The freshness clock runs at different speeds
Fish freshness is like an ice cube on a warm day: the warmer the surroundings, the faster it
changes. This is why temperature is one of the most important factors in protecting fish quality.
Rapid chilling does not make fish fresher; it slows the rate at which freshness is lost. Delayed
chilling or repeated warming can shorten usable life even if the fish is later returned to a
refrigerator or freezer.
What should be measured?
A proper time-and-temperature record is like a travel diary for the fish. It may include:
Harvest date and time
Time from harvest to initial chilling
Fish core temperature during receiving
Processing-room and product temperatures
Freezing time and frozen-storage temperature, where applicable
Transport and retail-storage temperatures
Duration and severity of every temperature excursion
Product temperature at delivery
A digital logger can record the conditions experienced by a shipment. A probe thermometer can
verify product or core temperature at important receiving and processing steps. Both instruments
should be calibrated.
Why an average temperature can be misleading
An average can hide a problem. A shipment may be very cold for most of its journey but remain
warm for several hours during loading. Its final temperature could look acceptable even though
freshness was lost during that warm period.
An effective standard should therefore specify:
Target temperature range
Maximum permitted temperature
Maximum duration outside the target range
Corrective action after an excursion
Who reviews and releases the batch
Chilled and frozen fish require different controls
Fresh and thawed unprocessed fish are commonly held at a temperature approaching that of
melting ice under European hygiene rules. Consumer guidance from the United States Food and
Drug Administration advises keeping seafood at 4°C/40°F or below and using it promptly, or
freezing it when it will not be used soon.
Frozen storage greatly slows deterioration but does not stop every quality change. Over time,
dehydration, protein changes and fat oxidation may cause freezer burn, loss of juiciness, rancid
flavours or texture damage. Stable frozen storage and moisture-resistant packaging are therefore
important.
The cold chain is only as strong as its warmest gap
Temperature control must continue through:
1. Harvest and farm or landing point
2. Transport to processing
3. Cleaning, cutting and packing
4. Chilling or freezing
5. Warehousing
6. Distribution
7. Retail or fulfilment
8. Last-mile delivery
9. Consumer storage
Even a well-controlled processing facility cannot compensate fully for poor handling before arrival
or after dispatch.
What consumers can do at home
Buy chilled or frozen fish near the end of a shopping trip.
Use an insulated bag for longer journeys.
Refrigerate or freeze the product promptly.
Keep the refrigerator at 4°C or below unless the product carries more specific instructions.
Follow the labelled use-by date and thawing instructions.
Do not repeatedly thaw and refreeze fish.
Avoid leaving seafood at room temperature for extended periods.
The FDA advises refrigerating or freezing perishable seafood within two hours, or within one hour
when ambient temperatures exceed 32°C/90°F.
REMEMBER
The harvest date tells you when the journey began. The temperature record tells you how
well freshness was protected along the way.