Ohmic heating is the newest and least used of the three technologies. Heat is generated rapidly and uniformly in the liquid matrix as well as in particulates, producing a higher quality sterile product that is suitable for aseptic processing. Some reports deal with ohmic heating and its comparison to the effects of conventional pasteurization. Insights into elea what pulsed electric field does for food is just astonishing. The food industry has shown a renewed interest in ohmic technology in recent years, with new systems being designed since the early 1990s. The potential applications of ohmic heating range from cooking, thawing, blanching, peeling, evaporation, extraction, dehydration, and fermentation. Guven2 1celal bayar university, faculty of engineering, food engineering department, 45140 manisa, turkey 2ataturk horticultural central research institute, food technology department, 77102 yalova, turkey received july 26, 2014. This kind of food heating processing operation is called ohmic heating. Effect on textural properties abstract the aim of this work was to verify the effects of ohmic heating oh treatment on texture of fresh solid food without pretreatment in brine solutions, subjected to constant electrical field gradient 1100 vm. Ohmic heating has immense potential for achieving rapid and uniform heating in foods, providing microbiologically safe and high quality foods. In the early twentieth century, electric pasteurization of milk was achieved by passing1 milk between parallel plates with a voltage difference ohmic heating. Ohmic heating applications have a tremendous potential in.
Inactivation of microorganisms in foods by ohmic heating. Nutritional impact of ohmic heating on fruits and vegetables. Oct 25, 2016 in ohmic heating the energy is dissipated directly into the food. Jun 01, 2009 ohmic heating has been shown, for example, to influence mass transfer properties 7,8. Ohmic heating has effects on quality parameters of food materials, such as inactivation of microorganisms and enzymes or decomposition of heat sensitive compounds, should be investigated. The success of ohmic heating depends on the rate of heat generation in the system, the electrical conductivity of.
Over 90% allergies are identified with 8 sorts of foods, with bovine milk included nowak wegrzyn and fiocchi, 2009. Due to internal heat generation, the heating is rapid and more uniform than traditional systems used for heating foods where heat must travel from the outside surface to the inside of the food. Feb 14, 2014 the book also deals with issues in ohmic heating equipment, ohmic heating modeling issues, and process validation issues. Lyng1 1school of agriculture, food science and veterinary medicine, agriculture and food science centre, college of life sciences, ucd dublin, ireland, 2 dipartimento di ingegneria chimica e. The concept originated back in the 1840s when james prescott joule showed that water would heat up when an electric current was passed through it. Download pdf ohmic heating in food processing free online. In ohmic heating electric currents are passed through the food in order to heat it. Processing food using an electric current don mercer.
Ohmic heating has also shown potential in the evaporation and concentration of foods e. Kinetics of microbial inactivation for alternative food. Ohmic heating, known as joule heating, can produce heat by flowing electric current through materials that can resist the flow of electricity. May 16, 2015 history the concept of ohmic heating of foods is not new in the nineteenth century, several processes were patented that used electrical current for heating flowable materials within the past two decades, new and improved materials and designs for ohmic heating have become available. Joule heating, also known as resistive, resistance, or ohmic heating, is the process by which the passage of an electric current through a conductor produces heat joules first law, also known as the joulelenz law, states that the power of heating generated by an electrical conductor is proportional to the product of its resistance and the square of the current. Changes in the electrical conductivity of foods during. These include ohmic heating, microwave heating 46, low electric field stimulation 7,8, highvoltage arc discharge 912, and highintensity pulsed electric field pef application 15. Journal of food processing and preservation, 20 1996 pp. The absence of a hot surface in ohmic heating reduces fouling problems and thermal damage to a product sastry and barach, 2000. The use of ohmic heating in processing of food industry. Ohmic heating provides rapid and uniform heating, resulting in less thermal damage than conventional heating and allowing manufacturers to obtain highquality products with minimum sensorial, nutritional, and structural changes. A new method of heating uses the natural electrical resistance of the food to generate heat. An experimental ohmic heating unit was designed and fabricated for continuous thermal processing of liquid foods.
The possibilities for ohmic heating include blanching, evaporation, dehydration, fermentation, extraction, sterilization, pasteurization and heating of foods. The unit was supported by a data acquisition system for sensing the liquid temperature distribution, line voltage and current with time. A large number of actual and potential applications exist for ohmic heating which include blanching, evaporation, dehydration, fermentation, sterilization, pasteurization, and heating of foods to serving temperature usafda, 2000. The stability of ohmic heating as a method used for processing is considered for the simple case of a homogeneous food. Ohmic heating is a novel thermal food processing operation in which electric currents are passed through conductive foods with the prime purpose of heating them and as food also has some resistive. The food material switched between electrodes has a role of resistance in the circuit.
