Thermal gelation of brown trout crude myofibrils and myofibrillar proteins from white and red muscles
Florence LEFÈVRE1 *, Marta GIL2, Benoit FAUCONNEAU1, Joseph CULIOLI3, Ahmed OUALI3
RÉSUMÉ Thermogélification des myofibrilles et des protéines myofibrillaires des muscles blanc et rouge de truite fario.
Les propriétés thermogélifiantes des myofibrilles et des protéines myofibril- laires (solubles en présence de sels) des muscles blanc et rouge de truite fario ont été suivies par analyse rhéologique. Le comportement rhéologique des protéines myofibrillaires est similaire à celui des myofibrilles quel que soit le type musculaire. Pour les myofibrilles comme pour les protéines myofibrillaires, des gels plus rigides ont été observés pour des valeurs basses de pH (5,6 par rapport à 6,0) et à faible forte ionique (0,2 M par rapport à 0,6 M KCl). Les interactions entre les myofibrilles ou entre les protéines myofibrillaires appa- raissent pour le muscle blanc à des températures plus basses (à partir de 20 °C) que pour le muscle rouge. Néanmoins les gels formés après un chauf- fage graduel jusqu’à 80 °C présentent une rigidité et une élasticité équivalente pour les deux types musculaires.
Mots clé : propriétés thermogélifiantes, protéines myofibrillaires, salmonidés, type musculaire, truite fario.
SUMMARY
Heat-induced gelation properties of brown trout crude myofibrils and of myofi- brillar proteins (salt soluble) from white and red muscles were analysed by ther- mal scanning rheometry. Rheological characteristics of myofibrillar protein were similar to those of myofibrils, regardless of the muscle type. For both myofibrils and myofibrillar protein, stronger gels were observed at low pH values (5.6 vs. 6.0) and low ionic strength (0.2 M vs. 0.6 M KCl). Interaction of
1 Station commune de recherches en ictyophysiologie, Biodiversité et environnement, Institut national de la recherche agronomique, Campus de Beaulieu, 35042 Rennes cedex, France.
2 Institut de Recerca i Tecnologia Agroalimentaries, Centre de Tecnologia de la Carn, Granja Camps y Armet, 17121 Monells, Girona, Spain.
3 Station de recherches sur la viande, Institut national de la recherche agronomique de Theix, 63122 St- Genès Champanelle, France.
* Correspondence
myofibrillar proteins and that of myofibrils occurred at lower temperatures in white muscle (starting at 20°C) than in red muscle. Gels observed after gradual heating to 80°C were equally strong and elastic for both muscle types.
Key-words: heat-induced gelation, myofibrillar protein, salmonid, muscle type, brown trout.
1 - INTRODUCTION
Heat-induced gelation is one of the main functional properties of muscle proteins. It is assumed to be involved in lipid and water holding capacity and in texture of meat and fish products (HAN-CHING, 1984; ASGHAR, 1985; SMITH, 1988). Many works have reported the thermal gelation of myofibrils in mammals (FRETHEIM et al., 1985; BOYER et al., 1996a), poultry (XIONG, 1993; XIONGand BLANCHARD, 1994a; 1994b) and fish (MONTEJANOet al., 1983; AUTIOet al., 1989;
LEFEVREet al., 1998). Heating myofibrils preparation produces complex changes in the rheological properties. This changes are related mainly to interactions between myosin (TEJADA, 1994) and other myofibrillar proteins which could contribute to the gelation process (for a review, see LEFEVRE et al., 1999).
Others muscle components such as lipids and collagen modify also the rheolo- gical characteristics of the myofibrillar protein gels after heating (SAMEJIMAet al., 1990; DE LAMBALLERIE-ANTONet al., 1993; LANet al., 1995b).
The demonstration of the exact contribution of myofibrillar protein to the thermal gelation process of myofibrils requires to remove muscle components other than myofibrillar protein. This is generally obtained by extraction of myofi- brillar protein at high ionic strength which gives the salt soluble protein (SSP). In mammals and poultry, thermal gelation properties of SSP are very similar to those of myofibril preparations (SMITH, 1991; CULIOLI et al., 1993; ROBE and XIONG, 1993; BOYER et al., 1996a). Thermal transitions are more apparent, however, and the gels observed after heating are much more rigid for SSP than for myofibril solutions (XIONG, 1993; BOYERet al., 1996a). Such a comparison of thermal gelation properties of myofibrils and myofibrillar protein (SSP) has never been made in the case of fish.
Thermal gelation properties of proteins are known to be strongly dependent on physico- chemical factors, in particular pH and ionic strength. Myofibrillar proteins from fish are much more sensitive to pH and ionic strength changes than are those from mammals and birds, and gelation properties have only been observed within a narrow range of pH and salt concentrations (COFRADESet al., 1997). Amongst fish species examined to date, myosin of cold-water fish is the more sensitive to the physicochemical environment as compared to warm- water fish (DAVIES et al., 1988). The effect of pH and ionic strength has been characterized on myofibrils of brown trout (LEFEVREet al., 2001), although the same is not true for myofibrillar protein (Salt Soluble Protein).
