Effect of freezing temperatures and time on mineral balance, particle size, rennet and acid coagulation of casein concentrates produced by microfiltration

The effects of freezing temperature and storage time on mineral partition, particle size, and rennet and acid coagulation properties of microfiltered casein concentrates (CC) were investigated. The total inorganic phosphate content of the CC decreased (P < 0.05) in the frozen samples, while the calcium and inorganic phosphate concentrations in the serum fraction were dependent on the freezing temperature; serum levels of Ca and Pi decreased (P < 0.05) during 12 days of storage at −20 and −40 °C, but increased at −80 °C. The frozen samples formed aggregates of different mass median diameters, and the average size was dependent on the temperature and days of storage. Rennet coagulation properties were significantly altered by storing at −80 °C. The storage modulus of acid gels made from frozen CC had higher values compared with acid gels made from unfrozen CC. The process of freezing thus influenced the stability of the CC.