The present invention relates to a novel process for the ozone treatment of unground plant materials such as wheat grains. According to the invention, this process consists in allowing the plant material to stand for at least one day after a prehumidification followed by an ozonization involving a complementary humidification that adds from 3 to 10% by weight of water, based on the dry weight of the plant material. This process is applied especially to wheat grains. In this case, a process according to the invention that enables the ozone to reach the core of the grains is carried out in order to manufacture so-called "technological" flours. The physical and chemical properties of such flours, observed as a function of the parameters of the ozonization process, are presented.