Kombucha homebrewers: Why “add sugar to taste” is wrong

A persistent myth advises that the tea brewed to make kombucha should be sweetened with “sugar to taste.” This is wrong.

The right information

As Hannah Crum explains in Chapter Four of her excellent Big Book of Kombucha, a standard recipe calls for one cup of sugar per gallon of water and 4-6 tablespoons of loose-leaf tea. The types of sugar can vary from plain white sugar to evaporated cane juice, honey, or maple syrup. But the ratio stays the same (adjusting down for honey and maple syrup, which are more concentrated).

The length of the fermentation determines the “taste” of the kombucha, not the amount of sugar used at the start. Crum explains:

A number of studies conducted since 2000 show that fermentation reduces the sugar in kombucha by varying amounts based on time, temperature, amount of starter liquid used, and likely many other factors researchers did not account for. Though the studies used varying recipes and techniques, they consistently showed that the reduction in sugar is modest at first and then quickly becomes increasingly marked from days 3 to 8, after most of the sugar has been cleaved and is waiting to be used more gradually. The reduction in sugar varied around 50 to 70 percent between 7 and 14 days and up to 80 percent after 30 days.

Misinformation

Otherwise reputable sources that misstate the facts include:

  • Homebrewer Alice Johnston’s recipe on the BBC Good Food website suggests adding 100-200g of sugar to 1.8L of water, which is a half- to one-cup per half-gallon. The minimum quantity she lists would do the trick, with no need to double that for a typical 1- to 2-week ferment. The recipe contradicts itself when she says to add “sugar (depending on how sweet you like it or the bitterness of your tea)” in Step 1, yet notes “After the first week, taste the kombucha daily – the longer you leave it, the more acidic the flavour will become” in Step 5. This recipe was picked up by the UK’s national Daily Express newspaper.
  • Sandor Katz, the author of the comprehensive book The Art of Fermentation, interviewed on The Splendid Table podcast, says to brew tea and “sweeten it with sugar to taste.” This replicates the advice given on p. 170 of his book, where he suggests, “The amount of sweetener may vary with your taste. Personally, I never measure the sugar, simply adding to taste.” However, he also points out that the length of fermentation will affect the acidity and that “you could ferment kombucha to the point that there is no sugar left.”
  • In a recipe exerted from FIZZ: A Beginners Guide to Making Natural, Non-Alcoholic Fermented Drinks by Elise van Iterson and Barbara Serulus, the website Chowhound recommends 50-100g of sugar per 1L water “to taste.”
  • At the other extreme, we have The National Geographic, where author Maria Pieri quotes Alice MacKinnon, who teaches a course on fermentation and pickling at the London Cookery School. Her recipe calls for a robust 200g sugar per 500ml water (or a full cup for a single pint!). They also suggest steeping the tea for a half-hour. Yikes!
  • Then there’s the CBC food blog from Canada, which manages to post an update titled A guide to making kombucha at home without bothering to include a recipe at all.

The bottom line

Brewing kombucha is easy, inexpensive, and safe. This simple beverage contains just four primary ingredients: tea, sugar, water, and the SCOBY, with its starter liquid. However, the duration of the steep, the temperature of the fermentation, even the shape of the vessel plays a role in the outcome. As with any recipe, finding the correct ratio of ingredients is vital for success. Just “sweetening to taste” will likely yield a weak tasting brew (if too little sugar is used) or could cause the brew to be sluggish (if too much is used). The taste is determined primarily by the length of time allowed for fermentation, not the amount of sugar in the tea. Shorter fermentation yields sweeter kombucha, longer times yield a more sour drink.

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