Q. Why is it not needful to put yeast into wine?
A. Because fruit contains carbon, hydrogen, oxygen, and nitrogen, in the form of “gluten;” and, therefore, ferments spontaneously.
(Gluten is explained fully in the Appendix.—Turn to the word in the Index.)
Q. Does not malt contain carbon, hydrogen, oxygen, and nitrogen, as well as fruit?
A. No; the sugar of malt contains carbon, hydrogen, and oxygen, but no nitrogen; in consequence of which, yeast (which contains nitrogen) is added to the wort.
Q. Why do not grapes ferment while they hang on the vine?
A. 1st—Because the skin lets out the water of the pulp, which causes the grapes to shrivel and dry up: and
2ndly—The skin prevents the admission of oxygen into the pulp, from the air without.
Q. What is the froth or scum of fermented liquors?