It’s fall season here in Toronto and grocery stores are carrying delicious, high grade apple cider that is seasonally pressed at local Ontario farms. I wait every year for the stuff and this time I was determined to brew some delicious hard cider.
So I was extremely distraught to find out they use my nemisis, potassium sorbate, to keep the stuff fresh.
Potassium sorbate is yeast killer. It stops fermentation dead in its tracks. It is a most powerful foe. There’s no way you can ferment around it.
Or is there?
After reading around online I came up with two possible approaches to defeating potassium sorbate (and similarly, sorbic acid). Both approaches are only proof of concept and my experiments are not scientific, however this is a good starting point to figure out which process I want to explore further.
Approach #1 was to overcome the potassium sorbate by bombing it with yeast. I poured one gallon of apple cider into an airlocked jug. Every eight hours I added 1 tsp of bread yeast (Lalvin 1118 too expensive, and unnecessary) over the course of two days, for a total six different doses of yeast.
The first three or four doses of yeast did nothing. The cider absorbed them completely. The last two doses, however, did kick off a gentle fermentation. Over the course of one week I observed a decrease in specific gravity from 1.050 to roughly 1.025. So conceptually this approach could work although it would require more yeast.
This is however a significant problem. There’s already 30g of yeast floating around in one gallon of cider, the liquid is cloudy, distinctly yellow and tastes horribly of yeast. Ultimately I wasn’t even able to drink through a small glass of the stuff. So I will consider this approach not useable.
Approach #2 was to kick off fermentation in a starter solution that does not contain any potassium sorbate, then add this to the main batch once the yeast is highly active. This was a technique I read about on fermentarium in a wonderful article titled Everything You Know About Potassium Sorbate Is Wrong. I decided to attempt this myself, with modifications.
First thing I tried was to ferment the batch with sediment from a previous batch of apple cider. Usually this works just fine. In this case, no dice. The potassium sorbate swallowed the sediment and killed it instantly.
So next I tried a process similar to the article. In a separate container, I pitched 5g of bread yeast into 250 mL of cheap apple juice. I waited 12 hours until the fermentation kicked into high gear. Then I poured this solution back into the main batch of cider.
This was enough to kick off a gentle, but consistent fermentation. Within four days the specific gravity had dropped from 1.050 to 1.030, which is not as fast as I’d like but still fast enough.
The next step in this project is to run a different experiment, with more controlled variables, to measure the effect of starter time, temperature and yeast concentration. I’d like to see if doubling the yeast dosage + allowing the starter 24 hours to kick off will result in stronger fermentation. More soon!