I made a 1 quart micro-batch of kombucha, following my usual recipe, except that in place of sugar I used Briess Pilsen omried malt extract (DME). Malt is a particularly interesting sugar source because a kombucha culture should be able to thrive on malt alone. In this case, malt + tea should have provided a surfeit of nutrition. Would this produce similar effects to my double-sugar kombucha?
After 12 days, pH was 3.2, and the flavor was thin (due to lack of sweetness), “grainy”, and sour. The sourness wasn’t obnoxious, and I think it would have fine if it had normal levels of sweetness. It reminded me of my glucose kombucha, but with fermentation stopped before all of the sugar was consumed and the acidity dominated (the glucose batch was pH 3.0). The 4mm scoby was solid for the top 3mm or so, but a little soft on the bottom. There was a clearly visible delineation between the soft and solid layers. So, while the scoby was a bit unusual, it was not particularly thin, and I think the answer to the question asked in my first paragraph is “no”.
I drank half of this plain, and in the other pint I steeped 1 tb (~.5 oz) Mosaic hop pellets. In an effort to maximize extraction, I stirred the pellets loose into the jar without a tea bag. Within an hour, the pellets had reduced to a green sludge floating on top. 24 hours later, the sludge had settled to the bottom. Surprisingly, it had taken on a pointedly bitter flavor that reminded me of Campari. By day four, the bitterness was still present, but there was a strong citrus flavor. If I were given this without any explanation, I would probably think it was unusually bitter grapefruit juice.
What kind of sugars make up Pilsen DME? We don’t have to guess. If you followed the link above, you may have noticed the following:
- 48% Maltose
- 14% Maltotriose
- 13% Glucose
- 19% Higher Saccharides
Maltose is two glucose molecules bonded together, and maltotriose is three. “Higher saccharides” is a generic term for a sugar made of three or more monosaccharides (usually glucose or fructose). So we know that 75% of this reduces to glucose, which not only ferments quickly, but is only 75% as sweet as white sugar (sucrose). I don’t know if maltotriose or the higher saccharides are fermentable by the kombucha culture (leaving residual sweetness), but malt extract as a whole certainly seems to be fermentable enough for making kombucha (unlike xylitol or lactose). However, converting maltotriose and maltose into glucose takes time, so making kombucha with malt might take a bit longer if the microbes aren’t as adapted to working on sucrose.