Influence of Immersion Freezing in NaCl Solutions and of Frozen Storage on the Viscoelastic Behavior of Mozzarella Cheese

Abstract

The freezing of Mozzarella cheese by immersion in NaCl solutions may be an innovative procedure for the dairy industry because combines conveniently salting and freezing processes. In this work, the influence of this type of freezing method and of the frozen storage of samples on the viscoelastic behavior of Mozzarella cheese was studied. Slabs (2x10x10 cm3) were immersed in 23% w/w NaCl solutions (control samples: 4ºC, 90 min; frozen samples: -15ºC, 180 min). Half of the frozen samples were immediately thawed at 4ºC. The other half was stored at -20ºC for 2 months and then was thawed at 4ºC (frozen-stored samples). Samples were stored at 4ºC and assayed at 1, 7, 14, 20, 27, 34, and 41 days. Rheological tests were carried out in oscillatory mode (parallel-plate geometry, diameter: 20 mm, gap: 1 mm, frequency: 1 Hz). Strain sweeps were run (0.001£g0£0.1) at 20, 40, and 60ºC, and temperature sweeps were run from 20 to 65ºC (1.33ºC min-1, g0=0.005). Similar crossover temperatures were observed after 20 days of ripening. The influence of temperature on complex viscosity was studied by an Arrhenius-type equation. Activation energy values of 15.9±0.4, 14.1±0.5 and 13.8±0.6 Kcal mol-1 were obtained at 41 days for control, frozen and frozen-stored samples, respectively. Although the immersion freezing of Mozzarella cheese affects some of the studied parameters, the differences observed between frozen and frozen-stored samples with control samples were small. Therefore, it was considered that the immersion freezing might be useful for the manufacture and commercialization of Mozzarella cheese.