Experimental cookery

To the many students in her "Experimental Foods" classes who through their interest and enthusiasm have always been a stimulus to further work, the author wishes to express her most grateful appreciation. EXPERIMENTAL COOKERY CHAPTER I THE RELATION OF COOKERY TO COLLOID CHEMISTRY The early lines of food work cannot be expressed better than in the words of Ostwald (1922). "Scientific study of the field still contents itself with chapters on analysis and the recognition of adulterants, but chapters dealing with the preparation of food are hardly started. Much as every one would like to obtain better food for less money, study of such questions is regarded as menial and best left to the cook. A scientific study of the preparation of food is considered as only amusing even in scientific circles." Later Ostwald remarks that the chapters that are missing in food prepa- ration are the ones to which colloid chemistry may be applied. Since so many phases of food preparation are based on colloid chemistry it seems necessary to include in this book a chapter on its relation to cook- ery. It is a short and brief outline. As such, it can be used as an intro- duction or as a summary or for both introduction and summary of the work on food preparation, although the subsequent chapters have been written with the idea that at least portions of this chapter will be used in connection with each of them. Thomas Graham's contributions constitute the foundations of colloid chemistry. His most important results were published between 1861 and 1864. But it is only since the publications of von Weimarn and of Ostwald in 1906 and 1907 that rapid development has been made in colloid chem- istry, and it is an even shorter time since the most extensive applications of it have been made to food preparation. Graham used the terms crystalloids and colloids to apply to definite materials. Crystalloids were dialyzable through parchment membrane, whereas colloids were not dialyz- able. The terms are now misleading, for we know that any crystalloid can, by a definite treatment and the selection of the right medium, be brought into the colloidal state. Many of the so-called colloids can be crystallized. The term colloidal state indicates that the material is dispersed in another substance, so that it is preferable to speak of colloidal systems rather than colloids. Colloidal systems differ from molecular ones in the size of the dispersed particles. This difference in size of the particles gives different physical properties to the system. Bancroft states that "adopting the very flexible definition that a phase 1 2 RELATION OF COOKERY TO COLLOID CHEMISTRY is called colloidal when it is sufficiently finely divided, colloid chemistry is the chemistry of bubbles, drops, grains, filaments, and films, because in each of these cases at least one dimension of the phase is very small. This is not a truly scientific classification because a bubble has a film round it, and a film may be considered as made up of coalescing drops or grains." A knowledge of colloid chemistry is necessary to have a real understanding of processes and methods used in a large number of industries and occupa- tions. Bancroft gives a list of 60 such occupations, which include: "cream, butter, cheese, and casein products; cooking and washing." Classification of Substances Based upon the Degree of Dispersion in Solution