Duration: 10/01/2000 to 09/30/2005

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

Today, the U.S. and world food industry is undergoing major changes driven by several economic, competitive and environmental necessities. The internal demand for ever-increasing growth, and consumer demand for greater value have resulted in several new products and processes. The product arena has witnessed the rapid growth of nutraceuticals, blurring the lines between food and medicine. The need to improve quality and retain nutritional value and bioactivity has resulted in study of a number of new thermal and nonthermal preservation technologies. Technologies such as high-pressure processing, pulsed electric fields (PEF), pulsed light processing, irradiation, ozonation, hurdle technology and ohmic heating, thermosonication, and manothermosonication are being investigated with the aim of producing high-value end products. While these developments are exciting, their advent comes in an era clouded by disease outbreaks due to newly discovered resistant pathogenic bacteria.

These drivers are changing the way foods are processed in ways that were not originally anticipated when this project began many years ago. However, the objectives of NC-136 take on special relevance in light of these new products and technologies. In the past, it was sufficient for a process authority or specialist to merely understand microbial death kinetics under thermal treatments. Specialists will have to confront processes and their combinations that can be of bewildering complexity, and indeed, a whole new body of knowledge is required. The Food and Drug Administration has acknowledged the crying need for such information by awarding recently a contract to the Institute of Food Technologists to collect and summarize information related to microbial death kinetics for alternative process technologies.

The NC-136 Committee, which has historically focused on thermal processes through multistation collaboration of engineers, food scientists, biochemists, microbiologists and other scientists, is in a prime position to adapt and expand its focus by inclusion of nonthermal technologies. In many ways, our original objectives are as relevant as ever; for example the need for physical property and kinetics information gain additional dimensions under alternative processes. The need for process models is as great as ever. Thus, we propose an expanded scope for the project.

The record of productivity for NC-136 during the current 5-year cycle (Table 1) demonstrates the Committee's ability to achieve its objectives. The level of funding through the USDA National Research Initiative (NRI) and other competitive grants (see also Appendix A) shows a considerable leveraging effect, and is indicative of the relevance and quality of the science. Many of these grants are from industry; NC-136 plays an important role in keeping US processors at the forefront of a global industry. Agricultural producers and consumers benefit in turn from a competitive, innovative domestic food processing industry. Rapid, substantive progress will be best achieved through the continued sharing of resources and unique capabilities that can be brought to bear through NC-136 (Appendix B).

Table 1. Productivity of NC-136 during 1995-99. Listings of specific accomplishments can be found under ^a Attachment C or^b Appendix A.

	Number (multistation)
Journal articles, peer-revieweda	520 (17)
Books and book chaptersa	102 (7)
Presentations	320 (8)
Theses and dissertationsa	92
Patentsa	15
USDA NRI grantsb	$1.75 million
Other competitive grants b	Over $16 million

Related, Current and Previous Work

A search of the CRJS (U.S.) and ICAR (Canada) databases identified over 40 current or recent projects that relate to the objectives ofNC-136 (Appendix C). One or more members of NC-136 serve as principal investigators on the majority of the U.S. projects. The Critical Review (Attachment C) identifies key research fronts under the respective objectives and the progress achieved on these fronts in the past five years. This section also describes the impacts of this research and identifies the critical needs that should be addressed in the next five years to respond to the opportunities and challenges presented in the justification statement. The needs identified in Attachment C will be addressed by NC-136.

These projects are diverse with respect to processes and commodities. However, the objectives will be accomplished in similar fashion through the coordinated application of transport phenomena, kinetics, biochemistry, microbiology and related sciences. The projects are diverse, because of the complex nature of foods and processing technologies. The complexity requires characterization of relevant physical-chemical properties of the food under investigation. Processes and process models must accordingly be adapted. Methods of measuring food physical properties are continually evolving and must be standardized. Process technology and consumer preferences likewise continually evolve and present new opportunities to produce products with improved nutritional and sensory characteristics at a price that consumers will pay. NC-136 provides member investigators with a unique "food engineering" forum in which they meet annually to share reports of their progress, exchange knowledge and experience, discuss areas of mutual interest, identify complementary capabilities, and ensure that cooperation continues. NC-136 does not duplicate any other Multistate Research Project and is currently the only such project that integrates food science and engineering.

Objectives

1. To develop and verify methods for measurement and prediction of engineering and biochemical properties of foods as needed in process design and analysis, and product development.
   
2. To measure and model process dependent kinetic parameters which affect food quality and safety attributes.
   
3. To identify and describe transport mechanisms occurring in food processes.
   
4. To develop mathematical models for analysis, design and improvement of food processes.
   
5. 
   

