Myosins from red and white bovine muscles: Differences measured by turbidimetric, calorimetric and rheological techniques

Abstract

Abstract:The aim of this study was to elucidate the functional performance of the most abundant protein component in meat, ie myosin, which is recognised as important for binding in meat products. As several genetic variants of skeletal myosin exist, myosins from two bovine muscles of different fibre type composition, M masseter and M cufaneus trunci were compared with respect to filament forming properties and denaturation characteristics. The principal methods used were turbidimetric measurements, which were used to monitor filament formation, calorimetry and rheology. The myosin systems were examined at two different salt levels (0.2 and 0.6 M NaC1) and at pH 5.5-7.0. The method of preparing myosin suspensions/solutions was also examined. Differences in the filamentforming process for the two myosins were detected. Measurements of turbidity revealed that at conditions of low pH and low ionic strength white myosin had a higher ultimate turbidity compared with red myosin. Early in the transition from low to high turbidity, red myosin had a higher turbidity than white myosin corresponding to reduced solubility. The turbidity increased with time of storing the myosin suspensions/solutions. This change was attributed to formation of filaments and further association of filaments. White myosin had a smaller apparent enthalpy of denaturation than red myosin. The calorimetric measurements recorded in 0.2 M NaCl suggested that the head and the rod of white myosin were less stable than the corresponding parts of red myosin. However, exceptions to this rule were found at pH 6.0. In 0.6 M NaCl the identification of the transitions for red myosin was more difficult. The method of preparing myosin suspensions affected calorimetric and rheological measurements. In 0.6 M NaCl and pH < 6.0 calorimetric thermograms of both myosins were affected by the preparation method. At pH 5.5 this change was interpreted as caused by denatur-* To whom correspondence should be addressed. 75J Scr Foad Agrrc 0022-5142/94/$09.00 t 1994 SCI Printed in Great Britain 76 B Egelandsdal, B K Martinsen, K Fretheim, M Pettersen, 0 Harbitz ation promoted by the dilution/rapid titration technique compared with dialysing the systems to pH 5.5 from pH 7. Differences in the filaments formed might, however, also contribute to the variations seen in the calorimetric thermograms. The gelling properties of white myosin were most sensitive to the preparation method used. Systems prepared by dialysis gave stronger heat-induced gels than those prepared by 'dilution'. White myosin always produced stronger gels than red myosin independent of the preparation technique. The rheological properties (at 80°C) of red myosin were less affected by the preparation method than were those of white myosin. At lower temperatures, however, there was more variation in the shapes of the rheological thermograms (G' versus temperature) for red myosin than in the corresponding thermograms of white myosin.

Denaturation and Aggregation of Myosin from Two Bovine Muscle Types

“…Thus, the formation of myosin oligomers at pH 5.5 may have helped to stabilize myosin against thermally induced denaturation (29). Results are in contrast to those of Egelandsdal et al (7), who reported that bovine cutaneous trunci (white) and M. masseter (red) had greater enthalpies at pH 6.0 than at pH 5.5 in 0.6 M NaCl, with the highest enthalpy being observed in white myosin at pH 6.0. The ∆H cal of VI myosin at pH 6.05 was 1496 kcal/mol and was similar to that reported for broiler gastrocnemius (leg) myosin (1588 kcal/mol) at pH 6.0 (9).…”

“…The first myosin transition peak occurred at a lower temperature and the final major peak occurred at a higher temperature at pH 5.50, when compared to transitions at 6.05 in both VI and SM myosin. Egelandsdal et al (7) found the same trend with pH for bovine masseter (red) and cutaneous trunci (white) myosin.…”

Changes in the Properties of Porcine Myosin during Postmortem Aging

“…This might indicate that during storage porcine myosin gradually lost its stability. Our results are in agreement with Egelandsdal and Martinsen (1994) who reported an increase in turbidity values of red and white bovine muscles during storage.…”

FUNCTIONAL DIFFERENCES OF MYOFIBRILLAR PROTEINS FROM FAST AND SLOW TWITCH MUSCLES1

“…For example, as the pH is increased from 5.5 to 6.4 there is a decrease in thermally induced gel rigidity of chicken (Asghar er al. 1984; Morita et al 1987) and beef (Fretheim et al 1986; Egelandsdal et al 1994) myosin. This is directly opposite to the trends in fracture properties Seen in chicken frankfurters (Baker er al.…”