The maximum rigidity of fish muscle protein gels, in particular of myosin gels, is observed at around pH 6.0 (WICKER et al., 1986; DAVIESet al., 1988;
BEASet al., 1990; CARECHEet al., 1991). At higher pH, thermal transition tempe- ratures for myosin are lower (BEASet al., 1990), demonstrating protein destabili-
zation and, consequently, a decreased gel strength. An optimal pH value for thermal gelation of fish minced muscle of around 6.0 has also been reported (AUTIOet al., 1989; LANet al., 1995a), although a higher optimal thermal gelation value of approximatively pH 7.0 is generally observed for surimi (KIM et al., 1993).
The effect of ionic strength on thermal gelation properties of muscle protein is dependent on the method used to set the ionic strength. High ionic strength obtained by salt addition on myofibrils affects positively gelation of fish muscle protein (CARECHE et al., 1991; CHEN, 1995). The effect of low ionic strength (< 0.3 M) is dependent in mammals on the method used (BOYERet al., 1996b). If low ionic strengths are obtained by adding small quantities of salt to crude pro- tein preparations, gel strength is generally lower than that observed at high ionic strength. If proteins are first solubilized at high salt concentrations (> 0.3 M) and low ionic strength is subsequently obtained by dilution or dialysis, gel strength is greater than at high ionic strength. A positive effect of low ionic strength has been demonstrated under such conditions for tilapia (WICKER et al., 1986) and for carp myosins (SANOet al., 1990). These effects have still to be demonstrated in salmonids.
The effect of muscle type on heat-induced gelation of proteins is well docu- mented in mammals and poultry but only few studies have been carried out on fish species (for a review, see LEFEVREet al., 1999). Fish skeletal muscle com- prises two main types: superficial red skeletal muscle, composed of slow-twitch oxidative fibers (JOHNSTON, 1982), and deep white skeletal muscle, composed of fast-twitch glycolytic fibers (STICKLAND, 1983; KIESSLINGet al., 1991). In sar- dine and tuna, the gels obtained after heating minced red muscle and myofibril- lar proteins from red muscle are less rigid than those from white muscle (TANAKAet al., 1988; LOet al., 1992). Brown trout myofibrils from white and red muscles can however form gels of equivalent rigidity after heating under stan- dard conditions (0.6 M KCl and pH 6.0) LEFEVREet al. (1998). In terrestrial ani- mals, the differences in thermal gelation properties between muscle types (FRETHEIMet al., 1985, 1986; FOEGEDING, 1987; XIONG, 1992, 1994; EGELANSDAL et al., 1995) are very dependent on pH and ionic strength due to differences in the physicochemical properties of the different protein isoforms characteristic of each muscle type. The same has been observed in brown trout, for which myo- fibrils from white muscle, at low pH (5.6) or low ionic strength (0.2 M KCl), form stronger gels than those from red muscle (LEFEVRE et al., 2001). Such diffe- rences related to muscle type have not been reported on myofibrillar proteins (SSP).
The objectives of this study were thus to determine if the rheological proper- ties of brown trout white and red muscles myofibrillar protein were affected by solubilization and if this could improve the characteristics of the gels formed after heating. In particular, the effects of low pH and low ionic strength on myo- fibrils preparation and extracted salt-soluble proteins were examined.
2 - MATERIALS AND METHODS
2.1 Fish samples
Brown trouts (Salmo trutta), body weight 2-3 kg, were obtained from the SEMII sea-water facilities (Salmoniculture expérimentale marine Inra-Ifremer, Camaret-sur-Mer, Finistère, France). Fish were killed by a blow to the head, bled, eviscerated immediately after death and transported on ice to the labora- tory where the experiment was carried out 24 to 48 h post mortem. The red muscle tissue from each side was carefully dissected along the median line after removing the skin and remains of white muscle were removed as much as possible. Deep lateral dorsal white muscle was excised only from the left fillet.
Each muscle sample was minced and blended to prevent any effect of the hete- rogeneity between the front and the caudal parts of the fillet.
2.2 Preparation of myofibrils and salt soluble protein (SSP)
Myofibrils were prepared according to the method of ZABARI (1984) with some modifications. White and red muscles were homogenised with an Ultra- turrax homogeniser in 5 volumes (weight/vol.) of 10 mM Tris, 4 mM EDTA, 90 mM KCl, 5 mM β-mercaptoethanol, 1 mM NaN3 and 1 mM PMSF (pH 7.0).
