Food Safety - Calibrating your Thermometers

Thermometers should be calibrated whenever the they are dropped, before first used, and when going from one temperature extreme to another.

Temperature is a critical measurement for ensuring the safety and quality of many food products. Whether monitoring temperatures at receiving, throughout production or final product storage and distribution, thermometer calibration is essential. The validation, verification reassessment section of the Hazard Analysis and Critical Control Point  system stated in the Code of Federal Regulations (9CFR 3:417.4) specifies that instruments used for monitoring critical control points must be calibrated. 

Sanitize thermometers before using and in between using. To clean and sanitize the thermometer, wash it in hot, soapy water, rinse, wipe it down, or you could use a sanitizing solution appropriate for for food contact surfaces. Allow the thermometer to sit in a sanitizing solution (5 ml or 1 teaspoon of household laundry bleach to 1 Liter or 1 quart of tap water) for two minutes. Then rinse the thermometer in hot water. Since most employees won't follow these procedures properly unless closely supervised, an alcohol swab might work best.

It is recommended that you keep a thermometer calibration log. Download a calibration log here

Ice Point Method		Boiling Point Method
►Fill an insulated  cup with crushed ice and water. ►The cup  must have enough crushed ice  to provide an environment of 32°F, so you may need to pack more ice into the cup  during the process. ► When the mixture of the water has stabilized in about four or five minutes, insert the thermometer to be calibrated to the appropriate immersion depth. ►Be sure to hold the stem of the instrument away from the bottom and sides of the container (preferably one inch) to avoid error. ► If your thermometer is not accurate within +/- 2°F of 32°F., adjust the thermometer accordingly. The ice point method permits calibration to within 0.1°F.		►  Place distilled water in a container and heat.   ►  After the water in the container has reached a complete “rolling” boil, insert the instrument to the appropriate immersion depth. ►  Be sure there is at least a two-inch clearance between the stem or sensing element and the bottom and sides of the container. ►  If your thermometer is not accurate within +/- 2°F of 212°F., adjust thermometer accordingly. The boiling point method permits calibration to within 1.0°F.