There are a variety of ferments and other materials which have the power of converting starch into dextrin and sugar. They are ptyalin in the saliva, amylopsin in the pancreatic juice, diastase, a ferment in the intestinal juice, and the substances inulin and lichen-in. The latter is obtainable from various lichens, such as Iceland moss. Mucin and certain gums are also amylolytic.

Of these different ferments, the one which is found to be of most practical service for predigestion is diastase.

The action of the diastase of malt resembles that of the ptyalin of the saliva and the amylopsin of the pancreatic juice, which alter starches into dextrin and maltose. It is prepared in several ways, as, for example, in meal of malt, which may be added to farinaceous foods, and in the form of malt extracts, and various malted foods (malted milk, etc.) are sold for invalid use or for infant feeding.

Taka-diastase is a stable concentrated form of diastase, said to possess the power of converting 100 times its weight of starch into sugar in ten minutes. The dose is 2\ grains after eating.

In such preparations the predigestion of amylaceous foods is carried to the extent of more or less complete conversion of the starch into dextrin and maltose. The diastase has no action in the stomach provided the acid gastric juice is being secreted, for it only causes fermentation in a neutral or alkaline medium; in fact, the ferment is probably destroyed before reaching the intestine, but it may act in the stomach for half an hour or so before the reaction of the gastric juice becomes too strongly acid. The presence of alkaline carbonates retards the action of diastase. In early infancy the amylolytic ferments of the salivary and pancreatic fluids are not well developed and are very meagre in quantity. If a young child is unable to digest milk for any reason, malted food may be ternporarily supplied in some cases, because in it the starch is already more or less completely digested and is ready for absorption. In general, the value of malted foods and malt extracts depends upon the predigested starch which they contain, which furnishes nutrition, rather than upon the action of the diastatic ferment within the alimentary canal.

Ground malt itself possesses even stronger digestive action upon starches than malt extracts. The latter contain the ferment diastase, dextrin, maltose, and a portion of the salt and some nitrogenous ingredients of barley. Both ground malt and malt extracts digest starches at a moderate heat, not exceeding 1500 F. There are many varieties of malted foods, but Liebig's Infant Food is a good illustration of this type. It is prepared as follows (see also P- 151):

Mix a half ounce each of ground malt and wheat flour, seven and one fourth grains of potassium bicarbonate with one ounce of water and five ounces of sweet cow's milk. Warm slowly and stir until thick. Remove from fire, stirring for five minutes, replace over fire, and remove when quite thick. As the diastase continues to act the mass will become thin and sweet. Boil and strain. It contains gluten and albumin of flour and barley, besides dextrin and maltose. The food thus prepared is very nutritious, for it not only contains the proteid materials of the milk, but those also of the wheat flour and malted barley (gluten and albumin), as well as the predigested starch. The malted foods which are made with desiccated milk and malted flour are deficient in fats, salt, and proteid material, but the lack of these substances can be supplied by the addition to the food, when used, of cream and beef juice. The digestibility of bread may be increased by adding 5 grains of diastase to the pound of flour mixed in the dough.

For manufacturing malted foods the wheat or barley flour should be baked in order to rupture the starch granules and make them more soluble.