Source: OHIO STATE UNIVERSITY submitted to NRP
PRESSURE-ASSISTED THERMAL PROCESSING: KEY ENGINEERING PROPERTIES AND PROCESS IMPROVEMENT
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
NRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
0201507
Grant No.
2005-35503-15365
Cumulative Award Amt.
(N/A)
Proposal No.
2004-02377
Multistate No.
(N/A)
Project Start Date
Jan 1, 2005
Project End Date
Dec 31, 2008
Grant Year
2005
Program Code
[71.1]- (N/A)
Recipient Organization
OHIO STATE UNIVERSITY
1680 MADISON AVENUE
WOOSTER,OH 44691
Performing Department
FOOD SCIENCE AND TECHNOLOGY
Non Technical Summary
Pressure-Assisted Thermal Processing (PATP) of low-acid foods has generated much industry interest because the combination of pressure and heat has been found effective in producing uniform sterilization conditions within foods, and allowing for rapid cooling to the preheated product temperature. Since temperature is a critical factor in this technology, temperature must be considered in development of a process filing; thus factors such as thermal properties that were hitherto considered insignificant in the high pressure context must be characterized in detail, just as in a retort thermal process. We propose to measure properties (thermal conductivity, specific heat, density, and electrical conductivity as function of pressure and temperature) of foods in-situ under high pressure processing, using a specialized, instrumented four-chamber pressure vessel. A further hurdle to development of PATP is the slow, cumbersome method of preheating products before loading into a pressure vessel. We propose to address this issue by investigating three methods for preheating that may reduce thermal exposure - conventional heating, microwave preheat and an in-situ ohmic preheat. The study will provide an improved body of knowledge regarding thermal distributions during and contribute to the development of database on properties of food materials under pressure.
Animal Health Component
40%
Research Effort Categories
Basic
30%
Applied
40%
Developmental
30%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
4045010202020%
4047299202020%
5015010202025%
5017299202025%
7127299202010%
Knowledge Area
501 - New and Improved Food Processing Technologies; 712 - Protect Food from Contamination by Pathogenic Microorganisms, Parasites, and Naturally Occurring Toxins; 404 - Instrumentation and Control Systems;

Subject Of Investigation
7299 - Research equipment and methods, general/other; 5010 - Food;

Field Of Science
2020 - Engineering;
Goals / Objectives
a) To determine the properties of critical interest for pressure assisted thermal processing applications(PATP); i.e. thermal conductivity, specific heat, density, as functions of pressure (P), temperature (T) and composition. b) To determine the properties of critical interest for PATP applications; i.e. thermal conductivity, specific heat, density, as functions of P, T and composition. c) Compare three different preheating methods; water bath immersion, microwave heating and in-situ ohmic heating with respect to their efficacy and product quality for PATP products.
Project Methods
We propose to measure properties (thermal conductivity, specific heat, density, and electrical conductivity as function of pressure and temperature) of foods in-situ under high pressure processing, using a specialized, instrumented four-chamber pressure vessel. We propose to compare three methods for preheating that may reduce thermal exposure - conventional heating, microwave preheat and an in-situ ohmic preheat.

