Change of Flavonoid Contents Before and After Cooking in Model Menu of Daily Meals

Abstract

Flavonoids have a variety of functions, such as antioxidant activity, and are expected to have a disease prevention effect. It is necessary to understand the amount of flavonoids in the meal that people consume actually, for investigation the relationship between the disease preventive effects of flavonoids and the amount of flavonoid intake. However, there are few reports on the flavonoid content in the meal that Japanese people usually eat. In this study, we investigated the amount of flavonoids contained in 19 meals that prepared during school lunch practice at a registered dietitian training facility, as model menus for the daily meals of Japanese people. In addition, we also compared the contents before and after cooking in order to investigate the changes in flavonoid content due to cooking. The values of flavonoid contents before and after cooking were obtained from samples that had been washed and peeled, and those that were cooked according to the recipes, respectively. The flavonoid (quercetin, kaempferol, daidzein, genistein, apigenin, and luteolin) contents of each dish were measured using high-performance liquid chromatography (HPLC). The average flavonoid contents before and after cooking were 7.03±0.49 mg/meal (0.21±0.04 mg/meal-25.96±1.90 mg/meal) and 7.31±0.56 mg/meal (0.08±0.02 mg/meal-31.57±2.11 mg/meal), respectively, with a large variation depending on the meal. Cooking noticeably diminished the flavonoid content in 16 out of 95 dishes and caused a significant increase in 10 dishes