Temperature.—Many a cook fails and knows not why, because she does not understand the influence of temperature upon materials and food. Flour and liquids for unfermented breads cannot be too cold, while for bread prepared with yeast, success is largely dependent upon a warm and equable temperature throughout the entire process.
Cooking Utensils.—The earliest cookery was probably accomplished without the aid of any utensils, the food being roasted by burying it in hot ashes or cooked by the aid of heated stones; but modern cookery necessitates the use of a greater or less variety of cooking utensils to facilitate the preparation of food, most of which are so familiar to the reader as to need no description. (A list of those needed for use will be found on [page 66].) Most of these utensils are manufactured from some kind of metal, as iron, tin, copper, brass, etc. All metals are dissolvable in certain substances, and some of those employed for making household utensils are capable of forming most poisonous compounds when used for cooking certain foods. This fact should lead to great care on the part of the housewife, both in purchasing and in using utensils for cooking purposes.
Iron utensils, although they are, when new, apt to discolor and impart a disagreeable flavor to food cooked in them, are not objectionable from a health standpoint, if kept clean and free from rust. Iron rust is the result of the combination of the iron with oxygen, for which it has so great an affinity that it will decompose water to get oxygen to unite with; hence it is that iron utensils rust so quickly when not carefully dried after using, or if left where they can collect moisture. This is the reason why a coating of tallow, which serves to exclude the air and moisture, will preserve ironware not in daily use from rusting.
"Porcelain ware" is iron lined with a hard, smooth enamel, and makes safe and very desirable cooking utensils. German porcelain ware is unexcelled for culinary purposes.
"Granite ware" is a material quite recently come into use, the composition of which is a secret, although pronounced by eminent chemists to be free from all injurious qualities. Utensils made from it are light in weight, easily kept clean, and for most cooking purposes, are far superior to those made from any other material.
What is termed "galvanized iron" is unsuitable for cooking utensils, it being simply sheet iron coated with zinc, an exceedingly unsafe metal to be used for cooking purposes.
Tin, which is simply thin sheet iron coated with tin by dipping several times into vats of the melted metal, is largely employed in the manufacture of cooking utensils. Tinware is acted upon by acids, and when used for holding or cooking any acid foods, like sour milk, sour fruits, tomatoes, etc., harmful substances are liable to be formed, varying in quantity and harmfulness with the nature of the acid contained in the food.
In these days of fraud and adulteration, nearly all the cheaper grades of tinware contain a greater or less amount of lead in their composition, which owing to its greater abundance and less price, is used as an adulterant of tin. Lead is also used in the solder with which the parts of tinware are united. The action of acids upon lead form very poisonous compounds, and all lead-adulterated utensils should be wholly discarded for cooking purposes.
Test for Lead-Adulterated Tin.—Place upon the metal a small drop of nitric acid, spreading it to the size of a dime, dry with gentle heat, apply a drop of water, then add a small crystal of iodide of potash. If lead is present, a yellowish color will be seen very soon after the addition of the iodide. Lead glazing, which is frequently employed on crockery and ironware in the manufacture of cooking utensils, may also be detected in the same manner.