Normativas no respetadas y soluciones propuestas por la Comunidad internacional

Over the last few decades, a number of attempts have been made to use this technique in several food processing applications (Palaniappan and Sastry 1990; de Alwis and Fryer 1990). Between the 1950s and 1970s, experiments were performed to use ohmic heating for thawing purposes. Faster thawing rates were observed, but satisfactory results were obtained only if good contact between the food and electrodes was maintained. Problems occurred with complex geometry. In some instances, microwave thawing has replaced the technology. Ohmic heating experiments have been performed on cut and peeled potato slices and corn on the cob to deactivate enzymes. An industrial process, “OSCO,” was developed in the 1970s to treat peeled and cut potatoes in solution before frying. Ohmic heating has been used as a rapid heating method for frankfurters, with electrodes spiked at both ends of the sausages. From 1930 to 1970, rapid heating methods for vending applications were developed for heating sausages, pizzas, and hamburgers. Early concepts in pasteurization and sterilization preceded the introduction of a reliable aseptic packaging technology. Modifications of can designs to include electrodes fixed either temporarily or permanently on containers were used to ohmically sterilize foods. Continuous ohmic heating was introduced in the United States for the pasteurization of milk in late 1920s as a successful commercial technique, referred to as the “Electro-Pure” process (Anderson and Finkelstein 1919). In the 1930s, 50 industrial electrical milk sterilizers were in operation but disappeared in the 1950s (Getchell 1935; Moses 1938). A review of problems in the early development of the ohmic heating technique is outlined by de Alwis and Fryer (1990). The problems resulted mainly from improper contact between electrodes and the food product. Electrolysis and product contamination were observed following the use of unsuitable

Ohmic Heating Effects on Rheological and Functional Properties of Foods 23

electrode materials. As well, adhesion of the product to the electrodes often occurred. The difficulty in ensuring good contact between electrodes for complex solid geometry was the reason for poor experimental results. Before a reliable aseptic packaging technology existed, rapid and continuous sterilization techniques using ohmic heating were not practical. As with packaging, recent develop- ments in pumping technologies have ensured that particulate foods move without any mechanical damage. This rapid and sophisticated technology requires a level of control only possible through the use of recent computer technology.

A milestone in the industrial achievement of ohmic heating includes the “ELECSTER” process for the pasteurization of milk, which is based on the “Electro-Pure” process and the “APV Baker Ohmic Heating Technology” for the sterilization of particulate foods (Skudder 1991). The latter was recognized as a commercial breakthrough at the 1996 annual meeting of the institute of food technolo- gists (IFT). APV Baker Ltd. received the Industry Achievement Award (Giese 1996) for the develop- ment of the ohmic heating technology for the sterilization of fluid containing particles. In France, the Centre Technique de la Conservation des Produits Agricoles (CTCPA) and Université Technologique de Compiègne (UTC) joined together to install an APV pilot plant unit to help European food com- panies in developing sterilization processes for liquids containing particles in 1995 (Zuber 1997). In France, the Association pour le développement de l’industrie de la viande (ADIV) and Électricité de France (EDF) formed an alliance to design, build, and evaluate a static ohmic heating unit for processed meats that are pumpable (Peyron 1996). Ohmic heating units have been in commercial operation in the United Kingdom and Japan since 1990 (Parrott 1992). In 1995, an ohmic heating unit was manufactured in Japan by Yanagiya Machinery (http://www.ube-yanagiya.co.jp/Yanagiya/ companyguide.htm) for tofu production. An ohmic heating unit was patented by Thomas R. Parker of the United Kingdom to produce Japanese-style breadcrumbs (Panko) (Anderson 2003). Furthermore, Anderson (2003) summarized commercialized ohmic heating systems that include Sous Chef Ltd. (in England), which processes low-acid meats and vegetables in bags; Wildfruit Products (a division of Nissei Co. Ltd. of Japan), which processes whole fruits; Papetti’s Hygrade Egg Products of Elizabeth, NJ (manufactured by Raztek) to process liquid eggs; and Emmepiemme SRL (in Piacenza, Italy), which processes different kinds of foods such as baby food, artichokes, carrots, mushrooms, ketchup, fruit nectars, fruit juice, peppers, cauliflower, tomato paste, sausages, pâté, and fruit puree.

Since the 1980s, ohmic heating has been seen as a promising development to solve problems encountered in aseptic processing of low-acid liquids containing particulates. Several authors (de Alwis, Halden, and Fryer 1989; Sastry and Palaniappan 1992) have demonstrated that in ohmic heating it is possible to heat the center of the particle faster than the liquid. Therefore, the cold spot of the particle is located at the surface. From a legislative point of view, ohmic heating of the liquids containing particulates becomes a special condition (Larkin and Spinak 1996). If it can be proven that the temperature at the center of all particles during ohmic heating is always greater than that of the liquid at the inlet of the holding tube then the calculated process time is simplified as for the establishment of an aseptic process of homogeneous liquid using only the temperature of the liquid at the inlet of the holding tube. In the ohmic heating process, biological validation may not be required to establish the process as in conventional thermal processing but only to verify it. The ohmic heater assembly can be seen in the context of a complete product sterilization or cook- ing process where there is already a holding tube, pumping, and a cooling system (Marcotte 1999). In this case, an ohmic heating column consisting of several electrodes would replace the conven- tional Swept Surface Heat Exchanger (SSHE). The food product is fed vertically from the bottom to the top of the column. Heating occurs in three sections between two electrodes. The food is then held in the holding tube for temperature equilibration between the liquid and solid. It is cooled in tubular heat exchangers before being packed in an aseptic environment.

Research and development in continuous thermal processing of foods has been mainly driven toward assessing the technical feasibility of new and rapid methods, based on the use of electric energy. Many ohmic heating systems have been developed at the research level (Palaniappan and Sastry 1990; Huang, Chen, and Morissey 1997; Marcotte 1999; Farid 2001; Shirsat et al. 2004a, b;

Jun and Sastry 2005; Lei et al. 2007; Sarang, Sastry, and Knipe 2008) as well as industrial levels (Allen, Eidman, and Kinsey 1996; Zuber 1997; Anderson 2003).