Progress 01/01/05 to 12/31/08

Outputs
OUTPUTS: By destroying pathogenic and spoilage organisms while keeping food chemistry basically intact, high-pressure technology enables pasteurization of foods with minimal effects on taste, texture, appearance, or nutritional value. Pressure assisted thermal processing is a sterilization process, where pressure in combination with modest can be used to inactivate bacterial spores. The purpose of this research was to develop in-situ methods to measure thermal conductivity, density, compressibility, and electrical conductivity of selected foods as a function of process pressure-temperature. To date, research results were disseminated in the form of 5 peer-reviewed journal articles and one book chapter. 3 additional manuscripts are at various stages of preparation. Two food engineering students completed their doctoral degree at Ohio State University and conducted research on in-situ food property measurement under pressure. Investigators and project personnel further disseminated research through oral or poster presentations during Annual Meeting of Institute of Food Technologists, Nonthermal Processing Workshop and short course , International Conference on High Pressure Biosciences, and European Food Conference. PARTICIPANTS: Associate Professor VM Balasubramaniam, Professor SK Sastry, Mr. Stephen Min and Mr. Raghupathy Ramaswamy, The Ohio State University TARGET AUDIENCES: Food scientists and engineers working in academia, food industry and academia. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
The purpose of this research was to develop in-situ methods to measure thermal conductivity, density, compressibility, and electrical conductivity of selected foods as a function of process pressure-temperature. Experiments were conducted using pressure equipment that had provision for in-situ temperature, voltage, DC current and impedance measurements. Thermal and electrical conductivity of food materials under pressure were estimated using a line heat source probe and electrical conductivity sensor, respectively. A variable volume piezometer estimated the compressibility, density, and reaction volume of food materials. The sensors were calibrated using suitable calibration materials, and the experimental data was compared against published literature to establish sensor specific calibration factors. Thermal conductivity of food materials increased with increase in pressure, moisture and temperature, but decreased with increasing fat content. Density of foods tested increased as a function of pressure at a rate that decreased with increasing pressure. Compressibility of tested foods decreased as a function of concentration. Temperature and pressure had a significant effect on electrical conductivity for all samples; conductivity increased as a function of pressure, peaked between 200 and 500 MPa and decreased above 500 MPa. Phosphoric acid and citric acid showed negative reaction volumes that decreased as a function of pressure. Sulfanilic acid and MES had relatively pressure stable, slightly positive reaction volumes. Results of the study will facilitate the evaluation of the process uniformity during high-pressure pasteurization and sterilization and further development of mathematical models for process optimization.

