The principal results of an investigation of the major physico-chemical properties of porcine milk were:
Heat stability: all individual porcine milks examined had poor heat stability and some coagulated in 2 min at 95°C; the Q10°C was high and variable and was 40 for some samples. Dialysis of porcine milk against bulk bovine milk did not influence its heat stability; removal of colloidal calcium phosphate (CCP) from porcine milk increased its heat stability 4-fold, but it was still very unstable. Unlike bovine milk, porcine milk did not exhibit a maximum-minimum in the heat stability-pH curve, but rather resembled bovine casein micelles suspended in milk dialysate. Addition of isolated bovine β-lactoglobulin to porcine milk did not influence its heat stability-pH curve.
Rennet coagulation: under similar conditions, porcine milk coagulated about 4 times faster than bovine milk and the resultant curd was about twice as soft. Dialysis of porcine milk against a large excess of bulk bovine milk did not influence its rennet coagulability nor did removal of 50% of its CCP, but complete removal of the CCP rendered porcine milk non-coagulable by rennin. Porcine milk was readily coagulated by rennin down to 5°C; its second-stage coagulation was independent of temperature – a characteristic due mainly to its high level of CCP.
Alcohol stability: porcine milk was coagulated by 66–68% (v/v) ethanol, as compared with 74% (v/v) for bovine milk.
Calcium stability: porcine milk was stable to at least 300 mM-CaCl2 at both 2 and 37°C.
Solvation: porcine milk contained significantly less water of hydration than bovine milk, 1·7g H2O/g casein compared with 2·0g H2O/g casein.