Microstructural changes in M. rectus abdominis bovine muscle after heating
INRA de Clermont-Ferrand-Theix, UR370 QuaPA, F-63122 St Genès Champanelle, France.Meat Science (Impact Factor: 2.62). 08/2010; 85(4):743-51. DOI: 10.1016/j.meatsci.2010.03.035
A histological and ultrastructural study was conducted to characterize changes in beef muscle structure after heating. Pieces of rectus abdominis muscle were heated at 100 degrees C over varying time frames from 15 min to 60 min and at 270 degrees C for 1 min; samples were then prepared for optical and transmission electron microscopy. After 15 min of heating, at 100 degrees C, a lateral shrinkage in fibre of 48% and an increase in gaps between the myofibrillar masses of 27% was noted. No more significant evolution was observed as heating duration escalated. The ultrastructure showed strong myofibril to sarcolemma detachments in which granular aggregates, coming in part from myofibrillar proteins, are stored. Neighbouring muscle fibres showed strong heterogeneity in morphological behaviour after thermal treatment, suggesting that differences in composition and structure of the cytoskeleton proteins in the different fibres can cause denaturation/shrinkage of the proteins at different times along the timescale of microstructural changes during heating. Short heating at high temperatures expanded the gaps between myofibrillar mass, but the overall changes in the ultrastructure were similar to those obtained when heating at 100 degrees C.
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ABSTRACT: Heating temperature is an important factor affecting meat palatability. This study aimed to evaluate the influence of heating temperature on some eating quality indicators, protein degradation and ultrastructure of pork muscle fibres and their correlations. Cooking loss (CL) increased gradually (P < 0.05) with increasing temperature. Warner-Bratzler shear force (WBSF) increased in two separate phases from 25 to 50 °C and again from 60 to 100 °C (P < 0.05), with a steady phase from 50 to 60 °C (P > 0.05); conversely, a significant increase in pH (P < 0.05) occurred between 50 and 60 °C. Strong correlations (P < 0.01) among pH, CL, WBSF and colour parameters L* and b* were observed following the heating process. Increasing temperature induced gradual degradation of many muscle proteins, but myosin was not significantly degraded until 80 °C and actin showed no visible degradation throughout the whole heating process. Meanwhile, the structure of muscle fibres also changed significantly on heating, with sarcomeres contracting transversely and longitudinally and becoming condensed, but there was no occurrence of breakage within fibres. Heating temperature has a great effect on eating quality indicators, protein degradation and ultrastructure of pork muscle fibres. .