Yeast in Wine-Making

You will often come across old recipes which do not give yeast as an ingredient. These depend upon the natural yeasts in the vegetable matter used, and should not, therefore, be relied upon; because the whole of wine-making practice really comes down to the matter of providing ideal conditions for the yeast, a living organism, to thrive and multiply. To do that the yeast must have sugar, it must have warmth, it must have oxygen, it must have a certain amount of nitrogenous matter, vitamins, and some acid. The ideal recipe will provide all these things; if any of them are lacking the ferment may ‘stick’, or temporarily stop.