Publications

  • Min,S. Sastry,S. K., Balasubramaniam,V.M. 2006. In-situ electrical conductivity measurement of foods under high pressure. Abstract No. 039J-04. Annual Meeting of Institute of Food Technologists, Annual Meeting of Institute of Food Technologists, Orlando, FL., June 24-28.
  • Ramaswamy,R. Balasubramaniam,V.M., Sastry,S. K., 2006. Thermal conductivity of selected liquid foods under high pressure. Annual Meeting of Institute of Food Technologists, Annual Meeting of Institute of Food Technologists, Orlando,FL. June 24-28, 2006.
  • Ramaswamy,R. Balasubramaniam,V.M., 2006. Compression heating behavior of fatty acids and solvents with varying polarity. Annual Meeting of Institute of Food Technologists, Annual Meeting of Institute of Food Technologists, Orlando,FL. June 24-28, 2006.
  • Balasubramaniam,V.M. 2007. High pressure processing-basics. Nonthermal processing short course, 2007 Annual Meeting of Institute of Food Technologists, Chicago, IL. July 27-28.
  • Min, S., Ramaswamy, R., V.M.Balasubramaniam, and S.K. Sastry. 2008. Pressure-Assisted Thermal Processing: Key Engineering Properties. Fifth International Conference on High Pressure Biosciences, San Diego, CA.
  • Min,S. Ramaswamy,R. Balasubramaniam,V.M., Sastry,S. K., 2008. Impact of Nonthermal technologies on physical and chemical properties of foods. Invited presentation. Workshop on innovative application of Nonthermal processing technologies in foods: Technology, safety, health, and consumer acceptability. Co-sponsored by Spanish National Research Council, IFT Nonthermal Processing Division, and European Federation of Food Technologists, Madrid, Spain. November 19-22
  • Ramaswamy, Raghupathy. 2007. Thermal behavior of food materials during high pressure processing. PhD Dissertation. The Ohio State University.
  • Min, S. 2008. Properties of Food and Buffer Solutions During High Pressure Processing: In-Situ Measurement of Density, Compressibility, Electrical Conductivity, and Reaction Volume. PhD Dissertation. The Ohio State University.
  • Ramaswamy,R., Balasubramaniam,V.M., Sastry,S. K., 2007. Thermal conductivity of selected liquid foods at elevated pressures up to 700 MPa. J. Food Engineering. 83 (3), 444-451.
  • Min S., Sastry S.K., Balasubramaniam VM. 2007. In-situ electrical conductivity measurement of select liquid foods under hydrostatic pressure to 800 MPa. J. Food. Eng 82(4):489-497.
  • Ramaswamy,R., Balasubramaniam,V.M. 2007. Effect of polarity and molecular structure of selected liquids on their heat of compression during high pressure processing. High Pressure Research. 27(2), 299-307.
  • Min S, Sastry S.K, Balasubramaniam V.M. 2008. Variable volume piezometer for measurement of volumetric properties of materials under high pressure. High Pressure Research. In press.
  • Rastogi, N.K., Nguyen,L. T., Balasubramaniam,V. 2008. Effect of pretreatments on carrot texture after thermal and pressure-assisted thermal processing. Journal of Food Engineering. 88(4):541-547
  • Balasubramaniam,V.M. 2007. High pressure processing of shelf-stable foods. 61st Annual Spring Meeting & Exhibition Research & Development Associates for Military Food & Packaging Systems, Inc April 17-19 Tucson, AZ
  • Balasubramaniam,V. Sastry,S. K., 2007. Pressure-Assisted Thermal Processing: Key Engineering Properties and Process Improvement. NC1023 USDA Regional committee meeting, University Park, PA. October 1-2, 2007.
  • Ramaswamy,R. Balasubramaniam,V.M., Sastry,S. K., 2007. Thermal conductivity of selected solid foods during high pressure processing. Abstract no. 096-38. 2007 Annual Meeting of Institute of Food Technologists, Chicago, IL. July 28-August 1.
  • Min,S. Sastry,S. K., Balasubramaniam,V. 2007. Pressure-volume relationships of select foods at 25C to 700 MPa. Abstract no. 008-13. 2007 Annual Meeting of Institute of Food Technologists, Chicago, IL. July 28-August 1.
  • Balasubramaniam,V.M. 2008. High pressure processing for food pasteurization and sterilization. Current status and future research needs. Symposia on emerging food processing technologies-2, 6th International Food Convention, Association of Food Scientists and Technologists, Mysore, India. December 15-19
  • Min, S., Sastry, S.K., and Balasubramaniam, V.M. 2008. Compressibility and density of select liquid and solid foods under pressures up to 700 MPa. Paper No. O-15.4, presented at the First European Food Congress, Ljubljana, Slovenia, Nov. 4-8, 2008.


Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: In-situ properties of food materials under pressure are useful for modeling heat transfer and temperature distribution during high-pressure sterilization and pasteurization. Thermal conductivity (k) of selected foods (carrot, guacamole, cheddar cheese, chicken breast and fat) as a function of pressure (0.1-700 MPa) and temperature (25-75C) was measured. Pressure-volume relationships at 25C were measured for sucrose solutions, apple juice, honey, soybean oil, clarified butter, chicken fat, soy protein isolate solutions, guacamole, carrot, cheddar cheese, chicken breast. Reaction volumes between selected buffering agents (citric acid, phosphoric acid, 2-(N-morpholino) ethanesulfonic acid (MES) and sulfanilic acid) and NaOH solutions were measured to 400 MPa at 25C. A polycarbonate sample holder with piston arrangement allowed sensor placement and pressure transmission. Use of custom-made pressure equipment enabled in-situ temperature, voltage, and current and impedance measurements. The experimentally determined values of calibration material were compared against published literature to establish probe specific calibration factors. PARTICIPANTS: Associate Professor VM Balasubramaniam, PI, Ohio State University Professor SK Sastry, Co-PI, Ohio State University Raghupathy Ramaswamy, Graduate Student Stephen Min, Graduate Student TARGET AUDIENCES: Results of the study will be helpful in the process characterization of pressure treated low-acid shelf stable foods. The study will provide improved understanding of role thermal process uniformity during high pressure processing. Improved knowledge on thermal effects under pressure will help food processors and regulators in the safety assessment of pressure treated products.

