Although the Texturometer was used in establishing the GF objective Texture Profile Analysis (TPA) of foods, it has been largely supplanted by the Instron. The Instron GF TPA parameters have been determined for the most part by the original Texturometer procedures. Some workers have chosen to measure only one or several of the GF TPA parameters; others have added new ones. Changes proposed to make parameter names more descriptive have not been universally adopted. Testing conditions (crosshead and chart speed, % deformation, etc.) have varied considerably and have often been poorly described. Multiple point non-GF TPA has been performed on foods using homemade as well as commercial instruments, e.g., Instron, Ottawa Texture Measuring System. Major shortcomings of studies involving TPA include poor experimental design, absence or improper use of statistical analysis and incomplete description of experimental materials and testing conditions. Despite certain shortcomings, TPA (GF or non-GF) via interpretation of stress-strain curves is, and will continue to be, extremely useful in evaluating the textural quality of foods, particularly when parameters can be correlated with sensory assessments.

Application of texture profile analysis to instrumental food texture evaluation

Mechanical properties of meat.

The tenderness of meat is probably the most important single factor in the consumer's assessment of its quality. This review describes the fundamental factors believed to be involved in determining the tenderness of meat. The contribution due to the pre-rigor contraction of the myofibrils and the possible control of this phenomena is discussed. The role of the connective tissue proteins is reviewed, particularly the effect of the age-related changes in the properties of collagen.

The basis of meat texture

A review of the methods used to measure meat texture indicates considerable confusion in terminology, test conditions, and interpretation of the readings that makes evaluation of the results a complex task. Standardization of the methods appears premature and until this is accomplished, the applied methodology must be reported fully. Errors due to instrument design can no longer be accepted since modern instruments that overcome this are readily available. A common error in terminology or interpretation is the use of the term shear to describe the rupture imposed on meat samples in popular tests. It is shown that meat generally ruptures in tension which is also the case during mastication; this explains why empirical measurements often relate to sensory readings. It is concluded that there is room for improvement in existing methods, particularly in the interpretation of the results using common sense, close observation and theoretical analysis.

Engineering assessment and critique of instruments used for meat tenderness evaluation

Contributions to the structural strength of meat samples by the myofibrillar and connective tissue components were altered by varying the myofibrillar contraction state, muscle type and the cooking temperature. Shear, tensile and adhesion measurements were used to evaluate quantitatively changes in the properties of the samples. Detailed examination of shear and tensile force-deformation curves suggested that the initial effect of shear, compression or tensile force was to produce a yield in the myofibrillar structure. After the initial yield, the applied force was probably resisted mainly by the connective tissue structure. Adhesion and tensile values showed changes which indicated a probable rearrangement of the collagen fibers in the connective tissue network as it adjusted to accommodate changes in the myofibrillar contraction state.

Possible relationships between shear, tensile, and adhesion properties of meat and meat structure

— The Instron tester served to evaluate physical properties of uncooked rabbit and beef muscle including work of rupture, breaking strength, break elongation elasticity and stress relaxation. These methods measure variations in muscle type, aging and post-mortem treatments comparably with shearing instruments. Shank showed higher tensile properties than tenderloin, less elasticity and lost more applied stress. With rabbit, the breaking force of longissimus dorsi unrestrained during rigor was .237 Ib/g ± 7.5% for samples 5.0 cm by 0.2–0.5 cm2 while restrained muscle gave .168 ± 9.9% and also exhibited higher elasticity and break elongation. Post-mortem aging decreased tensile properties and elasticity. Psoas muscle, characterized by more coextensive fibers, had higher tensile properties than longissimus dorsi.

D. W. Stanley

Papers

Evaluation of certain physical properties of meat using a universal testing machine