above 7 the milk was almost black. Hence, the sugar used, the reaction,
and temperature all influenced the development of the brown color. The
length of heating in connection with the temperature was important as
relatively high temperatures for a short period gave only slight develop-
ment of the brown color. It is almost impossible to retain the natural color
of fresh milk in the condensed milk products, for some brow^n discoloration
occurs in the unsweetened and sweetened product whether made from
whole or skim milk.
Whittier and Benton had shown that the hydrogen-ion concentration
increases at a rate which is the function of the lactose concentration and
the time and temperature of heating. Or, in other words, when milk is
heated for a sufficient time at high enough temperatures the lactose is
decomposed with formation of acid products. Hence, when milk is heated
with sucrose the increasing acidity inverts some of the sucrose to dextrose
and levulose, with the development of a brownish color. One example of
this is in the cooking of caramels, more brown color developing with long
slow cooking of the sucrose and milk. Another instance where this is used
to advantage is in making caramel pudding by boiling, in the can, sweetened
condensed milk for three hours or longer. The can and contents are chilled.
On opening the can it is found that the contents have developed the brown
color of caramelized products and are thickened to the consistency of a
pudding.
This combination of sugar with milk proteins to form a thickened
product is interesting in view of the fact that sucrose, dextrose, and levu-
lose prevent the heat coagulation of egg albumin.
The housewife also makes use of the effect of acid on sweetened con-
densed milk. If about Yi cup of lemon juice is stirred into the contents of
a can (about 1^ cups) of sweetened condensed milk, the mixture thickens
to a consistency that can be used for a pudding or pie filling and may be
thinned with water to a desired consistency. The explanation of the
thickening lies in the action of the acid on the complex sugar-protein
combination.
Cheese
Definition. The Food and Drug Administration defines cheese, in the
regulatory announcements, as "a product made from curd obtained from
the whole, partly skimmed, or skimmed milk of cows, or from milk of
other animals with or without added cream, by coagulating with rennet,
lactic acid, or other suitable enzyme or acid, and with or without further
treatment of the separated curd by heat or pressure, or by means of ripen-
ing ferments, special molds, or seasoning."
Classification of cheese. Cheese may be classified in many ways as
(1) method by which the curd is produced, i.e., acid or rennet coagula-
tion, (2) source of the milk, from cow, sheep, or goat, and (3) the
COAGULATION OF MILK FOR CHEESE 311
texture and consistency of the cheese, i.e., whether soft, semi-hard, or hard.
Many other classifications might be used but none of them are entirely
satisfactory.
Doane and Lawson list and describe nearly 300 cheeses. They state
there are probably about 18 distinct varieties of cheese.
For purposes of discussion, Rogers classifies cheese as follows:
Soft Hard
Unripened Semi-hard
Cottage Ripened by molds
Cream Gorgonzola
Neufchatel Roquefort
Ripened Stilton
Ripened by molds Ripened by bacteria
Camembert Brick
Brie Munster
Ripened by bacteria Very hard
Page 253
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AI-modernized reading of the original text
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above 7 the milk was almost black. Hence, the sugar used, the reaction,
and temperature all influenced the development of the brown color. The
length of heating in connection with the temperature was important as
relatively high temperatures for a short period gave only slight develop-
ment of the brown color. It is almost impossible to retain the natural color
of fresh milk in the condensed milk products, for some brow^n discoloration
occurs in the unsweetened and sweetened product whether made from
whole or skim milk.
Whittier and Benton had shown that the hydrogen-ion concentration
increases at a rate which is the function of the lactose concentration and
the time and temperature of heating. Or, in other words, when milk is
heated for a sufficient time at high enough temperatures the lactose is
decomposed with formation of acid products. Hence, when milk is heated
with sucrose the increasing acidity inverts some of the sucrose to dextrose
and levulose, with the development of a brownish color. One example of
this is in the cooking of caramels, more brown color developing with long
slow cooking of the sucrose and milk. Another instance where this is used
to advantage is in making caramel pudding by boiling, in the can, sweetened
condensed milk for three hours or longer. The can and contents are chilled.
On opening the can it is found that the contents have developed the brown
color of caramelized products and are thickened to the consistency of a
pudding.
This combination of sugar with milk proteins to form a thickened
product is interesting in view of the fact that sucrose, dextrose, and levu-
lose prevent the heat coagulation of egg albumin.
The housewife also makes use of the effect of acid on sweetened con-
densed milk. If about Yi cup of lemon juice is stirred into the contents of
a can (about 1^ cups) of sweetened condensed milk, the mixture thickens
to a consistency that can be used for a pudding or pie filling and may be
thinned with water to a desired consistency. The explanation of the
thickening lies in the action of the acid on the complex sugar-protein
combination.
Cheese
Definition. The Food and Drug Administration defines cheese, in the
regulatory announcements, as "a product made from curd obtained from
the whole, partly skimmed, or skimmed milk of cows, or from milk of
other animals with or without added cream, by coagulating with rennet,
lactic acid, or other suitable enzyme or acid, and with or without further
treatment of the separated curd by heat or pressure, or by means of ripen-
ing ferments, special molds, or seasoning."
Classification of cheese. Cheese may be classified in many ways as
(1) method by which the curd is produced, i.e., acid or rennet coagula-
tion, (2) source of the milk, from cow, sheep, or goat, and (3) the
COAGULATION OF MILK FOR CHEESE 311
texture and consistency of the cheese, i.e., whether soft, semi-hard, or hard.
Many other classifications might be used but none of them are entirely
satisfactory.
Doane and Lawson list and describe nearly 300 cheeses. They state
there are probably about 18 distinct varieties of cheese.
For purposes of discussion, Rogers classifies cheese as follows:
Soft Hard
Unripened Semi-hard
Cottage Ripened by molds
Cream Gorgonzola
Neufchatel Roquefort
Ripened Stilton
Ripened by molds Ripened by bacteria
Camembert Brick
Brie Munster
Ripened by bacteria Very hard