Knowledge / Testing and the packing process
Preventing Cold Shock in Pharmaceutical Shipping
Goods can become too cold during refrigerated shipping if packs are inserted too cold, separating layers are missing or the configuration provides insufficient protection against winter conditions. Identifying the cause requires the complete temperature history, sensor locations and packing data. A suitable PCM melting point alone does not rule out excessive cooling.
Practical guidance
Use measurement histories and packing data to identify why the goods became too cold and what to investigate.
An infrared measurement records the cooling element’s surface temperature. It does not fully show whether the medium inside is solid or liquid.
In this guide
- A temperature drop below the limit does not automatically mean freezing damage
- Preserve temperature histories and packing data
- Typical patterns and the next checks
- Why a return to normal temperature does not release the goods
- Check separating layers and coolant pack preparation
- What PCM can do to reduce excessive cooling
- Test the correction and assess the affected goods separately
A temperature drop below the limit does not automatically mean freezing damage
In packaging, cold shock describes critical exposure to cold. Where +2 to +8 °C is specified, falling below +2 °C already constitutes a temperature excursion. However, it proves neither that the goods have frozen nor that they have been damaged.
Quality assurance assesses duration and temperature using suitable product data. This assessment may be necessary even if the goods look unchanged.
Preserve temperature histories and packing data
Save the complete record from every relevant logger. Note which sensor was positioned where, when the shipper was packed and collected, and whether it was stored or opened in between. Add coolant pack type, preparation and product quantity.
Use photographs to compare the actual loading with the packing instructions. Without this information, a cold measurement often cannot be reliably assigned to a product position or packing error. The guide to +2 to +8 °C explains differences between small and large loads.
Typical patterns and the next checks
The following observations help narrow the investigation. They are not yet proof of a cause; several influences may act together.
| Observation | What to check |
|---|---|
| Sharp drop shortly after packing | Coolant pack type and preparation, missing separating layers or direct contact. Compare timings and initial temperatures with the specification. |
| Only one measurement at the edge drops | Sensor and affected container positions, shifted components or different clearances. Compare photographs with the tested configuration. |
| Drop after intermediate storage of the packed shipper | Storage temperature and duration. Check whether this waiting area was specified for the system with the packs used. |
| Late drop in cold surroundings | Check the configuration’s winter suitability and preparation for the cold transport stage. Do not assume a packing error prematurely. |
Then investigate a plausible cause in a controlled test. Change one factor as specifically as possible and document the other conditions. This shows whether the measure actually prevents the observed temperature drop.
Why a return to normal temperature does not release the goods
A brief, sharp drop can disappear in a time average. An average across several sensors can also conceal a cold edge position. Assess the relevant individual temperature histories.
Mean kinetic temperature, or MKT, is not general evidence against freezing either. Under certain model assumptions, it describes temperature exposure in relation to degradation processes; it does not generally rule out physical changes caused by freezing.
A subsequent return to a permitted temperature does not reverse possible damage. To decide on the goods, quality assurance needs temperature and duration, the relationship between the measurement and the product, and the product’s stability data.
Check separating layers and coolant pack preparation
Use all specified inner packaging, separating layers and spacers. Do not remove them to accommodate more goods. The EU GDP Guidelines require coolant packs to be arranged without direct contact with medicinal products.
Check item identification and preparation status. Water-based packs and PCM packs of the same shape are not automatically interchangeable. “Fully frozen” is correct only if the packing instructions specify exactly that state. The packing process guide shows how to organise checks at the workstation.
What PCM can do to reduce excessive cooling
A melting range close to the permitted product range can support the design. However, a PCM pack can be significantly colder than its melting point when packed. It therefore also requires a defined preparation procedure.
A tested year-round packout can reduce confusion between summer and winter variants. The number of packs, preparation and product quantity must still be followed. The article on PCM selection and preconditioning explains these relationships.
Test the correction and assess the affected goods separately
Test the changed preparation or loading at the previously problematic product positions and under relevant ambient conditions. A sensor in the centre alone can miss local cold areas.
Incorporate a confirmed correction into the packing instructions and train the relevant staff. The decision on goods already shipped remains separate: improved packaging does not retrospectively release a shipment that previously showed an excursion.
Sources
- EU GDP Guidelines 2013/C 343/01, Chapter 9. Chapter 9: transport, packaging and special storage conditions for medicinal products for human use.
Sources checked on 12 September 2026.
Investigate a temperature problem
Temperature histories, sensor positions, packing photographs and coolant pack preparation details support technical root-cause analysis. The responsible quality assurance team assesses whether the affected goods may be used.