Hartshorn

Hartshorn is the horn of male red deer.

Various substances were made from hartshorn shavings :

Hartshorn jelly or a decoction of burnt hartshorn in water was used to treat diarrhea. The coal of hartshorn, called calcinated hartshorn, was used as an absorbent, as well as in the treatment of dysentery. Salt of hartshorn (ammonium carbonate) was used as a for treatment of fevers, and as a smelling salt. Hartshorn was used to treat insect bites, sunstroke,stye, and snakebites.

Hartshorn salt (ammonium carbonate), also known simply as hartshorn, and baker's ammonia, was used as a leavening agent, in the baking of cookies and other edible treats. It was used mainly in the seventeenth and eighteenth centuries as a forerunner of baking powder. A half-teaspoon of hartshorn can substitute for one teaspoon of baking powder. It is called for in old German and Scandinavian recipes and, although rarely used in modern times, may still be purchased as a baking ingredient. Hartshorn helps molded cookies such as Springerle to retain their intricate designs during baking. Cookies made with hartshorn can be kept for a long time without hardening. Use of hartshorn may turn some ingredients, such as sunflower seeds, green.

Ammonium carbonate is especially suited to thin, dry cookies and crackers. When heated, it releases ammonia and carbon dioxide gases, but no water. The absence of water allows cookies to cook and dry out more quickly, and thinner cookies allow the pungent ammonia to escape, rather than to remain trapped, as it would in a deeper mass.

Ammonia released during the baking process reacts with glucose and fructose to form intermediate molecules that in turn, react with asparagine (an amino acid found in nuts, seeds, and whole grains) to form acrylamide, a carcinogen.

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Wikipedia