Methods

Although our understanding and control of chemical and microbial changes in foods have advanced substantially over the years, ensuring a wholesome and safe food supply is as important now as ever. The advances made by engineers and scientists in this Committee (NC- 136) over the past 20 years in the area of thermal processing have resulted in numerous improvements in processing technologies and the ultimate safety of foods. However, new processing technologies have widened the area of importance to include technologies based on alternative methods for microbial destruction (i.e., pulsed electric field, high pressure). Implementation of these technologies would greatly benefit both the consumer and the food processor; however regulators themselves are still in the learning stages regarding these alternative processing technologies. This Committee will provide significant input to the regulatory agencies regarding approval of these technologies.

OBJECTIVE A To develop and verify methods for measurement and prediction of engineering and biochemical properties of foods as needed in process design, analysis and product development.

PROCEDURES: Engineering and biochemical properties of foods needed for process design and analysis include rheological, thermal (both thermodynamic and transport), mass transfer and electrical properties. Development and standardization of methodologies for measurement of these properties is needed to ensure consistency of parameters across stations. Methods to predict these properties in different foods with different microstructure and composition are also needed. Opportunities for collaboration here will be vigorously pursued. One important task of the NC 136 Committee in the next five year cycle will be to develop and publish standard methods. A proposal has been (12/15/99) submitted to USDA NRI on behalf of NC 136 (by CA and NJ) to pursue these standards.

1. Rheological properties.

a. In the past, an ad hoc committee of this group (NC-136) has developed techniques for measuring yield stress in foods. Based on the work of this ad hoc committee, the vane method of measuring yield stress will be written up as a standard method for future reference. The Model Fluids ad hoc committee (IA, IN, MI, MN, NC, ND, NY-G and TX) will continue to address current issues, such as standard methods for characterization of food gels.

b. The effects of food composition and microstructural elements on rheological properties of foods remains an important area of study at several stations (IA, IN, MI, MO, NC, NY-G, SD, WA, WI). Techniques such as scanning and transmission electron microscopy, light microscopy, confocal microscopy, as well as spectroscopy techniques, will be used to characterize microstructural elements (air cells, crystals, gels, emulsion droplets, etc.) in foods. The role of these microstructural elements on rheological properties, and how they change during processing, can then be ascertained. For example, techniques for standardizing particle size measurement in foods will be developed (IL, IN, NC, ND, OH, TX, WA, WI).

c. An understanding of the relationships between rheological properties and sensory attributes of foods is important for quality control purposes. Development of new formulations and improvement of existing products can be enhanced through knowledge of these relationships. For example, spreadability has been expressed in terms of stresses and strains on the material by the MI station. This approach will be taken up by other stations (CA, IL, IA, MO, OR, SD, WI) to develop similar relationships for other important food properties.

2. Thermal and thermodynamic properties.

a. Accurate measures of thermal properties are needed for prediction of processing technologies where heating and cooling are involved. The use of differential scanning calorimetry (DSC) to measure physical and thermal properties of foods has increased recently due to advances in DSC instrumentation. The DSC ad hoc committee remains active, with a recent emphasis being developed on measuring glass transition temperatures in foods. Also, the use of modulated DSC techniques for measuring thermal properties will be explored. Participating stations include CA, IA, IN, MO, NC, ND, NE, NJ, OH, WA and WI.

b. The Thermal Conductivity ad hoc committee has been an extremely active group over the past few years. The results of this group on the thermal conductivity probe will be reviewed and a standard method published.

c. The effects of food composition and microstructural elements on thermal properties will be investigated at the IN, OH and WI stations.

3. Mass transfer properties.

a. Diffusivities of various compounds through food structures, edible films and packaging materials during manufacture and storage is important to product quality and stability. For example, diffusivities of flavor compounds during process and storage are critical, as is water migration either into or out of the food. Work in this area will be conducted by the IA, IN, NC, NE, NY-G and OH stations.

b. Flow driven by pressure gradient is important in microwave and other rapid heating processes such as frying. In microwave heating, for example, rapid internal evaporation generates pressures inside the food. Foods can get soggy on the surface due to too much moisture coming to the surface from inside due to pressure driven flow than can be removed from the surface by convection. Foods can also explode if sufficient pressure builds up inside. Permeability data describes such pressure driven flow and will be investigated by various stations (IA, IN, NE, NY-G, OH and WA).

c. Differences in food composition and microstructural elements can have substantial impact on mass transfer properties of foods. For example, water migration into foods depends on the structure of the food constituents. The effects of these parameters will be studied by the IN, OH and WI stations.