Impacts
While k under pressure increased with increase in moisture and temperature, it decreased with increasing fat content. Among the products tested, carrot had the highest k at 700 MPa and 75C (0.90 W/mC), while chicken fat had the lowest k (0.43 W/mC) under similar conditions. Density of all samples increased as a function of pressure. Compressibility of sucrose and protein solutions decreased as a function of increasing concentration. At 700 MPa, all samples, except ethanol, reduced in volume by 13-16%. pH change from 0.1 to 400 MPa was -0.48 for citric acid, -1.09 for phosphoric acid, 0.28 for MES, and -0.01 for sulfanilic acid.

Publications

  • Ramaswamy, R., Balasubramaniam, VM and Sastry, S. K. 2007. Thermal conductivity of selected liquid foods at elevated pressures up to 700 MPa. J. Food Engineering. 83 (3) 444-451
  • Ramaswamy, R., and Balasubramaniam, VM. 2007. Effect of polarity and molecular structure of selected liquids on their heat of compression during high pressure processing. High Pressure Research An International Journal. 27(2), 299-307
  • Min, S., Sastry, S. K., and Balasubramaniam, VM. 2007. In situ electrical conductivity measurement of select liquid foods under hydrostatic pressure to 800 MPa. Journal of Food Engineering 82(4), 489-497.
  • Balasubramaniam, VM. 2007. High pressure processing-basics. Nonthermal processing short course, 2007 Annual Meeting of Institute of Food Technologists, Chicago, IL. July 27-28.
  • Min, S., Sastry, S. K., and Balasubramaniam, VM. 2007. Pressure-volume relationships of select foods at 25C to 700 MPa. Abstract no. 008-13. 2007 Annual Meeting of Institute of Food Technologists, Chicago, IL. July 28-August 1.
  • Nguygen,, L., Rastogi, N., and Balasubramaniam, VM. 2007. Evaluation of instrumental quality of pressure-assisted thermally processed carrots. Abstract no. 189-05. 2007 Annual Meeting of Institute of Food Technologists, Chicago, IL. July 28-August 1.


Progress 01/01/06 to 01/01/07

Outputs
Data on properties of food materials as a function of pressure and temperature is useful for modeling heat transfer and temperature distribution during high-pressure pasteurization and sterilization. Thermal conductivity (k) and density of selected food materials were estimated under combined pressure-temperature conditions using a line heat source probe (for thermal conductivity measurements) and variable volume piezometer (for density measurements). A polycarbonate sample holder with piston arrangement allowed sensor placement and pressure transmission to the sample. Use of custom-made pressure equipment enabled in-situ temperature, voltage, current and impedance measurements. The measured k of water was compared with NIST values to establish probe specific calibration factors. The k values at atmospheric pressure for all tested materials compared closely with published data. k of carrots increased by 35% at both 25 and 50˚C, and the values were close to that of water (0.583-0.788 W/m˚C at 25˚C; 0.625-0.843 W/m˚C at 50˚C). Similarly, k values of cheddar cheese and pork tenderloin also increased during combined pressure-temperature treatment. Piezometer calibration with NIST data for water yielded a second order polynomial that expressed sample volume as a function of impedance. At 300 MPa, the sample with highest compressibility was olive oil, followed by, soybean oil, sunflower oil, carrot, 10% sucrose solution, raw chicken breast, applesauce, tomato puree, cheese, cooked chicken breast, and corn syrup. At 700 MPa, all samples except ethanol reduced in volume by 14-16%. Density of all samples at 25˚C increased as a function of pressure and was characterized by a second order polynomial.

