Taing, Kheang Chy (2003) The influence of rapid pH decline and high muscle temperature on the water holding capacity and softness of beef. Research Master thesis, Victoria University of Technology.

Abstract

The research in this thesis had two aims. The first was to develop an instrumental method to measure the softness of raw meat and the second was to investigate the influence of rapid pH decline and high muscle temperature post-mortem on the water holding capacity (WHC, that is, the muscles' ability to retain fluid) and softness of beef. For the instrumental analysis of muscle softness, different Instron compression (IC) methods were compared to sensory evaluation (SE) of meat. The instrumental methods involved compression of small muscle blocks (approximate size 4x5x6cm) parallel and perpendicular to the muscle fibre direction at 20 mm depths and also attaching cylindrical cores of meat (4.5 cm diameter) to the compression head to prevent the samples from collapsing. The most suitable method was compression of muscle blocks perpendicular to the muscle fibre direction to 5 mm depth, as this method was able to show that rapid pH decline and high muscle temperature gave softer meat than slow pH decline at a lower temperature. However, this method did not correlate with the SE scores; the SE method was not able to differentiate the variation in softness between samples. It was hypothesised that rapid pH decline and high muscle temperature post-mortem would lead to increased protein denaturation, reduced WHC , accelerated meat tenderisation and shortening of sarcomeres and hence soft and exudative meat. It was also hypothesised that these effects would be dependent on the muscle fibre type. In one of the experiments, electrically stimulated (ES) beef Longissimus dorsi (LD) muscles were hot boned from the carcasses and incubated in 37 and 14 °C water baths until rigor. We found that the pH decline rate of the muscles subjected to the high temperature was almost double that of the medium temperature treatment with increased protein denaturation, softer muscles and lower WHC. There were no differences in the sarcomere length or tenderness on day 1 or day 3 due to the treatments to indicate accelerated tenderisation. Thus the hypotheses that rapid pH decline and high muscle temperature post-mortem would lead to accelerated tenderisation or sarcomere shortening and subsequently exudative meat were not supported.

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