Meat texture of Piemontese young bulls measured by two physical methods

Warner-Bratzler (WBsf) and Texture Profile Analysis (TPA) are the most widely used mechanical methods to measure meat texture. The WBsf measures the maximum force (PF) required to shear round cores obtained from cooked meat. The TPA, based on the imitation of the chewing process and performed with a double-compression cycle on raw meat, gives a wide range of texture properties, such as hardness, cohesiveness, gumminess, springiness, adhesiveness and chewiness. To obtain more information from WBsf and TPA, some modifications to the original protocols were suggested: 1) to perform WBsf on raw meat strips in order to identify the initial yield (IY), as a measure of the strength of the myofibrillar structure and to calculate the difference between PF and IY (PF-IY) as an index of connective tissue toughness; 2) to perform TPA using a modified square compression cell that avoids transversal elongation of the sample; the stress at 20% and 80% of the maximum compression would assess the myofibrillar and connective tissue strength, respectively. The aim of this study was to compare the modified WBsf and TPA methods on beef during ageing and to assess correlations. At 2 and 10 days post mortem two steaks were taken from LTL muscle of 20 Piemontese bulls. Raw meat strips, 1 cm2 in cross section, were sheared perpendicular to the fiber direction with a WBsf device or compressed perpendicular to the fiber axis with a square compression probe (1 cm2) at 20% and 80% of sample thickness. Data were analysed by the GLM procedure. The lower IY and the higher difference PF-IY at d10 in comparison with d2 certify the tenderizing effect of ageing on myofibrillar tissue. No significant differences for PF were found, because the measurements were taken on raw meat and therefore the tenderizing effect of cooking on connective tissue was lacking. A significantly lower force was detected at d10 for hardness at 20%, which reflects the tenderizing effect of the proteolytic enzymes on the myofibers. On the contrary, as ageing does not influence the mechanical resistance of connective tissue, no significant differences were detected for hardness at 80%. Both methods are suitable to evaluate meat texture, but the poor correlations between the WBsf and TPA parameters (r ranged from -0.2 to 0.4 and four out of thirty were significant) indicate that these tests are complementary and measure different aspects of meat texture.