In a development that promises to revolutionize the way food has been pasteurized for the last century, Raztek Corporation of Sunnyvale, Calif. has developed Electroheating™ technology, a unique system for killing disease-causing pathogens in food by zapping the product with electricity for a fraction of a second, followed by rapid cooling. Now available for industrial and commercial use, Electroheating™ technology delivers extremely high temperature rates without significantly altering the original flavor, aroma or nutritional value of the food product.

Since the late 19th century, manufacturers have relied on conventional heat exchange technology to pasteurize and sterilize food in an attempt to kill harmful viruses and microorganisms such as Salmonella and Listeria. However, the application of high temperatures in conventional equipment even for a relatively short time frequently has an adverse effect on the taste of the treated food product.

The deficiencies of conventional heat technologies stem from the heat transfer mechanism, which is based on transfer of heat from a hot wall or tube to the product. In order to reach the desired temperature throughout the product, the temperature of the wall must be significantly higher than the temperature of the product being heated. This increases the risk of fouling and scorching the product near the walls which leads to the formation of off-flavors and lowers the nutritional value of the food product.

"We can bypass these difficulties by passing electrical current through the product because the heat is created from within, rather than transferred by exchange." says David Reznik, president and chief scientist of Raztek Corporation. "Furthermore, because Electroheating™ technology effectively kills bacteria in fractions of a second, the taste and aroma of the product remain unaffected."

Electroheating™ is based on the passage of electricity through a food product which serves as an electrical resistance. The electrical power introduced into the product is translated into heat as it passes along the flow line of the fluid. This allows rapid, uniform heating to occur without the risk of overheating or burning the product.

Donald Schulak, former Executive Vice President Emeritus of Tri-Valley Growers, has witnessed a demonstration of Electroheating™ and believes that the new technology has tremendous value within the food industry.

"In my experience in the food industry, if you have a demonstrable improvement in flavor, you have a major comparative advantage over your competition," says Schulak, "I’m not talking about advertising or promoting that the flavor is different. I’m talking about really having a better flavor."

Electroheating™ can be used to pasteurize or sterilize almost any food product but is particularly advantageous when heating concentrated, high viscosity, proteinaceous and otherwise hard to heat food products such as tomato paste, cheese spreads, baby food, and liquid egg.

"The technology is particularly suited for products that create problems in conventional heat exchangers. Most of the proteinaceous products, and especially thick and viscous products, are very difficult to heat quickly without burning and forming off-flavors," says Reznik.

The Electroheating™ system is constructed from non-conducting food grade materials and consists of a tube and two graphite electrodes on the internal side of two parallel walls. Suitable fittings allow the device to be connected to a commercial or industrial line. The entire unit takes up very little factory space, far less than conventional pasteurization heat exchangers.

The advantages of the Electroheating™ system are best illustrated in the treatment of proteinaceous fluids, such as liquid egg and blood, which tend to denature and coagulate. Fortunately, in some materials the time to effectively inactivate viruses and bacteria is shorter than the time required for the coagulation of the product. With Electroheating™, it is possible to raise the temperature above the normal coagulation point in a fraction of a second, then immediately cool the product before coagulation can occur. This is not possible with conventional heat exchange technology, as the desired temperature cannot be reached before coagulation.

Animal blood, for example, coagulates at about 130°F. Electroheating™ allows the product to be heated to 160°F within a fraction of a second. By driving up the heat in such a short time then rapidly cooling it, the product will not coagulate and Salmonella that may be present is destroyed. Treated animal blood has many applications and is widely used in the production of pet food.

Proteinaceous products from blood plasma are also widely used in the biotechnology field for the manufacturing of drugs. These products contain potentially harmful viruses and bacteria, which pose a risk to those who manufacture drugs as well as the consumer.

"Electroheating™ can be used to protect the public from harmful bacteria or viruses in almost any product which comes into direct human usage or consumption, whether it is food or human proteins which are used in the manufacturing of pharmaceutical drugs," says Carlos Figueroa, a Biochemical Engineer.

Traditionally, the pharmaceutical industry has avoided heating, as the medium or the product contain specific proteins which are critical to the manufacturing process and would be destroyed by the heat. As an alternative, a micro-filtration process is used to remove bacteria. However, this process does not effectively eliminate viruses which may be present.

"In situations where you are dealing with large amounts of proteinaceous material which will be used to manufacture pharmaceutical drugs, viruses cannot be simply filtered out," says Figueroa, "As it stands, there is almost no barrier to prevent viruses from entering into the manufacturing process."

