Kristen Fretheim

Myosins from red and white bovine muscles: Part 1—Gel strength (elasticity) and water-holding capacity of heat-induced gels

Abstract Myosins were isolated from bovine M. masseter (red) and M. cutaneus trunci (white) and characterized in terms of solubility, electrophoretic pattern and susceptibility to tryptic digestion. Dynamic rheological measurements showed that white myosin is generally the superior gel former: gel strength, expressed as storage modulus, is consistently higher (a) at all temperatures above the gel-inducing minimum, (b) in both 0·2 m and 0·6 m NaCl, (c) at all concentrations investigated (≤ 20 mg/ml) and (d) at pH ≥ 5·8. In 0·6 m NaCl at pH m NaCl lost about 15% liquid on centrifugation; gels in 0·6 m NaCl displayed an inverse relationship between storage modulus and loss of liquid. The gel strength and water-holding capacity of gels made from mixtures of red and white myosin were a linear function of mixture proportions in the case of 0·2 m NaCl; 0·6 m NaCl gave gels with unpredictable properties.

Slow lowering of pH induces gel formation of myosin

Abstract It has been found that solutions of myosin (10 mg/ml) form gels at 5°C if the pH is decreased slowly, by dialysis, to a value in the region of 2.5 to 5.5. Gel strength displays strong dependence on final pH, having a maximum at about pH 4.5. Salt (KCl) concentration was found to affect gel strength positively and linearly. Differential scanning calorimetry revealed that the myosin of pH-induced gels absorbed no thermal energy when heated, implicating acid-induced denaturation as the basis of gel formation. By comparison with heat-induced gelation of myosin and from the fact that low pH is conducive to filament formation, it is suggested that filaments may also be involved in the gelation process.

Polycyclic aromatic hydrocarbons in grilled meat products—A review

Abstract Current efforts to detect and quantify carcinogenic polycyclic aromatic hydrocarbons (PAH) in the environment include analyses of foods. Grilled foods have been under scrutiny for almost 20 years. In this review reports concerning PAH contamination of grilled meat products are discussed. It is evident that the level of contamination varies considerably, primarily due to the extent of fat pyrolysis which has taken place. If proper precautions against fat pyrolysis are taken, and out-of-the-ordinary fuels such as crumpled paper or cones are not used, the PAH contamination is reduced substantially. Furthermore, if the relatively low consumption of grilled meat products is taken into consideration public concern over possible health risks due to grilling appears unwarranted.

Effects of electrical stimulation and ageing of beef on the gelation properties and protein extractability of isolated myofibrils

The gelation properties of bovine myofibrils, as evaluated by dynamic rheological measurements, were shown to be very sensitive to the variables investigated: stimulation and/or ageing of the meat used, presence of 5 mM pyrophosphate and 5 mM MgCl(2) (PP) and concentration of NaCl (0·3 or 0·M). Statistical evaluation of final gel storage moduli (determined at 70°C) revealed ageing to have a consistent detrimental effect. Fresh, stimulated processing of meat), gave gels of about 40% lower elasticity (storage modulus) than did non-stimulated myofibrils; when PP was included in the gel-forming mixture no effect from electrical stimulation was seen. In spite of the negative effects observed for gel elasticity, the myofibrils in question displayed enhanced protein extractability prior to heating. Electrophoretic results suggest myosin degradation to be partly responsible.