4. Electrical properties.

a. The dielectric constant and dielectric loss factor are two important properties influencing microwave heating of foods. Changes in the dielectric constant during processing (i.e., protein denaturation, starch gelatinization, etc.) are of particular interest. For example, additional work is needed to quantify dielectric properties of foods at low temperatures for better prediction of thawing processes, and at high temperatures to model sterilization processes. An Electrical Properties ad hoc committee (IA, IN, NCFST, OH, PA, NY-I, WA) has recently been formed to coordinate efforts in this area.

b. Electrical conductivity and dielectric strength of foods are also important parameters controlling ohmic heating and pulsed electric field technologies. The Electrical Properties ad hoc committee will also coordinate efforts in this area.

c. An understanding of the effects of food composition and microstructural elements on electrical properties of foods is important for control of ohmic heating and pulsed electric field technologies. These relationships will be investigated by the IA, IN, NCFST, OH, PA, NY-I and WA stations.

5. Optical properties.

a. The color of a food product is an important indicator of food quality in many cases and needs to be measured quantitatively for automation in quality evaluation and process optimization. Measurement of the complex color of foods will be performed by the FL, IA, IN and NC stations.

OBJECTIVE B

To measure and model process-dependent kinetic parameters which affect food quality and safety attributes.

PROCEDURES: Quantification of the kinetics of chemical, biochemical, physical and microbial changes as foods are manufactured and progress through their storage and distribution systems is necessary for controlling product quality and food safety.

1. Physical processes.

a. Kinetics of crystallization in food systems continues to be an important area of study, primarily at the MI, ND and WI stations. The kinetics of crystallization lead to formation of structures and alteration of rheological properties in many foods. T he relationship between glass transition and crystallization will be studied at the OH and WI stations. Kinetics of sugar crystallization will be studied at ND and WI stations.

b. Kinetic properties affecting gelatinization and retrogradation are important to improving processes related to starchy foods. Kinetics of changes in starchy foods will be studied at IA, MO, NE, OH, NJ and WA stations.

2. Chemical reactions.

a. Kinetics of flavor changes will be studied at the CA, IA, and NY-G stations. The effects of processing parameters on reactions of nutraceutical components in foods will be studied at NY-G.

b. An understanding of the kinetics of changes during extrusion is important to control of product quality of extruded products. These changes will be studied by the IA, MI, MO and NE stations. For example, the destruction of Fusarium mycotoxins during extrusion processing of corn will be studied.

3. Microbial kinetics.

a. Destruction of microorganisms is the primary concern of many food processes. Microbial destruction kinetics in thermal processes has been the main focus of this group in the past and will continue to receive attention as needed in the future. Aseptic processes and other processes with HTST/UHT heat treatments will be studied at CA, FL, OH, NC and NCSFT. The effect of moisture during heat on microbial destruction kinetics will be studied at the MI station. Microbial destruction in nonthermal processes (pulsed electric fields, high pressure, etc.) is a relatively new area of study and constitutes a new direction for this committee. The kinetics of these processes will be studied at the NCSFT, OH, OR and WA stations.

4. Enzyme kinetics.

a. Kinetics of enzyme destruction during processing of foods is important to further processing steps and subsequent storage. The kinetics of enzyme destruction in oilseeds preparatory to oil extraction will be studied at IA and ND.

OBJECTIVE C To identify and describe transport mechanisms occurring in food processes.

PROCEDURES: Heat, mass and momentum transport rates are influenced by the physical and thermal properties, as determined in Objective A. In turn, these transport rates influence the kinetics of reactions, as determined in Objective B. Thus, determining transport rates and mechanisms are dependent on the knowledge gained in Objectives A and B, particularly in the context of controlling product quality and food safety during processing and storage of foods.

1. Heat transfer.

a. Heat transfer coefficients during aseptic processing of foods that contain particulates remains an important area of study. Work continues in this area at the FDA, IN, NY-I, NC and OH stations.

b. Heat transfer during deep fat frying will be studied at the CA, NC, OH and TX stations.

c. During extrusion processing, transport processes are important to controlling product quality. The rates of heat, mass and momentum transfer during extrusion, coupled with the kinetics of physical and chemical reactions, lead to the desired product characteristics. Transport processes in extrusion will be studied at the MN, OH, MO, NE, ND, NJ, SD and TX stations. Similar problems are encountered during microwave and infrared heating of foods, which will be studied at the NY-I, NC and PA stations. Furthermore, similar problems occur with in-container heat sterilization of thermally processed foods in which heat transfer rates change during processing (broken-heating curves). Work in this area will be undertaken at the FL station in collaboration with NY-G.