The homogenate was kept on ice for 1 h and then centrifuged at 2,000 ×g for 15 min at 2°C. The pellet was resuspended in the same buffer without Tris (pH 6.4) and centrifuged using the same conditions. The pellet was resuspen- ded in the same buffer without Tris and EDTA (pH 6.4), and the suspension was filtered through a strainer to remove collagen and centrifuged under the same conditions. The resulting pellet was used as crude myofibrils.
The myofibrils pellet was resuspended and solubilized for 20 min in 4 volumes (weight/vol.) of 40 mM phosphate buffer, 0.6 M KCl, pH 6.5, and then centrifuged at 30,000 ×g for 15 min at 2°C. The supernatant was filtered on cheesecloth, diluted with 10 volumes of cold distilled water and stored over- night at 4°C. The preparation was then centrifuged at 30,000 ×g for 10 min at 2°C and the resulting pellet was used as myofibrillar protein (salt soluble).
Finally, the myofibrils and myofibrillar proteins pellets were solubilized in a 40 mM phosphate buffer, pH 5.6 or 6.0, containing 0.6 M KCl, centrifuged at 500 × g for 5 min to remove air bubbles, and dialysed overnight against the same buffer before rheological analysis. To study the effect of low ionic strength (0.2 M KCl), protein preparations were dialysed a further night against the same phosphate buffer containing 0.2 M KCl.
Protein content was determined by the Biuret method (GORNALLet al., 1949) with BSA as a standard and it was adjusted to 15 g·L–1in all the samples before analysis.
2.3 Viscoelastic measurements
The rheological measurements of crude myofibrils and myofibrillar protein samples in phosphate buffer (0.04 M, 0.2 or 0.6 M KCl, pH 5.6 or 6.0) were car- ried out using a controlled-stress rheometer (Carri-Med CSL 100, Carri-Med
Ltd, Dorking, Surrey, UK) in oscillatory mode (0.1 Hz). Protein solutions were heated between the parallel plates (diameter = 4 cm, gap = 0.1 cm) from 20°C to 80°C with a heating rate of 1°C/min. Viscoelastic measurements were carried out under non-destructive conditions with a strain amplitude of 3%. Viscoelastic parameters, storage modulus (G’), loss modulus (G’’) and phase angle, (δ= arc- tan(G’’/G’)) were recorded. Sample dehydration was prevented by addition of paraffin oil.
2.4 Statistical analysis
This study was carried out in three independent experiments using three diffe- rent fishes. The significance of the differences between myofibrills and myofibrillar proteins were tested at 20°C (initial temperature), 50°C (intermediate temperature between low temperature interactions and stabilisation of interaction by high tem- perature) and 80°C (final temperature) for each characteristics of the gels (G’ and δ) using a one-way ANOVA. Differences were also analysed at each rheological transition temperature observed depending on the condition tested. Differences between means were tested using a Newman-Keuls test (p < 0.05).
3 - RESULTS
3.1 Myofibrillar protein extraction and pH effects at high ionic strength
The rheological profiles of white muscle myofibrils and myofibrillar proteins soluble at high ionic strength (0.6 M KCl) are presented in figure 1. For both pre- parations and pH values, the changes in storage modulus (G’) during heating at 1°C/min, accounting for the evolution in gel rigidity, were complex. At pH 6.0, an increase in the G’ value up to 50 N/m2was observed from 20 to 36°C, follo- wed by a sharp decrease until a minimum value observed at 41°C. G’ subse- quently increased up to 50 to 70 N/m2at 50°C and then leveled off until 80°C.
At pH 5.6, G’ increased sharply up to a plateau value (90 to 110 N/m2) between 28 and 35°C, followed by a decrease to a minimum value of 60-70 N/m2obser- ved at 39°C. This was followed by a two steps increase, the first step up to 50°C and the second up to 80°C, at which G’ maximum values between 130 and 160 N/m2were observed. The rigidity of the gels formed were significantly greater at pH 5.6 than at pH 6.0 for most of temperatures tested.
Phase angle, δ, values decreased throughout the heating process, reflecting an increase in gel elasticity as temperature increased, with a transition observed in the low temperature range between 25-32 and 30-37°C at pH 5.6 and 6.0, respectively. At 80°C, very elastic gels were observed (δ ≈ 3°) for both of the protein preparations and pH values. The elasticity of the gels formed at low temperatures (< 50°C) was higher at pH 5.6 than at pH 6.0, whereas no diffe- rence in gel elasticity was detected at higher temperatures.
No significant differences in the rheological parameters were observed bet- ween myofibril and myofibrillar protein (SSP) at the specific temperature tested (20°C, 50°C and 80°C) and at the rheological transition temperatures specific of
each pH (28, 34, 40, 57°C at pH 5.6; 37, 58°C at pH 6.0). The rheological pro- files were very similar. It could be observed that the effect of low pH on G’ was higher for myofibrillar protein (SSP) than for myofibrils and this difference obser- ved at, intermediate temperature (42°C-52°C) and high temperature (57-80°C) was only significant at the end of the thermal gelation process (+ 68% vs + 44%
at 80°C).
