Preparation of simulated milk ultrafiltrate
In milk, the serum phase is in a dynamic equilibrium with insoluble salts within the casein micelle and therefore saturated with respect to calcium phosphate depending on pH, temperature and other compositional factors. In this study, simulated milk ultrafiltrate (SMUF) was therefore considered as a dynamic medium that approximates ultrafiltration (UF) permeates of a certain milieu condition resulting in changes in calcium and phosphate content as detected by ion chromatography. Due to reported spontaneous precipitation of existing SMUF solutions and interference with measurements and experiments, SMUF solutions were developed according to the chemical composition and physical parameters of UF permeate at different temperatures. SMUF solutions were proven to be as stable as their corresponding ultrafiltration permeates as they were similar in composition and calcium activity. Calcium activity was considered as a useful parameter to estimate the onset of supersaturation and spontaneous precipitation depending on calcium concentration and pH.
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