Effects of sodium hexametaphosphate, sodium tripolyphosphate and sodium pyrophosphate on the ultrastructure of beef myofibrillar proteins investigated with atomic force microscopy

Myofibrillar protein isolated from beef muscles were treated with 3 phosphates (Sodium Hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate) with different concentrations of 0.3%, 0.6%, 0.9%, 1.2% respectively. Protein solubility, surface hydrophobicity and reactive sulfhydryl group was determined. Atomic force microscopy was used to observe the microscopic protein surface. SDS-PAGE was carried out to determine the proteolysis of myofibrillar protein. The solubility and surface hydrophobic bond of myofibrillar protein was highly increased and the diameter decreased by SHMP, TSPP, STPP. Reactive sulfhydryl groups increased after SHMP addition, but slightly decreased in STPP and TSPP treated MP. TSPP and STPP had the same effect on myofibrillar microstructure and was different from SHMP. Three phosphates all caused MP unfolding. The MP gel complexity was increased, and roughness was decreased after phosphates addition, indicating phosphates helped to construct a more ordered and smoother gel microcosmic surface.

Immunohistochemical quantification of fast-myosin in frozen histological sections of goat limb muscles

Fast-myosin in frozen histological sections of eight, 10, 11 and nine muscles of the upper forelimb, lower forelimb, upper hindlimb and lower hindlimb, respectively, of goats was quantified by an immunohistochemical micromethod based on the enzyme-linked immunosorbent assay. The structure of the muscles is well preserved during the immunohistochemical measurement. High fast-myosin levels (more than 201 mg/g total protein) were observed in the triceps brachii (lateral head), rectus femoris, vastus lateralis, semitendinosus, semimembranosus, gastrocnemius (lateral head) and long digital extensor muscles. In contrast, low fast-myosin levels (less than 50 mg/g) were found in the triceps brachii (medial head), superficial digital flexor, vastus intermedialis, and soleus muscles. Fast-myosin-positive fibres (type II or fast-twitch type) were distributed more in the superficial regions than in the deeper regions in the triceps brachii (lateral and long heads), biceps brachii, brachialis, biceps femoris, vastus lateralis, vastus medialis, semimembranosus and gastrocnemius (lateral and medial heads) muscles. In contrast, type IIfibres were distributed more in the deeper regions than in the superficial regions in the extensor carpi radialis, deep digital flexor, cranial tibial, deep digital flexor and superficial digital flexor muscles. When the results obtained by the immunohistochemical micromethod were compared with those obtained by biochemical techniques and by histomorphometrical analyses, high correlations were noted. This technique could be used in research projects to study the muscle characteristics that determine meat quality.

Myofibrillar protein from different muscle fiber types: implications of biochemical and functional properties in meat processing

Texture, moisture retention, and tenderness of processed muscle foods are influenced by the functionality of myofibrillar protein. Recent studies have revealed large variations in processing quality between red and white muscle groups that can be attributed to differences in the functional properties of myofibrillar protein associated with the type of fiber. Myofibrillar proteins from fast- and slow-twitch fibers exhibit different biochemical and rheological characteristics and form gels with distinctly different viscoelastic properties and microstructures. The existence and wide distribution of the numerous myosin isoforms in different muscle and fiber types contribute to the various functional behaviors of myofibrillar protein. The different sensitivities of fast and slow myofibrillar proteins to pH, ionic environment, temperature, and other external factors have been well documented and illustrate the importance of adjusting meat processing conditions, according to fiber type profile to achieve maximum protein functionalities, and hence, uniform quality of the final muscle foods.