PURPOSE: To prepare a semi-ripened food fiber having excellent effect to control the intestinal function, etc., by boiling and freezing dried vegetables such as leaf of Japanese radish, fermenting the resultant vegetable fiber with enzyme and yeast, and freeze-drying the fermented product quickly in the course of ripening process.

CONSTITUTION: Dried vegetables such as the leaf of Japanese radish are boiled, exposed to water stream to remove the harshness, cut to fine pieces, made to a ball, frozen, thawed with warm water, and dried to some extent. The obtained vegetable fiber is fermented with enzyme and yeast, and in the course of ripening, quickly freeze-dried to obtain the objective semi-ripened food fiber. The vegetable fiber can be activated by this process without lowering the activity to synthesize nucleic acids in the body, and the obtained food fiber is effective not only to control the intestinal function but also to energize the cell in the body, and exhibits the remedying effect to the paralysis of the peripheral nervous system, etc.