The Chemistry of Cookery

substitute the joint in an ordinary respectable meal of meat and pudding. [13] Before the Adulteration Act was passed, mustard flour was usually mixed with well-dried wheaten flour, whereby the redundant oil was absorbed, and the mixture was a dry powder. Now it is different, being pure powdered mustard seed, and usually rather damp. It not only lies closer, but is much stronger. Therefore, in following any recipe of old cookery-books, only about half the stated quantity should be used. [14] The reader who desires further information on this and kindred subjects will find it clearly and soundly treated (without any of the noxious pedantry that too commonly prevails in such treatises) in Dr. Andrew Combe’s _Physiology of Digestion_, which, although written by a dying man nearly half a century ago, still remains, like his _Principles of Physiology_, the best popular work on the subject. Subsequent editions have been edited and brought up to date by his nephew, Sir James Coxe. CHAPTER X. FAT—MILK. WE all know that there is a considerable difference between raw fat and cooked fat; but what is the _rationale_ of this difference? Is it anything beyond the obvious fusion or semi-fusion of the solid? These are very natural and simple questions, but in no work on chemistry or technology can I find any answer to them, or even any attempt at an answer. I will therefore do the best I can towards solving the problem in my own way. All the cookable and eatable fats fall into the class of ‘fixed oils,’ so named by chemists to distinguish them from the ‘volatile oils,’ otherwise described as ‘essential oils.’ The distinction between these two classes is simple enough. The volatile oils (mostly of vegetable origin) may be distilled or simply evaporated away like water or alcohol, and leave no residue. The fixed oils similarly treated are dissociated more or less completely. This has been already explained in Chapter VII. Otherwise expressed, the boiling point of the volatile oils is below their dissociation point. The fixed oils are those which are dissociated at a temperature below their