Source: NORTH CAROLINA STATE UNIV submitted to NRP
QUALITY AND SAFETY CONSIDERATIONS IN THERMAL PROCESSING OF FOODS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0196488
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 1, 2008
Project End Date
Sep 30, 2013
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695
Performing Department
Food, Bioprocessing, and Nutrition Sciences
Non Technical Summary
Quality and safety considerations have been increasingly important in food processing. The current project will deal with quality & safety aspects associated with aseptic processing of liquid and particulate foods by making use of alternative processing technologies and novel sensor technologies. Different thermal and non-thermal methods have been used in the past for processing foods. One of the main promises of aseptic processing revolves around the high quality of the processed food. Rapid and uniform heating is an important part of achieving a high quality product. In order to process a product uniformly in a conventional heating system (using tubular or shell & tube heat exchangers), one has to assure that the entire product is subjected to similar time-temperature combinations in the heating and holding sections of the processing system. In order to do this, determination of the residence times and temperatures of particles is essential. Another approach to uniformly heating a food product involves heating products volumetrically (as opposed to heating from outside to inside) as is the case with microwaves and radio frequency (RF) waves. Microwave heating has been used in the past to heat foods. However, most of the studies have relied on making use of randomly incident microwaves in heating foods. This approach has resulted in non-uniform temperature distribution within foods. The use of a technique wherein the microwaves are focused into a region through which the product flows, could potentially result in uniform heating of pumpable foods. Radio frequency heating heats up primarily the water molecules (highly polar molecules) present in the food. Heating is a result of the process of aligning and re-aligning of the water molecules to the RF field, causing friction within the product. Thus, all food products containing a relatively uniform distribution of water would get heated evenly by using radio frequency. Some of the other advantages of RF heating over conventional heating include instant cut-off and start-up of heating, reduced heating time, precise power control, better efficiency of heating, and higher throughput. Once established, radio frequency heating will be of tremendous use in the processing of pork and poultry, and in the rapid curing of certain cheeses. The high quality products could then be aseptically packaged and transported to different locations all over the world. This would serve as a starting point for other sectors of the food processing industry to explore the possibility of using radio frequency for heating various other viscous and particulate food products.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
50150102020100%
Knowledge Area
501 - New and Improved Food Processing Technologies;

Subject Of Investigation
5010 - Food;

Field Of Science
2020 - Engineering;
Goals / Objectives
The overall goal of the project is to come up with a system and procedure for thermally processing viscous and particulate foods and rendering the product commercially safe and of high quality. The specific objectives of the project are: (i) Develop a protocol for continuous flow microwave heating of particulate foods a. Determine the effect of viscosity, particle concentration, physical, thermal, and dielectric properties on the heating rates and temperature distribution within foods undergoing continuous flow microwave treatment (experimental studies) b. Perform mathematical modeling studies to determine the temperature distribution within particulates at the exit of the heating unit to evaluate the degree and uniformity of heating (ii) Assess the feasibility of continuous flow radio frequency for processing viscous and particulate foods a. Determine the effect of viscosity, particle size, particle concentration (volumetric), physical, thermal, and dielectric properties on the heating rates and temperature distribution within foods undergoing continuous flow radio frequency treatment (experimental studies) b. Perform mathematical modeling studies to determine the temperature distribution within the product at the exit of the heating unit to evaluate the degree and uniformity of heating
Project Methods
(i) Develop a protocol for continuous flow microwave heating of particulate foods The first step towards understanding the complex process of microwave heating involves determination of the dielectric properties (using a network analyzer and a coaxial probe) of the food product under consideration at the range of temperatures of interest. The second step is to conduct mathematical modeling studies (using ANSYS) to determine the optimum operating conditions for the process. This would involve coupling the electromagnetics, heat transfer, and fluid flow modules within the software. The third step involves running the product through a small-scale microwave unit - 5 kW unit and determining the temperature distribution at the exit of the system (using thermocouples located at various radial locations). The product will then be processed in a large-scale microwave unit - 60 kW microwave unit with split applicators delivering 30 kW each to the product. (ii) Assess the feasibility of continuous flow radio frequency for processing viscous and particulate foods In order to study the possibility and usefulness of RF heating for a variety of food products (viscous and particulate foods), a 30 kW continuous flow RF unit will be used. A tubular heat exchanger will be used in tandem with the RF unit. The RF unit will be used as a final heater to equalize or reduce any differences in temperature between the center of the particles and the fluid during the pre-heating process (using a conventional tubular heat exchanger). Four kinds of studies will be performed to analyze the appropriateness of RF for heating various foods products. The first study will involve batch processing of the product within the tube. The studies will be conducted for different values of product viscosity (0.01 - 10 Pa-s), product density (900 - 1100 kg/m^3), particle loadings (0 - 30%), and particle sizes (5 - 15 mm). The second study will involve the study of the kinetics of sucrose inversion within the product flowing continuously through the tube. These studies will be conducted for different product flow rates (1 - 6 gpm). The third study will involve the use of food products in a RF system to evaluate the quality of the processed foods. This involves rheological testing of the product (stress-relaxation tests and compression tests) before and after processing. The fourth study will involve pulsing the RF energy on/off. This is based on the fact that heating of the product takes place when the molecules are realigning themselves during the process of switching the direction of the electric field. Thus, pulsing would have the same effect, and also result in minimization of the energy requirements. The appropriate combination of pulsing and use of the conventional and RF unit to yield the most uniform process will then be determined.

