GROWTH AND METABOLIC-ACTIVITY OF A CHEESE STARTER IN CO2-ACIDIFIED AND NON-ACIDIFIED REFRIGERATED MILK

The growth and activity of two Lactococcus strains and one Leuconostoc strain in CO2-acidified and non-acidified refrigerated milk were eval uated separately and as a mixed culture to determine their suitability for use as a starter in the manufacture of Afuega'l Pitu, an acid-coa gulated Spanish cheese, from refrigerated CO2-acidified milk. The grow th of the strains studied and their production of organic acids were s imilar in CO2-acidified and non-acidified refrigerated or fresh milk, indicating that CO2 treatment does not affect the metabolic activity o f the strains. However, refrigeration enhanced the production of aceta ldehyde, ethanol and diacetyl in CO2-acidified and non-acidified milk. The level of diacetyl was also greater in refrigerated CO2-acidified milk than in refrigerated non-acidified milk. It was concluded that re frigerated milk acidified with CO2 can be satisfactorily used in the m anufacture of Afuega'l Pitu cheese, and that this technique can be als o used in the production of other acid-coagulated cheeses.