2. Mass transfer.

a. Modified atmosphere packaging is an important technology for preserving foods. Control of modified atmosphere packaging requires an understanding of mass transport processes into and out of packaging materials. Studies on mass transfer rates for better control of modified atmosphere packaging will be conducted at the FL and PA stations.

b. Diffusion rates of mobile components of foods (water, oils, flavor compounds, salts, etc.) through food structures are important to product quality. For example, moisture migration into dried foods can significantly impact product quality and limit shelf life. Mass transfer rates will be experimentally measured at the CA, IA, NC and WI stations. The baking process will be studied jointly by the IN and NY-I stations by combining detailed experimental measurements of moisture transport with modeling of multiphase porous media. The effect of crust formation on the redistribution and loss of moisture will be studied. Results will be used to optimize baking of tortilla chips.

c. Mass transfer rates through packaging materials will be studied at the CA, FL, IA and NC stations.

d. Interfacial phenomena play a key role in many areas of food processing. Development of critical structures (i.e., air cells, fat globules, etc.) is related to the mobility of molecules (proteins, gums, etc.) at and to these interfaces. Molecular interactions at oil-water and air-water interfaces will be studied at the IA, MI, NC and WI stations. The MI and OR stations will collaborate on a project investigating competitive adsorption of proteins with surfactants at oil-water interfaces and the effects of these interactions on uptake and/or delivery of nutrients and vitamins.

3. Momentum transfer.

Fluid flow profiles during aseptic processing, particularly of foods containing particulates, remain an important area of study. Although significant progress has been made over the past few years, our understanding of the complex interactions that lead to velocity profiles in complex processing equipment is still limited. Work on this topic continues at the PDA, NC, NCFST and OH stations.

OBJECTIVE D To develop mathematical models for analysis, design and improvement of food processes.

PROCEDURES: Mathematical models, based on results of the previous objectives, can be used to predict changes in quality attributes based on process variables. These models are based on a fundamental understanding of the mechanisms that underlie a process and the influence of process, product or equipment variables on the quality attributes of the food product. Models also provide insight on conditions that are needed to ensure food safety, particularly under conditions where experimental measurements may be unreliable. Once a model has been proven accurate, it can be used to simulate process conditions and reduce the need for pilot and plant- scale trials. In addition, mathematical models are an absolute necessity for sophisticated process control in the food industry. Strategies such as feed forward, adaptive, and artificial intelligence- based control are only possible with the availability of advanced mathematical models for food processes.

With the increased capabilities of computer technology and increased understanding of the physics of food processes, modeling is playing increasing roles in both design and research in industry as well as in academia. Models are being developed in-house in academia as well as by commercial facilities. There is need to share the appropriateness and accuracies of these models in describing various food processes. A modeling subcommittee was formed between (CA, NC, NY-I, OH, OR, SD and WA) that plans to start working toward three general objectives- a) Exchange of students between stations to share knowledge of software use and capabilities b) A workshop on modeling in meetings such as the Annual IFT meeting c) Evaluation of a number of software programs to solve one class of problems

1. Thermal processing.

a. One of the most significant manufacturing cost elements in the food canning industry is the destruction of entire retort batches of finished product that did not receive the specified scheduled process because of momentary deviations in retort temperature during the process. The FL station will be leading the development of an intelligent on-line computer-based control system for retort operations in canned food sterilization. Key to this system is the integrated on- line use of heat transfer models developed earlier for thermal process simulation. Other stations that will be consulted include NC, NJ NY-G, NY-I and OH.

2. Microwave sterilization.

a. Microwave sterilization has several advantages over conventional sterilization short process time results in less destruction of thermally sensitive components such as nutrients, texture and color. Commercialization of microwave sterilization of food has been affected primarily by the inability to predict and/or control the uniformity of heating and the verification of the safety of microwave sterilized food. WA station, together with NY-I station and the US Army Laboratories at Natick will be developing microwave sterilization product, process and equipment. Strong collaboration of complementary capabilities of mathematical modeling in NY-I station and process and product design experience of WA station will be used. At the NY-I station, coupled thermal-electromagnetic models will be developed that considers the dramatic changes in food properties as temperatures increase. A large number of industries have become partners to this project at the WA station where several products have already been microwave sterilized successfully.

3. Aseptic processing.

a. Prediction of heat transfer, lethality and quality degradation during aseptic processing of liquid foods, foods containing particulates and conventionally retorted foods continues as a priority. Although significant progress has been made in the past, much work remains to be done, particularly in foods containing particulates. Work in this area will be conducted by FL, IN, NY-I, NC and OH stations.

