Using a good insulating material alone does not prove a home-made bag performs well. Inspect the closure, seams, damage, cleanability of the inner surface, and how the product sits inside.
Before testing, record the product, packaging, load quantity, route, and opening sequence. Keep the measurement method and instrument position consistent; log start, intermediate stop, and handover observations on one form.
Repeat trials with similar loads and routes; note changes in outside conditions or stop order. If the product specification requires temperature records, use a suitable approved method and track instrument status.
If records differ substantially, inspect closure fit, seams, empty spaces in the load, and how long the bag stays open. If the liner cannot be cleaned or is damaged, decide with the quality lead whether it can be used for that product flow. Do not promise unverified performance or food safety.