Progress 10/01/12 to 09/30/13

Outputs
Target Audience:Food industry Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Several stuents were trained in the process. How have the results been disseminated to communities of interest?Several short courses were conducted to disseminate the results What do you plan to do during the next reporting period to accomplish the goals?We plan to develop the next generation of contimuous flow microwave processing.

Impacts
What was accomplished under these goals? Continuous flow microwave processing was commercialized.

Publications


    Progress 10/01/08 to 09/30/13

    Outputs
    Target Audience:Food industry Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Several graduate students were trained during this period. How have the results been disseminated to communities of interest?The results have been presented at conferences and also published in peer-reviewed journals. What do you plan to do during the next reporting period to accomplish the goals?Furhter work on improving the quality of viscous and particulate foods is planned for.

    Impacts
    What was accomplished under these goals? Various pumpable foods were thermally processed in a continuous flow microwave processing system. This involved determination of thermal, physical, and dielectric properties of the foods, running small-scale experiments, scaling-up, and conducting large-scale runs. It also involved developing tools to validate the process.

    Publications


      Progress 10/01/11 to 09/30/12

      Outputs
      OUTPUTS: The main objectives for the research work were: 1. Use continuous flow microwave processing to process particulate foods 2. Use continuous flow microwave as a pre-treatment technique to enhance the hydrolysis of cellulose to fermentable sugars and aid in the production of bioethanol PARTICIPANTS: K.P. Sandeep, Ken Swartzel, Josip Simunovic TARGET AUDIENCES: Food Industry PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

      Impacts
      Continuous flow microwave processing has been established as a viable technique for processing viscous foods. We are exploring the possibility of using the same technique to process particulate foods. We have developed formulated high-acid and low-acid foods for trial in the microwave system and will be conducting the tests shortly. Continuous flow microwave heating has shown the potential to enhance the hydrolysis of cellulose to fermentable sugars. We conducted small-scale and large-scale tests to assess the efficacy of the system and are in the process of analyzing the data to determine the optimum conditions to operate the system to maximize the yield of bioethanol.

