Fresh yeast is made of live cells, and the storage temperature decides how much reserve the cell keeps. In a sample held at 4 °C for 12 days the trehalose content stayed at 12.33 percent, in one held at 24 °C it fell to 0.24 percent, and the 24 °C sample lost 81.76 percent of its fermentative activity. Even if the pack looks intact, yeast that warmed on the way does not give the expected rise at the bakery.
When a complaint arrives, the three things the baker asks must already be in the record:
- The product lot and the supplier's storage instruction.
- The temperature it saw on the way: logger ID, dispatch and delivery times, pack-out description. Take the measurement at the point set in the product procedure, and do not enter an air reading as product temperature.
- Where it was put at the bakery: a designated cold area instead of the flour store, and how often that area's door is opened.
On a van that calls at ten bakeries in a morning, the lid opens at every stop and the air inside warms; the yeast reaching the last bakery carries a different temperature history from the first. If each handoff time and lot is kept separate, logger data matches the right delivery and it shows whether the delay was at the last stop.
A sourdough culture is alive too, and fermentation temperature is one of the parameters that determine the course and outcome of the fermentation. Carry fresh yeast and starter each under its own product instruction.
With a delivery temperature record, the argument between "the yeast was bad" and "the bakery used it wrongly" is short; without one the supplier cannot defend its product.