Nanomechanical characteristics of meat and its constituents postmortem: a review

Tenderness/toughness are two important factors in meat evaluation and can be well explained by their mechanical and nanomechanical characteristics, which in turn are highly affected by the complex arrangement of meat numerous constituents and the influence of endogenous enzymes on this biological structure. It has been also revealed that post-slaughter variations in muscle characters that make muscle to transform to meat are a consequence of changes in the nanomechanical properties of myofibrillar proteins through linkage with each other or even through their breakdown. However, background toughness that is related to the connective tissues exists just at the time of slaughter and does not change over the time. The most famous instruments that measure the mechanical characters of myofibrils in pico/nano scale are atomic force microscopy, also known as scanning force microscope, optical tweezer, and glass microneedle. In this regard, mechanical terms such as torsional strength, rotational Brownian motion, elastic modulus, viscoelasticity, flexibility, etc. are generally used to show different behavior of meat ultrastructure and the changes that usually occur in postmortem muscle. It is expected that the evaluation of nanomechanical properties of muscle cells and connective tissues, particularly when the muscle undergoes different changes, be useful in order to justify many features of meat postmortem.