Section C. Dairy Chemistry

Abstract

Fat (average) % Author Country Winter 3-64 Summer 4-16 Susiura(B) Mongolia and Manchuria Fat Lactose Protein Ash 3-5-4-0 5-0 3-3-3-5 0-75 Florentinno) Paris district The cases of adulteration of milk reported annually by the Ministry of Health (11) account for roughly 7-2% of the samples examined by public analysts.

Physico-chemical properties of casein micelles reformed from urea-treated milk

“…Similar concentration-dependent effects were observed with the turbidity and viscosity characteristics of urea-treated milk systems. It appears reasonable to suggest that the increased sensitivity of reformed micelles to Ca 2+ (to be discussed later) was responsible for the reduced second-stage renneting time, but this influence was more than offset at higher levels of urea by chemical modification of the casein, possibly through the production of homocitrulline from lysine and ammonium carbamate arising from urea decomposition (Hill & Cracker, 1968). Since CPF milk is readily precipitated by the rapid addition of high concentrations of Ca 2+ , but is not coagulable by rennin, it appears that a certain minimal size is necessary to bring about increased sensitivity to Ca during rennin coagulation.…”

“…The ethanol stability of casemate solutions is determined in the main by the concentration of divalent cations and the consequent ionization status of the carboxylic side-chains (Davies & White, 1958). Urea treatment causes extensive dissociation of casein micelles, probably by rupture of H 2 and/or hydrophobic bonds (Morr, 1967).…”

“…Since Ca 2+ are essential for the second stage of rennin action, the decrease in its duration at certain urea concentrations may be due to decreased stability of urea-treated milks to Ca 2+ . The up-swing in the duration of the second stage at higher urea levels may be due to carbamylation of e-NH 2 groups, since Hill & Cracker (1968) have shown that blocking these groups by dansyl chloride inhibits the second stage of rennin action.…”