Dietary tea reduces the iron content of beef

Abstract

We hypothesized that the lightness of Japanese beef was related to the concentration of heme iron. In Experiment 1, six Japanese Black heifers were allotted randomly to one of three treatment groups: a basal concentrate ration (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 slaughtered and the M. longissimus thoracis, M. semimembranosus, and M. gluteus medius 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. semimembranosus from the control cattle, and a∗ (redness) and √(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) indicated that inclusion of tea in the diet increased intramuscular lipid and reduced the muscle iron content. There was a significant negative correlation ( r 2=0.79) between muscle iron content and L ∗ value (lightness). For Experiment 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 × Holstein or Japanese Black × Japanese Black/Holstein. There was no relationship between muscle iron content and intramuscular lipid content ( r 2=0.001). In Experiment 3, samples of M. longissimus dorsi 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. longissimus thoracis from Japanese Black and Japanese Brown × Holstein cattle fattened in Japan was significantly less than the iron content of M. longissimus 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 green tea to Japanese cattle; also, there may be a genetic basis for the lower iron, and lighter color, of beef produced in Japan.