The tester(s) will smell the fish gill odour to assess the state of freshness.
[1] The test may be performed on both raw and cooked (without seasoning or other ingredients) fish, and the criteria are generally fish-species specific.
The test relies on human sensory perception as the input, although recently electronic tools have been developed to validate the readings.
Generally the test is important and relevant to daily activities in fish marketing.
The scale was originally developed at the Torry Research Station of the Central Science Laboratory.