Impacts
Results of the study will be helpful in process characterization of pressure treated foods including improved understanding of heat transfer under pressure. The knowledge on thermal effects under pressure will help food processors and regulators in evaluating the process uniformity during high pressure processing of foods.

Publications

  • Raghupathy Ramaswamy, V.M. Balasubramaniam and S.K. Sastry. 2007. Thermal conductivity of selected liquid foods at elevated pressures up to 700 MPa. J Food Eng. (Submitted)
  • Min, S., S.K. Sastry and V.M. Balasubramaniam. 2007. In-Situ Electrical Conductivity Measurement of Select Liquid Foods under Hydrostatic Pressure to 800 MPa". Journal of Food Engineering (submitted)
  • Min, S., S. K. Sastry, and V. M. Balasubramaniam. 2006. In-situ electrical conductivity measurement of foods under high pressure. Abstract no. 039J-04. Annual Meeting of Institute of Food Technologists, Orlando, FL. June 24-28.
  • Ramaswamy, R., V. M. Balasubramaniam, and S. K. Sastry. 2006. Thermal conductivity of selected liquid foods under high pressure. Abstract no. 039J-02. Annual Meeting of Institute of Food Technologists, Orlando, FL. June 24-28.


Progress 01/01/05 to 12/31/05

Outputs
Food property data under high pressure are scarce, due to lack of suitably instrumented and controlled pressure devices. Study of properties of foods under pressure will facilitate evaluation of process non-uniformities during high pressure processing (HPP). Experiments were conducted to estimate thermal and electrical conductivity of selected liquid foods in-situ under pressure, using a specialized, instrumented four-chamber pressure vessel. For thermal conductivity (TC), experiments were conducted using a line heat source probe approach. Construction of electrical conductivity (EC) sensor involved a pair of parallel platinized titanium electrodes and two polycarbonate sample holders. A polycarbonate tube sample holder with a moving piston arrangement facilitated sensor placement and transmission of pressure to the sample. Current, voltage, temperature, and pressure were recorded using a data logger and TC & EC values were calculated. TC probe was calibrated under pressure (up to 700 MPa) at 25C using water as the calibration fluid. The measured values were compared with NIST steam properties database to obtain probe specific calibration constants. After testing KCl solutions at atmospheric pressure from 20 to 50C, EC sensor was tested with 0.01m NaCl to 800MPa and 61C. EC results were within 4% of previously reported for NaCl solutions under pressure. TC of the tested liquid food materials including canola oil, honey and high fructose corn syrup (HFCS) increased linearly with increase in pressure. When pressure increased from 0.1-700 MPa, thermal conductivity of water increased from 0.61-0.82 W/mC, while for canola oil the values changed from 0.20-0.29 W/mC. Carbohydrates showed a similar trend, but had intermediate thermal conductivity values. For 0.1m NaCl at 25C, EC increased as a function of pressure from 1.13 S/m at 0.1MPa to 1.35 S/m at 400 MPa and 1.18 S/m at 800 MPa. Apple juice at 25C had a EC value of 0.248 S/m at 0.1MPa, 0.28 S/m at 400 MPa and 0.26 S/m at 800 MPa. Similar trends were also seen for orange and tomato juices. Soybean and olive oils had EC values too low for measurement.

Impacts
The study will provide an improved body of knowledge regarding thermal distributions during HPP and contribute to the development of database on properties of food materials under pressure. Further, knowledge of EC under pressure may pave the way for studies on microstructural and physico-chemical changes under pressure.

Publications

  • Ramaswamy, R., V.M. Balasubramaniam, and S.K. Sastry. 2005. Properties of food materials during high pressure processing. In: Encyclopedia of Agricultural, Food, and Biological Engineering. Heldman, D. (Ed.) Marcel Dekker, Inc., New York. .