nofima.no
Creating value
2013
15
financed by:
The Norwegian Seafood
Research Fund
Senior Scientist Karsten Heia uses light measurements (spectroscopy) to determine the remaining shelf life of fish with unknown background.
photo: audun iversen © Nofima
Fishmongers and fish shops focus on high quality of the
food they sell, and in order to be able to set a best-before date they need to know how long the fish has
been stored on ice or in refrigeration when they receive
it.
Stipulating shelf life involves several elements of
uncertainty, including how the fish is handled in the boat,
on land and during transport. For instance, leaving the
fish on the deck for several hours before chilling can
reduce the shelf life by several days.
Light provides answers:
Nofima has used light mea
surements (spectroscopy) to determine the remaining
shelf life of cod. By sending light through the cod fillet,
the scientists can see how much light is absorbed at
different wavelengths.
When the fish is exposed to oxygen, the iron bearing
proteins (heme proteins) in the fish muscle are oxidized.
In other words, the iron bonds with the oxygen in a
chemical reaction. The longer the cod is stored, the more
oxidized it becomes. Oxidation leads to changes in how
much light is absorbed when the scientists send light at
different wavelengths through the fish.
“By measuring oxidation changes in heme proteins,
we can find the remaining shelf life of fish and whether
the fish has been frozen and defrosted,” says Senior
Scientist Karsten Heia.
New technology:
The quality and shelf life of fish is
equally important for consumers, retailers, processors
and buyers, and is decisive for price. The next step is to
develop an instrument that makes it easy to use this
method.
“A handheld device that fish shop staff could easily
use to measure the remaining shelf life of the fish would
be extremely useful and ensure better quality,” says
Heia.
This method has previously been successfully tested
on salmon. The scientists are planning to expand the
method so it can also be used on saithe, halibut, monk-
fish and other species.
A new method makes it possible to establish the shelf life of fish
without knowing in advance how and for how long it has been stored.
Better measurement of shelf life
