Effect of thawing procedures on the properties of frozen and subsequently thawed casein concentrate

The effects of different thawing procedures on the properties of frozen casein concentrates (CCs) produced by microfiltration were investigated and compared with fresh CC. Samples (5% protein) were thawed directly (30 °C, 30 min) or stored (4 °C) for 1 or 3 d, and subsequently kept at 30 °C for 30 min or 5 h. No significant differences were found in particle size, zeta potential or rennet coagulation for CC diluted with water or permeate from ultrafiltration. The viscosity of frozen CC diluted with water was lower for samples thawed at 30 °C for 30 min than for fresh CC, but increased with prolonged thawing procedures (4 °C for 3 d). Using 4 °C for 3 d followed by 5 h at 30 °C resulted in earlier gelation and increased storage modulus (G’) during acidification, which was related to the increased free Ca²⁺ activity and decreased pH.