Torry Freshness Score is a systematic scoring system, originated in UK, based on objective sensory scoring method (tester(s) will smell the fish gill odour) to assess the state of fish or the fish freshness. The scoring system starts with 10 and declining. Ten (10) is the highest score for newly caught fish, 7 is in the neutral range, 6 is at the 'borderline', and 3 or lower score is considered spoiled.
Customers generally reject them when it is down at the 6 score or lower. It is done on both raw and cooked (without ingredients) fashion, and the criteria are generally fish species specific. The results of evaluation generally correlates to (density of) presence of microorganisms that cause spoilage, as lower score implies more presence of microorganisms. It relies on human sensory perception as the input, although recently they develop electronic tools to validate the job. Generally it is important and relevant in the daily activities in fish marketing.
More information at Torry Research Station part of Central Science Laboratory.