      Publications

      • No publications reported this period


      Progress 10/01/10 to 09/30/11

      Outputs
      OUTPUTS: Research projects with the following objectives were carried out: 1. Adopt continuous flow microwave processing to various pumpable foods 2. Develop sensors for process monitoring and validation 3. Improve quality of thermally processed foods 4. Validate cooking instructions for ready to eat foods These projects resulted in the development of protocols and tools to meet the goals of the project. Short courses were conducted to disseminate results from these projects. PARTICIPANTS: K.P. Sandeep, Josip Simunovic, Ken Swartzel TARGET AUDIENCES: Food industry PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

      Impacts
      The continuous flow microwave technology was expanded in use to different products and a company was formed to commercialize this technology for producing shelf stable fruit purees. The sensors that were developed are being evaluated and used for process validation. Process monitoring techniques have resulted in the improvement of product quality. Cooking instructions were assessed for ready to eat seafoods and recommendations were made for improving the instructions.

      Publications

      • Sandeep, K.P., Simunovic, J. 2012. Modeling and validation of continuous flow microwave processing of pumpable foods. IFT Paper No. 024-02. 2012 IFT Annual Meeting, June 25-28, Las Vegas, NV. Truong, V.D., Thompson, R.T,, Simunovic, J., Cartwright, G., Coronel, P., Kumar, P., Sandeep, K.P., Swartzel, K.R. 2012. Carotenoids and tocopherols in sweet potatoes subjected to pureeing and continuous flow microwave sterilization. IFT Paper No. 230-06. 2012 IFT Annual Meeting, June 25-28, Las Vegas, NV. Sandeep, K.P. 2012. Aseptic processing of multiphase foods: Fundamentals, product, process, equipment, and validation considerations. Institute for Thermal Processing Specialists (IFTPS) Annual Meeting. Mar. 6-9, San Antonio, TX. Sandeep, K.P. 2011. Pre-heat processing: Can pickles be safely processed without a pasteurizer 2011 Annual Meeting of Pickle Packers International, Oct. 26-28, Las Vegas, NV. Simunovic, J. and Sandeep, K.P. 2011. Microwave processing of dairy products. 2011. SDFRC Annual Meeting, Aug. 15-16, Raleigh, NC. Simunovic, J. and Sandeep, K.P. 2011. Continuous flow microwave heating for pasteurization and sterilization of dairy products. 2011. American Dairy Science Annual Meeting, July 10-14, New Orleans, LA.


      Progress 10/01/09 to 09/30/10

      Outputs
      OUTPUTS: Research projects with the following objectives were carried out: 1. Validate continuous flow microwave processing of pumpable foods 2. Develop sensors for process monitoring 3. Improve quality of thermally processed foods These projects resulted in the development of protocols and tools to meet the goals of the project. Short courses were conducted to disseminate results from these projects. PARTICIPANTS: K.P. Sandeep, Josip Simunovic, Ken Swartzel TARGET AUDIENCES: Food industry PROJECT MODIFICATIONS: Not relevant to this project.

      Impacts
      Continuous flow microwave processing was extended for use by local companies. This resulted in the creation of new jobs. We anticipate that this technology will be adopted by other companies and that it will create more jobs in NC. The sensors that are being developed will likely be used by one or more food processing companies to validate their continuous thermal process.

      Publications

      • Breidt, F., Sandeep, K.P., Arritt, F. 2010. Use of linear models for thermal processing of acidified foods. Food Protection Trends. Vol. 30(5): 268-272.


      Progress 10/01/08 to 09/30/09

      Outputs
      OUTPUTS: A short course on "Conventional and advanced continuous flow thermal processing" was conducted for industry, academia, and government organizations. This course served as a means of disseminating theoretical and practical aspects of thermal processing to processors, educators, and regulators. PARTICIPANTS: K.P. Sandeep, Josip Simunovic, Ken Swartzel, Van-Den Truong, Gary Cartwright, Prabhat Kumar, Lee-Ann Jaykus TARGET AUDIENCES: Food industry PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

      Impacts
      The previously developed and commercialized continuous flow microwave process (for sweetpotato puree) was applied to a variety of viscous products (fruit and vegetable purees) with a goal of producing shelf-stable products. These products will enable processors to distribute the products around the world with minimal concerns of shelf-life as these products have a shelf life of over a year. Significant development was also made in the field of process validation. A miniature electronic sensor (proof-of-concept) was developed that could be implanted within conservatively designed particles and pumped along with a food product to help ascertain the time-temperature history at the coldest point within the product. Immobilized spores were also packaged and implanted within these particles to serve as a means of confirmation of the efficacy of the product. These tools (electronic and biological) would facilitate process filing with the FDA.

