So I’ve been making my rich yoghurt with my Yogourmet for 3-1/2 years. It always seemed to turn out fine. It gets thick, tastes tart and I seemed to tolerate it. Appearances aside, something was very wrong.
After following the Pecanbread and BTVC-SCD groups on Yahoo I come to find out that many people have problems with their Yogourmets getting too hot. A quick check of the BTVC book will tell you that the allowable temperature range for culturing yoghurt is from 100 to 110 degrees F (38-43 degrees C). If it gets too hot, the temperature begins to kill the bacteria that is digesting the lactose in the milk. If this happens you wind up with yoghurt that has sugars you are trying to avoid and lacking the probiotics you are trying to seed in your gut.
I thought I’d investigate my Yogoumet and as it turns out, I’ve been cooking my yoghurt too hot all this time. Rats! I did a test using water in place of my usual half and half. Even after just 7 hours, the temperature of the water was above the allowable range at 116 degrees F. I tried removing the lid of the maker, leaving the jar’s lid in place to see if that would make the difference I needed. Even after more than 12 hours of topless heating, the temp of the test water decreased only two degrees. “Holy insufficient cooling, Batman!”
Luckily, there is an easy solution – a plug in dimmer switch. What’s that you ask? It’s a simple little device you can purchase at your local hardware store for $10 – 20 USD (see image at left). It’s designed to take an ordinary lamp and make it dimmable. You simply plug your Yogourmet into the dimmer switch and the dimmer switch into a regular electrical outlet. The trick is to figure out how much to “dim” your yoghurt and when to do it to obtain and maintain the right temperature.
In my experiments I let the yoghurt culture at full power (dimmer on full) for six hours at which point my yoghurt was 104 degrees F – perfectly in the acceptable range. Then I turned down the dimmer switch to about halfway. This maintained the temperature at about 105 degrees for the rest of the processing. Woohoo!
Your dimming experience may differ due to the type of dimmer you have and the ambient temperature of the room. Mine was in a kitchen with an average temperature of about 77 degrees F. You’ll have to experiment to calibrate your dimmer switch. The good news is that once you’ve done that, you shouldn’t have to do it again.
Once you’ve figured out the timing and setting of your dimmer switch, I’d recommend marking your switch at the dimmed position so you don’t have to figure it out each time.
I start counting my processing time when the yoghurt temperature reaches the acceptable range.
I’ve not done it, but another popular way to make yoghurt is to use a food dehydrator.
UPDATE 3.3.10: April tells me that she uses a digital egg incubator to do her yoghurt. She tells me that although they are pricey, they keep the temperature to within 1 degree. See the comments on this page for more info.