Changes in the Calcium and Inorganic Phosphorus Contents of Casein and Paracasein on the Preparation Process of Mozzallera Cheese

Abstract

The modified bovine milk (3% of fat, pasteurized at 65°C for 30 min) was added starter and rennet, then kept at 30°C for 40 min. The curds prepared from coagulated milk were treated successively by resting, addition of 2% NaCl and kneading to prepare Mozzarella cheese (MC). The amounts of calcium (Ca) and inorganic phosphorus (Pi) bound to casein or paracasein from the curds at each process were determined to obtain their molar ratios. The amounts of Ca and Pi in 1 g of casein sedimented from the untreated milk by ultracentrifugation were 32.4 and 15. 4 mg respectively, and the molar ratio of Ca/Pi was 1.62. Those in paracasein after cooking the coagulated milk with starter and rennet were 16.2 and 10.3 mg respectively. And the Ca/Pi ratio was lowered to 1.21. After resting, addition of 2% NaCl and kneading of the curds, the Ca/Pi ratio of paracasein was much more lowered to 1.06. In the curds prepared from the milk treated with starter and rennet at 30°C for 40 min, the intensity of as1-band decreased on urea-PAGE, whereas αs1-I band appeared. The intensity of x-band also decreased immediately after addition of rennet to the milk and a-band also appeared on SDS-PAGE. The intensity of β-band slightly decreased, but that of as2-band unchanged during the processing of milk.