SINCE the publication of my last paper, I have been told, by a lady to whom the readers of "Knowledge" are much indebted, that in the fatherland of potatoes, as well as in their adopted country, they are always boiled or steamed in their jackets; that American cooks, like those of Ireland, would consider it an outrage to cut off the protecting skin of the potato before cooking it; that they are more commonly mashed there than here, and that the mashing is done by rapidly removing the skins, throwing the stripped potato into a supplementary saucepan or other vessel, in which they may be kept hot until the preparation is completed.
Returning to the subject at the point where I left, it I must endeavor to describe the effect of cooking on gluten. It is usually described as "partly soluble in hot water." My own examination of this substance suggests that "partially soluble" is a better description than "partly soluble" (Miller) or "very slightly soluble" (Lehmann). This difference is not merely a verbal quibble, but very real and practical in reference to the rationale of its cookery. A partly soluble substance is one which is composed of soluble and also of insoluble constituents, which, as already stated, is strictly the case with gluten in reference to the solvent action of hot alcohol. A very slightly soluble substance is one that dissolves completely but demands a very large quantity of the solvent. I find that the action of hot water on gluten, as applied in cookery, is to effect what may be described as a partial solution, that is, effecting a loosening of the bonds of solidity, but not going so far as to render it completely fluid.
It appears to be a sort of hydration similar to that which is effected by hot water on starch, but less decided.
To illustrate this, wash some flour in cold water so as to separate the gluten in the manner described in No. 29; then boil some flour as in making ordinary bill-sticker's paste, and wash this in cold water. The gluten will come out with difficulty, and when separated will be softer and less tenacious than the cold-washed specimen. This difference remains until some of the water it contains is driven out, for which reason I regard it as hydrated, though I am not prepared to say that the hydration is of a truly chemical character, not a definite compound of gluten and water, but rather a mechanical combination—a loosening of solidity by a molecular intermingling of water.
The importance of this in the cookery of grain-food is very great, as anybody who aspires to the honor of becoming a martyr to science may prove by simply making a meal on raw wheat, masticating the