Figure 1
Thermal gelation profiles of white muscle myofibrils and salt soluble protein (SSP) Protein content 15 g·L–1. Phosphate buffer 0.04 M, 0.6 M KCl, pH 5.6 and 6.0. Heating rate 1°C/min (means of 3 experiments). Vertical bars correspond to: 2 x mean of SD in each pH conditions.
Figure 2
Thermal gelation profiles of red muscle myofibrils and salt soluble protein (SSP) Protein content 15 g·L–1. Phosphate buffer 0.04 M, 0.6 M KCl, pH 5.6 and 6.0. Heating rate 1°C/min (means of 3 experiments). Vertical bars correspond to: 2 x mean of SD in each pH conditions (or in all conditions for delta).
Changes in G’ and δvalues during heating of red muscle myofibrils and SSP obtained at high ionic strength are presented in figure 2. These rheological pro- files were much simpler than those of white muscle. At pH 6.0, an increase in G’
values started at 37°C and a plateau value (8 to 10 N/m2) was observed between 39 and 43°C, followed by an increase in G’ up to 60 N/m2at 80°C. For both pro- tein preparations at pH 5.6, the storage modulus, G’, increased as the tempera- ture increased from 20 to 80°C. A transition at low temperatures (37-40°C) was observed for myofibrils but not for myofibrillar proteins. Gels formed at pH 5.6 were, after heating, significantly more rigid than those formed at pH 6.0. Phase angle, δvalues decreased sharply at low temperatures (20 to 35°C) and then decreased more gently. At 80°C, an elastic gel (δ ≈3-4°) was observed for both protein preparations and pH values and no significant difference in gels elasticity could be measured. Myofibril and myofibrillar proteins showed the same rheologi- cal profiles and no difference was observed in the rheological parameter values.
Figure 3
Thermal gelation profiles of white muscle myofibrils and salt soluble protein (SSP) Protein content 15 g·L–1. Phosphate buffer 0.04 M, 0.2 M KCl, pH 5.6 and 6.0. Heating rate 1°C/min (means of 3 experiments). Vertical bars correspond to: 2 x mean of SD in each pH conditions (or in all conditions for delta).
3.2 Myofibrillar protein extraction and pH effects at low ionic strength
The effect of lowering ionic strength from 0.6 to 0.2 M KCl was only tested on white muscle protein as we did not have enough material from red muscles.
Changes in gel rigidity and elasticity of white muscle myofibrils and myofibrillar protein solubilized at low ionic strength, at pH 5.6 and 6.0, are presented in figure 3. For both protein preparations and pH values, a gel was observed before heating (20°C), with values in the order of 35 N/m2 and 80 N/m2 at pH 5.6 and 6.0, respectively. At pH 6.0, gel rigidity increased up to a maximum observed at around 30°C and decreased to a minimum value observed at 43°C.
An increase in gel rigidity was then observed up to a maximum of 150 N/m2at 55°C and no significant changes were observed up to 80°C. At pH 5.6, G’
increased up to a first transition (70 N/m2) at around 35°C and remained at this
value up to 40°C. A noticeable increase in gel rigidity was then observed up to a plateau value of 400-450 N/m2, observed at 70°C. Phase angle, δ, profiles were very similar for both pHs with an initial decrease from 20 to 30°C, followed by an increase up to a maximum value at 38 and 41°C for, pH 6.0 and 5.6, respec- tively, and finally δvalues decreased to reach a value of 2-3° at 80°C, which is characteristic of very elastic gels. Thus, the rheological thermal transition obser- ved at low ionic strength occurred at a lower temperature at pH 6.0 that it did at pH 5.6. Gel rigidity was always significantly greater at low ionic strength than at high ionic strength, and this over the entire temperature range tested.
The gels formed before heating were more rigid at pH 6.0 than at pH 5.6, and for temperatures higher than 50°C the rigidity of gels formed at pH 5.6 was significantly greater than at pH 6.0. At low temperatures (< 45°C), gels were more elastic at pH 6.0 but no difference in gel elasticity was observed between pH 5.6 and 6.0 at high temperatures (> 50°C).
As was observed at high ionic strengths, no difference in either the rheologi- cal profile or rheological parameter values was observed between myofibrils and SSP at low ionic strength.
3.3 Influence of muscle type
Thermal gelation profiles of white and red muscle proteins were very diffe- rent at pH 5.6 and 6.0, and 0.6 M KCl (figures 1 and 2). Higher rigidity values, with transitions in the rheological profile resulting from protein interactions, were observed for proteins from white muscle as compared to those from red muscle at low temperatures. At 80°C, no significant differences in either gel rigidity or gel elasticity were observed at the pHs examined and this for the two protein preparations (myofibril or SSP).
