A non-destructive temperature measurement method specified by Codex Alimentarius (CAC/RCP 8-1976) where a temperature probe is placed between frozen product cartons or packages to approximate product temperature without penetrating product packaging.
What It Measures
A between-pack reading captures the temperature of the air space between tightly packed product packages. Because this space is insulated from ambient air by the surrounding product mass, the temperature approximates product surface conditions rather than general air temperature.
This method is preferred over air temperature readings for compliance verification because it’s influenced by product thermal mass rather than equipment cycling. It’s preferred over destructive probe insertion because it doesn’t compromise product packaging or food safety.
Codex Specification
CAC/RCP 8-1976 specifies between-carton or between-package temperature reading as the inspection method for frozen foods during transport and distribution. The warmest package reading determines compliance — not the average, not the air temperature, and not the reading nearest the evaporator.
Target: -18°C at all points. Maximum tolerance during distribution: -12°C in the warmest package.
Limitations
Between-pack temperature still measures surface/interstitial conditions, not product core. For products that have experienced significant temperature excursions, core temperature lags behind surface by hours depending on product mass, packaging density, and surrounding conditions. A between-pack reading of -14°C after a thermal event may mask a core temperature of -8°C.
For receiving inspection of goods arriving from external suppliers, between-pack readings provide better screening than air temperature but should be supplemented with IR surface screening and visual inspection of packaging condition. See our receiving inspection article for the complete inspection protocol.
Related Terms: Air Temperature vs Product Temperature, Temperature Excursion, Glycol Buffered Probe
Related Articles: Your Freezer Says -15°C. Your Product Says -6°C. Both Are Correct. | The Receiving Inspection You’re Not Doing