As you know, an important factor in cheesemaking is temperature. Temperature at which we add culture to the milk, temperature of the milk when we add rennet, and the eventual temperature the milk reaches as we stir the curds. Most cheese (and frothing) thermometers have a little screw on the back of the dial that allows you to move the needle forward and backward. Before your first use, you should calibrate the thermometer to make sure the temperature is accurate. But because this screw can slip when the thermometer is knocked or cleaned (or falls on the floor, which sometimes happens in my kitchen!), you should periodically check to make sure the temperature reading is still accurate.
There are two “formal” ways to do this: using ice water or boiling water. In either case, it is advised that you use distilled water because the dissolved solutes in tap water can effect both freezing and melting points. Another factor to remember if using the boiling water method is that water boils at 205 degrees at our altitude here in the Boulder/Denver area. A complete explanation of how to calibrate using both of these methods can be found at http://www.foodsafety.unl.edu/haccp/helpful/thermcalibration
While it’s a good idea to use one or the other of these methods when you first begin using a new thermometer and perhaps occasionally later on, there is a real quick check you can do each time you use your cheese thermometer without going to all this trouble. Before sticking the thermometer in your cold milk, just take a quick look at the temperature reading at room temperature. If you keep your house at approximately 70 degrees, your thermometer should read this approximate temperature!
For home cheesemaking, having your thermometer within + or – 2 degrees of the actual temperature is probably good enough to keep from having an adverse affect on your cheesemaking success. But big variances could definitely affect your results. Recently I learned that one of my thermometers had gotten way off (I think the screw is loose). It was actually off by 15-20 degrees! I had several unexplained “failures” which a quick look at the temperature using the simple “room temp” method would have prevented. Hope this info saves you some of the frustration these failures caused me!
posted by Kate Johnson
