The Chemistry of Cookery

of flour. The mixture is left to stand for six or twelve hours, when it will have become what is called a _ferment_. After straining through a sieve, to separate the skins of the fruit, it is mixed with the sack of flour, water, &c. It is evident from this that it would not pay to add such a quantity in such a manner as a mere adulterant. The baker uses it for improving the bread, from his point of view. The _stuff_ or _rocky_ consists, according to Tomlinson, of one part of alum to three parts of common salt. The same authority tells us that the bakers buy this at 2_d._ per packet, containing 1 lb. in each, and that they believe it to be ground alum. They buy it thus for immediate use, being subject to a heavy fine if they keep alum on the premises. The quantity of the mixture ordinarily used is 8 oz. to each sack of flour weighing 280 lbs., so that the proportion of alum is but 2 oz. to 280 lbs. As one sack of flour is (with water) made into eighty loaves weighing 4 lbs. each, the quantity of alum in 1 lb. of bread amounts to 1/160th of an oz. The _rationale_ of the action of this small quantity of alum is still a chemical puzzle. That it has an appreciable effect in improving the _appearance_ of the bread is unquestionable, and it may actually improve the quality of bread made from inferior flour. One of the baker’s technical tests of quality is the manner in which the loaves of a batch separate from each other. That they should break evenly and present a somewhat silky rather than a lumpy fracture, is a matter of trade estimation. When the fracture is rough and lumpy, one loaf pulling away some of the just belongings of its neighbour, the feelings of the orthodox baker are much wounded. The alum is said to prevent this impropriety, while an excess of salt aggravates it. It appears to be a fact that this small quantity