Family 3. Heat-Acid Precipitated Cheese

All cheese making involves a coagulum of milk proteins which is normally formed in one of three ways.

  1. Enzymatic coagulation of the primary milk protein, casein, where the enzyme, rennet, is the primary coagulating agent. Acid production by lactic cultures encourages coagulation and has important effects on the final cheese texture, but the primary coagulating agent is rennet. This is true for Cheese Families 2, and 4 - 7.
  2. The second type of coagulation is acid induced coagulation of casein, as in Cheese Family 1, where the acid is produced by natural fermentation or sometimes by the slow release acidulating agent, glucono-delta-lactone. All the cheese in Family 1, are acid coagulated in the temperature range of 20 - 35°C. In this temperature range, a pH of less than 4.9 is required to form the coagulum, although some fresh cheese is fermented to pH as low as 4.4.
  3. The third type of coagulation, like the second, is primarily acid induced, but no fermentation is involved and the acid is added to hot milk at temperatures in the range of 75 - 100°C. This process has the unique properties that: (i) The heat treatment denatures the whey proteins which can then be coagulated along with the casein and recovered in the cheese, hence, a huge yield advantage; (ii) The recovered whey proteins have a great capacity to bind water so that a high moisture but firm cheese can be produced, hence, another huge yield advantage; (iii) Acid coagulation at high temperatures requires less acidification, so the final cheese is much less acid with pH in the range of 5.2 to 6.0 rather than the range 4.4 - 4.8 required for the Family 1 varieties.
  4. Finally, the inclusion of whey proteins prevents cheese melting so this process can be used to produce frying/cooking cheese such as ricotta and Paneer.

Varieties: Ricotta (Italy), Channa and Paneer (India), some varieties of Latin American white cheese.

Coagulation: Coagulation is accomplished by direct acidification of heated milk. High heat treatment of milk (temperatures greater than 75°C) causes denaturation of the whey proteins. Subsequent acidification of the hot milk coagulates both casein and whey proteins, so that most of the milk protein is recovered in the cheese.

pH Control: The final acidity (pH) is determined by the amount of acid added. Final pH is normally in the range of 5.3 - 5.8. Any organic acid can be used, but lactic and citric acids are most common.

Moisture control: Moisture can be reduced by holding the curd in the hot curd-whey mixture after coagulation, and by draining and pressing procedures. Moisture is generally high (55 - 80%) due to the high water holding capacity of whey proteins.

Curing: Heat-acid precipitated varieties are normally consumed fresh. An exception is Mizithra, a type of ricotta cheese which is cured, dried, and consumed as a grating cheese. It is also possible in some cases to hot pack heat-acid varieties to obtain extended shelf life. High concentrations of whey proteins decrease cheese meltability and account for the excellent cooking properties of heat-acid precipitated cheese.