Carbon dioxide stunning boosts pork tenderness by reshaping muscle cell pathways

By examining energy metabolism, muscle fiber structure, and protease activity, researchers found that CO₂ stunning alleviates stress, preserves ATP, and promotes apoptosis—a programmed cell death that activates tenderizing enzymes—leading to consistently more tender meat.

Tenderness is one of the most critical quality attributes determining consumer acceptance of pork, yet pre-slaughter handling and stunning techniques can profoundly alter meat properties. Stunning ensures animals are insensible before slaughter, minimizing pain and facilitating processing. Electrical stunning (ES) remains widely used but often induces intense muscle convulsions, accelerating glycogen depletion, lactic acid accumulation, and pH decline—conditions that can lead to pale, soft, exudative (PSE) meat. This compromises tenderness, water-holding capacity, and overall value. Carbon dioxide stunning (CS), by contrast, induces unconsciousness through cerebral acidosis and avoids physical trauma, but infrastructure costs have slowed adoption in some regions. Despite promising results, the cellular mechanisms by which stunning influences postmortem meat quality have remained unclear. Addressing this knowledge gap is critical for improving meat consistency and reducing industry losses.

A study (DOI: 10.48130/fmr-0025-0011) published in Food Materials Research on 31 July 2025 by Chunbao Li’s team, Nanjing Agricultural University, provides fresh insight into the biological mechanisms connecting stunning methods to pork quality.

In this study, researchers employed a comparative experimental approach to examine how ES and CS influence postmortem muscle physiology and meat quality in pigs. Serum indicators of stress, biochemical composition, histological changes, and modes of muscle cell death were systematically analyzed. The findings revealed that ES induced markedly higher serum cortisol and lactate levels compared to CS, reflecting greater pre-slaughter stress due to convulsions and intense muscle activity. This heightened stress accelerated anaerobic glycolysis, leading to rapid glycogen and ATP depletion, lactic acid accumulation, and a faster decline in pH, ultimately causing protein denaturation, impaired water-holding capacity, and paler meat. In contrast, CS preserved higher ATP and glycogen levels and reduced lactate accumulation, resulting in more favorable pH dynamics and improved tenderness. Microscopic evaluation showed that ES produced densely packed muscle fibers at early postmortem stages, while CS maintained larger intercellular spaces and a higher myofibrillar fragmentation index, both of which correlate with better tenderness. Moreover, apoptosis was predominant in CS samples, with increased caspase-3 activity supporting proteolysis and tenderization, whereas ES promoted necroptosis under energy-depleted conditions, limiting these benefits. Supplementing ES pork with ATP improved tenderness by reactivating apoptotic pathways and increasing protease activity, underscoring ATP’s central role in determining cell death mode and meat quality. Together, these results confirm that CS reduces stress, promotes apoptosis-driven proteolysis, and yields consistently superior pork quality compared to ES.

This study provides compelling evidence that CO₂ stunning improves pork tenderness by promoting apoptosis-driven protease activity and moderating stress-induced biochemical disruptions. For meat producers, adopting CS could reduce the incidence of PSE pork, enhance consumer satisfaction, and improve processing efficiency. Beyond immediate industry benefits, the findings introduce a novel conceptual framework: postmortem meat quality can be actively managed through control of muscle cell death modes. Interventions that sustain ATP levels—such as dietary creatine supplementation or postmortem ATP treatment—may further optimize tenderness outcomes. These insights could help standardize stunning practices globally and guide innovations in animal welfare and meat science.

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References

DOI

10.48130/fmr-0025-0011

Original Source URL

https://doi.org/10.48130/fmr-0025-0011

Funding information

This study was funded by the Jiangsu Agriculture Science and Technology Innovation Fund (Grant Nos JASTIF, CX(22)2046), the Ministry of Finance, and the Ministry of Agriculture and Rural Affairs (Grant No. CARS-35).

About Food Materials Research

The open-access journal Food Materials Research (e-ISSN 2771-4683) is published by Maximum Academic Press in partnership with Nanjing Agricultural University. The article types include original research papers, reviews, methods, editorials, short communications, and perspectives. All articles published in Food Materials Research represent significant advances in the genetic, molecular, biochemical, physiological processes and pathways related to food materials and sources and will provide scientific information towards overcoming technological limitations in developing conventional and alternative foods.