During the COVID-19 pandemic, demand for home-delivered convenient and premium food products surged. Pieminister, the UK’s number one premium pie maker, saw a significant increase in shipped pie orders during this time too.

And although the business had used ambient couriers for years, the technical team lacked complete confidence in the process, especially with the increasing frequency of heatwaves in the UK.

The challenge set to Anna Setterfield, technical manager at Pieminister and her team was to develop some defined procedures for transporting their range of ambient pies when temperatures exceeded 25 °C.

Anna explains the issues that the company faced with its existing ambient-delivery method:

“The ambient delivery method that we had in place was fine – it consisted of using variable ice pack quantities based on predicted temperatures, modular ice packs arranged around the products and recycled cardboard insulation, validated by ourselves the previous year. We wanted to create a system that was more defined for ourselves and our customers. End to end cold chain validation is not usual for the manufacturer to undertake but we pride ourselves on quality and food safety is an integral part of our quality commitment.”

Prompted by the hot summer for 2020 and the prospect of unpredictable heatwaves going forward, Anna took on the project as a KPI in 2021 and started investigating the process, setting up trials and validating a potential new procedure.

“I wanted any procedure that we put in place to confirm that pies shipped via ambient courier would remain within the chill chain (<8 °C) for up to 30 hours, representing the worst-case timeframe from packing to customer delivery”, she explains.

A structured trial process

Anna initiated a structured investigation and validation programme that included controlled environment testing. A partner microbiology laboratory provided access to a temperature-controlled “hot box,” capable of maintaining specific ambient temperatures for defined periods of time. This allowed accurate simulation of extreme delivery conditions.

Packing trials were then introduced with each trial box packed according to existing procedures but now using variations of ice packs and ambient temperatures.

Temperature Testing

Temperature monitoring, using food compliant SL52T button data loggers from Signatrol was also introduced. The SL52T is a self-contained, multiple use, miniature temperature data logger with the ability to record up to 8,000 temperatures over the temperature range of -40°C to +85°C with an accuracy of ±0.5°C. 

In each trial the data loggers were placed inside the pies to record the precise start temperature. Repeat trials were undertaken where variations or anomalies occurred so that a complete picture could be observed and any concerns reviewed. Use of the Signatrol data loggers ensured accurate, independent temperature validation throughout the 30-hour simulation window.

As a result of the information gathered in the trials, Anna and her team were able to develop a robust and consistent procedure for delivery of all products from packing at the factory to receipt by the customer. The trial revealed that the initial pie temperature was extremely important. The starting temperature of the pies was tightened from <8 °C to <5 °C as the trial revealed that pies must be <5 °C before packing as this impacts the ability of the products to remain under 8 °C on delivery.

Following a HACCP review, this is now designated as a Critical Control Point (CCP) for Pieminister’s ambient-delivery process.

New Packing Procedures

A defined packing procedure was also introduced to include defined ice pack requirements suitable for a range of UK ambient temperatures. Temperature threshold limits were introduced too meaning that in temperatures above 26 °C, the largest box format can no longer be shipped via ambient courier; only smaller configurations are permitted. And when the temperature reaches above 30 °C, orders require pre-10.30 am delivery, as testing confirmed that safe temperatures can only be guaranteed for only 24 hours under these conditions.

Chill Chain Customer Assurance

“These trials enabled Pieminister to have complete confidence in the chill chain of our pies and our ability to consistently deliver safe products to customers. The use of Signatrol’s temperature data loggers enabled us to give precise and accurate information to justify the use of additional ice packs and the pre-10.30am delivery to the production and supply chains. Our customers can be satisfied that they are receiving safe products of the highest possible quality”, Anna concludes.