4 - DISCUSSION AND CONCLUSIONS
4.1 Influence of myofibrillar protein extraction
The extraction of myofibrillar protein (salt soluble protein) can be considered as a further step in protein purification as it involves the removal of stroma pro- tein, in particular collagen, and lipids that are present in myofibril preparations. In many species, extraction of salt-soluble protein significantly improves the ther- mal gelation capacity of muscle proteins. In rabbit (CULIOLIet al., 1993; BOYERet al., 1996a) and chicken (XIONG, 1993), the rheological profiles are very similar for myofibril and SSP preparations, although gel rigidity is higher for SSP than for myofibrils. In the present study, however, no differences in gelation properties were observed between myofibrillar protein (salt soluble protein) and myofibrils, regardless of the muscle type, pH and ionic strength. An interaction between pH and protein preparation (myofibrillar protein compared to myofibrils) was howe- ver observed at high ionic strength. This suggests that stroma proteins and lipids could affect the thermal gelation process of brown trout myofibril but these effects were limited. LEFEVREet al. (2001) concluded that the ultrastructure of gels from trout myofibrils was more related to that of myofibrillar protein compa-
red to rabbit myofibrils which are more related to that of myofibrils itself (BOYER et al., 1996a). The thermal gelation properties of fish myofibrils may be less sen- sitive to the presence of contaminants such as collagen and lipids than are those of rabbit myofibrils. Although these contaminants were not easy to solubilize and to separate by electrophoresis, the electrophoretic pattern of the myofibrils and myofibrillar protein (SSP) were however very similar both in white muscle and in red muscle (data not shown) and this explains that only minor differences were observed in thermal gelation properties. Alternatively, the characteristics of the contaminants may differ from those of rabbit. NISHIOKA et al. (1983), however, showed that myofibrils from dolphinfish generate more rigid gels than do acto- myosin preparations at the same protein concentration.
4.2 Influence of pH
The higher thermal gelation capacity of brown trout myofibrils at low pH (5.6) compared to pH 6.0 (LEFEVREet al., 2001) was confirmed in this study and the same was observed for SSP for both muscle types. This optimal pH for thermal gelation may represent a protein solubility threshold and it is suggested that, at such pHs, the myofibrils are in a very unstable state even at low temperatures (BEASet al., 1990), which would favor protein denaturation and aggregation bet- ween proteins. In fish, optimum pHs for gelation of muscle proteins are consi- dered to be close to pH 6.0 (WICKERet al., 1986; AUTIOet al., 1989; CARECHEet al., 1991; LANet al., 1995a), but a pH range between 5.5 and 6.0 has not been extensively tested with fish muscle protein. HIRAHARAet al. (1990) reported that differences in pH for maximum thermal gelation can be observed depending on fish species and thus a pH of 5.6 could be specific to salmonid species. Maxi- mal thermal gelation capacity has also been observed at a pH lower than 6.0 for chicken (XIONG and BLANCHARD, 1994a), rabbit (SAMEJIMA et al., 1992) and bovine (EGELANDSDALet al., 1995) myofibrils.
This contrasts with the pH value, around pH 7.0, where maximum thermal gelation of surimi has been reported (KIMet al., 1993; JOSEPHet al., 1994). Pro- tein concentrations of surimi-type preparations are substantially higher (around 15% protein) than those of isolated proteins, however, and this would greatly affect pH dependent protein interactions. The presence of additives in surimi may also explain such a difference.
4.3 Influence of ionic strength
The addition of salt generally improves the thermal gelation process. A posi- tive effect of salt addition was thus reported for heat-induced gelation of surimi from different species (ROUSSEL and CHEFTEL, 1990; GOMEZ-GUILLEN et al., 1997), myosin solutions from carp (SANOet al., 1990) and myofibrils and myosin from rabbit (BOYERet al., 1996b).
When proteins are first dissociated at high ionic strength, a positive effect of low ionic strength is reported on protein thermal gelation for myofibrils from rab- bit (BOYER et al., 1996b), beef (STONE and STANLEY, 1994; EGELANDSDALet al., 1995) and trout (LEFEVREet al., 2001). A similar result has been observed on tila- pia myosin by WICKER et al. (1986), who demonstrated that gels are tenfold more rigid at low ionic strength than at high ionic strength. In rabbit, the forma- tion of protein filaments organized in a strand-type network was observed and
was associated with low ionic strength (BOYERet al., 1996b) and it is suggested that the same phenomenon may occur in fish.
4.4 Influence of muscle type
The marked effect of muscle type on the thermal gelation properties of brown trout myofibrils has already been reported (LEFEVREet al., 1998, 2001).
