One of the first questions in a long power cut concerns what sits in the freezer. The answer depends on a few measurable variables.
How long does a freezer stay cold?
A freezer whose door never opens holds its cold for a definite period through a cut.
A full freezer holds forty-eight hours.
A half-full one holds twenty-four.
Those figures apply on the condition that the door never opens.
The ambient temperature matters too; those periods hold in a room at twenty degrees and shorten by around thirty percent at thirty.
| Situation | Time | Note |
|---|---|---|
| Full, door closed | 48 hours | The best case |
| Half full, door closed | 24 hours | Medium |
| A quarter full | 10-14 hours | Risky |
| Each opening | -1 to -2 hours | Loss |
| Ambient above 30 °C | 30% shorter | Summer conditions |
| Ice packs added | +6-10 hours | Gain |
Why does the fullness matter so much?
Frozen food acts as a store of cold in its own right.
Every frozen item sits at minus eighteen degrees and needs energy to warm.
Raising a kilogram of frozen food to zero degrees takes around 350 kilojoules.
Where the freezer is full the total energy required runs large and the warming happens slowly.
Empty space holds air, and air conducts heat fast.
Half-full freezers can therefore get filled with bottles of water before a cut; the freezing water creates an additional store of cold.
What does opening the door cost?
That is the commonest mistake made during a cut.
Cold air leaves at every opening and air at room temperature takes its place.
One opening costs an hour or two off the total.
A freezer opened five times drops its forty-eight hours to forty.
The reflex to "just have a look" is therefore the most expensive move.
The door closes when the cut begins and does not open again until the power returns.
How does the temperature get monitored?
The route to knowing the temperature without opening the door is preparing in advance.
The simplest method is the coin test.
Water goes into a small container and freezes.
A coin goes on top of the ice once frozen.
The position of the coin gets read after the cut; where it still sits at the surface nothing thawed, and where it has sunk partway or to the bottom the ice melted and refroze.
What can be saved?
Not every product gets judged the same way after a cut.
Products still holding ice crystals and firm to the touch can be refrozen.
Products fully thawed but held below four degrees can be used provided they get cooked.
Products that passed four degrees and waited longer than two hours go in the bin.
Meat, poultry, fish and seafood are the riskiest group; where doubt exists they go in the bin.
Bread, pastry and fruit are more tolerant; even thawed they carry a low risk in safety terms.
Why is refreezing a problem?
Two separate processes run.
The first is a microbiological process; bacteria multiply past four degrees.
Refreezing does not kill them; it only halts their activity.
The second is a structural process; crystals from the first freeze damage the cells.
The crystals grow larger in a second freeze.
The result is both a risk to safety and a clear loss of texture; the product never returns to its original state.
What happens before a cut?
Planned cuts get announced in advance and preparation becomes possible.
The freezer goes to its lowest setting; made a few hours before, that adjustment creates a reserve of cold.
Empty spaces get filled with bottles of water.
Ice packs get frozen.
The products get stacked tightly; a tight arrangement reduces air gaps and slows the transfer of heat.
What happens if the cut runs long?
A few options remain in cuts passing forty-eight hours.
The first is dry ice; placed in the freezer it can hold the temperature for days.
Ten kilograms of dry ice holds a freezer of half a cubic metre for two or three days.
Ventilation becomes necessary and it does not get handled with bare hands.
The second is moving; the products go somewhere with power.
The third is eating them; partly thawed products can be cooked and then frozen, since a cooked product falls into a different category from a raw one.
What happens once the power returns?
The first step is measuring the temperature.
Where no thermometer exists the texture of the products gets checked.
Those still partly frozen stay where they are.
Those thawed get judged separately.
Doubtful products go in the bin; no risk gets taken where a smell, a colour or a change in texture appears.
A list of the products and their state gets written; that record can get asked for where insurance or business records apply.
What changes in a business?
The rules run stricter in commercial operations.
Temperature logging is obligatory; loggers keep measuring through the cut.
Freezers stay on the priority circuit in businesses holding a generator.
Products get assessed against HACCP procedures after a cut.
Doubtful products get destroyed and a record gets kept; those records get asked for during inspections and form part of the food safety system.
Does a fridge differ from a freezer?
Yes, and the difference is clear.
A fridge holds four hours with the door kept closed.
A freezer holds twenty-four to forty-eight.
The reason is the difference in temperature; a fridge runs at four degrees and a freezer at minus eighteen.
The products in a freezer need far more energy to warm.
Priority in a cut therefore goes to what sits in the fridge; dairy, meat and cooked dishes begin carrying risk after four hours.
