514 THE POPULAR SCIENCE MONTHLY. 



THE CHEMISTEY OF COOKEEY. 



By W. MATTIEU WILLIAMS. 



XXXIL 



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 pro- 

 tecting skin of the potato before cooking it ; that they are more com- 

 monly mashed there than here, and that the mashing is done by rapid- 

 ly removing the skins, throwing the stripped potato into a supplement- 

 ary 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 en- 

 deavor to describe the effect of cooking on gluten. It is usually de- 

 scribed 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 prac- 

 tical 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 effect- 

 ed 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 difiiculty, and when separated will be 

 softer and les8 tenacious than the cold-washed specimen. This differ- 

 ence 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 com- 

 pound 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 



