Abstract: A process for treating a hydrocarbon plant substrate containing glucids and proteins is disclosed wherein said substrate is hydrolyzed with a hydrosolubilizing enzyme to form hydrosolubilized glucids, the resulting product is fermented with yeast at a pH from 3 to 5 and the fermented product is subjected to thermolysis at a temperature ranging from 80.degree. C. to 140.degree. C. for a period of time of 30 seconds to one hour to obtain a food product having a higher protein content than the starting plant material and a particular flavor which is dependent upon the thermolysis conditions employed.