MILK
Mother Ambroisine had just milked the goat for breakfast. While Emile
and Jules were crumbling their bread each in a cup of milk, foamy and
still warm, Uncle Paul, who takes advantage of every occasion for
enriching the intelligence of his young nephews with new ideas, thus
began the conversation:
“What a priceless resource we have in milk; what delicious breakfasts
with this food so nourishing, so light, so appetizing! To judge by the
reception you are giving it at this moment, you know well how to
appreciate its value.”
“For my part,” Emile declared, “I like milk better than anything else
Mother Ambroisine can give us, especially when the bread is toasted a
little over the coals.”
“I don’t need anything of that sort,” said Jules, “to make the milk
first-rate.”
“Since you like milk so much, you shall learn something about it; then
your breakfast will give you a double benefit, food for the body and
food for the mind.
“Let us speak first of a property the effects of which you have
doubtless seen more than once without paying attention to them. At
times the milk turns, as they say; in other words, it curdles. Why is
that? You do not know. I will tell you.
“Here is a glass of milk just as it came from the goat. It is of
irreproachable fluidity without the slightest trace of curdling. I
squeeze into it a drop of lemon juice, one only, and stir the liquid.
Immediately a great change is effected: one part of the milk clots and
rises to the surface in thick white flakes; another part remains
liquid, but loses its whiteness and becomes like slightly turbid water.
If I let the glass stand for some time, the curd collects at the
surface and floats on a clear liquid. With a drop of lemon juice I have
just made the milk turn quickly.”
Emile examined with lively interest the contents of the glass thus
speedily transformed. His uncle, whom nothing escapes, perceived it.
“What is it you are looking at so attentively?” he asked.
“Your experiment,” Emile answered, “reminds me of what happened to my
milk one day at breakfast. To my toasted bread, which Jules turns up
his nose at, I wanted to add something still better. I had an orange
and I took it into my head to squeeze the juice into my cup of milk,
thinking to make a delicious drink of the mixture. Who was the fool
that time? It was giddy Emile. The milk instantly curdled, just like
this when you squeezed the lemon juice into it. Trying to improve my
cup of milk, I only made it so that I had to throw it all away, it had
gone so bad.”
“I wish I could have seen the face Emile made,” said Jules, “when he
saw the result of his improvement.”
“I was much surprised, I admit,” Emile rejoined, “to find how two
things, orange juice and milk, each excellent by itself, could make
such a nasty drink when mixed.”
“In future, my friends, you will know that anything sour makes milk
turn. What I brought about with lemon juice you effected with orange,
which contains, though in small quantity and masked by the sweet flavor
of the fruit, exactly the same ingredient that gives the lemon its sour
taste.
“The juice of sorrel leaves, that of green grapes, and of unripe fruits
in general, vinegar, and in fact everything with a similar taste, make
milk turn at once. These sour-tasting substances are called acids.
Vinegar is an acid; that which gives its sourness to the lemon is
another; green grapes contain a third; sorrel leaves furnish a fourth.
The number of acids is very considerable. All those that we need to
know anything about have this same sharp flavor, sometimes stronger,
sometimes weaker; all, in short, make milk curdle just as I showed you
with the acid of the lemon.
“From theory let us turn to practice. Cleanliness in everything is of
the first importance, but in the care of milk especially must one be
scrupulous in this particular. The vessels for holding it and keeping
it any length of time must be carefully and thoroughly cleaned as often
as they are used, if one would avoid the risk of its turning. Suppose a
few drops of old milk or some remnants of any kind of food are left in
a pot, tucked away where they are hard to get at: these impurities soon
turn sour, especially in warm weather, and the milk, finding an acid
substance in the vessel, quickly spoils and curdles. How often the milk
itself is blamed for this accident when want of cleanliness is the sole
cause!
“Milk contains three principal substances, namely: cream, or fatty
matter from which butter is made; casein, or curds, used for making
cheese; and, finally, a substance with a slightly sweet taste called
sugar of milk. These three ingredients taken away, hardly anything is
left but water. To separate these three, one proceeds as follows:
“Left standing in a cool place and exposed to the air, milk becomes
covered, sooner or later, according to the season, with a thick oily
layer that takes the name of cream. This is the material from which
butter is made. It rises to the surface unaided and separates when
simply exposed to the air. It is removed with a skimmer.
“What is left is skimmed milk, of the same whiteness, the same
appearance, as the original milk, but deprived of its fatty matter.
Into this skimmed milk let us pour a few drops of some acid, lemon
juice for example. The milk turns and thick white flakes are formed.
Those flakes are the curd, the casein, in short the material of which
cheese is composed.
“After the casein has been removed there remains nothing but a
transparent liquid that might be taken for water slightly tinted with
yellow. This liquid is called whey. It contains little besides water
with a small quantity of sugar of milk which gives it a slightly sweet
taste. It is especially in Switzerland that sugar of milk is obtained
on a large scale by the evaporation of the liquid that remains after
removing the cream and curds from the milk. In spite of its name this
substance has nothing in common with ordinary sugar, the white
loaf-sugar we use; it is a dull-white substance, rather hard, crunching
under the teeth, and of a slightly sugary taste. It is used only in
pharmacy.
“Cream and casein constitute the nutritive ingredients of milk, and
determine its food value. The milk that is richest in these
constituents is sheep’s milk, next comes goats’ milk, and last of all
cows’ milk. Although of little value to us, sugar of milk claims our
attention for a moment on account of the change it undergoes to the
great detriment of the milk itself. Little by little, especially when
exposed to the heat of summer, this sugary matter sours and becomes an
acid. That is what makes milk sour if kept too long. Of course when
this sourness shows itself the milk soon curdles. Coagulation takes
place as if an acid had been added to the milk. Hence, to keep milk for
some time and prevent its turning sour of its own accord, this
acidulation of the sugar of milk must be delayed. This is done by
taking care to boil the milk a little every day.”