Setpoint vs pulp temperature on a reefer

The setpoint is the temperature you instructed the container to hold. The pulp temperature is the temperature inside the fruit itself, measured with a probe pushed into it. They are different numbers, and the second one is the one that decides what arrives.

A reefer conditions air. It has no way to reach into a pallet and cool the fruit at its centre, so pulp temperature follows the air slowly, from the outside in, at a rate set by how the load is stacked and how much heat the fruit is producing. On a properly pre-cooled load the two converge within a day and stay together. On a load that was stuffed warm they may never meet at all.

Why the log can be perfect and the fruit still wrong #

The unit’s temperature log records air, because air is all it can measure. Cargo cut in the afternoon and stuffed the same evening carries field heat that the container is not sized to remove — a reefer holds a temperature, it does not pull one down. The load sits above specification for days while the unit runs flat out and writes a flawless record.

This is the single most common shape of a quality dispute. The log proves the setpoint held, so nothing was wrong with the equipment, and yet the consignment lost days of shelf life before it reached open water. What went wrong happened at the packhouse, before the doors closed.

Colder is not safer #

The other half of the trap is the instinct to buy margin by dropping the setpoint. Chilling-sensitive commodities are damaged well above freezing: internal browning, pitting, or fruit that simply refuses to ripen. Avocados, pineapples and bananas each have their own floor, and none of the injuries are visible until the fruit is cut open at destination.

The setpoint is a specification that comes from your protocol or your exporter, agreed before loading and not adjusted in transit. The pulp temperature at stuffing is what tells you whether that specification ever had a chance.

FAQ #

Why did my fruit arrive warm when the container held setpoint? #

Almost always because it was loaded warm. The container maintains air temperature but cannot remove field heat at any useful speed, so cargo stuffed before it was pre-cooled spends the first days of the voyage above specification while the log looks correct.

Should I ask for the pulp temperature at loading? #

Yes, and get it in writing. It is the one measurement that separates a pre-shipment problem from a cold-chain problem later, and once the container has sailed nobody can reconstruct it.

Is a lower setpoint safer for a long voyage? #

No. Chilling injury develops above freezing and is commodity-specific, so a setpoint below the fruit’s threshold causes damage rather than buying margin. Extra days come from controlled atmosphere and from correct pre-cooling, not from a colder box.