Molasses Fermentation (Journey Into Rum Part 3)

Check out my Journey Into Rum Part 2 Post

This is the third post documenting our journey to create our Shakespeare Distillery rum. This time we prepared for our molasses fermentation. The fermenter has a 2000 litre capacity. Since it was our first test run we decided to only make a 1000L pilot batch. We were replicating experiment #31, which we replicated in our previous small scale rum experiments.

Molasses Wash Preparation

We filled the iStill fermenter with 1000L of water, but that volume wasn’t enough to reach the internal heating element. We were forced to add another 500L of water to cover the heating element. Our tap water was 11°C and it took 4.5 hours for the water to reach 34°C. So it ended up being a bad idea to use the fermenter’s heating element to try and heat the water.

In the future, we decided to heat the water in a still and then pump the heated water over into the fermenter. Doing so would undoubtedly cut down on our production time.

Transferring the Molasses

After the water was heated to the desired temperature, we used an electric screw pump (sourced from Italy) to transfer the molasses from the IBC to the fermenter. Ideally, we would have connected a hose from the bottom of the IBC to the pump and waited for gravity to simply force the molasses down into the hose and into the pump. However, the camlock we ordered did not arrive in time, so we were forced to connect the hose to the top of the IBC and then to the pump.

The pump has a sensor to make sure that the pump never runs dry, i.e. runs without liquid, as this would damage the pump. Initially, the pump did not run when we turned it on because it was dry inside. We tried to prime the pump with water to get it started, but molasses is much more viscous than water, so the water quickly went through the pump without carrying any of the molasses through. In the end, we had to prime the pump with the molasses itself.

It was quite a sticky business and the molasses ran down onto my clothes and onto the floor. After a few starts and stops we finally got the pump primed and the molasses going into the fermenter.

Adjusting the Molasses Wash

We needed to make sure our molasses wash was 14°Brix, so a bit more water was added to bring the it down to 14°Brix. Citric acid was also added to achieve our desired pH. Dried baker’s yeast was then pitched into the fermenter. The molasses fermentation took seven days to complete, before we transferred it into the still for our rum distillations.

All-in-all, we had to stay 2.5 hours later than our usual end time to get everything finished. Needless to say, a lot of improvements could have been made in our production process that day to make everything faster and cleaner. The floor had to be mopped four times before we could walk on it without it making sticky squeaking sounds.

Watch it on YouTube Below