We get a lot of questions here at the brewery about pH (and about whether or not you need to check), and the most common one is “do I really need to check my brew’s pH?” As with most things in life, the answer isn’t always so black and white, but here’s how we usually like to answer: “do you want your brew to taste great every time, be consistent every time, and make sure you never lose a batch?” Of course you do! But don’t worry, it’s ridiculously easy and nothing to be afraid of. And we’re gonna let you in a little home brewing secrete because we tell it like it — raw and uncut. In a home production setting, to get consistent results, at a minimum it’s important to check your pH at the beginning of your ferment. After that, we will discuss more below. But first, we need to understand what pH is and how it affects kombucha.
What is pH?
There’s a lot to learn about pH, but here’s what’s important for kombucha: pH is a measure of acidity or basicity of a liquid solution. A pH less than 7 is acidic, and a pH greater than 7 is basic. Just like the Richter scale for earthquakes, the pH scale is logarithmic. This means each whole number pH value below represents a 10x increase or decrease vs the next whole number. For example, pH 4 is ten times more acidic than pH 5 and 100 times (10 times 10) more acidic than pH 6.
How does pH affect kombucha?
From the experience of somebody drinking a kombucha, pH mostly just affects the flavor. The lower the pH, the more acid in the kombucha, and thus the more vinegary tartness in the flavor. However, the important information is in the biochemistry and getting your brew started.
Here’s the deal: when you first start your ferment, your brew is at the most vulnerable to foreign invaders (mold, other yeasts, and bacteria). This is because because there is far less beneficial bacteria bacteria (and the beneficial acid they produce) to fend off the bad guys. So how do you fend off the bad guys? pH! The bacteria and yeast in a healthy kombucha scoby thrive in an acidic environment of 4.5 of less. The invaders that can spoil your kombucha thrive in less acidic environments of above 4.5. This is why it is so important to check the pH of your brew a few minutes after adding your starting liquid. Starting a batch with too high of pH is almost always the reason a batch (brewed from a previously healthy scoby) fails.
Never start your brew higher than 4.5! Here at the brewery, we start at 4 and finish at 3. Remember, the lower you start, the more yeast and bacteria you added with the starter liquid, so the faster your ferment will finish.
When you start your brew…
We suggest starting your ferment at a pH of 4, but never start higher than 4.5. Starting higher will exponentially increase the likelihood of your batch going bad — and it will also take longer to ferment. Most commercial breweries start at a pH of 4 and finish at a pH of 3. (If we keep in mind the logarithmic nature of the pH scale, that means the kombucha becomes 10x more acidic during the fermentation, due to the magic of the yeast and bacteria!)
The most common reason for inconsistent results at home is because of inconsistent starting pH. If it has been months since you’ve made a batch and your booch turned to vinegar, you won’t need as much starter. If it’s been fermenting less than a week and you need to make more, you’ll need more starter, because that batch is not nearly as strong. But how will you know..unless you check your starting pH, every time!
A batch of kombucha ferments faster or slower for two reasons: how much starting liquid and how strong, and temperatures during fermentation. In the home brew settings, you can go either way: test pH every couple of days, or don’t test at all and drink your booch when it’s ready. Totally personal preference, however, consistently testing your batches will help you produce more consistent product and up your booch game in general. In a commercial brewery setting, it’s imperative to check your pH levels every few days.
But I’ve never had a batch go bad, and I’ve never checked my pH!
We get it. Most people who’ve never checked their pH and who can read directions have never had a batch go bad. That’s not the point. The point is consistent, brewery quality kombucha at home, every time. You get that by starting with the same pH, every time!
What do I do if I don’t have enough starter liquid to get my pH to 4.5?
Whoa Nelly, you’re in a bit of a pickle! No promises, but there’s a simple way you can probably save your batch. Get some distilled white vinegar, and add it just a little bit at time till you get your pH down. Because your low on good bugs (beneficial bacteria and yeast), you probably want to start a little lower than you normally do to give your brew the best fighting chance. We suggest 3.5-3.8 when trying to revive a scoby — or when you didn’t start with quite enough starter liquid.
So what’s the bottom line?
Bottom line, you should check your pH when you start your batch, every time. The easiest way for the home brewer to do this is with test strips. It’s cheap and easy, just checkout our store to find them.