Milk and Milk Products

Abstract

Milk is the first food of young mammals produced by the mammary glands of female mammals. It is a mixture of fat and high-quality protein in water and contains some carbohydrate (lactose), vitamins, and minerals. Milk and milk products may be obtained from different species, such as goats and sheep, although the focus of this chapter is on cow’s milk and milk products.

Glossary

Buttermilk, cultured

Pasteurized low-fat or nonfat milk to which bacteria are added to ferment lactose to the more acidic lactic acid that clots the casein in milk.

Casein

Primary protein of milk, colloidally dispersed.

Casein micelles

Stable spherical particles in milk containing α_s-, β-, and κ-casein, and also colloidal calcium phosphate. The micelles are stabilized by κ-casein, which exists mainly at the surface; the α_s- and β-casein fractions are located mainly in the interior of the micelles.

Cheese

Coagulated product formed from the coagulation of casein by lactic acid or rennin; may be unripened or bacteria ripened; made from concentrated milk.

Churning

Agitation breaks fat globule membranes so the emulsion breaks, fat coalesces, and water escapes.

Coagulate

The formation of new cross-links subsequent to the denaturation of a protein. This forms a clot, gel, or semisolid material as macromolecules of protein aggregate.

Creaming

Fat globules coalesce (less dense than the aqueous phase of milk) and rise to the surface of unhomogenized, whole, and some low-fat milk.

Cultured

See fermented.

Evaporated milk

Concentrated to remove 60 % of the water of ordinary fluid milk; canned.

Fermented

(Cultured) enzymes from microorganisms or acid that reduce the pH and clot milk by breaking down the organic substrates to smaller molecules.

Fortified

Increasing the vitamin content of fresh milk to contain vitamins A and D to levels not ordinarily found in milk.

Homogenization

Dispersion of an increased number and smaller fat globules to prevent creaming.

Imitation milk

Resembles (looks, tastes like) the traditional product but is nutritionally inferior—contains no butterfat or milk products.

Lactose intolerance

Inability to digest lactose due to the absence or insufficient level of intestinal lactase enzyme.

Maillard reaction

The first step of browning that occurs due to a reaction between the free amino group of an amino acid and a reducing sugar; nonenzymatic browning.

Milk solids nonfat (MSNF)

All of the components of milk solids except fat.

Milk substitute

Resembles (looks, tastes like) traditional product and is nutritionally equal; contains no butterfat (e.g., filled milk).

Overrun

The increase in volume of ice cream over the volume of ice cream mix due to the incorporation of air.

Pasteurization

Heat treatment to destroy pathogenic bacteria, fungi (mold and yeast), and most nonpathogenic bacteria.

Rennin

Enzyme from the stomach of milk-fed calves used to clot milk and form many cheeses.

Ripening

The time between curd precipitation and completion of texture, flavor, and color development in cheese. Lactose is fermented, fat is hydrolyzed, and protein goes through some hydrolysis to amino acids.

Sterilization

Temperature higher than that required for pasteurization, which leaves the product free from all bacteria.

Sweetened, condensed milk

Concentrated to remove 60 % of the water, contains 40–45 % sugar.

Total milk solids

All of the components of milk except for water.

Whey

Secondary protein of milk, contained in serum or aqueous solution; contains lactalbumins and lactoglobulins.