      Publications

      • Xiao, D., Golden, D.A., Davidson, P.M., Sandeep, K.P., Zhong, Q. 2009. Inactivation of Escherichia coli K-12 on strawberries by dense phase carbon dioxide. IFT Paper No. 026-02. 2009 IFT Annual Meeting, June 6 - 9, Anaheim, CA.
      • Stam, C.N., Smiley, R.D., Simunovic, J., Truong, V.D., Sandeep, K.P., Jaykus, L.A. 2009. (026-16) Immobilized Bacillus spores for use as biological indicators in validating continuous flow microwave aseptic processing of a multiphase food product. IFT Paper No. 026-16. 2009 IFT Annual Meeting, June 6 - 9, Anaheim, CA.
      • Kumar, P., Simunovic, J., Truong, V.D., Swartzel, K.R., Cartwright, G.D., Sandeep, K.P. 2009. Temperature distributions and dielectric properties of vegetable purees under continuous flow microwave heating. IFT Paper No. 225-28. 2009 IFT Annual Meeting, June 6 - 9, Anaheim, CA.


      Progress 10/01/07 to 09/30/08

      Outputs
      OUTPUTS: Considerable effort was geared towards moving a developed technology - continuous flow microwave processing - from the stage of research and development to the stage of commercialization. This involved streamlining of the processes of determination of properties (offline and inline at high temperatures and pressures), conducting modeling & small-scale studies, developing sterilization solutions, scaling up of small-scale runs (and conducting runs that last several hours to mimic what is encountered in the food industry), and incorporation of process validation tools. Techniques and setups were developed to measure various thermal, physical, and dielectric properties of foods (and their constituents) under consideration. This gives us a more realistic estimation of the properties and also enables real-time control of process parameters as a response to change in properties. This will enable both quality control and safety of the operation. The current scaled-up process has been commercialized for aseptic processing of sweetpotato puree. We are in the process of developing a modified version of this setup for processing particulate foods. Once developed, we anticipate that this process and system can be used for not only processing foods currently retorted, but also in starting new lines of products that are of higher quality. As far as validation tools go, we are working on different technologies that can be used for it. One of the promising technologies revolves around the use of electronic temperature sensing devices. We have developed a "proof-of-concept" electronic sensor that can be used to determine the internal temperatures of particles as they flow through a continuous aseptic processing system. This sensor is in the process of being re-designed to meet the size, density, and thermal properties requirements of particulates encountered in aseptic processing of particulate foods. We are also in the process of developing microbiological indicator units that can be used to calibrate and validate other sensors which are electronic or chemical in nature. These units or packs can be pumped along with the food under consideration and will undergo the same thermal treatment as the food. Once we collect these units at the end of the process and enumerate the survivors, we will be able to determine the degree of thermal treatment delivered to the food product. All of the above steps are geared towards validating an aseptic process and producing food products of high quality. PARTICIPANTS: K.P. Sandeep Josip Simunovic Ken Swartzel Van-Den Truong Gary Cartwright Prabhat Kumar TARGET AUDIENCES: Food industry. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

      Impacts
      The results from the above study was used by Yamco LLC to start commercial production of sweetpotato puree using aseptic processing techniques coupled with microwave heating. The product has proven to be superior in quality, with no compromise in safety. We anticipate that a similar approach will be used for extending the line of products that can be processed using the above mentioned methodologies and tools.

