Mathematical modeling of deposit removal from stainless steel pipeline during cleaning-in-place of milking system with electrolyzed oxidizing water

The safety of raw milk depends on a clean milking system during the milk production. The milking system cleaning widely used on dairy farms is a highly automated process called cleaning-in-place (CIP), comprising of: i) warm water rinse; ii) alkaline wash; iii) acid wash; and iv) sanitizing rinse before the next milking event. Electrolyzed oxidizing (EO) water is an emerging technology, which consists of acidic and alkaline solutions produced by the electrodialysis of dilute sodium chloride solution. Previous studies showed that EO water can be an alternative cleaning solution for milking system CIP. Despite the progress made to enhance the CIP performance, the mechanisms behind the cleaning processes were still largely unclear. Therefore, this study was undertaken to evaluate the deposit removal rate during the EO water CIP using a stainless steel surface evaluation simulator. Deposit removal data from the simulator formed the basis for developing mathematical models. Stainless steel straight pipe specimens were placed at the end of undisturbed entrance length along the simulator pipeline. The weight of milk deposits on the inner surfaces of the specimens was measured after the initial soiling, and then after certain time durations within the warm water rinse, alkaline wash, and acid wash cycles. A unified first order deposit removal rate model dependent on n^th power of remaining deposit mass was proposed for all three cycles. Experimental results showed that the milk deposit on the inner surfaces of the specimens was removed rapidly by the warm water rinse within 10 s of rinse time. For the alkaline and acid wash cycles, the co-existence of a fast deposit removal at the beginning of the wash cycle and a slow deposit removal throughout the entire wash cycle were inferred. The developed models fit the experimental data well with small root mean square errors and percent error differences.