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Correlations between successive measurements of myofibrillar resistance of raw Longissimus dorsi muscle during ageing
PII:
Mear Science, Vol. 49, No. 2, 249-254, 1998 0 1998 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0309-1740/98 $19.00+0.00
s0309-1740(97)00130-7
Correlations Between Successive Measurements of Myofibrillar Resistance of Raw Longissimus dorsi Muscle During Ageing J Lepetit* Station (Received
de Recherches
08 January
sur la viande,
1997; revised version
& C. Hamel INRA,
received
THEIX-63122
Ceyrat,
26 June 1997; accepted
France 03 November
1997)
ABSTRACT The feasibility of meat classtjication soon after rigor, based on an ageing criterion, was investigated with a view to obtain sets of regularly aged meat as well as to optimize storage. Muscle fibre resistance was measured on the m. longissimus dorsi of 45 heifers on days 1, 2, 8 and 14, and the resistance values obtained on d@erent days were correlated. Resistance on day 2 was predictive of about 65% of the variation observed on day 8, i.e. when the meat has reached approximately 92% of the tenderization recorded between days I and 14. In this study, the predictions based on day I resistance were less accurate because the baseline reference was too close to rigor. A class dejned at day 2 as the meat which has a resistance lower than 20 N cme2, will give fully aged meat at day 8. This class represent 52% of the initial population The various classes of meat, which reach full ageing at different times, can be despatched through variable length marketing circuits so as to achieve fulI ageing before getting to the consumers. 0 1998 Elsevier Science Ltd. AN rights reserved
INTRODUCTION rate of beef is particularly slow, which poses storage problems and their related economic consequences; but even more problematic is the fact that the tenderization rate varies considerably between animals. Meat is usually sold within 1 week and not all meats are fully aged at that time. As a result, consumers do not get constantly aged meat and the resultant tenderness variability adds to that associated with connective tissue. Reducing the tenderness variations linked to the ageing process is a step toward marketing meat of more constant quality. Different approaches can be investigated which would make it possible to market more aged meat. The tenderization
1. Ageing results from both enzymatic and non-enzymatic phenomena. Studies on these enzymatic (Koomaraie et al., 1988; Kendall et al., 1993; Dransfield et al., 1992; Dransfield et al., 1994; Geesink et al., 1994; Hortos et al., 1994) and non-enzymatic *To whom correspondence
should be addressed.
Tel: 73 62 4000; Fax: (3) 73 62 4089. 249
250
J Lepetit, C Hamel
(Takahashi et al., 1995) phenomena have provided some understanding of the effect of storage conditions on the mechanism of tenderization. But these studies have also shown that many variables are involved in the tenderization process (pH, ionic strength, temperature decrease after slaughter, enzyme and inhibitor levels and Ca++ level.). This raises the problem of ageing process predictability because of the degree of inaccuracy of all these variables. 2. Selecting animals with high tenderization rate may be another possible way to improve ageing. Indeed, calpastatin activity is highly inheritable (Shackelford et al., 1994). 3. Controlling the level of tenderization of meat by different means during early storage should be investigated as a way to classify meats. Fast-ageing meats would be directed toward short marketing circuits and slow-ageing meats toward longer marketing circuits. This would avoid long storage of already aged meat and would prevent marketing meat which is not fully aged. The feasibility of this approach was the purpose of this study. Several probes or methods for assessing the degree of meat tenderization have been described. Some are biochemical (MacBride and Parrish, 1977; Ouali, 1984; Yano et al., 1995), some are mechanical and directly measure the strength of the myofibrillar structure by tensile tests (Locker and Wild, 1982) or by compressive tests (Lepetit and Sale, 1985). Mechanical measurements of myofibrillar resistance are closely linked to the biochemical events that occur in the myofibrillar structure during ageing (Lepetit et al., 1986) and to variations of tenderness during ageing, as assessed by a panel (Touraille et al., 1990). MATERIALS
AND METHODS
This study involved 45 heifers (mean age 36months). Carcasses were chilled at a commercial slaughter house. The temperature at 2cm below the surface in the m. Longissimus dorsi was about 9°C at 10 hr post mortem. Twenty four hours after slaughter slices (4 cm thick) were obtained from m. Longissimus dorsi, vacuum packed and stored at 3 f 1°C These slices were frozen on the day after slaughter at 30 hr post mortem and on days 2,4, 8 and 14. Freezing was performed in an alcohol bath at -20°C. Under such conditions, freezing time is about 5min and ensures minimal structural degradation by ice crystals (Bevilacqua et al., 1979). The slices were then stored at -20°C and thawed in a water bath at 10°C before measurement. The resistance of myofibrillar structure was measured on raw meat by compression according to Lepetit and Sale (1985). With this method, muscle fibre resistance is approximately 40N cm-* when meat is in full rigor and 8N cm-* in aged meat. The measurements were performed on samples at room temperature. The values presented are the means of about 10 measurements. Sarcomere lengths have been determined by the laser diffraction method described by Cross et al. (1981) the day after slaughter. Means are obtained from 30 measurements. RESULTS The myofibrillar structure resistance curve during storage shows huge inter-animal variations (Fig. 1). This indicates that even when animals are selected according to those biological characteristics (young and female) which are known to have a positive influence on tenderization, that does not solve the problem of the variability of the tenderization rate. Some muscles reached the limit value of 8 N cm-* within 2 days post mortem while others did not reach this value even after 14 days.
