Abstract
The effect of stunning method (percussion or asphyxia) for rainbow trout was evaluated in terms of blood chemistry (glucose and lactate), muscle activity (initial pH), skin and fillet colour, fillet gaping, water content, final pH, and sensory attributes (quality index, QI). After 8 days of ice storage, stunning method had no significant effects on QI, skin colour, water content, or gaping frequency. In contrast, fillet lightness, redness, hue, and chroma were significantly affected by perimortem stress although to a modest degree only. Another experiment was set up to study the effect of gutting (gutted vs not gutted trout) on the same quality parameters after ice storage for 1, 7, 14, and 21 days. For both gutted and not gutted fish, water content, as well as gaping and QI scores, increased progressively. Throughout storage, gutting had a distinct effect on QI scores as gutted fish consistently exhibited lower QI scores. Thus, for evaluations by QIM, it is important to take into consideration whether the fish are gutted or not. If a QI score of 15 is defined as maximum shelf life, the shelf life of gutted and not gutted rainbow trout was 3 and 2 weeks, respectively. The QIM scheme for Atlantic salmon was considered useful, without modifications, for shelf life studies of rainbow trout. Skin and fillet colour were not affected by gutting. Increasing storage time leads to some minor, but not consistent, significant changes in skin dorsal and belly lightness, yellowness, hue, and chroma