食肉の風味に影響をあたえる骨格筋の特性について

It is often perceived that different parts of meat have different textures and flavors. This difference is partly due to the amount and quality of fat in the meat, but the texture and flavor also differ in the lean part of the meat. Lean meat consists mainly of muscle fibers, which can be classified into slow- and fast-twitch muscle fibers, which differ in contractile and metabolic properties. Muscle fiber type composition is known to influence meat quality although its mechanism is not fully understood. First, we examined whether the amount of free amino acids, an important taste compound, differed among muscle fiber types. We hypothesized slow-twitch fibers have higher oxidative abilities with higher TCA cycle substrates leading to produce a variety of amino acids. Twenty-one skeletal muscle samples were collected from various muscle tissues of carcasses of Japanese Black castrated cattle and electrophoresis was performed to determine muscle fiber type composition. We revealed an obvious positive correlation between the composition of slow-twitch fibers and total free amino acid content. Next, we examined taste intensities of meat by taste sensor, and found significant positive correlations of the composition of slow-twitch fibers with umami taste, and with richness. This result suggests that high levels of slow-twitch fibers can induce strong umami taste and richness in beef. Lastly, we further investigated water-soluble compounds other than free amino acids in beef. We separated beef hot water extracts by reversed-phase chromatography and evaluated the sensory characteristics of each fraction using the Check-All-That-Apply (CATA) method, and found that each fraction formed a different flavor. Among the fractions, there were some fractions that were evaluated as "meat flavor-like" suggesting the existence of compounds that characterize beef flavor. Further investigation is needed to identify compounds to contribute these substances and their relationship to muscle fiber type.