THE MEASUREMENT OF SHEAR FORCE BY CORE LOCATION IN LONGISSIMUS DORSI BEEF STEAKS FROM FOUR TENDERNESS GROUPS1

Sixty-four longissimus muscle steaks obtained from carcasses of Bos indicus or Bos taurus cattle were used to evaluate shear force requirements from the dorsal to lateral portion of the steak. Steaks were assigned to one of four tenderness groups based on preliminary analysis of shear force requirements of adjacent steaks used in the study. Six dorsal to lateral core positions were incorporated into the test procedures. Shear force requirements of cores of steaks in very tender and tender groups tended (P>0.05) to decrease from the dorsal to lateral position. The increase in shear values from dorsal to lateral was dramatic (P<0.01) in the tough and very tough groups. It appears that overall shear value influences the variation in shear values within the muscle. Location effects of tenderness within the longissimus muscle could be useful in future studies of the physical/biochemical effectors of tenderness.     

DIFFERENTIATION OF MYOFIBRILLAR AND CONNECTIVE TISSUE STRENGTH IN BEEF MUSCLES BY WARNER-BRATZLER SHEAR PARAMETERS

Heat induced changes in aged bovine m. longissimus dorsi (LD) and m. biceps femoris (BF) were studied by water bath cooking to 60, 70 or 80°C at slow (.12°C/min) and fast (.6°C/min) heating rates. Forcedeformation curves from the Warner-Bratzler (WB) shear device were used to evaluate specific changes in the myofibrillar (WB M-force) and connective tissue component (WB C-force) of tenderness. Other measurements include WB peak force value, cooking loss, collagen solubility and sensory evaluations. Differences due to muscle type were significant in all parameters except collagen solubility. Both WB M- and WB C-force were reduced by slow heating rate but for samples heated to 80°C, WB M-force was affected only by heating rate below 60°C while WB C-force was most influenced above 60°C. Effect of final temperature resulted in higher WB M-force from 60°C to 70°C, whereas WB C-force was most affected from 70°C to 80°C. On the contrary, WB peak force was less affected by final temperature. Due to concomitant and opposing changes in myofibrillar and connective tissue strength with increasing end point temperature, it is concluded that improvements in interpretations with regard to heat-induced changes and response of heat treatment in various muscles may be increased by measurement of WB M-force and WB C-force from shear force-deformation curves.     

IDENTIFICATION OF THRESHOLD LEVELS FOR WARNER-BRATZLER SHEAR FORCE IN BEEF TOP LOIN STEAKS

Threshold Warner-Bratzler shear (WBS) values were determined by regression analysis of WBS force values and trained sensory panel overall tenderness ratings of beef top loin steaks from A- and B-maturity carcasses (n = 678). Guidelines for retail and foodservice beef were based on 50 and 68% confidence levels, respectively, for overall tenderness ratings of "slightly tender." Due to the extreme variation in tenderness that exists in the current U.S. beef population, more stringent confidence levels were not practical. Threshold WBS values for retail and foodservice beef were 4.6 and 3.9 kg, respectively. When these values were tested against the population of beef in the National Consumer Retail Beef Study, the 4.6 kg value was 88.6% accurate at determining whether or not a steak would be rated less than "slightly tender"by consumers.     

FACTORS AFFECTING TENSILE AND WARNER-BRATZLER SHEAR VALUES OF RAW AND COOKED MEAT

The influence of slit width on the force deformation curves obtained for raw and cooked meat of different myofibrillar contraction states was investigated with a modified version of the Warner-Bratzler (WB) shear device. Decreasing the clearance or compressing the sample directly onto a base plate (i.e. no slit) had little effect on the initial yield force values. Meat samples retained most of their original tensile strength after compression to initial yield on the shear device. Even cold-shortened cooked samples compressed to peak force values retained over 30% of their original tensile strength. Peak tensile and peak WB shear force measurements were highly correlated: R²= 0.71, 0.94 and 0.88 for raw, stretched/cooked and contracted/cooked samples, respectively. The slopes (WB on tensile) of the regression lines were increased by both cooking and by contraction to below rest length. These results indicate that components other than tensile in the WB shear force measurements were increased by cooking and by myofibrillar contraction.     

MEASUREMENT OF PEA TENDERNESS

Abstract Twenty one tenderometers were compared in processing plants for their accuracy of measurement using wax wafers as the test material. The results indicate that there are serious differences among the tenderometers and that the accuracy of measurement is unsatisfactory for the purpose of grading peas to establish the price paid to the grower. If a relationship of compatible trust is to remain between the processor and the grower, serious consideration must be given either to better calibration of currently used tenderometers or to devising some other method of grading and paying for peas.     

MEASUREMENT OF PEA TENDERNESS

The effect of pendulum inertia on Pea Tenderometer readings was examined by recording the pendulum angle and the torque that it applies to the peas during a test. The effect was significant at the critical point in the test cycle where the torque is at a maximum. It was concluded that this affects the standardization of the Tenderometer.     

EFFECT OF INDIVIDUAL MUSCLES AND CONNECTIVE TISSUE LEVELS ON THE SENSORY AND SHEAR PROPERTIES OF RESTRUCTURED BEEF STEAKS

Restructured steaks were made from slices of forequarter muscles known to be different in tenderness. Additional steaks were made from pieces that were sorted to contain either epimysium, intramuscular connective tissue sheets or no visible connective tissue. Texture panels and shear force values could discriminate between steaks from some of the different muscles. High correlations ( P < 0.05) existed between connective tissue amounts and the sensory evaluations of residual connective tissue toughness and instrumental shear force values.     

USE OF MECHANICAL TENDERIZATION TO INCREASE THE TENDERNESS OF BULLOCK BEEF1

The biceps femoris (BF), semimembranosus (SM) and longissimus dorsi (LD) muscles from bullocks and steers were passed through a mechnical tenderizer zero (OX), once (1X), twice (2X) or three times (3X). All three muscles were evaluated for cooking loss, cooking time and textural properties on an Instron Universal Testing machine. In addition, LD muscle steaks were presented to a sensory panel for evaluation. The passing of the SM and LD muscles through a mechanical tenderizer one or two times decreased peak load and fail energy and increased peak elongation and fail load values. LD steaks from bullocks not passed through the mechanical tenderizer (OX) were least esy to fragment, had the most detectable connective tissue and had lowest overall tenderness ratings. Passing bullock beef once (1X) through a mechanical tenderizer improved palatability ratings to a level comparable to untenderized steer beef.     

COOKING AND SHEARING METHODOLOGY EFFECTS ON WARNER-BRATZLER SHEAR FORCE VALUES OF PORK

Pork loin chops from 50 carcasses were used to evaluate the effect of cookery method and shearing methodology on Warner-Bratzler shear (WBS) force values. Chops were cooked to an internal temperature of 70C on either an electric openhearth grill or in a commercial convection oven. After a 2 h cooling period, five 1.27-cm diameter cores from each chop were sheared once through the center of the core with either: (1) a Warner-Bratzler machine; (2) an Instron Universal Testing Machine with a WBS device in compression; or (3) an Instron Universal Testing Machine with a WBS device in tension. Chops cooked in the convection oven had lower (P < 0.03) WBS force values than chops cooked on an open-hearth grill (2.78 vs 2.98 kg, respectively). Shear force values obtained with the Warner-Bratzler machine were lower (1.93 kg; P < 0.01) than those from the Instron with either the WBS device in compression (3.53 kg) or in tension (3.18 kg).