Dietary tea reduces the iron content of beef

We hypothesized that the lightness of Japanese beef was related to the conc entration of heme iron. In Experiment 1, six Japanese Black heifers were al lotted randomly to one of three treatment groups: a basal concentrate ratio n (40% flaked corn) or the same diet and either 2 kg/d wheat bran or 0.5 kg /d green tea. After feeding the diets for 174 d, the cattle were slaughtere d and the M. longissimus thoracis, M. semimembranosus, and M. gluteus mediu s were sampled for meat color, iron, and lipid content. The iron content of the M. semimembranosus from the tea-fed cattle was lower than in M. semime mbranosus from the control cattle, and a* (redness) and root(a*(2)+b*(2)) ( saturation) values were lower in M. semimembranosus from bran- and tea-fed cattle than in control cattle. Treatment main effects (across muscles) indi cated that inclusion of tea in the diet increased intramuscular lipid and r educed the muscle iron content. There was a significant negative correlatio n (r(2)=0.79) between muscle iron content and L* value (lightness). For Exp eriment 2, the effect of beef breed type on meat color and iron content of M. longissimus thoracis was investigated using stored meat samples from six breeds from a previous fattening experiment done under a high nutritional plane. Muscle iron content was significantly lower in Japanese Black cattle than in Japanese Black x Holstein or Japanese Black x Japanese Black Holst ein. There was no relationship between muscle iron content and intramuscula r lipid content (r(2)=0.001). In Experiment 3, samples of M. longissimus do rsi were obtained from 17 Wagyu crossbred and 3 Angus crossbred cattle fed a corn concentrate diet in the USA for 148 d. Iron content of the M. longis simus thoracis from Japanese Black and Japanese Brown x Holstein cattle fat tened in Japan was significantly less than the iron content of M. longissim us dorsi from cattle raised in the USA. Overall, the data indicate that it is possible to lower muscle iron, and lighten muscle color, by feeding gree n tea to Japanese cattle; also, there may be a genetic basis for the lower iron, and lighter color, of beef produced in Japan. (C) 1999 Elsevier Scien ce Ltd. All rights reserved.