The main types and what they are good for
| Type | Best for | Limitations |
|---|---|---|
| Digital probe (thermistor) | Everyday checks of cooked, cooled and chilled food; the kitchen workhorse | Response takes a few seconds; probe tip must reach the centre of the food |
| Thermocouple with interchangeable probes | Fast readings; thin foods; special probes for frozen packs or surfaces | Costs more; probes need care |
| Infrared (non-contact) | Quick screening of delivery surfaces and display shelves | Reads surface only, not core; affected by shiny surfaces and packaging |
| Dial (bimetal) probe | Thick foods where a long stem can reach the centre | Slow; senses over a length of stem, so poor for thin foods |
| Fridge or freezer thermometer | Left in the cabinet to show air temperature without opening a probe | Shows air, not food; can be slow to respond |
| Min/max or data logger | Showing the warmest and coldest points since last reset, or a full record | Must be reviewed and reset; see the guide to data loggers |
What to look for when buying
- Accuracy: food probes are commonly specified to about ±1 °C; check the stated accuracy across the range you need, including freezer temperatures.
- Range: from below −18 °C for freezers up to cooking and reheating temperatures above 75 °C.
- Response time: a faster probe means staff actually wait for the reading.
- A thin, pointed probe tip that penetrates food easily and gives readings in thin items.
- Water resistance and a robust case for a wet kitchen.
- Easy calibration or a calibration certificate, and the ability to adjust if it drifts.
- A probe cover and a clip so it lives in a pocket, not in a drawer.
Using a probe correctly
Insert the tip into the thickest part of the food, away from bones and the container. Wait until the reading settles. For liquids, stir first and probe the centre. For packed chilled food at receiving, place the probe between two packs and press them together, so you don't pierce the packaging. For frozen food, use a probe designed for frozen product or sandwich it between packs; forcing a standard probe into frozen food damages it.
Infrared thermometers are useful for screening, such as checking the surface of every crate in a delivery in seconds, but confirm any borderline reading with a probe.
Checking accuracy: the ice-point method
The simplest check is the ice-point test, recommended by food-safety extension services. Fill a glass with crushed ice, add cold water to make a slush, stir and wait a minute. Insert the probe into the middle, without touching the sides or bottom. It should read 0 °C. If it reads more than about 1 °C off, adjust it if it allows, or replace it.
The boiling-point test is less reliable because water boils below 100 °C at altitude, by roughly 1 °C for every 300 m, and tap water and conditions vary. Check probes regularly, for example weekly, and whenever one is dropped, and record the check.
Keeping probes clean
A probe that goes from raw chicken to a cooked dish carries bacteria with it. Clean and sanitise the probe before and after each use, especially between raw and ready-to-eat food. Probe wipes designed for food contact are convenient; a wash, rinse and food-safe sanitiser also works. Store probes clean and covered.
How many thermometers a kitchen needs
At least one probe per working section, so no one has to go looking, plus a spare in case one fails its check. Give each refrigerator and freezer its own cabinet thermometer or logger. A receiving station benefits from its own probe and an infrared screener. Label each instrument so its calibration record can be traced.
Frequently asked questions
- Can I use an infrared thermometer to check if food is cooked?
- No. Infrared thermometers read only the surface temperature. The centre of a piece of meat or a pot of rice can be much cooler than its surface. Use a probe thermometer for cooking, cooling and reheating checks.
- How often should food thermometers be calibrated?
- Check them regularly, commonly weekly in busy kitchens, and whenever a thermometer is dropped or gives a reading that looks wrong. The ice-point check takes a few minutes. Record each check so you can show your readings are reliable.