      Publications

      • Simunovic, J., Coronel, P., Truong, V.D., Cartwright, G.D., Swartzel, K.R., Sandeep, K.P. 2008. Development and commercialization of microwave-assisted aseptic processing and packaging of vegetable purees. IFT Paper No. 084-06. 2008 IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.
      • Kumar, P, Coronel, P., Simunovic, J., Sandeep, K.P. 2008. Continuous flow microwave sterilization of high acid and low acid tomato-based products: Dielectric properties and microwave heating characteristics. IFT Paper No. 132-10. 2008 IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.
      • Jasrotia, A.K.S., Simunovic, J., Sandeep, K.P., Palazoglu, T.K., Swartzel, K.R. 2008. Design of conservative simulated particles for validation of a multiphase aseptic process. Journal of Food Science. Vol. 73(5): E193-E201.
      • Coronel, P., Simunovic, J., Sandeep, K.P., Kumar, P. 2008. Dielectric properties of pumpable food materials at 915 MHz. International Journal of Food Properties. Vol. 11(3): 508-518.
      • Brinley, T., Truong, V.D., Coronel, P., Simunovic, J., Sandeep, K.P. 2008. Dielectric properties of sweetpotato puree at 915 MHz as affected by temperature and chemical composition. International Journal of Food Properties. Vol. 11(1): 158-172.
      • Zhu, J., Kuznetsov, A.V., Sandeep, K.P. 2008. Investigation of a particulate flow containing spherical particles subjected to microwave heating. Heat and Mass Transfer. Vol. 44: 481-493.
      • Kumar, P., Coronel, P., Truong, V.D., Simunovic, J., Swartzel, K.R., Sandeep, K.P. , Cartwright, G.D. 2008. Overcoming issues associated with the scale-up of a continuous flow microwave system for aseptic processing of vegetables purees. Food Research International. Vol. 41(5): 454-461.
      • Coronel, P., Simunovic, J., Sandeep, K.P., Kumar, P. 2008. Sterilization solutions for aseptic processing using a continuous flow microwave system. Journal of Food Engineering. Vol. 85(4): 528-536.
      • Kumar, P., Coronel, P. Simunovic, J., Sandeep, K.P. 2008. Thermophysical and dielectric properties of salsa con queso and its vegetable ingredients at sterilization temperatures. International Journal of Food Properties. Vol. 11(1): 112-126.
      • Sandeep, K.P. 2008. Advances in tools and technologies associated with thermal processing of viscous and multiphase foods. 5th International Thermal Processing Conference: New Thermal Technologies. Camden & Chorleywood Food Research Association (CCFRA), Chipping Camden, UK. June 25-26.
      • Kumar, P., Palazoglu, T.K., Simunovic, J., Sandeep, K.P. 2008. Microwave-assisted aseptic processing of multiphase foods: Concurrent microwave heating of particulates and identification of critical components. IFT Paper No. 090-03. 2008 IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.
      • Coronel, P., Simunovic, J., Swartzel, K.R., Truong, V.D., Sandeep, K.P. 2008. Potential for minimization of color degradation of aseptically processed banana purees by continuous flow microwave sterilization. IFT Paper No. 133-07. 2008 IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.
      • Simunovic, J., Palazoglu, T.K., Coronel, P., Kumar, P., Stam, C., Swartzel, K.R., Jasrotia, A.K.S., Cartwright, G.D., Sandeep, K.P. 2008. Monitoring and validation of microwave-assisted aseptic processing of multiphase foods: Comprehensive overview. IFT Paper No. 095-30. 2008 IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.
      • Kumar, P., Palazoglu, T.K., Simunovic, J., Sandeep, K.P. 2008. Microwave-assisted aseptic processing of multiphase foods: Heating comparison of real and simulated particles and confirmation of conservative heating behavior. IFT Paper No. 095-31. 2008 IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.
      • Coronel, P., Simunovic, J., Truong, V.D., Swartzel, K.R., Sandeep, K.P. 2008. Method and system for monitoring and measurement of color degradation of food materials under sterilization level temperatures. IFT Paper No. 095-34. 2008 IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.
      • Simunovic, J., Coronel, P., Swartzel, K.R., Truong, V.D., Sandeep, K.P. 2008. Rapid microwave heating for preservation of fruit pulps and homogenates: Dielectric properties and heating characteristics of berries. IFT Paper No. 133-12. 2008. IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.
      • Steed, L., Truong, V.D., Sandeep, K.P., Kumar, P., Simunovic, J., Swartzel, K.R., Cartwright, G.D. 2008. Nutraceutical content and quality of purple-fleshed sweet potato puree as affected by canning and microwave-assisted aseptic processing. IFT Paper No. 133-19. 2008 IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.
      • Kumar, P., Palazoglu, T.K., Simunovic, J., Sandeep, K.P. 2008. Microwave-assisted aseptic processing of multiphase foods: Concurrent microwave heating of particulates and identification of critical components. IFT Paper No. 095-25. 2008 IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.
      • Kumar, P., Simunovic, J., Cartwright, G.D., Amezquita, A., Stam, C., Sandeep, K.P. 2008. System for insertion, monitoring and recovery of implant-carrying simulated food particles for design, monitoring and validation of microwave-assisted multiphase aseptic processing. IFT Paper No. 095-27. 2008 IFT Annual Meeting, June 28 - Jul. 1, New Orleans, LA.