Myojibrillar resistance of raw Longissimus
40T
dorsi muscle
251
A
35 --
0
1 0
I
2
4 Time
6 post-mortem
6
10 (days)
12
14
I
Fig. 1. Evolution of the resistance of Longissimus dorsi muscle fibres from 45 heifers during storage. The mean value of sarcomere length measured on the 45 animals is 184 & 0.09hm which means that cold shortening has been avoided. This slight contraction compared to the rest length value of about 2pm has no effect on meat toughness (Marsh and Leet, 1966) To evaluate the usefulness of a measurement at a definite time post mortem for predicting resistance at a later time, we correlated the resistance values measured at different times. The resistance measured on (i) days (i = 1, 2, 4, 8) was correlated with the resistance measured on (k) days (k > i; k = 2, 4, 8, 14). Two tests were used: Pearson’s and Spearman’s. The latter is the rank correlation and eliminates problems of non-linearity. According to Pearson’s correlation coefficient [Fig. 2(a)], a measurement made on day 1 (30hr post mortem) can predict about 650/ o ( r2-0.65) of the variation observed on day 2 and day 4 and about 50% of that observed on day 8. A measurement made on day 2 can predict about 80% of the variation observed on day 4 and 65% of the variation observed on day 8, i.e. when meat has reached about 92% of day 1 day 14 tenderization. These results demonstrate a close correlation between successive resistance values during ageing. Therefore early measurements can serve as predictors of further evolution of meat. The results obtained with Spearman’s correlation coefficient [Fig. 2(b)] were similar, which shows that there is no pronounced non linearity between the resistance values measured at different times post mortem. But with Spear-man’s coefficient the differences between predictions made at different times were smaller than with Pearson’s coefficient. For example, the prediction of the tenderization values after 8 days post mortem was the similar when computed from day 1, day 2 or day 4 values. This is because only a few curves crossed each other and so most retained the same order at the different times. There is an obvious trend for the correlation between resistance values measured at two different times post mortem to become weaker as the interval between these 2 times increases. But in this experiment we observed that the correlation between resistance values on day 1 and day 2, i.e. with a 1 day interval, was about O-8 for both types of tests, whereas the correlation between resistance values on day 2 and day 4, i.e. with a 2day interval, was stronger, in the order of 0.9. This can be because on day 1 some muscles have not reached full rigor. For a muscle not in full rigor on day 1, low resistance on day 1 will correspond to high resistance on day 2 and that will reduce the correlation coefficient
---5% J Lepetit, C Hamel
252 (a)
1 T
0.9
0.6 -0.7 --
-m-Resist.
