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issue: January 2004 APPLIANCE Magazine

Engineering Ice-Making Machines
A Clean Machine

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Antimicrobial AlphaSan® from Milliken Chemical helps Manitowoc Ice in Manitowoc, WI, U.S. deliver an unprecendented sanitation level for the company's ice-making machines.

You don't stay an industry leader for more than 30 years without constant innovation and a strong commitment to quality. Manitowoc Ice, Inc., a world-leading manufacturer of commercial ice machines, has proven that over and over again.

The company has recorded a long line of industry firsts, from the invention of a patented vertical evaporator design that revolutionized the ice making industry to being the first refrigerated equipment maker to convert to alternative refrigerants. This year, Manitowoc achieved another first with the introduction of machine parts that incorporate Antimicrobial AlphaSan from Milliken Chemical (Spartanburg, SC, U.S.), a continuous-acting antimicrobial agent that reportedly will stay effective for the life of the part.

Sanitation is a critical issue for the hospitality industry. Restaurants, hotels, and other businesses spend significant amounts of money each year to repair and clean ice machines. Biofilm or "slime" is a by-product of the microbes that live everywhere: on our hands, in the water we drink, and in the air we breathe. The moist environment inside an ice-making machine is a perfect environment for microbes to thrive and is one of the leading causes of ice machine breakdowns. Yet Manitowoc's biofilm prevention system, which includes AlphaSan, reportedly provides an unachievable level of sanitation. While a regular cleaning program is still necessary, the new prevention system is said to enable less frequent and less severe cleaning, which can reduce the amount of operating downtime. Manitowoc's portfolio of sanitation products includes its built-in self-cleaning system (SeCS), Automatic Cleaning System (AuCS), Guardian slime inhibitor, Arctic Pure water filter, and now AlphaSan. "While each of these products independently improve the sanitation of an ice machine, working together they provide a solution to sanitation issues that is unmatched in the industry," says Mike Rimrodt, product manager for Manitowoc.

The plastic parts that incorporate AlphaSan in the ice machine are the water distribution tube and the attached vinyl tube. According to Mr. Rimrodt, "The parts were selected because they are difficult to clean, and when they are not cleaned or are cleaned poorly, the distribution of water over the evaporator is not consistent. If the water does not pour over the evaporator consistently, the efficiency of the machine is reduced."

According to Aric Axness, business development manager for Milliken Chemical, organic antimicrobials work by leaching out of a solid such as plastic or a coating to the surface. They generally have deficiencies with respect to thermal stability, toxicology, broad spectrum microbial performance, and durability. AlphaSan is an inorganic antimicrobial based on silver. Its mechanism of action is through ion-exchange, not migration to the surface. There are several types of active ingredients of inorganic antimicrobials such as copper and zinc, although silver is widely recognized as the most effective. There are more than 40 different technologies utilizing silver as an active antimicrobial ingredient.

"The main feature that distinguishes AlphaSan from other silver-based antimicrobials is that its carrier is a specialized ceramic based on zirconium phosphate," Mr. Axness says. "This ceramic carrier acts as a sponge for silver ions. This 'sponge' allows for a controlled release of silver based on its environment. When the microbial population is high on an AlphaSan-treated surface, the carrier allows for a greater exchange rate of silver into the environment to control the bioburden. Conversely, when the environment has a low-microbial population, a lower amount of silver is released to control this population. This enables AlphaSan to offer the best protection against the varying levels of microbes on a surface over time while conserving silver ions for longer durability."

Another important feature of AlphaSan's ceramic carrier is that it doesn't form color, he adds. "Silver has a strong affinity to bind with other ions to form silver salts, silver oxides, and other color forming groups. Many of AlphaSan's competitors' silver-based antimicrobials form color in plastics and coatings due to a less controlled release of silver ions. This formation of color is not only aesthetically displeasing, it reduces the surfaces antimicrobial effectiveness," Mr. Axness explains.

Three years of research and development work, including controlled laboratory testing and 12 months of life cycle testing went into the decision to include AlphaSan in Manitowoc ice machines. According to Mr. Axness, "Manitowoc, focusing on having the best quality products, wanted to make certain that AlphaSan would provide long-term antimicrobial performance, which is why there was so much R&D involved with this project. Manitowoc and Milliken worked to incorporate AlphaSan in a number of water contact components of its ice machines with its part suppliers. In addition to laboratory testing, extensive field testing was performed under a variety of conditions to demonstrate the inhibition of microbial growth on the treated components of Manitowoc's ice machines. Finally, key distributors and end use customers were involved to corroborate the value of antimicrobial properties in Manitowoc's ice machines before an official commercial launch moved forward."

A number of other antimicrobial products were also tested in the process. While not the first ice machine company to utilize antimicrobials, Manitowoc wanted to avoid the shortcomings, such as severe discoloration, taste or odor problems, and limited durability associated with alternative antimicrobial technologies.

"AlphaSan's superior performance gives us an immediate competitive advantage," says Mr. Rimrodt. "Because it's compounded directly into the plastic part, an effective concentration is constantly generated at or near the surface of a part. AlphaSan's unique ability to effectively control the release of silver not only protects against discoloration of the plastic, but our testing has shown it will also remain functional over the life of the part. This slow release allowed us to stay aligned with the industry standard of white plastic, which avoids disguising the growth of slime and biofilm."

Another advantage to using the product, says Mr. Rimrodt, is that it does not require replenishment and it lasts the life of the ice machine. "This was a major decision point for Manitowoc when investigating the possibility of incorporating this product into our machines," he notes. "The cost-to-benefit ratio tips easily in favor of incorporating the product when you factor in its life expectancy and no re-occurring costs directly associated with the product. Manitowoc as a company does not have re-occurring cleaning costs that are factored back into the equation, but our customers do. The incorporation of AlphaSan into the product improves our customers' operating costs and satisfaction levels with the equipment. The benefit to Manitowoc is then translated into brand loyalty and increased sales."

According to Mr. Axness, Milliken's initial focus on bringing AlphaSan to market had been to solve microbial growth issues on surfaces in an industrial/processing environment. However, he says more and more projects have been moving forward utilizing AlphaSan in products used by the general public, like Manitowoc's ice machines. "We see momentum moving toward solving odor, staining, and decomposition issues on product surfaces used by consumers," he says.


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