      Progress 10/01/06 to 09/30/07

      Outputs
      OUTPUTS: The main emphasis of this project during the past year has been to improve the safety and quality of viscous and particulate foods by means of continuous flow microwave processing. Towards this goal, we have processed various viscous (cheese sauces, salsa con queso, sweet potato puree etc) and particulate foods (such as soups) in a 60 kW continuous flow microwave system. It was seen that the products heated relatively uniformly and very rapidly in comparison to conventional techniques. Sensors implanted within particles were used to monitor the time-temperature history at cold spots within the system and ensure that the product received adequate heat treatment. The safety of the process was thus ensured. This technology can be used for processing various viscous and particulate foods aseptically. PARTICIPANTS: Josip Simunovic: Food Science at NC State Prabhat Kumar: Food Science at NC State

      Impacts
      A commercial processing facility for sterilization and aseptic packaging of sweet potato purees in Snow Hill, NC, based on the methods and processed developed by our team is the first such installation in the world, and indicates a potential for significant further developments and additional similar facilities.

      Publications

      • Coronel, P., Simunovic, J., Sandeep, K.P., Kumar, P. 2008. Preparation of sterilization solutions for aseptic processing of foods in continuous flow microwave systems operating at 915 MHz. Journal of Food Engineering. Vol. 85: 528-536.
      • Brinley, T.A., Stam, C.N., Truong, V.D., Coronel, P., Kumar, P., Simunovic, J., Sandeep, K.P., Cartwright, G.D., Swartzel, K.R., Jaykus, L.A. 2007. Feasibility of utilizing bio-indicators for testing microbial inactivation in sweetpotato purees processed with a continuous flow microwave system. Journal of Food Science. Vol. 72(5): E235-E242.
      • Kumar, P., Coronel, P. Simunovic, J., Sandeep, K.P. 2007. Measurement of dielectric properties of pumpable food materials under static and continuous flow conditions. Journal of Food Science. Vol. 72(4): E177-E183.
      • Kumar, P., Coronel, P. Simunovic, J., Sandeep, K.P. 2007. Feasibility of aseptic processing of a low-acid multiphase food product (salsa con queso) using a continuous flow microwave system. Journal of Food Science. Vol. 72(3): E121-E124.


