Chapter 7
Milk, Fermentation, and Fermented
and Nonfermented Dairy Products
Although this chapter is devoted to milk and other dairy products, it begins with a discussion of
fermentation because of the importance of this process to dairy products.
FERMENTATION
Background
Numerous food products owe their production and characteristics to the fermentative activities of
microorganisms. Many foods such as ripened cheeses, pickles, sauerkraut, and fermented sausages are
preserved products in that their shelf life is extended considerably over that of the raw materials from
which they are made. In addition to being made more shelf stable, all fermented foods have aroma
and flavor characteristics that result directly or indirectly from the fermenting organisms. In some
instances, the vitamin content of the fermented food is increased along with an increased digestibility
of the raw materials. The fermentation process reduces the toxicity of some foods (for example, gari
and peujeum), whereas others may become extremely toxic during fermentation (as in the case of
bongkrek). From all indications, no other single group or category of foods or food products is as
important as these are and have been relative to nutritional well-being throughout the world.
The microbial ecology of food and related fermentations has been studied for many years in the
case of ripened cheeses, sauerkraut, wines, and so on, and the activities of the fermenting organisms
are dependent on the intrinsic and extrinsic parameters of growth discussed in Chapter 3. For example,
when the natural raw materials are acidic and contain free sugars, yeasts grow readily, and the alcohol
they produce restricts the activities of most other naturally contaminating organisms. If, on the other
hand, the acidity of a plant product permits good bacterial growth and at the same time the product is
high in simple sugars, lactic acid bacteria may be expected to grow, and the addition of low levels of
NaCl will ensure their growth preferential to yeasts (as in sauerkraut fermentation).
Products that contain polysaccharides but no significant levels of simple sugars are normally stable
to the activities of yeasts and lactic acid bacteria due to the lack of amylase in most of these organisms.
To effect fermentation, an exogenous source of saccharifying enzymes must be supplied. The use of
barley malt in the brewing and distilling industries is an example of this. The fermentation of sugars
149
Milk, Fermentation, and Fermented
and Nonfermented Dairy Products
Although this chapter is devoted to milk and other dairy products, it begins with a discussion of
fermentation because of the importance of this process to dairy products.
FERMENTATION
Background
Numerous food products owe their production and characteristics to the fermentative activities of
microorganisms. Many foods such as ripened cheeses, pickles, sauerkraut, and fermented sausages are
preserved products in that their shelf life is extended considerably over that of the raw materials from
which they are made. In addition to being made more shelf stable, all fermented foods have aroma
and flavor characteristics that result directly or indirectly from the fermenting organisms. In some
instances, the vitamin content of the fermented food is increased along with an increased digestibility
of the raw materials. The fermentation process reduces the toxicity of some foods (for example, gari
and peujeum), whereas others may become extremely toxic during fermentation (as in the case of
bongkrek). From all indications, no other single group or category of foods or food products is as
important as these are and have been relative to nutritional well-being throughout the world.
The microbial ecology of food and related fermentations has been studied for many years in the
case of ripened cheeses, sauerkraut, wines, and so on, and the activities of the fermenting organisms
are dependent on the intrinsic and extrinsic parameters of growth discussed in Chapter 3. For example,
when the natural raw materials are acidic and contain free sugars, yeasts grow readily, and the alcohol
they produce restricts the activities of most other naturally contaminating organisms. If, on the other
hand, the acidity of a plant product permits good bacterial growth and at the same time the product is
high in simple sugars, lactic acid bacteria may be expected to grow, and the addition of low levels of
NaCl will ensure their growth preferential to yeasts (as in sauerkraut fermentation).
Products that contain polysaccharides but no significant levels of simple sugars are normally stable
to the activities of yeasts and lactic acid bacteria due to the lack of amylase in most of these organisms.
To effect fermentation, an exogenous source of saccharifying enzymes must be supplied. The use of
barley malt in the brewing and distilling industries is an example of this. The fermentation of sugars
149