Experimental investigation, numerical simulation and RSM modelling of the freezing and thawing of Mozzarella cheese

Abstract

Freezing can be used to preserve functionality of Mozzarella cheese allowing export to distant markets but limited tools are available for prediction of freezing and thawing times as a function of composition and processing variables. Freezing and thawing processes were experimentally and numerically assessed for six Mozzarella samples, differing significantly in block size and composition. Numerical simulations using an enthalpy method were developed to build a validated and robust model for solving heat and mass transfer equations. A decrease in salt (NaCl) content from 1.34 % w/w to 0.07 % significantly altered the temperature of phase change from ∼–4.5 °C to –3 °C. Simulations showed minimal impact of salt migration on the salt in free moisture content deeper than ∼1–2 centimeters from the surface during freezing, with a slight increase of 8–10 % salt in free moisture at the block center. A response surface methodology (RSM) model was fit to the simulated data providing a useful tool for predicting freezing and thawing times for block sizes and a wider range of operating conditions enabling future process optimization. The RSM model indicated that increased salt content increased freezing time but decreased thawing time.