A noninvasive study of milk cleaning processes: Calcium phosphate removal

High temperature, high pH milk processing results in the formation of mineral rich deposits that are > 70% mineral and < 30% protein by weight. This research investigates the removal of P-32 labeled mixtures of calcium phosphate dihydrate (brushite, CaHPO4 . 2H(2)O) and hydroxyapatite (Ca-5(PO4)(3)OH) from stainless steel tubes using a solid scintillation technique. Experiments were performed at pH values ranging from 2.86-7.82 and flow rates from 3.8-11.4 L/min. Previous cleaning models are reviewed and a mass transfer model is proposed which, when compared to the experimental results suggests that film removal is due to both dissolution and mechanical effects due to shear stress. A modified first order model is presented which incorporates the effects of the solvent flow rate and pH on decontamination rates. This first order model is in agreement with the experimental results over the range of pH and flow rates investigated.