164 Chapter 7
Casein — Manufacture
and Composition
Casein Manufacture
The principal steps involved in the manufac-
ture of rennet casein and acid casein are out-
lined in Figure 7.1 and described in further
detail below.Fat Separation
Whole bovine milk is centrifuged to separate
the cream (i.e., fat) from the skim milk that
is then pasteurized (72 ° C; 161.6 ° F for 15
seconds) to eliminate pathogenic bacteria and
inactivate indigenous enzymes.Precipitation/Coagulation
Acid precipitation: Acid casein is precipi-
tated from pasteurized skim milk by brief but
turbulent agitation of the skim milk with
dilute (0.25 mol L - 1 ) acid (sulphuric or hydro-Casein Products
Types of Casein Products
Due to its ease of production and natural
abundance, casein has been produced com-
mercially since the early 20th century. Hence,
the technology for the production of casein
products is well established and has been
regularly improved (Mulvihill 1992 ,
Mulvihill and Fox 1994 , Mulvihill and Ennis
2003 ).
Two main types of casein are produced
commercially: rennet casein and acid casein.
Rennet casein is prepared by enzyme - induced
coagulation. Acid casein is prepared by iso-
electric precipitation using either mineral
acid, an acidogen (e.g., gluconic acid - δ -
lactone), or in situ fermentation of lactose to
lactic acid using suitable lactic acid starter
cultures. Other types of casein products are
micellar casein, individual caseins, and
casein - derived peptides.
Figure 7.1. Process for manufacture of acid casein and rennet casein (Adapted from Huffman and Harper
1999 ).
Skim milkCookingDewheyingWashingDryingCaseinCoagulantWaterWater WaterWaterPrecipitant