The word “protein” was coined by Jöns Jakob Berzelius in 1838. For the previous 150 years, however, there had been the concept of an “animal substance, ” slight variants of which were thought to make up muscles, skin, and blood. In each form the substance was initially believed to be gluey. But it turned into hard, hornlike material when heated and became foul-smelling when kept under moist, warm conditions, giving off an alkaline vapor. This contrasted with the properties of starch and sugar and most whole plants that went to acid during damp, warm storage.

For people interested in nutrition, the obvious question was: “How does the animal kingdom, which as a whole lives on the plant kingdom, convert what it eats into the apparently very different animal substance?” Humans were, of course, included in the animal kingdom and assumed to have essentially the same nutritional system as animals. Some eighteenth-century discoveries threw light on the problem.

In 1728, the Italian scholar Jacopo Beccari announced that he had discovered the presence of a material with all the characteristics of “animal substance” in white wheat flour. When he wetted the flour to make a ball of dough, then washed and kneaded it in water, the fine, white starchy particles washed out. What remained was a sticky pellet of gluten, which, if its origin were unknown, would be judged animal in nature. Beccari concluded that the presence of this portion of preformed “animal substance” made wheat particularly nutritive. Wheat flour, as a whole, did not show animal properties because the greater quantity of starch overwhelmed the reactions of the gluten.