4. Extrusion.

a. Models for extrusion processing will be developed at the MN, MO, ND, NE, NJ and OH stations.

5. Frying.

a. Frying of foods is an important process, but one that is extremely complex. Models of heat and mass transfer during frying of foods, coupled with the physical changes that occur during frying, are still needed. Work in this area will be done by the CA, NY-Ithaca, NC and TX stations.

Measurement of Progress and Results

Outputs

Outcomes or Projected Impacts

• The research conducted by NC-136 members will further knowledge regarding the application of new technology, the modeling and prediction of food processes, and the continued improvements in process efficiency and food safety. Also, this research will lead to development of new or standardized methods for measuring food properties and the development of new food products and processes. </P> <P>The immediate beneficiaries of this research will be industry, government agencies, and other university scientists, who will have access to findings through peer-reviewed journal articles, abstracts, presentations at scientific meetings and workshops, books, and book chapters. A number of participating stations have extension centers that will facilitate transfer of findings to industry. Summaries of key findings will also be freely accessible through the project web site. Agricultural producers will also benefit by having greater access to global markets via exports of processed products, and in many cases, through vertical integration with processors. <I>The U.S.</I> <I>consumer is the ultimate beneficiary.</I> This research will contribute to a safer food supply, preserved foods that better retain the nutritional and sensory attributes of fresh foods and yet are more convenient to prepare, and processed products that better serve the evolving needs and tastes of consumers. </P>

Milestones

(0):0

Projected Participation

View Appendix E: Participation

Outreach Plan

Organization/Governance

NC-136 is organized according to the guidelines in the USDA Multistate Research Manual, as found at http://aster.uvm.edu/rr/rrman.htm. Membership includes an administrative advisor (Dr. Ian Gray), a CSREES representative (Dr. D.R. Rao) and project leaders from 18 cooperating stations, FDA and NCFST. Project leaders are listed in Attachment A.

Meetings are held annually, typically in October. The secretary for the coming year is elected at the end of each meeting. The previous secretary moves up to vice-chair and vice-chair to chair. These three officers, the past chair, and the administrative advisor constitute the executive committee.

The dates of the annual meeting (typically two or three days) are determined by the host and the chair after consulting the Committee at the preceding meeting. The chair develops an agenda for the upcoming meeting in consultation with the executive committee. The annual meeting includes technical reports from each represented station, discussion of results and future areas of collaboration, and meetings among smaller ad hoc committees. The location of the meeting for the coming year is determined by vote at the end of each meeting. Meetings are typically held at or near a member station and hosted by the official representative of that station. Minutes are prepared by the secretary and sent to members. An annual report is prepared by the chair, submitted to the administrative advisor, and posted at http://ncl36.foodsci.purdue.edu/ (the NC-136 web site).

Although the specific objectives for NC-136 have been modified from past years to accommodate new alternative processing strategies, the procedures (interactive structures) for attaining the objectives remain the same. The success of this Committee over the years has been due to the strong collaborative nature of the group to resolve issues that are not easily resolved by a single research group. Figure 1 shows the flow of these interactions (two-way) between the ad-hoc committees and the entire Committee. The ad-hoc committees are an essential element for solving specific issues that arise. Ad-hoc committees are formed when an issue is identified by the Committee. The interested stations develop a specific objective and collaborate to resolve the issue together. When the issue has been resolved and the results reported back to the Committee, the ad-hoc committee is dissolved and members move on to work on another issue. This structure allows for individual cooperation between stations, and provides a mechanism for addressing major problems of interest across all the stations.

Figure 1. Project structure, showing ad hoc Committees and flow of information

Currently, NC-136 has a number of active ad hoc committees as described in the Procedures, with new ones being planned for future activities. Most of these ad hoc committees were formed under the existing structure of Committee objectives, although they still remain important in the context of the revised objectives. With the new objectives, it is anticipated that additional ad hoc committees will be developed to target specific issues related to alternative processing technologies.

Collaboration is also fostered on an informal basis at the annual meetings, for example between members with similar interests such as in the areas of frying, microwave processing, nonthermal pasteurization and sterilization methods. Members engage in dialog throughout the year via the NC 136 list server, which is maintained by Dr. Brian Farkas.

Literature Cited

Attachments

Land Grant Participating States/Institutions

CA, DE, FL, GA, GU, IA, IL, IN, MD, MI, MO, MS, NC, ND, NE, NJ, NY, OH, OR, PA, SD, TX, WA, WI

Non Land Grant Participating States/Institutions

Food and Drug Administration, Industry Consultant, National Center for Food Safety & Tech./Illinois Institute of Technology, National Program Leader