One-Step Cleaning-in-Place for Milking Systems and Mathematical Modeling for Deposit Removal from Stainless Steel Pipeline Using Blended Electrolyzed Oxidizing Water

Abstract

Cleaning-in-place (CIP) is widely used on dairy farms to clean and sanitize the inner surfaces of milking system components after the milking event is completed. Recently, an increasing number of dairy farms are adopting a one-step CIP process, which combines the alkaline wash and acid wash cycles into one wash cycle. This one-step CIP has the advantage of reducing time, energy consumption, and chemical usage. Electrolyzed oxidizing (EO) water is an emerging technology that produces alkaline and acidic EO water by electrolyzing a dilute sodium chloride solution. Previous studies in our lab have shown that by blending the alkaline EO water with the acidic EO water at a certain ratio, the blended solution can be used as a one-step CIP alternative. Therefore, this study was undertaken to evaluate the deposit removal process during a one-step CIP wash cycle using the already optimized blended EO water solution and a stainless steel surface evaluation simulator. Stainless steel straight pipes were used as testing specimens, and the remaining milk deposit mass on the inner surfaces of the specimens was evaluated. A two-term exponential decay kinetic model was developed for the one-step blended EO water wash; the mathematical model comprises an initial fast deposit removal along with a slow deposit removal throughout the entire one-step wash. The proposed models were in agreement with the experimental data, with acceptable root mean square errors (0.08 mg mg-1 m-2) and low percentage error differences (5.16%). The relative light unit (RLU) reading from the adenosine triphosphate (ATP) bioluminescence method was also used as an indirect evaluation method at every time sampling point during the one-step wash cycle. Furthermore, scanning electron microscopy (SEM) was used to understand the residual deposit morphology on the specimen inner surfaces and qualitatively evaluate the cleanliness of the inner surfaces after the one-step wash. On average, 60% reduction of deposit coverage in the viewing area was observed after the blended EO water one-step wash as compared to after the warm water rinse cycle. Moreover, results showed that at the completion of the blended EO water one-step wash, the specimens could be considered clean, as indicated by the RLU cutoff reading for stainless steel material. Therefore, it is concluded that the developed and validated mathematical model for the blended EO water one-step wash could be used for CIP of the simulator.