabbage into a crock with only the last round of bacteria and expect it to yield the same delightful results as a ferment that has gone through all of the natural stages of complex fermentation . No no no.
And this explains why we don’t advocate continuously brewing kombucha. In our years of experience in home fermenting and commercially brewing kombucha, we have never tasted a kombucha made using the continuous brewing method that meets our standards for a robust, complex and delightful 'buch. Continuous brewed kombucha results in a profile that skews toward too much acetic acid. You can tell because it tastes like vinegar.
Not only that, but kombucha cultures that have at some point in the their history gone through a period of continuous brewing seem to lose the ability to ferment at the earlier stages altogether – the cultures seem to have lost the pioneering species and have become concentrated with the microbial species typical of later stages of fermentation. You can always tell a SCOBY has a continuous brew heritage by the immediate formation of the “vinegar” flavor that is characteristic of acetic acid just hours after a new batch is inoculated. This is not the kombucha that we like to drink and we think it may not have the same nutritive characteristics as those that are allowed to go through all stages of fermentation in batch brewing. We have also never seen a SCOBY recover their pioneering abilities.
If you are in the market for a new SCOBY, we highly recommend you start with a SCOBY guaranteed to have never been used to continuously brew kombucha. Your crock, palette and belly will thank you.