Homebrewed Yeast Extract

Two most common components of almost every agar are some kind of hydrolyzed meat or vegetal protein and yeast extract. Today we’re going to look at possibility of making yeast extract at home.

After bottling the Troubadour (Raspberry aged Berliner Weisse) I had 3-4 liters of yeast, bacterial, and raspberry sediment left in the carboy and decided to try and make yeast extract out of that. I collected about 2L and thought about how to break the cells open. The sediment (in parts) was first placed into a blender and blended on highest speed for several minutes with additions of the meat tenderizer. This served two purposes – the shearing force to physically break the cells open and release their contents into the solution as well as to make the solution hypertonic, as meat tenderizer has a hefty amount of salt in it, to help the surviving cells die and provide addition protease to chew up the released peptides. After that, some RO water was added to make it around 3L and it was left until the following evening near the heater. After maybe 5-10 minutes it started looking like cell lysate, for those of you familiar with such things. The following evening I put it all into a pot, boiled for a few minutes, let cool until the morning, and transfer into flasks. This “soup” was then filtered through a cloth and 4 layers of paper towel. No matter how much I tried to get it to be clear, I could not and started thinking that most likely I can’t do it, at least not at home. Just to take it one step further I decided to take some of it to the lab and centrifuge. After spinning at 5000rpm for 10 minutes, there was some sediment and the resulting supernatant was still cloudy. When 1-2 mL of it is taken, it is crystal clear, but collectively it is not, which makes sense if there is a lot of protein there. The taste is horrible, but then what do you expect? All of it was pressure-cooked and is sitting on the shelf. It is quite acidic and I’ll bump the pH up to around neutral with some NaOH before using. Most likely I’ll use it in my next batch of plates at something around 1:10-1:50 vol.