0.6 --
Dayt
0.5 --
+
Resist. Day 2
0.4 --
~4
Resist. Day 4
t
Resist._Day 6
0.3 --
~
0.2 -0.1 -01
0
I
2
4
6
6
10
12
14
12
14
Time post - mortem (days)
0
2
4
6
ITime post-mortem
6
10 (days)1
Fig. 2. Correlation coefficients between resistance values measured at different times post mortem. Each curve represents the correlation coefficients between the resistance, noted in legend, and the resistance measured at different times post mortem, noted in the absciss.
between day 1 and day 2 resistances. So, when the industrial conditions are such that some muscles are still pre-rigor on day 1, it is preferable to make predictive measurements on day 2. Moreover, meat resistance varies rapidly very close to rigor, so that minor variations of the experimental conditions (time of measurement, temperature of the cold room) may induce wider variations in resistance values than if measurements are made at a later stage. Measurements made on day 2 can be used to define meat classes according to their level of tenderization. A class of meat can be defined as the group of meats which exhibits a day 2 value below a given threshold or as the group of meats whose day 2 resistance value is between two set limits. According to classes, different percentages of meats will be fully aged at the same time post mortem. To define the percentage of fully aged meats in each class we grouped the mean values of each class at each time post mortem, according to the test of Newman and Keuls (Snedecor and Cochran, 1957). The fully aged meats were defined as those whose resistance values were not significantly different from 8 N cm-2. Four thresholds were applied to the values obtained on day 2 (20, 25, 30, 45 N cm-*), which means, for example, in the first option (20N cm-*) that all the animals with day 2 resistance values below 20N cm-* were retained. The percentage of animals retained in
fvfyofbrihr
resistance of raw Longissimus
253
dorsi muscle
100
1 90
3
60
E m $a
60
70
z 8 g
50
40
g
30
n
20
10 0
0
2
4
6
6
10
12
14
Time post-mortem (days) Fig. 3. Percentage of aged meats vs time of storage when meats were selected on day 2. In the legend, 20 N cm-* refers to a group of animals whose resistance on day 2 was below 20 N cm-*. The values in bracket represent the percentage of animals in the population.
each case were respectively 52, 71, 91, and 100% of the original population. The percentage of aged meats in each class on each day are represented in Fig. 3. A day 2 selection of the muscles with resistance values below 20N cme2 will produce 100% fully aged meats on day 8, whereas only 70% of aged meats will be obtained if no threshold is applied.
CONCLUSION The inter-animal differences in tenderization observed during ageing are specially evident immediately after rigor. Therefore measuring muscle fibre resistance on the first days post mortem can help select meats that will be fully aged at a selected time of distribution or marketing. This would lead to better storage cost control and more constant meat quality. In this experiment, the optimal early prediction time was on day 2, although day 1 could be more appropriate depending on pre-rigor storage temperature and on the use of electrical stimulation.
ACKNOWLEDGEMENTS The authors wish to thank J. Canistro, A. Kerkeb and F. Gorce Bardag for technical assistance and Philip Rousseau-Cunningham for English proofreading and rewriting.
REFERENCES Bevilacqua, A., Zaritvky, N. E. and Calvelo, A. (1995) Histological measurements of ice in frozen beef. Journal of Food Technology 14,237-25 1. Cross, H. R., West, R. L. and Dutson, T. R. (1990) Comparison of methods for measuring sarcomere length in beef Semitendinosus muscle. Meat Science 5, 261-266.
254
J Lepetit,
C Hamel
Dransfield, E., Etherington, D. J. and Taylor, M. J. (1992) Modelling post-mortem tenderisationII: enzyme changes during storage of electrically stimulated and non stimulated beef. Meat Science, 31, 75-84. Dransfield, E. (1994) Modelling post-mortem tenderisation-V: inactivation of calapains. Meat Science 37, 391409. Geesink, G. H., Smulders, F. J. M. and Van Laack, R. L. J. M. (1994) The effect of calcium-, sodium- and zinc-chlorides treatment on the quality of beef. Sciences des Aliments 14,485502. Hortos, M., Gil, M. and Sarraga, C. (1994) Effect of calpain and cathepsin activities on myofibrils from porcine Iongissimus muscle during conditioning of normal and exudative meat. Sciences des Aliments. 