1.1 INTRODUCTIONDairy processing equipment is complex and requires frequent cleaning and sanitization. Cleaning and sanitization play an essential role in the dairy industry in ensuring quality products by preventing microbial contamination and avoiding reduced performance of processing equipment due to fouling. Most dairy processing equipment is cleaned using a highly automated technique, called clean-in-place (CIP), which is a method of cleaning the internal surface of pipelines or processing equipment by jetting, spraying or circulating cleaning solutions without opening or dismantling them. the equipment (Romney, 1990). CIP cleaning includes four steps: rinsing with water to remove loose dairy residue; washing with alkaline detergents to remove proteins and fats most attached to the surfaces of the equipment; rinse again with water to remove detergent residues and dissolved dirt; and finally rinsing with disinfectant to reduce bacterial contamination (Lloyd, 2008). Electrolyzed water is a mixture of alkaline and acidic solutions, produced by electrolysis of a dilute solution (0.1%) of sodium chloride. This process produces an alkaline electrolyzed reducing water (ER) containing sodium hydroxide (pH approx. 11.0 and ORP approx. -850 mV) and an acidic electrolyzed oxidizing water (EO) containing 10-100 ppm chlorine (pH 2.5, ORP approx. 1168 mV) (Huang et al., 2008; Al-Haq et al., 2005). Unlike conventional CIP chemicals, which are usually stored and handled in concentrated forms, electrolyzed water can be produced on site and offers an attractive alternative to conventional cleaning and sanitization solutions. As described in Chapter 1, the use of electrolyzed water for CIP cleaning offers the possibility of reducing production costs by reducing... half the paper... the same or better cleaning efficiency compared to a conventional CIP procedure which uses conventional detergents and disinfectants. The application of electrolyzed water for CIP procedures of processing equipment in dairy production plants has not been reported in the literature. No information was found regarding the cleaning of equipment used to heat treat milk and dairy products, dirt which is relatively difficult to remove due to protein denaturation and mineral deposition. The objective of this work was to investigate the cleaning ability of electrolyzed water for CIP cleaning and sanitization of a pilot-scale stainless steel test vessel used to heat treat milk. Response surface modeling was employed to optimize the settings of a CIP process using electrolyzed water. Variables included temperatures and treatment times for both ER alkaline water treatments and EO acidic water treatments.