We learn from the researches of Horace T. Brown (Chemical Society's Transactions, 1890, pp. 458-528; and 1892, pp. 352-364) that certain grains contain a greater or less amount of an unorganised ferment (enzyme) which, during digestion, has the power to dissolve the walls of the cells of the grain, and thus to expose their contents to the action of the digestive fluids. The membrane which forms the walls of these cells is thin, tender, and is composed of nearly pure cellulose. The enzyme in question has no power to attack starch or the woody and more or less lignified fibre of hay, and does not become fully developed in the grain until the grain has become ripe. True ripening of the grain takes place only after more or less of the original moisture of the grain has been given off. The abundant presence of this enzyme in good oats furnishes us with an explanation of the great rapidity with which the contents of these grains become broken up in the early stages of digestion, and confirms the high estimation in which oats are held as a food for horses; for without this enzyme a considerable portion of the flour of the oats would be unaffected by the gastric and pancreatic juices, and would enter the caecum undigested. "The animal itself, besides affording a favourable temperature, a suitable mixture of fluids, and plenty of mechanical movement, does not contribute to the dissolution of the cell-membrane, which is wholly brought about by the enzyme pre-existent in the grain" (Brown). This writer (Proceedings of the Royal Society, 63, 1898, page 3) has found that most of this enzyme exists in the inner layer of the husk (aleurone layer).

This enzyme of grain, like those animal enzymes, ptyalin and pepsin, is a chemical substance, and is different from the ferments produced by bacteria. According to Gamjee, the activity of enzymes is destroyed by exposure to a temperature of 1260 F., which is a fact that probably explains the reason why the feeding value of good oats becomes lessened by the process of kiln-drying or parching. Barley, which either contains very little of this enzyme or is wholly deficient of it, is almost always improved by parching.

Diastase is an unorganised ferment that converts starch into malt-sugar (maltose) and British gum (dextrin), and thus renders it soluble. Diastase is formed only during germination, as in malting.

The reaction, as given by Bloxam, is :

3C6H10O5 (starch) + H10 =C12H12O11 (maltose) + C6H10O5 (dextrin).

Cerealin, which was discovered by Mege Mouries, is an enzyme that occurs in bran. Its action is similar to that of diastase, but is much slower.