Met-myoglobin formation, accumulation, degradation, and myoglobin oxygenation monitoring based on multiwavelength attenuance measurement in porcine meat.

We propose a simple, rapid, and nondestructive method to investigate formation, accumulation, and degradation of met-myoglobin (met-Mb) and myoglobin oxygenation from the interior of porcine meat. For the experiment, color photos and attenuance spectra of porcine meat (well-bled muscle, fat, and mixed) were collected daily to perform colorimetric analysis and to obtain the differences of attenuance between 578 and 567 nm (A578-A567) and between 615 and 630 nm (A630-A615), respectively. Oxy-, deoxy-, and met-myoglobin concentration changes over storage time were also calculated using Beer­Lamberts' law with reflectance intensities at 557, 582, and 630 nm. The change of A578-A567 was well matched with the change of myoglobin oxygenation, and the change of A630-A615 corresponded well with the formation and degradation of met-Mb. In addition, attenuation differences, A578-A567 and A630-A615, were able to show the formation of met-Mb earlier than colorimetric analysis. Therefore, the attenuance differences between wavelengths can be indicators for estimating myoglobin oxygenation and met-Mb formation, accumulation, and degradation, which enable us to design a simple device to monitor myoglobin activities in porcine meat.

Usefulness of electromagnetic induction type of force transducer and actuator for myofibril mechanics.

A high performance device for measuring force and length change during myofibril contraction is fabricated. The principle of a device depends on the law of electromagnetic induction. Homogenized myofibrils were attached between two wires exposed in the uniform magnetic field by silicon adhesive under an inverted microscope. The purpose of this study is to examine performance whether the electromagnetic induction type of device actually works. Sensitivity and time resolution of force transducer was 50nN and 1ms respectively. Working displacement and time resolution of actuator as length transducer was 1-20 µm and 1.2 ms. We confirmed the performance of the device by showing appropriate force response to changes in length during myofibrils contraction, and possibility of application of the device to myofibril mechanics is discussed.

Measurement of muscle fiber stiffness during stretch with two continuous different velocities in skeletal muscle fibers.

Ca2+ activated single glycerinated muscle fibers were stretched by 3% of its slack length Lo with moderate velocities ranging from 0.015 to 0.15Lo, and muscle fiber stiffness during and after stretch was measured by applying sinusoidal vibrations (peak-to-peak amplitude, 0.1% of Lo, 2kHz). During a single stretch, the fiber was first stretched by 1.5% with a velocity, and then it was further stretched by 1.5% with another velocity. It is suggested that, during stretch, a considerable fraction of cross-bridges slow down their cycling rate and increase their force-generating ability.