On the composition of food and how it is adulterated : with practical directions for its analysis / by W. Marcet.

  • Marcet, W. (William), 1828-1900.
Date:
1856
Catalogue details

Licence: Public Domain Mark

Credit: On the composition of food and how it is adulterated : with practical directions for its analysis / by W. Marcet. Source: Wellcome Collection.

    25/236 (page 5)
    bread, the dough is made to ferment by the action of leaven or yeast, previous to its introduction into the oven. Three materials^ therefore, are indispensably necessary to bread, namely, meal, leaven or yeast, and water. To these salt may be added as equally essential. Leaven, much used in France, Germany, and Sv^^itzerland, consists of a portion of the dough already undergoing fermentation; and, according to Liebig's views, it has the property of inducing by its presence a similar molecular change and chemical decomposition in the fresh dough with vi^hich it is mixed. Yeast, employed in England instead of leaven, is obtained from the fermentation of the wort in the manufacture of beer; its chemical composition bears a strong analogy to that of leaven; and it possesses the same power of inducing the fermentation of the dough. Fer- mentation raises the dough by the evolution of gas through its entire mass, the gas in question being carbonic acid; a small quantity of sugar and some alcohol also result from the same process, these various products owing their forma- tion to the decomposition of a part of the starch, and a little sugar preexisting in the flour, from the action of the fer- ment. During the process of baking, the whole of this alcohol and some carbonic acid are given out by the dough, and consequently a loss of flour is incurred. The reader will be astonished at the amount of alcohol, or spirits of wine, dissipated by the heat of the oven; thus, in London, the quantity of bread consumed annually, supposes the evolution of about three hundred thousand gallons of spirits, which, at the price of nineteen shillings per gallon, would be worth two hundred and eighty-jive thousand pounds. All the experiments undertaken with the view of prevent- ing the loss of this alcohol have failed; and in the military bakehouse at Chelsea, twenty thousand pounds have