Article pp.89-92 du Vol.23 n°1 (2003)

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SCIENCES DES ALIMENTS, 23(2003) 89-92

FOCUS : JSMTV

Proteomic analysis of destructured pork muscle

T. Sayd, E. Laville, V. Santé, G. Monin¹

INTRODUCTION

In pork meat, defect of destructuration is localised in deep region of ham muscles. It presents some characteristics comparable to “PSE” meat defect:

exudation, discolouration, myofibrillar fragmentation, and increase of extracellu- lar space. Genetic factors (Halothane sensitivity gene) or environmental condi- tions (stress before and during slaughter) are known to favour development of such a defect (Franck et al., 2000, 2002), but underlying biochemical and phy- siological mechanisms are not determined.

Muscle proteins separation according to 2 dimensions (isoelectrical point and molecular weight) is well suited for the simultaneous study of expression of a great number of proteins. In the present study we intended to identify molecular changes associated with muscle destructuration. Electrophoretic profiles of normal and defective zones of a same muscle were compared. The objective of this preliminary study was to appreciate the interest of 2-dimensional electrophoresis applied to the study of destructured meat.

METHODS

Ham semimembranosus muscles of experimental pigs (see communication of Laville et al) were sampled 24h post mortem, in normal and destructured zones. Histochemical slices were stained with hematoxyline-eosine-saffran.

Analysis of protein solubility according to the method of Joo et al. (1999) and 2- dimensional muscle protein electrophoresis were performed. Isoelectrofocalisa- tion was conducted in a non-linear pH 3-10 gradient (Bio-Rad, 17 cm). The second dimension was performed on SDS-PAGE 11% acrylamide gels.

1. Station de Recherches sur la Viande, INRA, 63122 Saint-Genès Champanelle.

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90 Sci. Aliments 23(1), 2003 T. Sayd et al.

RESULTS

Histochemical slices showed characteristics of destructuration comparable to those described in literature (Franck et al., 1999; Minvielle et al., 2001 and the communication of Labas et al.). They permitted to verify the stage of lesions in samples (Figure 1). In destructured zones, proteins solubility was reduced (figure 2), confirming resemblance with PSE meat. The figure 3 shows electrophoretic profiles of the normal and the destructured zones, in a same muscle.

Many spots distributed on the pH 3-10 gradient and a 5 to 200 kDa scale of molecular weights were observed. Differences of intensity of spots were observed (figure 2, encircled zones). We observed new and more coloured proteins in destructured zone.

Figure 1

Histochemical slices of semimembranosus muscle 24 h post mortem

Figure 2 Protein solubility 110

90 70 50 30 10

–10 Destructured Normal

mg/g muscle

adductor

semi membranosus

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Proteomic analysis of destructured pork muscle 91

Figure 3

2D electrophoretic gels of semimembranosus muscle at 24 hours post mortem Differences of protein solubility between the two zones indicate that protein denaturation probably occurred post mortem as it is currently observed in PSE meat. Because they are less extractible, denaturated proteins could contribute to differences of electrophoretic profiles.

At 24 hours post mortem proteolysis has began in normal muscle. In destructured state, proteolysis may be modified as it is observed in PSE meat.

Increase of spots number and intensity in destructured meat suggest an accele- ration of proteolysis. Control muscles sampled just after slaughter are required to study effects of proteolysis on electrophoretic profiles.

CONCLUSIONS AND PERSPECTIVES

These observations are preliminary, they will be confirmed on more samples.

The next stage will consist in identification of proteins or fragments with mass spectrometry. This approach will provide information on mechanisms of defect initiation and will permit to identify molecular markers of the defect.

IPG3 - 10 NL SDS PAGE

Destructured zone Normal zone

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92 Sci. Aliments 23(1), 2003 T. Sayd et al.

REFERENCES

FRANCK M., BÉNARD G., FERNANDEZ X., BARBRY S., DURAND P., LAGANT H., MONIN G., LEGAULT C., 1999. J. Rech.

Porcine France, 31, 331-338.

FRANCK M., MONIN G., LEGAULT, C., 2000.

J. Rech. Porcine en France, 32, 345-350.

FRANCK M., SVENSSON G., VON SETH G., JOSELL A., FIGWER P., POIREL M.T., MONIN G., 2002. Meat Sci., in press.

JOO S., KAUFFMAN R., KIM B., PARK G., 1999. Meat Sci. 52: 291-297.

MINVIELLE B., LE STRAT P., LE BRET B., HOUIX Y., BOULARD J., CLOCHEFERT N., 2001. Rech. Porcine France, 33, 95- 101.

This study was realised as part of the programme AQS 00 P0577 of Research Agency “Approches explicatives, diagnostique et préventive des vian- des déstructurées dans la filière porcine” in collaboration with ITP, CTSCCV and ENV-Lyon (scientific co-ordinator Gabriel Monin, INRA).