pH Control

  •  with respect to cheese quality and safety, the most important process control factor is the development of acidity
  • increasing acidity causes:
    • syneresis (due to reduced charge repulsion on casein micelles) and moisture expulsion
    • solubilization of calcium phosphates
    • disruption of casein micelle structure with alterations in curd texture
    • reduced lactose content by fermentation to lactic acid
  • acid development occurs mainly within the curd because most bacteria are trapped in the gel matrix during coagulation
  • final pH (acidity) is dependent on the amount of acid developed during manufacture and the residual lactose which will ferment during early curing and cause further acid development
  • the residual lactose content is mainly determined by the moisture content, washing which removes lactose by leaching, and the extent of fermentation
  • ability of culture to ferment galactose is also important
  • both the rate of acid development and the amount of acid development (as measured by final pH) are important
  • eg., final pH of Swiss is the same as Cheddar but Cheddar cheese reaches pH 5.2 after about 5 hours while Swiss cheese requires about 15 h to reach this pH
  • it is important to maintain uniform rate of acid development; if acidity develops too slow or too fast, adjust the amount of culture rather than changing cooking time or temperature
  • pH at draining largely determines the mineral and residual sugar contents of the cheese and from the sugar, the final pH
  • salting reduces the rate of acid development, and, therefore, the time and amount of salting is important to the pH at 1 day and 7 days following manufacture.