Modeling of deposit removal from milk contact surfaces in water rinse cycle during milking system cleaning-in-place process

The safety of dairy products is maintained by the quality and safety of the raw milk, which largely depends on the cleaned and sanitized milking system used during the milk production. The milking system cleaning process widely used on current dairy farms is a highly automated process called as cleaning-in-place (CIP). The conventional four-step milking system CIP includes: i) warm water rinse; ii) alkaline wash; iii) acid wash; and iv) sanitizing rinse before the next milking event. There have been studies to enhance the CIP performance and evaluate alternative CIP experimentally, but the mechanisms behind the cleaning processes are largely unclear. This research is undertaken to evaluate the deposit removal rate for the warm water rinse cycle of the CIP process and propose a mathematical model to describe the deposit removal process by the warm water rinse. Three 152.4 mm (6″) stainless steel straight pipe specimens were placed at the end of undisturbed entrance length, and the distance between the end of the first specimen to the beginning of the next specimen is 1.1 m (3.5′). The mass of milk deposit on the specimen was measured after the initial soiling process, then after a 20 and 30-s of warm water rinse. A first order kinetic model is considered for the initial model development based on previous studies, where the deposit removal rate was dependent on the warm water rinse time duration. Results showed that deposit on the inner surfaces of the specimens were removed rapidly by the warm water rinse initially within 20 seconds (p<0.05), but slowed down after 20 s of warm water rinse. At the end of 30 s warm water rinse, more than 95% of the initial deposit was removed. Moreover, no significant differences (P>0.05) were observed experimentally of the deposit removal amount and rate for the specimens located at three different distances from the inlet.