Understanding salt diffusion in dairy-based systems: A model approach using rennet-coagulated micellar casein...

Understanding salt diffusion is essential for optimizing salt uptake during cheese production. Although multiple interacting factors complicate this process, the utilization of a model cheese system offers a controlled platform to evaluate their relative influence. This study developed a model using renneted gels prepared from micellar casein concentrate and investigated the use of salty whey, a secondary byproduct of Cheddar production, as an alternative salting medium. We assessed the effects of varying the pH, fat, and calcium contents of the model cheese and salting temperature on salt migration. Salt diffusivity was modeled using Fick's second law. Increasing calcium content during formulation of the model system (0%-1% wt/wt, weight basis) significantly increased salt penetration. Similarly, salting at 30°C significantly enhanced salt diffusion compared with salting at 20°C or 40°C. Diffusion coefficients of salt in the model cheese systems ranged from 3.1 × 10^-9 to 8.5 × 10^-9  m²/s. Increasing calcium level promoted a more continuous compact protein matrix, which in turn increased salt diffusion; in contrast, fat globules hindered salt movement within the matrix. Analysis of Fourier transform infrared spectra indicated that higher levels of salt migration corresponded to more ordered protein secondary structures with stronger hydrogen bonding. The diffusivity of salty whey, however, was less than that of brine, likely due to the higher osmotic pressure and viscosity of the former.