      Progress 10/01/05 to 09/30/06

      Outputs
      The goal of the project was to improve the quality of viscous and particulate foods. In an effort to accomplish this, continuous flow microwave processing was used as the technique to heat the product and render it commercially sterile. Several viscous and hard-to-heat particulate food products were processed in a continuous flow microwave heating system. The system and process parameters had to be optimized for different food products to ensure relatively uniform heating of the product. Measurement of dielectric properties of the foods, mathematical modeling, and test runs in a small-scale microwave unit were precursors to full-scale runs in a two-stage 60 kW microwave system. Sweetpotato puree was one of the products that was aseptically processed using this technique and it was found to be shelf-stable under extended period of storage. We expect to use this technique for several more products, thereby improving the quality of these products. Another facet of improving the quality of these products is rapidly cooling the products after it is subjected to rapid and uniform heating in the microwave unit. Triple tube coolings units, helical heat exchangers, corrugated heat exchangers, and multi-tube heat exchangers are being used to rapidly cool the product after the product has received adequate heat treatment. The combination of rapid heating and rapid cooling will minimize the over-processing of the product, thereby improving product quality. We hope and anticipate that processors of dairy, vegetable, and meat products will take advantage of this technology in the near future, for products of interest to them. The continuous microwave processing technology was also made use of, for blanching peanuts. Initial studies showed that there was a potential for the formation of off-flavors when peanuts are blanched using microwaves. Thus, efforts were geared towards optimizing system and process conditions to eliminate or minimize these off-flavors. Processing and sensory studies were used to arrive at the optimum parameters to achieve this.

      Impacts
      The successful implementation of continuous flow microwave heating can potentially change the way products are processed commercially. It can also pave the way for the development of new food products. The conservative particle designed with a cavity at its center can be used by food processors to validate multiphase aseptic processing. Many such particles can be designed and fabricated depending on the food product under consideration and its thermal diffusivity.

      Publications

      • Schirack, A.V., Drake, M.A., Sanders, T.H., Sandeep, K.P. 2006. Impact of microwave blanching on the flavor of roasted peanuts. Journal of Sensory Studies. Vol. 21(4): 428-440.


      Progress 10/01/04 to 09/30/05

      Outputs
      The overall project goals were to develop new methods for thermal processing of foods and to enhance the quality of processed foods. Some of the individual studies undertaken towards meeting these goals include experimental & modeling studies related to continuous flow microwave processing of liquid and particulate foods, development of tools to validate aseptic processing of multiphase foods, and determination of residence time distribution of multiple particles in four different configurations of holding tubes. The dielectric properties of various food materials were determined under batch and continuous flow situations (both at temperatures as high as 150 deg C). Based on the dielectric properties, their potential to be processed by microwave heating was assessed and appropriate system and process parameters were used to process the foods in the 5 kW microwave unit. Based on the results of this preliminary run, parameters were modified for final runs in the 60 kW microwave unit. Mathematical modeling of continuous flow microwave heating is underway and the results of this can be used to design a continuous flow microwave process. This process involves solving the governing equation for fluid flow, heat transfer, and electromagnetics. The effect of temperature on the physical, rheological, thermal, and dielectric properties of the foods under consideration was also accounted for. The model has been developed for simple geometries and is now being modified to depict the microwave system in our pilot plant facilities. A software was developed to determine the characteristics of a simulated particle (constructed of plastic) that can be used to validate mutiphase aseptic processing. The results of this study were utilized to develop a particle with an implant within its cavity to serve as the critical point within an aseptic processing system. If the center of this particle received adequate heat treatment, then the entire product would be rendered commercially sterile. Experiments were conducted with thermocouples at the center of these simulated particles and several real food particles to determine the time-temperature history within these particles. Results showed that the simulated particles exhibited conservative thermal characteristics and could hence potentially serve as a validation tool for multiphase aseptic processing. The residence time distribution (RTD) of multiple particles in straight, single helical, double helical, and chaotic holding tubes were determined. RTD in the chaotic holding tube was narrower than that in other holding tubes under some of the processing conditions, thereby indicating that the chaotic holding tube could be beneficial in delivering a relatively uniform heat treatment to a particulate food product. The effect of angle of inclination of the vertical section of the chaotic holding tube was also assessed. It was seen that RTD in the single helical holding tube was the narrowest for most of the process parameters studied.