14, 503-515. Kendall, T. L., Koomaraie, M., Arbona, J. R., Williams, S. E. and Young, L. L. (1993) Effect of pH and ionic strength on bovine m-calpain and calpastatin activity. Journal of Animal Science 71, 96104. Koomaraie, M., Babiker, A. S., Merkel, R. A. and Dutson, T. R. (1988) Role of Ca+ +-dependent proteases and lysosomal enzymes in post-mortem changes in bovine skeletal muscle. Journal of Food Science 53, 1253-1257. Lepetit, J. and Sale, P. (1985) Analyse du comportement rhtologique de la viande par une methode de compression sinusoidale. Sciences des Aliments 5, 521-540. Lepetit, J., Sale, P. and Ouali, A. (1986) Post-mortem evolution of Rheological properties of the myofibrillar structure. Meat Science 16, 161-174. Locker, R. H. and Wild, D. J. C. (1982) A machine for measuring yield point in raw meat. Meat Science 13, 71-82. MacBride, M. A. and Parrish, F. C. (1977) The 30 000 dalton component of tender bovine Zongissimus muscle. Journal of Food Science 42, 162771629. Marsh, B. B. and Leet, N. G. (1966) Studies in meat tenderness. III. The effect of shortening on tenderness. Journal of Food Science 31,450-459. Ouali, A. (1984) Sensitivity to ionic strength of Mg-Ca Enhanced ATPase activity as an index of myofibrillar ageing of meat. Meat Science 11, 79-88. Shackelford, S. D., Koohmaraie, M., Cundiff, L. V., Gregory, K. E., Rohrer, G. A. and Sawell, J. W. (1994). Heritabilities and phenotypic and genetic correlations for bovine post-rigor calpastatin activity, intramuscular fat content, Warner-Bratzler shear force, retail product yield, and growth rate. Journal of Animal Science 72, 857-863. Snedcor, G. W. and Cochran, W. G (1957) Statistical Methods. 6th edition. Iowa State University Press. Ames, Iowa, USA. Takahashi, K., Hattori, A. and Kuroyanagi, H. (1995) Relationship between the translocation of paratropomyosin and the restoration of rigor-shortened sarcomeres during post-mortem ageing of meat-a molecular mechanism of meat tenderization. Meat Science 40, 413423. Touraille, C., Aurier, B., Lepetit, J. and Bayle, M. C. (1990) Maturation de la viande bovine:evaluation par des methodes mecaniques et sensorielles et par des consommateurs. Viande et Produits Carries. 11, 291-292. Yano, Y., Kataho, N., Watanabe, M., Nakamura, T. and Asano, Y. (1995) Evaluation of beef aging by determination of hypoxanthine and xanthine contents:application of a xanthine sensor. Food Chemistry 52, 439445.
Mear Science, Vol. 49, No. 2, 249-254, 1998 0 1998 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0309-1740/98 $19.00+0.00
s0309-1740(97)00130-7
Correlations Between Successive Measurements of Myofibrillar Resistance of Raw Longissimus dorsi Muscle During Ageing J Lepetit* Station (Received
de Recherches
08 January
sur la viande,
1997; revised version
& C. Hamel INRA,
received
THEIX-63122
Ceyrat,
26 June 1997; accepted
France 03 November
1997)
ABSTRACT The feasibility of meat classtjication soon after rigor, based on an ageing criterion, was investigated with a view to obtain sets of regularly aged meat as well as to optimize storage. Muscle fibre resistance was measured on the m. longissimus dorsi of 45 heifers on days 1, 2, 8 and 14, and the resistance values obtained on d@erent days were correlated. Resistance on day 2 was predictive of about 65% of the variation observed on day 8, i.e. when the meat has reached approximately 92% of the tenderization recorded between days I and 14. In this study, the predictions based on day I resistance were less accurate because the baseline reference was too close to rigor. A class dejned at day 2 as the meat which has a resistance lower than 20 N cme2, will give fully aged meat at day 8. This class represent 52% of the initial population The various classes of meat, which reach full ageing at different times, can be despatched through variable length marketing circuits so as to achieve fulI ageing before getting to the consumers. 0 1998 Elsevier Science Ltd. AN rights reserved
INTRODUCTION rate of beef is particularly slow, which poses storage problems and their related economic consequences; but even more problematic is the fact that the tenderization rate varies considerably between animals. Meat is usually sold within 1 week and not all meats are fully aged at that time. As a result, consumers do not get constantly aged meat and the resultant tenderness variability adds to that associated with connective tissue. Reducing the tenderness variations linked to the ageing process is a step toward marketing meat of more constant quality. Different approaches can be investigated which would make it possible to market more aged meat. The tenderization
1. Ageing results from both enzymatic and non-enzymatic phenomena. Studies on these enzymatic (Koomaraie et al., 1988; Kendall et al., 1993; Dransfield et al., 1992; Dransfield et al., 1994; Geesink et al., 1994; Hortos et al., 1994) and non-enzymatic *To whom correspondence
should be addressed.
