Flavor Change: Why ZBiotics Changed in July 2021

If you are familiar with ZBiotics’ flavor, you know that until July of 2021, it had a mild and earthy flavor with no aftertaste. That was by design. The product naturally had no flavor (or the flavor of water, to be more precise), but we added some natural flavors reminiscent of the ubiquitous earthy environment that our B. subtilis probiotic bacteria come from.

However, with our newest batches of ZBiotics since July of this year, there is a new bitter aftertaste. This is not due to us changing any ingredients or the formulation at all, but instead due to a change in our manufacturing process. We wanted to write up a quick explanation for why and how the change occurred, in case our customers have questions.

In short, we switched to using a method of concentrating our probiotic bacteria that uses heat (spray-drying) instead of cold (freeze-drying). While this heat does not affect the probiotic, it did enhance the bitter flavor of one of the residual amino acids from our fermentation process (specifically lysine – a natural and essential amino acid found in basically any food that contains protein), giving the product a bitter taste.

The new process: spray-drying

As we scaled up our processes to meet demand we switched from freeze-drying to spray-drying as the method to dry our probiotic for shipping and storage. Spray-drying is faster and suitable for large volumes, which helps us keep ZBiotics in stock and available. Spray-drying uses a small amount of heat to remove the last amount of water from our concentrated probiotic after fermentation. This heat is just enough to remove the water, but not so hot that it damages our probiotic. We did lots of testing to verify this before switching over.

Why the bitter flavor?

This heat from the spray-drying is enough to affect the small amounts of amino acids that remain from fermentation.

At ZBiotics we grow our probiotic B. subtilis on a vegan protein source made from yeast extract that contains lots of amino acids, among other things. When B. subtilis grows in fermentation it consumes most of the amino acids as a food source. However, B. subtilis doesn’t use all amino acids equally. It is known to leave some behind, including histidine, valine, methionine, leucine, and – most importantly for this story – lysine (citation).

Lysine is the amino acid remaining in the highest concentration (almost 56% remains!), and while most amino acids have neutral or umami flavors, lysine can impart a bitter taste. Furthermore, this bitterness is increased when the mixture is heated, as is the case during spray-drying. A study looking at the causes of bitterness from amino acids from yeast extract found that lysine was one of the main causes after heating (citation).

In that study, taste testers could detect bitterness with just 1.3 mg/L of lysine present. An analysis of our process shows that as much as 8.44 mg/L lysine could be present after the active ingredient has been formulated in final bottles. This is 6.5x above the detection limit, so we would expect most drinkers to detect the flavor, and indeed they do.

Summing things up

It is important to note that while lysine tastes bitter, it is an extremely common and essential amino acid, and thus poses no health risks or other issues beyond the taste. If you’ve eaten food today, then you’ve almost assuredly consumed lysine. Furthermore, we have extensively tested the product from these new batches that use spray-drying, and the ability of the bacteria to break down acetaldehyde is not affected at all. It performs as well as – if not slightly better than – previous batches. So while the flavor has changed, nothing else about the product has.

This part of the story of ZBiotics may only be around for a short time as we continue to improve delivery of the world’s first genetically engineered probiotics, so experience it while you can! You are participating in a little piece of ZBiotics history!