Dr Larissa Balakireva, CEO & Founder of NovoCIB, was awarded with the Trophy of
"Femmes en Or 2011, Femme de l'Innovation"
in September 2011

Texture and Water Holding Capacity of fish muscle are of major importance for commercial value and consumer acceptance of raw and smoked salmon. Fish welfare during harvesting and slaughter has also received increasing a lot of attention during last decade. All these parameters are closely related to the rate of postmortem ATP hydriolysis in fish muscle and can be quantified with PRECICE® Nucleotide Assay Kit.

ATP breakdown in post mortem muscle

As soon as respiration stops, metabolically active muscle continue de hydrolyse ATP, and in early post mortem ATP pool is maintained due to creatine kinase reaction. Once phosphocreatine has been degraded, muscle glycogenolysis is used to to rephosphorylate ADP to ATP with glycogen being metabolized through anaerobic glycolysis. The breakdown of ATP results in ADP, which is utilized by the adenylate kinase reaction for ATP and AMP formation. AMP is deaminated to inosine monophosphate (IMP), which accumulates in postmortem muscle. The pre-slaughtering stress and exercise encountered before death provoke fast depeletion of glycogen stored in fish muscle. Since glycolysis is required to slow the rate of ATP breakdown, in its absence, ATP is degraded too fast.

Measuring nucleotides to detect stress and texture problems

The concentration of IMP in fish muscle is maximal at the beginning of rigor when the totality of ATP is breaken down. Once released, IMP starts to be hydrolyzed by fish autolytic enzymes. Too fast post mortem ATP breakdown due to the stress and early release of IMP results in advanced IMP degradation and low IMP content.

Erikson* and co-authors have reported that K values of baseline and stressed farmed Atlantic salmon (Salmo salar) were 18% and 38% after 2 days postmortem, corresponding to 82% of IMP and 62% of IMP. According to authors, "the main benefits of reducing pre-slaughtering stress might not be the slight enhancement of freshness but the improved texture properties of the muscle. Also pre-rigor period remained much longer (about 20h) when handling stress was eliminated". Indeed, it has been documented that accelerated ATP breakdown leads to pH drop and to release of cathepsin that hydrolyzes muscle connective tissue and provokes muscle softening. As another a consequence of pH drops, the net surface charge on muscle proteins is reduced whish results in loss of their water-holding capacity.

PRECICE® Nucleotide Assay Kit allows easy measurement of IMP, inosine and hypoxanthine concentration in fish muscle.

Effect of stress on salmon nucleotides

Low IMP measured between day 3 and day 5 after slaughtering results from too fast ATP breakdown and indicates harvest stress or inappropriate storage temperature.
High IMP indicates low pre-slaughtering stress.

PRECICE® Nucleotide Assay Kit is first quantitative spectrophotometric assay for measuring the rate of ATP degradation through estimation of relative content of IMP in fish and meat muscle. This assay developed in convenient microplate format offers the opportunity for rapid caracterisation of ATP degradation rate in wide range of fish species and at various conditions. The kit is also available in spectrophotometer version.

1.England EM, Scheffler TL, Kasten SC, Matarneh SK, Gerrard DE. (2013) Exploring the unknowns involved in the transformation of muscle to meat. Meat Sci. 2013 Dec;95(4):837-43
2. Thomas Larsson, Turid Mørkøre, Kari Kolstad, Tone-Kari Østbye, Sergey Afanasyev, and Aleksei Krasnov Gene Expression Profiling of Soft and Firm Atlantic Salmon Fillet PLoS One. 2012; 7(6): e39219
3. U. ERIKSON, A.R. BEYER andT. SIGHOLT Muscle High-Energy Phosphates and Stress Affect K-Values during Ice Storage of Atlantic Salmon (Salmo salar) Journal of Food Science (1997), v 62, pp. 43-47.

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