The effects of stress and storage temperature on the colour and texture of pre-rigor filleted farmed cod (Gadus morhua L.)

Abstract

This experiment deals with the e¡ects of pre-slaughter stress and storage temperature on muscle pH, ¢llet contraction, colour and texture in pre-rigor ¢lleted farmed cod ¢llets. The ¢sh were either sedated with a low dose of MS-222 (14.3 mg L À 1 ) (unstressed groups) or exposed to the air for 3 min (stressed groups) before being submerged in a benzocaine bath (150 g L À1 ). The ¢sh were then killed by a blow to the head, their gills cut, ¢lleted and ¢nally stored at either 4 or 20 1C. The stressed groups had signi¢cantly lower pH values after slaughter (pH 5 7.0) than the unstressed groups (pH 5 7.3). This di¡erence was maintained until post rigor for the ¢sh stored at 4 1C, but at 20 1C it was immediately overshadowed by a decrease in pH caused by temperature-dependent processes. The length contraction and changes in registered colour values were more pronounced at both the higher temperature and the higher level of pre-slaughter stress. Again temperature dominated, but signi¢cant and consistent effects were registered from stress. No signi¢cant e¡ects of stress on texture post rigor were observed. It is concluded that high storage temperature masks the majority of e¡ects caused by pre-slaughter stress on the measured variables. Stress management protocols, however, are important when the ¢llets are kept at the common storage temperature of 4 1C.

Biochemical, physical and sensory quality of ice-stored Atlantic cod (Gadus morhua) as affected by pre-slaughter stress, percussion stunning and AQUI-S™ anaesthesia

“…The mean gaping score after 7 days of storage was 0.7 with no difference between the groups (Table 2). No significant differences were observed between our groups with regard to fillet hardness (Table 3), which is similar to the findings of Stien et al [4]. However, there were significant differences between fillet locations, where the anterior part was harder than the middle or the posterior part for all the groups.…”

“…Kristoffersen et al [5] reported a higher pH value, 7.9, for farmed cod killed with as little pre-slaughter activity as possible. In our stressed fish, the values were typical, pH 7.0, and were in accordance to previously reported pH values for stressed cod [4][5][6]. Low pH at the time of killing is widely recognised as an indicator of handling stress.…”

“…Comparable values (pH 7.2-7.5) are reported for unstressed farmed Atlantic cod [4,6]. Kristoffersen et al [5] reported a higher pH value, 7.9, for farmed cod killed with as little pre-slaughter activity as possible.…”

“…Reduced stress prior to slaughter has been shown to have a positive influence on flesh quality, e.g. gaping and colour, for farmed Atlantic cod [4,5]. Misimi et al [6] reported for farmed Atlantic cod that greater activity immediately prior to death results in a more rapid drop in muscle pH and a shorter period to the onset of rigor.…”

The influence of anaerobic muscle activity, maturation and season on the flesh quality of farmed turbot

“…Higher drip losses in turbot can be explained by the fact that the turbot fillet is relatively lean compared to the salmon fillet. Pre rigor fillets from lean species such as Atlantic cod (Gadus morhua) have approximately 6-7% drip loss after 7 days of ice storage (Kristoffersen et al 2007) and will during rigor shrink by 20% (Stien et al 2005). For species with high values of body fat, such as Atlantic salmon, the fillets will shrink approximately by 10% .…”