Tel: 73 62 4000; Fax: (3) 73 62 4089. 249
250
J Lepetit, C Hamel
(Takahashi et al., 1995) phenomena have provided some understanding of the effect of storage conditions on the mechanism of tenderization. But these studies have also shown that many variables are involved in the tenderization process (pH, ionic strength, temperature decrease after slaughter, enzyme and inhibitor levels and Ca++ level.). This raises the problem of ageing process predictability because of the degree of inaccuracy of all these variables. 2. Selecting animals with high tenderization rate may be another possible way to improve ageing. Indeed, calpastatin activity is highly inheritable (Shackelford et al., 1994). 3. Controlling the level of tenderization of meat by different means during early storage should be investigated as a way to classify meats. Fast-ageing meats would be directed toward short marketing circuits and slow-ageing meats toward longer marketing circuits. This would avoid long storage of already aged meat and would prevent marketing meat which is not fully aged. The feasibility of this approach was the purpose of this study. Several probes or methods for assessing the degree of meat tenderization have been described. Some are biochemical (MacBride and Parrish, 1977; Ouali, 1984; Yano et al., 1995), some are mechanical and directly measure the strength of the myofibrillar structure by tensile tests (Locker and Wild, 1982) or by compressive tests (Lepetit and Sale, 1985). Mechanical measurements of myofibrillar resistance are closely linked to the biochemical events that occur in the myofibrillar structure during ageing (Lepetit et al., 1986) and to variations of tenderness during ageing, as assessed by a panel (Touraille et al., 1990). MATERIALS
AND METHODS
This study involved 45 heifers (mean age 36months). Carcasses were chilled at a commercial slaughter house. The temperature at 2cm below the surface in the m. Longissimus dorsi was about 9°C at 10 hr post mortem. Twenty four hours after slaughter slices (4 cm thick) were obtained from m. Longissimus dorsi, vacuum packed and stored at 3 f 1°C These slices were frozen on the day after slaughter at 30 hr post mortem and on days 2,4, 8 and 14. Freezing was performed in an alcohol bath at -20°C. Under such conditions, freezing time is about 5min and ensures minimal structural degradation by ice crystals (Bevilacqua et al., 1979). The slices were then stored at -20°C and thawed in a water bath at 10°C before measurement. The resistance of myofibrillar structure was measured on raw meat by compression according to Lepetit and Sale (1985). With this method, muscle fibre resistance is approximately 40N cm-* when meat is in full rigor and 8N cm-* in aged meat. The measurements were performed on samples at room temperature. The values presented are the means of about 10 measurements. Sarcomere lengths have been determined by the laser diffraction method described by Cross et al. (1981) the day after slaughter. Means are obtained from 30 measurements. RESULTS The myofibrillar structure resistance curve during storage shows huge inter-animal variations (Fig. 1). This indicates that even when animals are selected according to those biological characteristics (young and female) which are known to have a positive influence on tenderization, that does not solve the problem of the variability of the tenderization rate. Some muscles reached the limit value of 8 N cm-* within 2 days post mortem while others did not reach this value even after 14 days.
