Composition of Cheese. 21 



tion, and collects rapidly at the bottom of the cask as vinegar. 

 But such a change does not take place if the alcoholic liquid is 

 left for ever so long in a clean cask filled with such a liquid. 

 Contact with air, subdivision of the liquid into drops, and the 

 presence of the porous wood-shavings, are necessary for the 

 transformation. These casks do not at first produce vinegar 

 as rapidly as after they have been in use for some time and 

 become thoroughly soaked with vinegar-ferment. And this is 

 another peculiarity of all ferments, that, under favourable cir- 

 cumstances, they reproduce themselves from other materials in 

 immense quantities. Thus fresh and active yeast is generated 

 in great abundance in fermenting malt-liquor, whilst the original 

 yeast employed in brewing is more or less decomposed and be- 

 comes what is called inactive yeast. These chemical facts, well- 

 known to the manufacturers of vinegar and to the intelligent 

 brewer, have a direct bearing on cheese-making. 



At the very beginning of her operations a good dairywoman 

 unconsciously carries on a steady and constant battle with these 

 remarkable ferments, and it is very interesting to the chemist to 

 see her proceed in the most rational and philosophical manner. 



No milk is admitted into the cheese-tub before it has been 

 carefully strained through a cloth, lest a little bit of a dead leaf or 

 any similar matter, accidentally blown into the milk in its pas- 

 sage from the milking-place to the dairy, should spoil the flavour 

 of the cheese. No sooner has the cheese left the tub than she 

 begins to pour scalding water into it, to scrub it, and to make it as 

 clean and sweet as possible. In good dairies no utensil is allowed 

 to remain for a moment dirty, but hot water and clean brushes 

 are always close at hand to scrub the pails and make them 

 almost as white as snow. The dairywoman probably knows 

 nothing about the nature of the ferment, which is rapidly formed 

 when a little milk is left at the bottom and adhering to the sides 

 of the wooden milk-pails ; she is unconscious that here, as in 

 the vinegar process, the conditions most favourable to chemical 

 change are present, and that the sugar of the milk, in contact 

 with plenty of air and porous wood, is rapidly changed into 

 lactic acid, whilst at the same time a peculiar milk-ferment is 

 produced ; all this may be a perfect mystery to her, but, never- 

 theless, guided by experience, she thoroughly avoids everything 

 that favours the production of ferment, or taint, as she calls it, by 

 leaving no vessel uncleaned, by scalding all that have been in use 

 with boiling water, and if ever so little milk be accidentally spilt 

 on the floor of the dairy, taking care that it is at once removed, 

 and the spot where it fell washed with clean water. 



It is, indeed, surprising how small a quantity of ferment taints 



