Impact of photostimulation for delayed maturity on flesh quality of brook trout (Salvelinus fontinalis) stored under refrigerated conditions

The artificial prolongation of daylight is generally used to delay sexual maturation in many cultured species, mainly in salmonids. This may have a negative impact on flesh quality. Therefore, we aimed to investigate the impact of photostimulation on post-mortem changes; sensory, textural and nutritional characteristics of flesh of brook trout, Salvelinus fontinalis. Farmed brook trout were randomly divided into four experimental groups, according to photoperiod and sex for 112 days. Fish body traits and flesh quality of experimental fish were examined by body weight (g), gonadosomatic, hepatosomatic and perivisceral fat indices (%), rigor index (%), pH changes, fillet contraction (%), gaping, flesh water losses, textural, colour and sensory analyses and finally fat content and fatty acid (FA) composition. The results of pH measurement and rigor mortis showed that lower values of pH were measured in fish under artificial photoperiod (AP) during the entire measurement with faster progress of rigor mortis in comparison to fish under natural photoperiod (NP, control). In colour measurement, significant differences were detected in lightness L*, where NP fish (mature) were lighter than AP fish (immature). Significantly higher fillet contraction (p < 0.05) more than 7% were observed among AP females compared to the control groups. Finally, we documented that extension of light period has a positive effect on the sensory evaluation, the fat content and FA composition of brook trout flesh, but the effect is only minimal.