Electroheating™ Technology has already been successfully implemented on an industrial scale at Pappetti’s high-grade Egg Products in New Jersey, where liquid egg product is Electroheated at flow rates of 25,000lb/hour. Papetti was particularly interested in the technology as a means to extent the shelf-life of the product and reduce the down time required for cleaning conventional heaters.

"With Electroheating™ technology we are getting a much longer shelf-life than we did with conventional heat exchangers." says Ted Polny, Plant Manager at Papetti. "This is accomplished without the off-flavors associated with high temperatures."

Extended shelf-life allows manufacturers to dramatically reduce the number of product returns. This is significant from the point of view of handling the product when it is returned as well as reducing the amount of money that must be re-credited to the customer’s account.

Additional savings can also be realized by reducing the cleaning costs and down-time associated with cleaning conventional heat exchange units. Because the Electroheating™ device does not cause scorching, the system can be effectively operated 24 hours a day, seven days a week.

"In the past, we would have to stop every six to eight hours and do a clean-up. Now, we are able to run extended shifts," says Polny.

Electroheating™ is now being considered in the dairy industry to produce shelf stable milk without the traditional off-flavor. Although shelf stable milk is sold on a large scale in Europe, demand in the United States has been low due to the off-flavor of the milk created by the sterilization process. While many Europeans have become accustomed to this flavor, Americans have rejected it. This has prevented several large manufacturers from entering the potentially lucrative U.S. marketplace.

"The technology is ideal for shelf-stable milk manufacturers because we can treat the product at extremely high temperatures without the adverse effects of heat on the flavor of the product," says Reznik.

Shelf stable milk is sterilized milk in which all forms of bacteria are destroyed by temperatures of 250°F or higher. Pasteurized milk, on the other hand, is treated at a temperature of approximately 170°F to kill only pathogenic bacteria, such as Salmonella and Listeria. Pasteurized milk must then be refrigerated to slow the remaining bacteriological activity, while shelf stable milk may be stored at room temperature for many months.

The major concern in sterilizing milk at high temperatures of at least 250°F is the effect on the taste and quality of the milk. In order to minimize heat damage, the industry has developed techniques based on injection of steam at high temperature and pressure. However, the process still creates an unpleasant flavor in the milk.

In 1995, Raztek began experiments to create shelf-stable milk without the corresponding off-flavor. Tests were conducted on raw milk, pasteurized milk, sterilized milk (shelf-stable), and Electroheated milk. The Electroheated milk was treated at temperatures of approximately 310°F followed by rapid cooling.

Chemical analysis of the milk samples indicated the composition of Electroheated milk was free of oxidative damage occurring in conventional HTST (High Temperature, Short Time) or UHT (Ultra-High Temperature) commercial products. Amazingly, Electroheated milk was similar to raw milk in aroma and taste.

"The interesting thing is we started with pasteurized milk that was already heat treated. Some heat damage was already there. In Electroheated milk, we found that some constituents which had been destroyed in conventional pasteurization had been re-formed in the milk," says Reznik.

In the fresh juice industry, Electroheating™ technology will enable commercial production of high quality citrus products which could not be manufactured using conventional techniques. This is particularly significant in light of the recent discovery that some strains of coli can be found in apple juice, prompting several federal and health officials to call for a review of whether pasteurization should be required for all broadly distributed fruit juices. Although some juices are already being pasteurized, most manufacturers prefer to refrigerate their product rather than suffer the adverse effects of heat on flavor and nutritional value.

Initial tests conducted by Raztek Corp. have confirmed the practicality of Electroheating™ fresh fruit juice without affecting the original flavor, aroma and nutritional value of the product. By utilizing the technology, bacteria is destroyed without affecting the fresh, natural flavor and nutritional value that consumers demand.

"In samples of freshly squeezed orange juice which was Electroheated, no off-flavor was noticed and tasters could not differentiate between the fresh and the Electroheated product," says Reznik.

Upon viewing the demonstration at the Raztek lab in Sunnyvale, California, Tri-Valley’s Schulak was impressed. "I was amazed that you could send a temperature so high over such a short interval and then cool it so quickly after it was processed," he explains, "My first impression was of the overwhelming, natural aroma of the orange juice which had just been processed."

Raztek offers experimental runs on the Electroheating™ system at its facilities in Sunnyvale, California, in order to produce samples and establish the feasibility of implementing the technology. Manufacturers who feel the system may have benefit within their market are encouraged to contact Raztek Corporation for a demonstration.