Effect of Heat-cooking on Nutritional Availability of Iron and Selenium Contained in Beef

Abstract

Effect of heat-cooking on nutritional availability of iron and selenium contained in beef was examined. Three kinds of diets (casein diet, raw beef diet and roast beef diet) containing protein of 16%, iron of 20μg/g and selenium of 110ng/g were prepared. In the casein diet, sources of protein and iron were casein and ferric citrate, respectively and sources of selenium were casein (15ng/g) and selenite (95ng/g). In the raw or roast beef diet, sources of protein, iron and selenium were the raw or roast beef powder. Eighteen male four-week Wistar rats were divided into three groups and fed the casein, raw beef or roast beef diet for four weeks. Hemoglobin, serum transferrin saturation and iron contents in liver and kidney were significantly lower in the rats fed the beef diets than those fed the casein diets. Among the rats fed the beef diets, lower values tend to be observed in the rats fed the roast beef diet than in those fed the raw beef diet. In serum and hepatic selenium contents, the rats fed the raw beef diet showed significantly lower values than the other rats. Selenium contents of the rats fed the roast beef diet were similar to those of the rats fed the casein diet in serum and liver, but was significantly higher in kidney. Glutathione peroxidase activities of the rats fed the beef diets tended to be lower than those of the rats fed the casein diet in liver and kidney, and in particular, a significant difference was observed between the casein and roast beef groups. In a ratio of glutathione peroxidase to selenium content, the roast beef group showed significantly lower values than the other two groups in the liver and kidney. These results leads a possibility that heat-cooking reduces a nutritional availability of iron and selenium contained in beef.