In the nineteenth century, several processes were patented that used electrical current for heating flowable materials. How is ohmic heating different from conventional thermal processingit is possible to process large particulate foods up to 1 inch that would be difficult to processusing conventional heat exchangers. Ohmic heating is a food processing operation in which heat is internally generated within foods by the passage of alternating electric current. Ohmic heating oh is an alternative food processing technology for effectively inactivating microorganisms that depends on the heat that has. Ohmic heating, also known as joule heating, electrical resistance heating, and direct electrical resistance heating, is a process of heating the food by passing electric current. The book also deals with issues in ohmic heating equipment, ohmic heating modeling issues, and process validation issues. Ohmic heating of foods during aspetic processing ima. Lyng and others published ohmic heating of foods find, read and cite all the research you need on researchgate. The basic principle of ohmic heating or joule effect is the dissipation of electrical energy in the form of heat kumar et al. This technology is also known as joule heating, electrical resistance heating. Ohmic heating for the food industry consists of using electrical energy to heat foods as a method of preservation, which can in turn be used for microbial inactivation or several other processes such as pasteurization, extraction, dehydration, blanching or thawing.
A package made of flexible pouch materials was powered through a pair of metal foil electrodes extending out. Ohmic heating is a developing innovation, with vast number of real and future applications. Ohmic heating is an electroheating technique based on the passage of electrical current through a food product having electrical resistance. Pdf ohmic heating for food products aaradhana patel. A viscous food product containing particulates enters the continuousflow ohmic heating system via a feed pump hopper. In this method electrical energy is transformed into thermal energy. The authors discuss various applications of ohmic heating applied to different classes of foods, such as muscle foods meat, poultry, and fish, dairy products, fruits, and vegetables. Food, which contains water and ionic salts in abundance is the most suitable for ohmic heating palaniappan and sastry, 1991. Back pressure is maintained at a constant 2 bar when sterilizing highacid food producta at temperatures of 9095c. Results showed that the ohmic heating rate of beans increased with increasing the blanching time as a direct result of the increase of electrical conductivity. The milk has a few proteins, where around 30 of them presents allergenic potential, where the casein and. The case of a single spherical solid food particle with temperaturedependent conductivity surrounded by a liquid sauce is considered to model the. Technology, applications and modelling of ohmic heating. While some evidence exists for nonthermal effects of ohmic heating, the principal mechanisms of microbial inactivation in ohmic heating are thermal in nature.
Ohio state university scientist sudhir sastry explains the process of ohmic heating and how it makes food safer while maintaining high quality and flavor. Food manufacturers warm to ohmic heating technology. The success of ohmic heating depends on the rate of heat generation in the system, basic. Ohmic heating is an alternative preservation techniquea. Apr 29, 2012 ohmic heating or joule heating has immense potential for achieving rapid and uniform heating in foods, providing microbiologically safe and high quality foods. Ohmic heating as an alternative food processing technology by. Like microwave heating, ohmic heating can preserve foods by the application of heat and has the ability to very rapidly heat foods with minimal destruction. Academic press is an imprint of elsevier 30 corporate drive, suite 400, burlington, ma 01803, usa 32 jamestown road, london nw1 7by, uk 525 b street, suite 1900, san diego, ca 921014495, usa. Ohmic heating presents a large number of actual and potential future applications, including its use in blanching, evaporation, dehydration, fermentation, extraction usa fda, 2000, sterilization, pasteurization and heating of foods to serving temperature in the military field or longduration space missions sastry et al,2009. The process is known as ohmic heating since it relies on resistance, measured in ohms, to heat the food. Ohmic heating, also referred as joule heating, electrical resistance heating or electroconductive heating, is defined as a process in which the material to be heated for example a reaction mixture, which behaves as an electrical ohmic heater, is heated by passing an ac electrical current through it. General principles of ohmic heating and critical process parameters. Ohmic heating joule heating, resistance heating, or electroconductive heating generates heat by passage of electrical current through food which resists the flow of electricity.
The heating rate of foods is directly dependent on the electric voltage gradient and electric conductivity of foods. For the purposes of this paper, the term of ohmic heating will be used exclusively. Ramesh, in encyclopedia of food sciences and nutrition second edition, 2003. Ohmic heating is a food processing process where an electric current is passed through the food with the main purpose of heating it. In oh there is no need to transfer heat through solidliquid interfaces or inside solid particles once the energy is dissipated directly into the foods. Temperature dependent electrical conductivities of fruit purees during ohmic heating. Beyond heating, applied electric field under ohmic heating causes electroporation of cell membranes, which increase extraction rates, and reduce gelatinization.
