Only a nose would know for sure if these shrimp were good or not.

AT THE SEATTLE DISTRICT Lab of the United States's Food and Drug Administration, James Barnett bends over a package of Thailand shrimp. He scoops up a handful, crushes some between his fingers and takes a deep whiff. "If it smells good, it's good," he says.

Mr. Barnett's job is nothing to sniff about. He is one of only four in the whole of the US. His official title of National Sensory Expert translates, in layman's language, to "top nose". What he turns his trained nose up to, gets turned down and does not reach the US consumer.

The USFDA currently relies on national experts in nosing (technically called "organoleptic testing" or "sensory evaluation"). Based on the West Coast (Seattle), on the East Coast (Boston, New York) and in Florida, these top noses are supported by two or three dozen junior noses, officially "original analysts" or "check analysts", depending on who gets the first waft.

Those junior noses nose their way into batches of raw, frozen, canned and processed products shipped to the US from all over the world and judge representative units (called "sub samples", or "subs") brought in by inspectors from ports of entry. Two junior noses who disagree refer to a top nose.

Mr. Barnett estimates that for canned product alone, he must have nosed through at least 6,000 cans in 1993. Districts from all over the US, except those in the Northeast, turn to him for a final smell of approval - or disapproval. "

There is no glamour to being a seafood nose," says Mr. Barnett. Unlike wine - and perfume noses who huddle around pleasant concoctions in pristine surroundings talking about aroma, fragrance and bouquet, seafood noses go aboard fishing vessels, inside factories, around ports and markets in search of fishy smells from the characteristically fresh to the downright stinking. Their technical vocabulary includes words such as "decomposed," putrid" and "rotten".

The noses come from diverse ethnic, educational and professional backgrounds. Mr. Barnett himself, before taking up a post in Seattle in 1990, tasted tea for over nine years in New Orleans.

The principles are the same, according to him, but seafood noses rely more on smell. They never taste raw, unprocessed foods because of potential health risks. They may - not always taste "commercially sterile retorted product with container integrity", such as canned tuna, but will not swallow. They take periodic 15-minute breaks to avoid being "saturated" with odours - more often, if there is a lot of bad product; less frequently, if most of the stuff is good.