Go Ferment a Watermelon!

I will preface this with the fact that it all ends horribly! But this little experiment got me thinking, and in hindsight, might have been a great learning curve for a new book a friend of the club has just released, Speed Brewing by Mary Izett.

The club was discussing a watermelon Kรถlsch recipe for a beer to pour at an event we were attending. A crazy idea came from that thread that we could just ferment watermelon juice to make a sort of cider. So, I took it upon myself to find a 17 lbs watermelon and juice it! Watermelons are about 80% water, so I used a juicer to remove as much of the pulp as possible. The result was a delicious pink drink. From 17 lbs, I was able to get about 3/4 of gallon - a perfect amount for a test batch! 

Shortly after juicing, it was clear that the juice still had a lot of pulp. As it turns out, watermelon juice is actually clear, and the pink hue only comes from the small parts of flesh floating in it. I tried to let it settle as much as possible, but found it difficult (and time consuming) to strain it perfectly. Since this was only a test, I just went with it, figuring the pulp would settle out much like trub in a beer after fermentation. 

A few interesting stats:

  • 17lbs watermelon = 3/4 gallon liquid
  • 1.041 OG - double what I thought it would be. 
  • 5.42 pH - still needed some acid if it's going to be stored long. 
  • Pitched KV-1116 yeast which ferments to a nice dry cider with stone fruit and white grape characteristics.

The wine yeast did a great jobI However, It did produce a slight sulphur smell. While giving it some time to settle and let some of the sulphur smell to dissipate, a pellicle started forming on the top. I did not acidify the liquid, which is where this all went wrong. Despite sanitizing all the containers, utensils, fermenter and the juicer, this brew got infected! 

I decided to let the pellicle go the full route, figuring a sour watermelon cider might be pretty tasty! Imaging a watermelon warhead candy flavor. Unfortunately the infection was not by a good bug. It went from a ropy smell (suspect pediococcus), to a sick aroma (butyric acid) and never came back. I ended up dumping this brew, which I wish I had done outside because my apartment smelled like puke for 3 hours!

This experiment was a good one. A lot was learned, even though nothing drinkable came out of it. Next year's watermelon season is going to be a tasty one! For interesting fermentations like this that don't go wrong, check out Speed Brewing! Many of the Brewmies have made recipes from the book with great success - one even award-winning!

Merlin U Ward

Merlin is an award-winner homebrewer and marketing enthusiast. When he's not making beer, he's working as the Marketing Manager of Brooklyn Brew Shop. He lives by the quote: "Beer makes everything better!"