The greater thermal stability of myofibrils from red muscle was confirmed in the present work and the same results were demonstrated for SSP at both pH 5.6 and 6.0. Differences in thermal stability between red and white fish myofibrillar proteins have similarly been reported by differential scanning calorimetry of myosin from black marlin (LOet al., 1991) and on actomyosin ATPase activity in carp and tuna (WATABEet al., 1983; TAGUCHIet al., 1989). Due to the homoge- nous fiber-type composition of white and red muscles in fish, these results may be related to the differences in rheological transition temperature of myofibrils and myosin between slow and fast-twitch muscles, as it has been demonstra- ted in mammals (CULIOLIet al., 1993; BOYERet al., 1996a, 1996b).
In mammals and poultry it is generally admitted that white, fast-twitch oxida- tive muscle proteins exhibit a higher heat-induced gelation property than red, slow-twitch glycolytic ones (FOEGEDING, 1987; XIONG, 1992; CULIOLIet al., 1993;
EGELANDSDALet al., 1995; LIUand FOEGEDING, 1996; BOYER et al., 1996a). The effect of muscle type on gelling ability of proteins, however, has been found to be very dependent on their physicochemical environment, pH and ionic strength, in poultry (ASGHARet al., 1984; AMATOet al., 1989) and trout (LEFEVRE et al., 2001). In trout, no differences between muscle types were observed at pH 6.0 and 0.6 M KCl. Conversely, when the pH or ionic strength are lowered, heat-induced gels from white muscle myofibrils are stiffer than those of red muscle myofibrils (LEFEVREet al., 2001). In the present study, no differences in gel rigidity after heating were observed between the muscle types, regardless of the pH. In other species, such as beef, chicken and turkey, a comparable or higher gel rigidity has been observed for red muscle proteins (XIONG, 1994; LAN et al., 1995a). It would thus appear that the effect of muscle type deserves fur- ther investigation.
In conclusion, this work demonstrated that extraction, at high ionic strength, of myofibrillar proteins from trout white and red muscles did not significantly modify the rigidity of gels obtained after heating up to 80°C. However, we confirmed that a higher thermal gelation capacity of brown trout muscle pro- teins was observed at low pH (5.6) and low ionic strength (0.2 M KCl), as com- pared to pH 6.0 and high ionic strength, including for salt-soluble proteins.
ACKNOWLEDGEMENTS
We wish to thank Drs. C. BOYER-BERRI and S. JOANDEL-MONIER for helpful discussions. Many thanks to Dr. M.A.JOHNSONfor proofreading the English text.
Received 21 August 2000, revised 9 April 2001, accepted 17 May 2001.
REFERENCES
AMATO P.M., HAMANN D.D., BALL H.R.Jr., FOEGEDING E.A., 1989. Influence of poultry species, muscle groups, and NaCl level on strength, deformability, and water retention in heat-set gels. J. Food Sci., 54, 1136-1140, 1157.
ASGHAR A., MORITA J., SAMEJIMA K., YASUI T., 1984. Biochemical and functional characteristics of myosin from red and white muscle of chicken as influenced by nutritional stress. Agric. Biol. Chem., 48, 2217-2224.
ASGHAR A., 1985. Functionality of muscle proteins in gelation mechanisms of structu- red meat products. Crit. Rev. Food Sci., 1, 27-106.
AUTIO K., KIESVAARA M., POLVINEN K., 1989. Heat-induced gelation of minced rain- bow trout (Salmo gairdneri): Effect of pH, sodium chloride and setting. J. Food Sci., 54, 805-808, 823.
BEAS V.E., WAGNER J.R., CRUPKIN M., ANON M.C., 1990. Thermal denaturation of hake (Merluccius hubbsi) myofibrillar proteins - A differential scanning calorimetric and electrophoretic study. J. Food Sci., 55, 683- 687.
BOYER C., JOANDEL S., ROUSSILHES V., CULIOLI J., OUALI A., 1996a. Heat-induced gelation of myofibrillar proteins and myosin from fast- and slow-twitch rabbit muscles. J.
Food Sci., 61, 1138-1142.
BOYER C., JOANDEL S., OUALI A., CULIOLI J., 1996b. Ionic strength effects on heat- induced gelation of myofibrils and myosin from fast- and slow-twitch rabbit muscles. J.
Food Sci., 61, 1143-1148.
CARECHE M., CURRALL J., MACKIE I.M., 1991. A study of the effects of different fac- tors on the heat-induced gelation of cod (Gadus morhua, L) actomyosin using res- ponse surface methodology. Food Chem., 42, 39-55.
CHEN H.H., 1995. Thermal stability and gel- forming ability of shark muscle as related to ionic strength. J. Food Sci., 60, 1237-1240.
COFRADES S., CARECHE M., CARBALLO J., COLMENERO F.J., 1997. Thermal gelation of chicken, pork and hake (Merluccius mer- luccius L.) actomyosin. Meat Sci., 47, 157- 166.
CULIOLI J., BOYER C., VIGNON X., OUALI A., 1993. Heat-induced gelation properties of myosin - Influence of purification and muscle type. Sci. Aliments, 13, 249-260.
