Dairy products and milk-based food ingredients - Natural Food Additives, Ingredients and Flavourings - page 435

In the production of acid casein, the casein in skimmed milk (pH 6.5-6.6) is
precipitated with either organic acid (usually lactic acid) or mineral acid (usually
hydrochloric acid) at pH 4.6, the isoelectric point of casein. In the production of
lactic acid casein, skimmed milk is usually acidifi ed by the addition of lactic acid
bacteria to precipitate the casein. Pasteurised skimmed milk is inoculated with,
for example, Lactococcus lactis sub-species Cremoris at a rate of 0.1-0.5% of the
milk and incubated at 22-26°C for 14-18 hours. When the milk has reached pH
4.6-4.7 and a coagulum has formed, it is heated to 50-55°C by steam injection, or
a combination of indirect and direct heating, which causes the casein to contract
and expel whey through syneresis. Most of the whey can be removed by passing
the casein curd across inclined screens through which the whey drains. Residual
whey proteins, lactose and soluble minerals can be removed by using a series of
water-fi lled tanks and decanter centrifuges. Finally, the lactic acid casein is dried
in a fl uidized bed dryer and packaged.
Hydrochloric acid casein can be made by a similar process, except the skimmed
milk is directly acidifi ed using mineral acid rather than bacterial starters. Rennet
casein is also manufactured by means of coagulating the casein in skimmed milk,
but at pH 6.5-6.6, using chymosin and then refi ning and drying similarly to acid
casein. Rennet casein is used as an ingredient in processed cheese manufacture
and in non-food manufacture (e.g. the production of buttons, paper coating, etc.).
Caseinates are made from acid casein. The water solubility of acid casein is
very low and limits its functional properties and uses as a food ingredient.
However, acid casein may readily be dissolved in sodium hydroxide (NaOH),
potassium hydroxide (KOH) or calcium hydroxide (Ca(OH) 2 ) to produce,
respectively, sodium caseinate, potassium caseinate and calcium caseinate. The
water solubility of calcium caseinate is much lower than sodium caseinate and
potassium caseinate. Caseinate solutions are spray-dried to produce powders
which are used widely as food ingredients, particularly sodium caseinate, which
exhibits a range of functional properties including water-binding, fat emulsifi cation
and stabilisation. It is used to supplement the protein content of sports and dietetic
products, to add lysine to baked goods to improve texture, to modify the texture
and add protein to breakfast cereals and nutrition bars, as a stabiliser in dairy and
non-dairy desserts, as a component in glaze mixes, and also in processed cheeses,
soups, sauces, bouillon, and salad dressings. It is used in many comminuted meat
products to emulsify fat and bind water. When used as an emulsifi er in meat
products (e.g. in the form of pre-formed emulsions in sausage manufacture), its
presence allows salt-soluble meat proteins to gel, bind water and improve texture
and succulence.

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17.4.3 Lactose
The raw material for lactose production is commonly cheese whey although UF
permeate, which is the by-product of whey protein production, may also be used.
Whey is concentrated by evaporation to 60-65% dry matter to supersaturate the
lactose. It is then transferred to stirred crystallising tanks in which it is seeded