Myojibrillar resistance of raw Longissimus
40T
dorsi muscle
251
A
35 --
0
1 0
I
2
4 Time
6 post-mortem
6
10 (days)
12
14
I
Fig. 1. Evolution of the resistance of Longissimus dorsi muscle fibres from 45 heifers during storage. The mean value of sarcomere length measured on the 45 animals is 184 & 0.09hm which means that cold shortening has been avoided. This slight contraction compared to the rest length value of about 2pm has no effect on meat toughness (Marsh and Leet, 1966) To evaluate the usefulness of a measurement at a definite time post mortem for predicting resistance at a later time, we correlated the resistance values measured at different times. The resistance measured on (i) days (i = 1, 2, 4, 8) was correlated with the resistance measured on (k) days (k > i; k = 2, 4, 8, 14). Two tests were used: Pearson’s and Spearman’s. The latter is the rank correlation and eliminates problems of non-linearity. According to Pearson’s correlation coefficient [Fig. 2(a)], a measurement made on day 1 (30hr post mortem) can predict about 650/ o ( r2-0.65) of the variation observed on day 2 and day 4 and about 50% of that observed on day 8. A measurement made on day 2 can predict about 80% of the variation observed on day 4 and 65% of the variation observed on day 8, i.e. when meat has reached about 92% of day 1 day 14 tenderization. These results demonstrate a close correlation between successive resistance values during ageing. Therefore early measurements can serve as predictors of further evolution of meat. The results obtained with Spearman’s correlation coefficient [Fig. 2(b)] were similar, which shows that there is no pronounced non linearity between the resistance values measured at different times post mortem. But with Spear-man’s coefficient the differences between predictions made at different times were smaller than with Pearson’s coefficient. For example, the prediction of the tenderization values after 8 days post mortem was the similar when computed from day 1, day 2 or day 4 values. This is because only a few curves crossed each other and so most retained the same order at the different times. There is an obvious trend for the correlation between resistance values measured at two different times post mortem to become weaker as the interval between these 2 times increases. But in this experiment we observed that the correlation between resistance values on day 1 and day 2, i.e. with a 1 day interval, was about O-8 for both types of tests, whereas the correlation between resistance values on day 2 and day 4, i.e. with a 2day interval, was stronger, in the order of 0.9. This can be because on day 1 some muscles have not reached full rigor. For a muscle not in full rigor on day 1, low resistance on day 1 will correspond to high resistance on day 2 and that will reduce the correlation coefficient
---5% J Lepetit, C Hamel
252 (a)
1 T
0.9
0.6 -0.7 --
-m-Resist.
0.6 --
Dayt
0.5 --
+
Resist. Day 2
0.4 --
~4
Resist. Day 4
t
Resist._Day 6
0.3 --
~
0.2 -0.1 -01
0
I
2
4
6
6
10
12
14
12
14
Time post - mortem (days)
0
2
4
6
ITime post-mortem
6
10 (days)1
Fig. 2. Correlation coefficients between resistance values measured at different times post mortem. Each curve represents the correlation coefficients between the resistance, noted in legend, and the resistance measured at different times post mortem, noted in the absciss.
between day 1 and day 2 resistances. So, when the industrial conditions are such that some muscles are still pre-rigor on day 1, it is preferable to make predictive measurements on day 2. Moreover, meat resistance varies rapidly very close to rigor, so that minor variations of the experimental conditions (time of measurement, temperature of the cold room) may induce wider variations in resistance values than if measurements are made at a later stage. Measurements made on day 2 can be used to define meat classes according to their level of tenderization. A class of meat can be defined as the group of meats which exhibits a day 2 value below a given threshold or as the group of meats whose day 2 resistance value is between two set limits. According to classes, different percentages of meats will be fully aged at the same time post mortem. To define the percentage of fully aged meats in each class we grouped the mean values of each class at each time post mortem, according to the test of Newman and Keuls (Snedecor and Cochran, 1957). The fully aged meats were defined as those whose resistance values were not significantly different from 8 N cm-2. Four thresholds were applied to the values obtained on day 2 (20, 25, 30, 45 N cm-*), which means, for example, in the first option (20N cm-*) that all the animals with day 2 resistance values below 20N cm-* were retained. The percentage of animals retained in
fvfyofbrihr
resistance of raw Longissimus
253
dorsi muscle
100
1 90
3
60
E m $a
60
70
z 8 g
50
40
g
30
n
20
10 0
0
2
4
6
6
10
12
14
Time post-mortem (days) Fig. 3. Percentage of aged meats vs time of storage when meats were selected on day 2. In the legend, 20 N cm-* refers to a group of animals whose resistance on day 2 was below 20 N cm-*. The values in bracket represent the percentage of animals in the population.
each case were respectively 52, 71, 91, and 100% of the original population. The percentage of aged meats in each class on each day are represented in Fig. 3. A day 2 selection of the muscles with resistance values below 20N cme2 will produce 100% fully aged meats on day 8, whereas only 70% of aged meats will be obtained if no threshold is applied.
CONCLUSION The inter-animal differences in tenderization observed during ageing are specially evident immediately after rigor. Therefore measuring muscle fibre resistance on the first days post mortem can help select meats that will be fully aged at a selected time of distribution or marketing. This would lead to better storage cost control and more constant meat quality. In this experiment, the optimal early prediction time was on day 2, although day 1 could be more appropriate depending on pre-rigor storage temperature and on the use of electrical stimulation.
