EFFECT OF MILK-COMPOSITION ON THE PARTITION-COEFFICIENTS OF DIACETYL,ACETALDEHYDE, AND ETHANOL IN ACIDIFIED MILK-PRODUCTS

Acidified milk samples were prepared with fat concentrations from 0 to 20% and SNF concentrations from 8 to 12%. The partition coefficients of diacetyl, acetaldehyde, and ethanol were determined in these acidif ied samples at pH 4.4 and 4.6 and at 30 and 50 degrees C. Gas chromato graphic headspace analysis was used to quantitate these flavor compoun ds after the system reached equilibrium.The pH did not affect the part ition coefficients. Partition coefficients were dependent on the incub ation temperature and were higher at 50 degrees C. Concentration of th e flavor compounds significantly affected their distribution between t he air and aqueous phases. Diacetyl, acetaldehyde, and ethanol partiti on coefficients increased as SNF and milk fat concentrations increased in the milk matrix at either concentration of compounds or incubation temperature. The partition coefficients were highest in a milk matrix that contained 12% SNF or 20% milk fat. There were no interaction eff ects of SNF by fat, SNF by pH, fat by pH, or SNF by fat by pH on the p artition coefficients; an interaction of fat by pH for diacetyl existe d. The partition coefficient for acetaldehyde was higher than the part ition coefficient for diacetyl. The partition coefficient was lowest f or ethanol.