Thermal gelation of brown trout myofibrils from white and red muscles: effect of pH and ionic strength

Abstract

The effects of pH and ionic strength on the thermal gelation of brown trout myo®brils from white and red muscles were analysed by thermal scanning rheometry. The highest gelation ability was obtained at low pH (around 5.6) whatever the ionic strength. No effect of ionic strength was observed at pH 5.6; however, at pH 6.0, lowering the salt (KCl) concentration to 0.3 M or less improved the characteristics of the gels formed. The effects of pH and ionic strength on myo®brils from both muscle types appeared to be similar, but red muscle proteins were less sensitive to changes in their physicochemical environment. Consequently, the differences between muscle types appeared to be dependent on pH and ionic strength. Solubility measurements revealed large differences between muscle types and between different pH values. Ultrastructural observations con®rmed that different kinds of gels were formed depending on the physicochemical conditions and muscle type origin. INTRODUCTIONThe thermal gelation properties of myo®brillar proteins have been studied in a large variety of animals. 1 The capacity to produce gels at relatively low temperature is speci®cally observed in aquatic organisms, and this property has been used for processing ®sh myo®brils in surimi-like products. Thermal gelation properties based on interactions between proteins are very dependent on the physicochemical environment, especially pH and ionic strength. 1 Both ionic strength and pH act on myo®bril dissociation prior to heating and on protein charges, which in turn affect protein±protein and protein±solvent interactions during heating. Susceptibility of thermal gelation to physicochemical conditions varies between animal species. Proteins from ®sh are much more sensitive to changes in pH and ionic strength than those from mammals and birds and can form a gel only in a narrow range of pH and salt concentration. 2 Amongst ®sh species, myosin from cold-water ®sh is more sensitive to changes in the physicochemical environment than myosin from warm-water ®sh. 3 Fish muscle proteins, especially myosin, show an optimal thermal gelation around pH 6.0. 3±6 As the pH increases above this value, the transition temperature of myosin decreases, 5 and this is associated with protein destabilisation and consequently a lower gel-

Effect of pH on the physicochemical and heat-induced gel properties of scallop Patinopecten yessoensis actomyosin

“…6. The scallop actomyosin gel showed the highest strength at pH 5.6 (12.83 g), which was consistent with previously reported results for myofibrils extracted from brown trout [3]. The high gel strength of scallop actomyosin at pH 5.6 was primarily due to the aggregation of protein molecules.…”

“…pH is considered to be one of the most important factors affecting the gelation ability of myofibrillar protein. Proteins from fish are more sensitive to changes in pH than those from mammals and can only form a gel in a narrow pH range [3]. The optimum pH for gelation ability is often reported to be between 5.5 and 7.0 [4].…”

The Effectiveness of Clove Extract on Oxidization-Induced Changes of Structure and Gelation in Porcine Myofibrillar Protein

“…Numerous studies have shown that mild protein oxidation can improve the protein gel network by changing the arrangement of myosin, while excessive oxidation can produce a large number of aggregates that cannot form a dense gel network structure [55][56][57]. Lund et al [58] showed…”

“…Numerous studies have shown that mild protein oxidation can improve the protein gel network by changing the arrangement of myosin, while excessive oxidation can produce a large number of aggregates that cannot form a dense gel network structure [55][56][57]. Lund et al [58] showed that the oxidation of thiol groups of proteins transformed into intermolecular disulfide bonds and affected the stiffness and elasticity of protein gels. The addition of CE promotes protein unfolding, as confirmed by the exposure of hydrophobic groups in previous studies [25], which may disrupt the hydrogen bonding of α-helix and promote the conversion of α-helix to other three secondary structures.…”

Ultrastructure of longissimus dorsi myofibrillar proteins and heat-induced gels as observed with atomic force microscopy: effects of pH values and sodium ions

“…[4] It is a complex dynamic process that the secondary structure and the structural features of the myofibrillar proteins changed significantly in the process of heating. [5] Heat-induced gelation properties based on interactions among myofibrillar proteins are dependent on many factors, such as pH, ionic strength, protein concentration, type of muscle as well as the heat-induced temperature and so forth, [6,7] especially pH and ionic strength. [1,8,9] The previous studies had mainly focused on water-holding capacity, texture, and the qualitative microstructure; [10][11][12][13][14][15] however, quantitative ultrastructural studies are rarely executed in details.…”