Tap water and table salt may be safer and cheaper for milk production cleanup

UNIVERSITY PARK, Pa. -- A safer option for cleaning milking systems on dairy farms may also decrease cleaning time and cost, according to a team of Penn State engineers.

"We use very harsh chemicals in an acid-based and alkaline-based cleaning system on farms," said Robert Graves, professor emeritus of agricultural and biological engineering. "We want to minimize the hazard to the people using this stuff."

The researchers studied the effectiveness of the first three cycles of the Cleaning-in-Place process -- warm water rinse, alkaline wash and acid rinse -- using electrolyzed oxidizing, or EO, water in place of harsher chemicals typically used in the alkaline and acid washes.

EO water is the product of electrolyzed tap water combined with table salt, NaCl. In electrolysis, an electrical current passes through the liquid to break the water and salt into smaller components -- a hydrogen ion and hydroxide ion for water and a sodium and chlorine ion for salt. Two electrodes placed in the water, one positive and one negative, separate the positively and negatively charged ions in the solution so the acid water is drained separately from the alkaline water. The combination of the chlorine and hydrogen ions produce hypochlorous acid in the acidic water, with a pH of approximately 2.7, and the combination of hydroxide and sodium ions produce sodium hydroxide in the alkaline water, with a pH of approximately 11.5. These chemicals in each solution provide the cleaning and sanitizing properties, but the solutions consist mostly of water.

Cleaning-in-place, or CIP, is a method many farms employ for cleaning the pipes that transport milk after it leaves a cow. CIP consists of four steps. The first is a warm water rinse, which removes most of the residual milk soils. The second is an alkaline wash, which removes soils including lipids, proteins and other organic materials. The third is an acid rinse, which removes minerals and slows the growth of microorganisms. The fourth is a sanitizing rinse, which is run immediately before the next round of milking.

The researchers found the use of EO water was just as effective as the chemicals traditionally used, which can be harmful to humans if touched or ingested.

The researchers constructed a mock milking system using a stainless steel pipeline. Before they began testing, they soiled the pipeline to simulate the situation before a farmer cleans their system. They accomplished this by running milk through the system and letting the residue dry. They repeated this for a total of five times. They ran the first three cycles of the CIP process, stopping several times per cycle to measure the remnants within the removable sections within the pipeline. The weight of each was measured before and after it was soiled for comparison. It was determined that more than 90 percent of the residue was removed solely with the warm water rinse. The researchers reported their results in a recent issue of the Journal of Food Engineering.

The researchers were the first to mathematically model each step in the CIP process using EO water, studying how much residue was removed as time passed. For each step, they found that less time than currently recommended is needed to effectively clean the system. In effect, after a certain period of time, the wash cannot remove any further residue. They recommended shortening the warm water rinse by 20 seconds, alkaline wash by seven minutes and acid wash by four minutes. This shortened the cycle by 55 percent while maintaining about the same effectiveness.

Not including the purchase of the machine necessary to create the EO water, the use of EO water combined with the shortened run time allow for a 30 to 40 percent cheaper cleaning process. The decrease in cost comes largely from the decreased run time, meaning a decrease in the amount of cleaning fluid that needs to be heated, and the decreased cost in producing the chemicals. While the machine may be expensive for smaller farms at this time, the researchers believe the technology will soon become affordable to a wider range of farmers as more companies invest in the technology.

"EO water is a cleaning solution and sanitizing solution," said Ali Demirci, professor of agricultural and biological engineering and affiliate of the Huck Institutes of the Life Sciences. "Meat, fish, fruit and vegetables can be sanitized using the EO method."

EO water also cuts down on environmental hazards caused by chemical spills during transportation and storage. Instead, machines can produce EO water at the farms, eliminating the need for transportation and storage.

Also working on this project was Xinmiao Wang, first author and recent Penn State Ph.D. now at the School of Food Science and Biotechnology at Zhejiang GongShang University in China as faculty and Virendra Puri, distinguished professor of agricultural and biological engineering.

The U.S. Department of Agriculture and Pennsylvania Agricultural Experiment Station supported this work. Hoshizaki Electric Co. Ltd. provided the technical support for the EO water generator used.

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Last Updated June 16, 2016