Preference of taste or both aroma and taste between Wagyu (Japanese Black Cattle) beef and imported beef on market was compared to reveal reasons why Wagyu beef is considered to be more palatable than imported beef in Japan. Panelists ate heated beef samples and assessed preference on taste by pinching their noses and both aroma and taste by not pinching their noses. As a result there was no difference in preference on taste between both samples, but in the case of both aroma and taste Wagyu beef was significantly preferred to imported beef. Wagyu beef presented a preferable, sweet and fatty aroma, which was different from the conditioned raw beef aroma, while imported beef did not present such an aroma.Therefore, the existence of such an aroma was presumed to be one of the reasons why Japanese people preferred Wagyu beef to imported beef. We proposed to name this aroma Wagyu beef aroma.The optimum cooking temperature to generate Wagyu beef aroma was found to be 80℃. This aroma was almost absent in Wagyu beef immediately after slaughter. The experiment on additional storage of Wagyu beef slices suggested that a considerable high level of fat-marbling and contact with oxygen were necessary to generate Wagyu beef aroma. On the other hand, an antibacterial agent, chloramphenicol, did not inhibit the generation of Wagyu beef aroma in highly marbled beef stored under air, indicating that a group of bacteria including Brochothrix thermosphacta which is essential for the generation of the conditioned raw beef aroma were not responsible for the generation of Wagyu beef aroma.

No abstract

In our previous paper, a desirable odor generated in raw beef by conditioning, i. e., the conditioned raw beef aroma, was suggested to be produced by some kinds of bacteria at the site containing both leans and fats in the presence of oxygen. Thus, we isolated such a bacterium and examined some of its features. Bacterial isolates from beef loins were screened on sterile lean extract with floating sterile adipose tissue or sterile fat to obtain the bacterium producing the conditioned raw beef aroma. Of 89 isolates, one isolate (H 25W) producing this odor apparently was obtained. H 25W was gram-positive and catalase-positive, and occurred as unbranched rods in short chains. It was nonmotile and grew on the streptomycin-thallous acetate-actidione medium. These features implied that H 25W was Brochothrix thermosphacta, a very common bacterium in market meats. Some other features (oxygen-requirement, etc.) of H 25W coincided with those of Brochothrix thermosphacta. Furthermore, the type culture strain of Brochothrix thermosphacta ATCC 11509 demonstrated to have produced the conditioned raw beef aroma. Thus, H 25W which produced the conditioned raw beef aroma was strongly suggested to be Brochothrix thermosphacta.