Meat Science
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Changes in tenderness of a range of beef muscles with ageing

BRAHMAN NEWS SEPTEMBER 2007 Issue #156

There is renewed interest in opportunities to upgrade the quality and value of certain cuts of beef such as chuck, topside, silverside and thick flank.

Two recent American studies have investigated, inter alia, tenderness of numerous different muscles from beef carcases of various yield-grade and quality-grade combinations. Muscle effects were observed in both studies as determined by Warner-Bratzler shear (tenderness). USDA quality grade had an effect on shear force for most muscles, with USDA Select generally being tougher than USDA Choice (premium). In one of the studies, the effects of post-mortem ageing on the tenderness of 17 individual beef muscles from two USDA quality grades was studied.

The muscles were removed from primal cuts obtained from a commercial packing plant. Steaks were prepared from each muscle, vacuum packed and aged at 2°C for 2, 4, 6, 10, 14, 21 or 28 days. At the end of the ageing period, the steaks were cooked and tenderness assessed by measurement of Warner-Bratzler shear force.

Sixteen of the 17 muscles studied benefited from ageing (i.e. shear values decreased). The exception was a small muscle (the M.teres major) found in the muscle groups of the chuck and blade. Generally, muscles that had higher shear force values 2 days post-mortem responded more to ageing – for both the ‘Choice’ and ‘Select’ quality grades.

In general, muscles from the premium Choice grade improved more rapidly in tenderness from 2 to 10 days than corresponding muscles from the lower Select grade. Select-grade muscles required 20 days or more of ageing to achieve a majority of their ageing response; some muscles, including ones in the topside (M. semimembranosus), silverside (M. biceps femoris and M. semitendinosus), thick flank (M.rectus femoris), and rump (M. gluteus medius) required up to 28 days ageing at 2°C. A majority of ageing response was competed by Choice muscles 4 to 6 days sooner than for comparable Select muscles.

The study was in general agreement with earlier reports that ranked the tenderloin (psoas major) and blade (infraspinatus) among the most tender, and the topside (semimembranosus) and silverside (biceps femoris) among the least tender both before and after ageing.

This study has particular relevance to processors and distributors of vacuum-packed economy cuts for the domestic market here: if ageing chillers operate at 0°C or lower, the time to achieve most of the possible reduction in toughness through ageing may be longer than 4 weeks.