Effect of Cooking on the Content of Dietary Fiberand Method
for Determination of Dietary Fiber in Vegetables Yoko SAITO and Yasuko OHIWA
Department of Food Science and Nutrition, Faculty of HomeEconomics,
Koriyama Women's University Kaisei
The effects of cooking on the contents of dietaryfiber in 11 kinds of vegetables were studied using Prosky methodand modified Prosky method, and the contents of dietary fibermeasured by both methods were compared in each other. In themodified Prosky method, dietary fiber values were determinedwithout subtraction of crude protein (nitrogenΧ6.25) inenzyme digested residue.
Boiling or simmering increased the amounts of dietary fiber incarrot, edible burdock, onion and cabbage, but noticeably decreasedthose in santohsai, Chinese chive and Chinese cabbage. Frying anddeep-frying increased the amounts of dietary fiber in carrot,edible burdock, Japanese radish, cabbage, spinach, santohsai,Chinese cabbage and sweet pepper, but decreased those in onion,Chinese chive and komatuna.
The content of crude protein in enzyme digested residue was greaterin leafy vegetables except cabbage(44~126mg/g) than in rootvegetables(24~37mg/g), and was further increased by cooking in mostkinds of vegetables. The contents of dietary fiber determined bythe modified Prosky method were 10 to 50% larger than thosedetermined by Prosky method in raw leafy vegetables, but in rootvegetables the contents of dietary fiber determined by both methodswere not so different each other.
From above results it was supposed that the composition of nitrogencontaining compounds in enzyme digested residue was needed for theaccurate determination of the content of dietary fiber especiallyin leafy and cooked vegetables.
Key words: vegetables, cooking, dietary fiber, Prosky method,modified Prosky method |
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