Effect of automated pre rigor stretching on beef tenderness development
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This thesis discusses the effects of pre rigor stretching technology by SmartStretchTM/ SmartShapeTM (4S) technology on beef tenderness development in M. longissimus dorsi. Twelve steers (approximately two years of age) were selected and slaughtered at the Ruakura abattoir under a standard slaughtering process. Both loins (M. longissimus dorsi) from all animals were randomly allocated into two treatments [stretching (4S) or control] (left or right) depending upon sides and three ageing times (1, 7 and 14 days of ageing). Assigned stretching loins were stretched with a 4S machine (Fix-All Services Company Ltd, Hamilton, New Zealand) whereas non-stretched loins (controls) were wrapped in cling polyethylene film. Initial and final lengths of 4S stretched loins were measured. The entire sampling and treatment process was conducted in approximately around one hour and then all meat loins were transported to a laboratory for storage at -1.5°C. At 24 hours post mortem, the length of the stretched loins was measured again and all meat loins were cut into three sections in preparation for three different ageing times. The meat sections of 7 and 14 day aged loins were weighed to determine for purge loss measurement prior to vacuum packaging. At the assigned ageing times (1, 7 and 14 days of ageing), each loin was separated into five parts for different measurements including shear force (two tenderometers), sarcomere length, drip loss and biochemistry analysis (proteolysis). The meat loins aged for 7 and 14 days were reweighed to determine purge loss. The results showed that there was on average a 33% increase in length by 4S and there was no significant difference in pH value due to the 4S treatment. In addition, there was no significant difference for sarcomere length between treatments. Shear force values were not influenced by 4S (P > 0.05); however, ageing contributed to an improvement in tenderness (P < 0.05). Moreover, there was no significant effect of the 4S treatment on water-holding capacity of loins. A Western blot assay showed that there was no stretching effect on extent of proteolysis of desmin degradation early post mortem; however, with ageing apparent evidence on muscle protein degradation was observed. For a fuller picture of the value of 4S treatment, the 4S technology should be applied to a range of beef muscles to attain with different percentage increases in length, types of cattle, either electrical stimulated or not, various pH values, different ageing times and temperatures to explore optimal extent of stretching to achieve maximum meat tenderness.