      Impacts
      The successful implementation of continuous flow microwave heating can potentially change the way products are processed commercially. It can also pave the way for the development of new food products. The conservative particle designed with a cavity at its center can be used by food processors to validate multiphase aseptic processing. Many such particles can be designed and fabricated depending on the food product under consideration and its thermal diffusivity.

      Publications

      • Coronel, P., Truong, V.D., Simunovic, J., Sandeep, K.P. 2005. Aseptic processing of sweet potato puree using a continuous flow microwave system. (Accepted for publication in Journal of Food Science)


      Progress 10/01/03 to 09/30/04

      Outputs
      The overall project goals were to develop new methods for thermal processing of foods and to enhance the quality of processed foods. Some of the individual studies undertaken towards meeting these goals include experimental & modeling studies related to continuous flow microwave processing of liquid and particulate foods, determination of heat transfer coefficients in a triple tube heat exchanger, development of tools to validate aseptic processing of multiphase foods, and determination of residence time distribution of multiple particles in four different configurations of holding tubes. The dielectric properties of various food materials were determined and their potential to be processed by microwave heating was assessed. Mathematical modeling of continuous flow microwave heating is underway and the results of this can be used to design a continuous flow microwave process. This process involves solving the governing equation for fluid flow, heat transfer, and electromagnetics. The effect of temperature on the physical, rheological, thermal, and dielectric properties of the foods under consideration was also accounted for. A new method to accurately determine heat transfer coefficients in a triple tube heat exchanger was developed theoretically. This technique was then used to experimentally determine the heat transfer coefficients in a triple tube heat exchanger. This technique will enable processors to accurately determine the exit temperatures of different product streams in a triple tube heat exchanger and thereby design an efficient heating process. A software was developed to determine the characteristics of a simulated particle (constructed of plastic) that can be used to validate mutiphase aseptic processing. The results of this study were utilized to develop a particle with an implant within its cavity to serve as the critical point within an aseptic processing system. If the center of this particle received adequate heat treatment, then the entire product would be rendered commercially sterile. Experiments were conducted with thermocouples at the center of these simulated particles and also real food particles to determine the time-temperature history within these particles. Results showed that the simulated particles exhibited conservative thermal characteristics and could hence potentially serve as a validation tool for multiphase aseptic processing. The residence time distribution (RTD) of multiple particles in straight, single helical, double helical, and chaotic holding tubes were determined. RTD in the chaotic holding tube was narrower than that in other holding tubes under some of the processing conditions, thereby indicating that the chaotic holding tube could be beneficial in delivering a relatively uniform heat treatment to a particulate food product. The effect of angle of inclination of the vertical section of the chaotic holding tube was assessed, and recommendations were made regarding the optimum angle of the coil. Nevertheless, it should be noted that RTD in the single helical holding tube was the narrowest for most of the process parameters studied.

      Impacts
      The successful implementation of continuous flow microwave heating can potentially change the way products are processed commercially. It can also pave the way for the development of new food products. The conservative particle designed with a cavity at its center can be used by food processors to validate multiphase aseptic processing. Many such particles can be designed and fabricated depending on the food product under consideration and its thermal diffusivity.

      Publications

      • Zhong, Q., Sandeep, K.P., Swartzel, K.R. 2004. Continuous flow radio frequency heating of particulate foods. Journal of Innovative Food Science and Emerging Technologies. Vol. 5(4): 475-483.
      • Palazoglu, T.K., Sandeep, K.P. 2004. Effect of tube curvature ratio on the residence time distribution of multiple particles in helical tubes. Lebensmittel-Wissenschaft und-Technologie. Vol. 37: 387-393.


      Progress 10/01/02 to 09/30/03

      Outputs
      This project was initiated less than 2 months ago. The goals of the project are to improve the quality of viscous and particulate foods by designing efficient heat excahngers and holding tubes and also by the use of microwave and radio frequency energy in processing these foods.

      Impacts
      None

      Publications

      • No publications reported this period