DAVIES J.R., BARDSLEY R.G., LEDWARD D.A., POULTER D.A., 1988. Myosin thermal stability in fish muscle. J. Sci. Food Agric., 45, 61-68.
DE LAMBALLERIE-ANTON M., CULIOLI J., OUALI A., 1993. Gélification thermique des proteines myofibrillaires de dinde. In : COLIN P., CULIOLI J. RICARD S.H. (eds), Proc. 11th Eur. Symp. on the Quality of Poultry Meat, Tours, 4-8 octobre 1993, 300-307.
EGELANDSDAL B., MARTINSEN B., AUTIO K., 1995. Rheological parameters as predic- tors of protein functionality - A model study using myofibrils of different fiber-type com- position. Meat Sci., 39, 97-111.
FOEGEDING E.A., 1987. Functional proper- ties of turkey salt-soluble proteins. J. Food Sci., 52, 1495-1499.
FRETHEIM K., EGELANDSDAL B., HARBITZ O., SAMEJIMA K., 1985. Slow lowering of pH induces gel formation of myosin. Food Chem., 18, 169-178.
FRETHEIM K., SAMEJIMA K., EGELAND- SDAL B., 1986. Myosins from red and white bovine muscles: Part-1 Gel strength (elasti- city) and water-holding capacity of heat-indu- ced gels. J. Food Chem., 22, 107-121.
GOMEZ-GUILLEN C., SOLAS T., MONTERO P., 1997. Influence of added salt and non- muscle proteins on the rheology and ultra- structure of gels made from minced flesh of sardine (Sardina pilchardus). Food Chem., 58, 193-202.
GORNALL A.G., BARDAWILL C.J., DAVID M.M., 1949. Determination of serum proteins by means of the Biuret reaction. J. Biol.
Chem., 177, 751-766.
HAN-CHING L., 1984. Valorisation du pois- son et perspectives de développement de nouveaux produits : la texturation de la chair de poisson. Science et Pêche. Bull. Inst.
Pêch. Marit., 347, 3-8.
HIRAHARA H., TANAKA M., NAGASHIMA Y., TAGUCHI T., 1990. Thermal gelation of stri- ped marlin and sardine myosins. Nippon Sui- san Gakkaishi, 56, 545.
JOHNSTON I.A., 1982. Biochemistry of myo- sins and contractile properties of fish skeletal muscle. Mol. Physiol., 2, 15-29.
JOSEPH D., LANIER T.C., HAMANN D.D., 1994. Temperature and pH affect transgluta- minase-catalyzed “setting” of crude fish actomyosin. J. Food Sci., 59, 1018-1023, 1036.
KIESSLING A., STOREBAKKEN T., ASGARD T., KIESSLING K.H., 1991. Changes in the structure and function of the epaxial muscle of rainbow trout (Oncorhynchus mykiss) in relation to ration and age - I. Growth dyna- mics. Aquaculture, 93, 335-356.
KIM S.H., CARPENTER J.A., LANIER T.C., WICKER L. 1993. Setting response of Alaska pollock surimi compared with beef myofibrils.
J. Food Sci., 58, 531-534.
LAN Y.H., NOVAKOFSKI J., MCCUSKER R.H., BREWER M.S., CARR T.R., MCKEITH F.K., 1995a. Thermal gelation of pork, beef, fish, chicken and turkey muscles as affected by heating rate and pH. J. Food Sci., 60, 936-940, 945.
LAN Y.H., NOVAKOFSKI J., MCCUSKER R.H., BREWER M.S., CARR T.R., MCKEITH F.K., 1995b. Thermal gelation properties of protein fractions from pork and chicken breast muscles. J. Food Sci., 60, 742-747.
LEFEVRE F., FAUCONNEAU B., OUALI A., CULIOLI J., 1998. Thermal gelation of brown trout myofibrils: Effect of muscle type, hea- ting rate and protein concentration. J. Food Sci., 63, 299-304.
LEFEVRE F., CULIOLI J., JOANDEL-MONIER S., OUALI A., 1999. Muscle polymorphism and gelling properties of myofibrillar proteins from poultry, mammals, and fish. In: XIONG Y.L., HO C.T., SHAHIDI F. (eds.) Quality Attri- butes of Muscle Foods, 365-391, Kluwer Academic / Plenum Publishers, New York.
LEFEVRE F., FAUCONNEAU B., OUALI A., CULIOLI J., 2001. Thermal gelation of brown trout myofibrils from white and red muscles:
Effect of pH and ionic strength. J. Sci. Food Agric., (in press).
LIU M.N., FOEGEDING E.A., 1996. Thermally induced gelation of chicken myosin isoforms.
J. Agric. Food Chem., 44, 1441-1446.
LO J.R., MOCHIZUKI Y., NAGASHIMA Y., TANAKA M., ISO N., TAGUCHI T., 1991.
Thermal transitions of myosins subfragments from black marlin (Makaira mazara) ordinary and dark muscles. J. Food Sci., 56, 954-957.
