Computer Vision‐Based Evaluation of Pre‐ and Postrigor Changes in Size and Shape of Atlantic Cod (Gadus morhua) and Atlantic Salmon (Salmo salar) Fillets during Rigor Mortis and Ice Storage: Effects of Perimortem Handling Stress

Abstract

The present study describes the possibilities for using computer vision-based methods for the detection and monitoring of transient 2D and 3D changes in the geometry of a given product. The rigor contractions of unstressed and stressed fillets of Atlantic salmon (Salmo salar) and Atlantic cod (Gadus morhua) were used as a model system. Gradual changes in fillet shape and size (area, length, width, and roundness) were recorded for 7 and 3 d, respectively. Also, changes in fillet area and height (cross-section profiles) were tracked using a laser beam and a 3D digital camera. Another goal was to compare rigor developments of the 2 species of farmed fish, and whether perimortem stress affected the appearance of the fillets. Some significant changes in fillet size and shape were found (length, width, area, roundness, height) between unstressed and stressed fish during the course of rigor mortis as well as after ice storage (postrigor). However, the observed irreversible stress-related changes were small and would hardly mean anything for postrigor fish processors or consumers. The cod were less stressed (as defined by muscle biochemistry) than the salmon after the 2 species had been subjected to similar stress bouts. Consequently, the difference between the rigor courses of unstressed and stressed fish was more extreme in the case of salmon. However, the maximal whole fish rigor strength was judged to be about the same for both species. Moreover, the reductions in fillet area and length, as well as the increases in width, were basically of similar magnitude for both species. In fact, the increases in fillet roundness and cross-section height were larger for the cod. We conclude that the computer vision method can be used effectively for automated monitoring of changes in 2D and 3D shape and size of fish fillets during rigor mortis and ice storage. In addition, it can be used for grading of fillets according to uniformity in size and shape, as well as measurement of fillet yield measured in thickness. The methods are accurate, rapid, nondestructive, and contact-free and can therefore be regarded as suitable for industrial purposes.

Effect of trawling with traditional and ‘T90’ trawl codends on fish size and on different quality parameters of cod Gadus morhua and haddock Melanogrammus aeglefinus

“…Low pH at the time of killing is widely recognised as an indicator of handling stress, as reported in salmon [27], eel [28] and turbot [29]. Typical initial muscle pH values reported for exhausted cod is about 7.0 [30][31][32], which is lower than that reported for our cod, namely, pH 7.2-7.3 (Table 5). Surprisingly, this means that the cod in our experiment were just partially affected by capture stress.…”

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

“…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.…”

“…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. Sveinsdóttir et al [7] evaluated sensory characteristics of unstressed and stressed farmed cod by using a trained sensory panel and consumer evaluation tests.…”

Quality Assessment of Aquatic Foods by Machine Vision, Electronic Nose, and Electronic Tongue

“…), and grey mullet (Mugil cephalus) have been successfully separated using images of fish swimming in an aquarium [16]. Besides sorting of fish, CVS has been used to describe the rigor contractions of unstressed and stressed Atlantic salmon (S. salar) and Atlantic cod (G. morhua) fillets by monitoring the transient two-and three-dimensional changes in the geometry [17]. This method has been found suitable for industrial purposes.…”