ACKNOWLEDGEMENTS The authors wish to thank J. Canistro, A. Kerkeb and F. Gorce Bardag for technical assistance and Philip Rousseau-Cunningham for English proofreading and rewriting.
REFERENCES Bevilacqua, A., Zaritvky, N. E. and Calvelo, A. (1995) Histological measurements of ice in frozen beef. Journal of Food Technology 14,237-25 1. Cross, H. R., West, R. L. and Dutson, T. R. (1990) Comparison of methods for measuring sarcomere length in beef Semitendinosus muscle. Meat Science 5, 261-266.
254
J Lepetit,
C Hamel
Dransfield, E., Etherington, D. J. and Taylor, M. J. (1992) Modelling post-mortem tenderisationII: enzyme changes during storage of electrically stimulated and non stimulated beef. Meat Science, 31, 75-84. Dransfield, E. (1994) Modelling post-mortem tenderisation-V: inactivation of calapains. Meat Science 37, 391409. Geesink, G. H., Smulders, F. J. M. and Van Laack, R. L. J. M. (1994) The effect of calcium-, sodium- and zinc-chlorides treatment on the quality of beef. Sciences des Aliments 14,485502. Hortos, M., Gil, M. and Sarraga, C. (1994) Effect of calpain and cathepsin activities on myofibrils from porcine Iongissimus muscle during conditioning of normal and exudative meat. Sciences des Aliments. 14, 503-515. Kendall, T. L., Koomaraie, M., Arbona, J. R., Williams, S. E. and Young, L. L. (1993) Effect of pH and ionic strength on bovine m-calpain and calpastatin activity. Journal of Animal Science 71, 96104. Koomaraie, M., Babiker, A. S., Merkel, R. A. and Dutson, T. R. (1988) Role of Ca+ +-dependent proteases and lysosomal enzymes in post-mortem changes in bovine skeletal muscle. Journal of Food Science 53, 1253-1257. Lepetit, J. and Sale, P. (1985) Analyse du comportement rhtologique de la viande par une methode de compression sinusoidale. Sciences des Aliments 5, 521-540. Lepetit, J., Sale, P. and Ouali, A. (1986) Post-mortem evolution of Rheological properties of the myofibrillar structure. Meat Science 16, 161-174. Locker, R. H. and Wild, D. J. C. (1982) A machine for measuring yield point in raw meat. Meat Science 13, 71-82. MacBride, M. A. and Parrish, F. C. (1977) The 30 000 dalton component of tender bovine Zongissimus muscle. Journal of Food Science 42, 162771629. Marsh, B. B. and Leet, N. G. (1966) Studies in meat tenderness. III. The effect of shortening on tenderness. Journal of Food Science 31,450-459. Ouali, A. (1984) Sensitivity to ionic strength of Mg-Ca Enhanced ATPase activity as an index of myofibrillar ageing of meat. Meat Science 11, 79-88. Shackelford, S. D., Koohmaraie, M., Cundiff, L. V., Gregory, K. E., Rohrer, G. A. and Sawell, J. W. (1994). Heritabilities and phenotypic and genetic correlations for bovine post-rigor calpastatin activity, intramuscular fat content, Warner-Bratzler shear force, retail product yield, and growth rate. Journal of Animal Science 72, 857-863. Snedcor, G. W. and Cochran, W. G (1957) Statistical Methods. 6th edition. Iowa State University Press. Ames, Iowa, USA. Takahashi, K., Hattori, A. and Kuroyanagi, H. (1995) Relationship between the translocation of paratropomyosin and the restoration of rigor-shortened sarcomeres during post-mortem ageing of meat-a molecular mechanism of meat tenderization. Meat Science 40, 413423. Touraille, C., Aurier, B., Lepetit, J. and Bayle, M. C. (1990) Maturation de la viande bovine:evaluation par des methodes mecaniques et sensorielles et par des consommateurs. Viande et Produits Carries. 11, 291-292. Yano, Y., Kataho, N., Watanabe, M., Nakamura, T. and Asano, Y. (1995) Evaluation of beef aging by determination of hypoxanthine and xanthine contents:application of a xanthine sensor. Food Chemistry 52, 439445.