How Slaughter Methods Affect Grouper Quality and Freshness During Cold Storage

Greg Howard
12th September, 2024

How Slaughter Methods Affect Grouper Quality and Freshness During Cold Storage

Image Source: Natural Science News, 2024

Key Findings

  • The study by Shanghai Ocean University found that gradient cooling (M5) is the best method for slaughtering groupers, causing the least stress and oxidative damage
  • Gradient cooling (M5) resulted in the highest activity of the SDH enzyme, indicating better energy metabolism in the fish
  • Fish slaughtered by gradient cooling (M5) had superior flesh quality, with better texture, pH, and lower levels of TVB-N and TBA
The aquatic processing industry is increasingly focused on ensuring that fish are slaughtered under high welfare standards. This shift aims to address both ethical concerns and the quality of fish flesh post-slaughter. A recent study by Shanghai Ocean University[1] investigated the effects of various slaughtering methods on the energy metabolism, apoptosis (programmed cell death), and flesh quality in grouper (Epinephelus fuscoguttatus). The study assessed five different slaughtering methods: M1 (lethality by hammering), M2 (gas mixture causing death), M3 (lethality by clove oil anesthesia + ice slurry), M4 (lethality by ice slurry), and M5 (lethality by gradient cooling). A total of 120 groupers were used, with 24 fish per treatment group. The results indicated that gradient cooling (M5) led to the least oxidative damage and apoptosis, suggesting it may be the most effective method for maintaining fish welfare and flesh quality. One key finding was that the succinate dehydrogenase (SDH) enzyme activity was highest in the M5 group. SDH is an enzyme involved in the energy production process within cells, and higher activity indicates better energy metabolism. Conversely, the M2 group, subjected to a gas mixture, showed the highest serum glucose levels and DAPI staining fluorescence, both markers of stress response. This suggests that the gas mixture method induces significant stress in the fish. The study also measured various indicators of flesh quality, including texture, pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), and K value. The M5 samples consistently showed better results across these metrics, indicating superior flesh quality. These findings are consistent with earlier studies that highlighted the importance of minimizing pre-mortem stress to maintain fish flesh quality[2]. Previous research has shown that handling and stunning methods significantly impact fish welfare. For instance, a study on seabream and seabass found that hypothermia-based stunning methods, although common, are not entirely adequate due to the delayed onset of unconsciousness[3]. This aligns with the current study's finding that gradient cooling, which likely induces unconsciousness more rapidly, results in better outcomes. Moreover, the study's conclusion that gradient cooling has the least effect on antioxidant enzyme activities is significant. Antioxidant enzymes play a crucial role in protecting cells from oxidative damage, which can degrade flesh quality over time. This finding ties in with research on the effects of various coatings on fish flesh preservation, which also emphasized the importance of minimizing oxidative damage to maintain quality during storage[4]. The study by Shanghai Ocean University provides valuable insights into how different slaughtering methods affect grouper welfare and flesh quality. By demonstrating that gradient cooling is the most effective method, it offers a potential solution to the industry's challenge of balancing welfare standards with product quality. This research builds on previous findings by providing concrete evidence that less stressful slaughtering methods lead to better outcomes, both ethically and commercially.

BiochemAnimal ScienceMarine Biology

References

Main Study

1) Effects of different slaughtering methods on the energy metabolism, apoptosis process and quality of grouper (Epinephelus fuscoguttatus) during cold storage at 4 °C.

Published 11th September, 2024

https://doi.org/10.1002/jsfa.13862

Related Studies

2) Pre-mortem stress and the subsequent effect on flesh quality of pre-rigor filleted Atlantic salmon (Salmo salar L.) during ice storage.

https://doi.org/10.1016/j.foodchem.2014.11.111

3) Twenty Years of Research in Seabass and Seabream Welfare during Slaughter.

https://doi.org/10.3390/ani11082164

4) Multifunctional bioactive coatings based on water-soluble chitosan with pomegranate peel extract for fish flesh preservation.

https://doi.org/10.1016/j.foodchem.2021.131619


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