How to Use a Temperature Probe Correctly
Measuring the temperature of foods during cooling, cooking and hot holding is not just a question of preventing contamination incidents in the short term. It is a data set that must be logged and stored on an ongoing basis as part of a robust HACCP approach. A cook’s temperature probe designed specifically for the purpose is an essential piece of kit.
Choosing the right probe
Food service professionals can pick from a variety of thermometers. These range from conventional dial thermometers, usually oven-proof, to instant-read digital meat thermometers. There is no place in the kitchen for mercury-filled thermometers, other than mounted on the wall to measure ambient temperature, or inside a freezer or walk-in chiller.
Calibrating your probe
Even top of the range thermometers should be checked monthly for accuracy. A little science proves useful here, namely the freezing and boiling point of water. Test that your thermometer records 0°C when placed into a bowl of icy water, and 100°C when immersed into a freshly boiled beaker of water. For the older dial thermometers with an adjustable nut, it is possible to recalibrate with a gentle turn or two, but if a digital thermometer is giving an inaccurate reading, it is best to return it to the manufacturer.
What you should be measuring
Your thermometer is an invaluable tool in checking that the internal temperature of meat has reached a safe level. These temperatures vary according to the type of meat, or whether it is a bone-in joint etc. You should also be regularly monitoring the temperature of foods in hot holding or fast cooling, with the probe inserted to the thickest part of centre.
When measuring the safe internal temperature of bone-in joints or poultry, always insert the probe into the thickest part of the meat, without touching the bone itself. Beware of any promise of instant-read. You should leave the probe in the meat for up to 2 minutes for an accurate reading. When gauging the temperature of stews or sauces, do not leave the probe resting upright on the bottom, or touching the sides of the container, as this will give a reading of the pot or pan, not the food.
Use a cook’s thermometer long enough, and you will quickly discover that the temperature dial of a domestic or even commercial oven bears little relation to the reality inside. There can be significant variation between different areas of the oven, especially when food placement interrupts the circulation of hot air. As a result, you should leave an oven-proof thermometer inside the oven for an accurate reading of roasting temperature.
Avoid cross-contamination
Because your thermometer is inserted into the most-affected parts of meat or food for bacterial growth, it is vital to sterilize it between each use. Otherwise you will be unwittingly spreading harmful bacteria throughout your kitchen. Keep your probe immersed in a beaker of sanitizer or bleach when not in use, and sterilize it with an alcohol swab before each use.
Get the most out of your probe
Of course, your temperature probe is the first defense in your food safety programme. Each reading should be logged and displayed where holding temperatures are concerned. This ensures not only that incoming shifts are aware of holding conditions, but also that records are complete and up to date should a food safety incident occur.
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