杏吧原创

FISHING boats should be packed with peat moss instead of expensive freezers,
say Norwegian researchers. The peat can keep fish fresh for weeks, and would
make shipping to distant ports dirt cheap, they claim.

鈥淚f my pipe dream comes true we might save the Norwegian economy billions of
kroner every year,鈥� says Terence Painter of the Norwegian University of Science
and Technology in Trondheim.

Sphagnum moss, which over hundreds of years compacts down to form peat bogs,
is an incredibly effective natural preservative. A fully clothed 2000-year-old
body, 6000-year-old crumbs of uneaten bread and 1800-year-old kegs of butter
have all been recovered in good condition from such bogs.

At first researchers thought that the lack of oxygen, low temperature and
acidic environment banished decomposers such as bacteria. Others later suggested
that chemicals called tannins in the peat acted as a preservative. But Painter
has proposed that an unusual oxopolysaccharide鈥攁 sugar with reactive
carbonyl groups attached鈥攊s responsible. He named the complex sugar
鈥渟辫丑补驳苍补苍鈥�.

Painter and his colleagues Yngve B酶rsheim and
Bj酶rn Christensen set out to
demonstrate the preservative ability of this sugar using strips of salmon skin
and whole zebra fish. 鈥淭here鈥檚 a lot of peat here in Norway and very little of
it is used. There鈥檚 also a huge fishery, so we hoped we could connect the two,鈥�
says Painter. The Norwegian government is sponsoring the study.

The researchers encased the fish samples in beds of either untreated peat,
sphagnum moss, a powdered white extract including all the polysaccharides in the
moss, or wood cellulose as a control. The fish were periodically removed, rinsed
with water, checked for colour changes and sniffed for signs of decay. After
between 9 and 28 days, the fish were removed to a bed of nutrients to see how
long it would take before bacteria began to grow.

Fish that had been stored in the peat or moss stayed fresh for about a month,
and bacterial growth after removal was delayed by between 7 and 12 days.

鈥淎fter two days of normal keeping, the smell of putrefaction is disgusting.
After four weeks at room temperature in peat, it smells fresh. It鈥檚 absolutely
staggering,鈥� says Painter.

The researchers suspect that the carbonyl groups help preserve the fish by
tanning the skin, making it unappealing to bacteria. 鈥淓xposure to wood smoke has
exactly the same effect,鈥� Painter says. The same chemical process also gives
bread crusts, soy sauce and black coffee their colour.

Sphagnum moss that had been chemically reduced to remove the carbonyl groups
had no preservative effect. Painter thinks this proves that sphagnan sugar is
the active ingredient. 鈥淚 consider the case closed.鈥�

He believes the peat could be used all over the world as a cheap
preservative, but he adds that more tests still need to be done鈥攕uch as
taste tests. 鈥淚鈥檓 eager to sit down and eat a salmon preserved in peat,鈥� he
says. 鈥淚 would have eaten these fish but they were quite small.鈥