Properly processed and packed fruit preparations are potential readymade energy sources for immediate consumption. The heating of a homogeneous food in a shear layer close to a wall is analysed. It is also referred to as joule heating, electrical resistance heating and electroconductive heating. Industrial applications and potential use of ohmic heating. Ohmic heating is one of the earliest forms of electricity applied to food pasteurization 1. Basics of ohmic heating a novel food preservation technique. Ohmic heating or joule heating has immense potential for achieving rapid and uniform heating in foods, providing microbiologically safe and high quality foods. The advantage of ohmic treatments over conventional methods is the lack of high wall temperatures and limiting heat transfer coefficients requirements. In ohmic heating the energy is dissipated directly into the food. Ohmic heating oh is defined as a process wherein electric current is passed through materials with the primary purpose of heating them. In ohmic heating oh, foods are made part of an electric circuit and the heat is directly generated inside foods when the electric power is applied and the current passes though them. Abstract ohmic heating offers an alternating to conventional heating because it simultaneously heats both phases by internal energy generated through electrical energy. The volumetric properties resulting from ohmic heating cause heat to be spread evenly on the material. Ohmic heating in food processing covers several aspects of ohmic heating.
Ohmic heating conventional and advanced food processing. Ohmic heating in food processing 1st edition hosahalli. The process enables solid particles to heat as fast as liquids, thus making it possible to use high temperature short time sterilization techniques on particulate foods. A large number of potential applications exist for ohmic heating, including blanching, evaporation, dehydration, fermentation, sterilization, pasteurization, and heating of foods. Changes in the electrical conductivity of foods during ohmic heating. Rahman, 1999 ohmic heating is one of the newest methods of heating foods. Introduction ohmic heating theory ohmic heating effects commercial applications conclusions ohmic heating treatment handbook of food safety engineering wiley online library. Industrial applications and potential use of ohmic heating for fluid foods h. Irradiation, microwave, and ohmic processing of foods. Ohmic heating sometimes also referred to as joule heating, electrical resistance heating, direct electrical resistance heating, electroheating, and electroconductive heating is defined as the process of passing electric currents through foods or other materials to heat them. Ohmic heating is an alternative fast heating technique for food products, which takes its name from ohms law. Design and evaluation of electrical resistance unitohmic. The success of ohmic heating depends on the rate of heat. Ohmic heating in the food industry new food magazine.
Influence of process parameters markus zell1, denis a. Changes in the electrical conductivity of foods during ohmic. Due to these drawbacks, the use of direct heating through a joule effect, such as ohmic heating, has gained increased attention in the food industry. The future utilization of ohmic heating by the industry will. The electrical conductivity of food components is critical to ohmic heating. Design and performance evaluation of an ohmic heating unit for liquid foods. There is a slight change in the heating curves of potato halden. Volumetric heating of foods using applied electric current ohmic heating allows both solid and liquid components of a food to be heated at similar rates, enabling rapid sterilisation.
Electrical conductivity is a key parameter in the design of an effective ohmic heater. Electrical conductivities of selected solid foods during. Download pdf ohmic heating in food processing free. Ohmic heating has unique characteristics with associated advantages, which will certainly have significant impact on the nutritional values of ohmically heated products. May 04, 2012 how is ohmic heating different from conventional thermal processingit is possible to process large particulate foods up to 1 inch that would be difficult to processusing conventional heat exchangers. Ohmic heating for the food industry consists of using electrical energy to heat foods as a method of preservation, which can in turn be used for microbial. Ohmic heating is considered very suitable for thermal processing of particulatesinliquid foods because the particulates heated simultaneously at similar or faster rates than the liquid. Electrical conductivities of six different fresh fruits red apple, golden apple, peach. It describes the importance of ohmic technology and how to implement it in practice, addressing basic theory, principles. A new method of heating uses the natural electrical resistance of the food to generate. Ohmic heating has been shown, for example, to influence mass transfer properties 7,8. Both irradiation and microwave heating employ radiant energies which affect foods when their energy is absorbed, whereas ohmic heating raises the temperature of foods by passing an electrical current through the food.
Use of ohmic heating for aseptic processing of food. May 02, 2012 ohio state university scientist sudhir sastry explains the process of ohmic heating and how it makes food safer while maintaining high quality and flavor. Interest in ohmic heating was rekindled in the 1980s, when investigators were searching for viable methods to effectively sterilize liquid large particle mixtures, a scenario for which aseptic processing alone was unsatisfactory. Ohmic heating process in ohmic heating, main alternating current is passed directly through a conductive food, which causes heat generation within the food. There has been a resurgence of interest in ohmic heating a novel food sterilising technique that came to the fore in the 1980s following refinements to the technology that have improved. The electrical conductivity affects the diffusion from a food sample and at a steadystate temperature, differences in sample. Ohmic heating ohmic heating is referred to as joule heating, electrical resistance heating or electroconductive heating. If food product containing starch then care should be taken during ohmic heating because it causes starch gelatinization.
237 1153 978 1125 699 616 1499 675 1502 965 705 553 566 81 512 1288 637 1530 738 1004 233 742 249 811 518 1071 635 1028 297 1461 1428 206