Abstract
The bright and yellow color of yellow alkaline noodles (YAN) is a desirable end-use quality. There is a high correlation between dough discoloration and polyphenol oxidase (PPO) activity in wheat seed. It was possible to estimate the grain PPO activity by the 3, 4-dyhydroxy-L-phenylalanine (L-DOPA) method, which is a simple method of evaluating wheat grain PPO activity, using grains of hard wheat varieties from the Hokkaido region of Japan. However, the correlation of grain PPO activity with YAN discoloration was lower than that of flour PPO activity. Therefore, a simple method of evaluating PPO activity using wheat flour was developed to achieve more efficient selection for the breeding program. It was described as follows; a glass test tube with a flat bottom containing 0.2g of wheat flour and 4ml of a 10mM L-DOPA solution was shaken for 1 hour and left for 18 hours at room temperature; the L*, a*, and b*values of the suspension were then measured. There was a high negative correlation between the L*value measured by the present simple method and the PPO activity in wheat flour measured by the conventional method (oxygen-electrode method). Therefore, we concluded that the L*value measured by the simplified L-DOPA method, could be applied to select the lines possessing lower PPO activity, and consequently less YAN discoloration.
