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Rest before slaughter improves fillet quality: study

September 11, 2020  By  Nestor Arellano

South American catfish (photo by Lerdsuwa CC BY-SA 3.0: https://commons.wikimedia.org/wiki/User:Lerdsuwa)

Previous studies have shown that exercise improves fish health and growth.  A recent research now indicates that giving fish ample resting time before they are harvested and slaughtered results in better quality fillets.

Results of the study can be useful for operators of aquaculture facilities in developing protocols relating to the management of fish stocks as well as harvesting procedures. The researchers found that incorporating adequate resting time for fish to pre-harvest procedures can avoid factors that are detrimental to fish meat quality.

“In aquaculture, the procedures involved in pre-slaughter management are recognized as a critical point in the management of fish welfare and have important effects on meat quality,”  according Letícia Emiliani Fantini, a graduate in animal science from the Mato Grosso do Sul State University, in Brazil.


Fantini and her colleagues conducted a study funded by Brazil’s National Research Council- CNPq and the Federal University of Grande Dourados. The study was carried out using surubim (Pseudoplatystoma spp.), a South American catfish specie.

In aquaculture systems, fish are typically stocked at high densities. Activities associated with harvest, such as crowding and transport to the processing plant can result in stress from increased physical activity, according to the researchers.

Stress can cause fish metabolism to be anaerobic. This leads to a faster depletion in pH and early rigor mortis. This can cause problems because fish filleting can only be done when fish are in their pre- or post-rigor condition.

Early rigor mortis also results in more ruptures to muscle tissues that could lead to gaping, changes in flesh colour, reduced juiciness and softness. Early rigor mortis also reduces fish flesh capacity to hold water. This in turn, reduces shelf life of the product.

The shorter resting times (zero and two hours, more stressed fish) resulted in a faster establishment of rigor mortis, the study found.

Fish subjected to four  and eight hours of rest entered rigor mortis 3.5 hours after slaughter and these animals had muscle pH different in the measurement performed three hours after slaughter.

“The resting time of four to eight hours is effective to reestablish homeostasis after transporting surubim, which provides fillets with higher quality and greater length of the pre-rigor mortis period,” the study concluded.

For more on this study, click on this link.

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