LO J.R., ENDO K., NAGASHIMA Y., TANAKA M., TAGUCHI T., 1992. Effect of added buta- nol on the thermal gelation of tuna dark and ordinary muscle proteins. Nippon Suisan Gakkaishi, 58, 107-112.
MONTEJANO J.G., HAMANN D.D., LANIER T.C., 1983. Final strengths and rheological changes during processing of thermally indu- ced fish muscle gels. J. Rheol., 27, 557-579.
NISHIOKA F., MACHIDA R., SHIMIZU Y., 1983. Kamaboko-forming ability of dolphin- fish myosin. Bull. Jap. Soc. Sci. Fish., 49, 1233-1238.
ROBE G.H., XIONG Y.L.L., 1993. Dynamic rheological studies on salt-soluble proteins from three porcine muscles. Food Hydrocol- loids, 7, 137-146.
ROUSSEL H., CHEFTEL J.C., 1990. Mecha- nisms of gelation of sardine proteins - Influence of thermal processing and of various additives on the texture and protein solubility of kamaboko gels. Int. J. Food Sci.
Technol., 25, 260-280.
SAMEJIMA K., ISHIOROSHI M., LIVERA W.C.D., 1990. Effect of added fatty acids on heat-induced gelation of myosin. Proc. 36th Int. Cong. Meat Sci. Technol. Havana, Cuba, 27 août - 1 septembre 1990, 306-311.
SAMEJIMA K., LEE N.H., ISHIOROSHI M., ASGHAR A., 1992. Protein extractability and thermal gel formability of myofibrils isolated from skeletal and cardiac muscles at different post-mortem periods. J. Sci. Food Agric., 58, 385-393.
SANO T., NOGUCHI S.F., MATSUMOTO J.
J., TSUCHIYA T., 1990. Effect of ionic strength on dynamic viscoelastic behavior of myosin during thermal gelation. J. Food Sci., 55, 51-54, 70.
SMITH D.M., 1988. Meat proteins: Functional properties in comminuted meat products.
Food Technol., 42, 116-121.
SMITH D.M., 1991. Factors influencing heat- induced gelation of muscle proteins. In: PAR- RIS N., BARFORD R. (eds.), Interactions of Food Proteins, 454, 243-256, ACS Symp.
Ser., USA.
STICKLAND N.C., 1983. Growth and deve- lopment of muscle fibres in the rainbow trout (Salmo gairdneri). J. Anat., 137, 323-333.
STONE A.P., STANLEY D.W., 1994. Muscle protein gelation at low ionic strength. Food Res. Int., 27, 155-163.
TAGUCHI T., LO J.R., TANAKA M., NAGA- SHIMA Y., AMANO K., 1989. Thermal activa- tion of actomyosin Mg-ATPases from ordinary and dark muscles of tuna and sar- dine. J. Food Sci., 54, 1521-1523, 1529.
TANAKA M., LO J.R., YANG C.C., NAGA- SHIMA Y., TAGUCHI T., 1988. Thermal gela- tion of dark meat and myosin pastes from sardine and tuna. J. Tokyo Univ. Fish., 75, 257-261.
TEJADA M., 1994. Gelation of myofibrillar fish proteins. Rev. Esp. Cienc. Tecnol. Alim., 34, 257-273.
WATABE S., MARUYAMA J., HASHIMOTO K., 1983. Myofibrillar ATPase activity of mac- kerel ordinary and dark muscles. Nippon Sui- san Gakkaishi, 49, 655.
WICKER L., LANIER T.C., HAMANN D.D., AKAHANE T., 1986. Thermal transitions in myosin-ANS fluorescence and gel rigidity. J.
Food Sci., 51, 1540-1543.
XIONG Y.L.L., 1992. Thermally induced inter- actions and gelation of combined myofibrillar protein from white and red broiler muscles. J.
Food Sci., 57, 581-585.
XIONG Y.L., 1993. A comparison of the rheo- logical characteristics of different fractions of chicken myofibrillar proteins. J. Food Bio- Chem., 16, 217-227.
XIONG Y.L.L., 1994. Myofibrillar protein from different muscle fiber types - Implications of biochemical and functional properties in meat processing. Crit. Rev. Food Sci. Nut., 34, 293-320.
XIONG Y.L., BLANCHARD S.P., 1994a.
Dynamic gelling properties of myofibrillar protein from skeletal muscles of different chicken parts. J. Agric. Food Chem., 42, 670- 674.
XIONG Y.L.L., BLANCHARD S.P., 1994b.
Myofibrillar protein gelation: Viscoelastic changes related to heating procedures. J.
Food Sci., 59, 734-738.
ZABARI M., 1984. Contribution à l’étude du polymorphisme de la myosine du muscle squelettique chez les animaux de boucherie.
Ph. D. Thesis, Université de Clermont-Fer- rand II.
