Engineering for food safety and quality

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
501	5010	2020	100%

Progress 10/01/10 to 09/30/15

Outputs
Target Audience:Members of the target audience include academic, industry and government food professionals, graduate and undergraduate students. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Three graduate students were trained in novel techniques for Food Materials Science. How have the results been disseminated to communities of interest?By publishing book chapters and lecture notes. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Responding to the national need to improve the nutritional quality of foods, this project is dedicated to expanding the knowledge and developing the technology needed to fulfill the daunting task of ensuring that the diet of every citizen is safe and wholesome. To this effect, new technology including bi-continuous delivery systems and microcapsules produced from zein were developed in part in connection with this project. Two book chapters were published and their material incorporated into lectures and lab exercises for a new course in Food Materials Science. The course covers fundamental concepts on the impact of microstructure on food's processing, textural, sensorial, and nutritional properties. Emphasis is placed on nutrient microencapsulation and delivery to both general and targeted populations. Course materials will serve as basis for upcoming online and MOOC courses.

Publications

Type: Book Chapters Status: Published Year Published: 2015 Citation: Padua, G.W. and Nonthanum, P. 2015 Bi-continuos delivery systems. In: Nanotechnology and functional foods: Effective delivery of bioactive ingredients. Eds. Sabiov C., Chen H. and Yan R. July, 2015. Wiley-Blackwell Publishing.
Type: Book Chapters Status: Published Year Published: 2015 Citation: Padua, G.W. and Guardiola, L. 2015. Microcapsules produced from zein. In: Microencapsulation and Microspheres for Food Applications. Ed. Sagis, L.M.C. Academic Press.

Progress 10/01/13 to 09/30/14

Outputs
Target Audience: Members of the target audience include food professionals, graduate students, undergraduate students, and high school students. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Three graduate students were trained as lab instructors for the course FSHN 595 Food Materials Science. How have the results been disseminated to communities of interest? By publishing book chapters and lecture notes. What do you plan to do during the next reporting period to accomplish the goals? A new project on 3D printing of foods will be initiated. This project's goal is to develop the interest of undergraduate students on the principles and practice of food engineering by providing students with a novel and exciting tool. 3D printing will be used to demonstrate food materials science concepts and to engage students in hands-on activities related to food manufacturing.

Impacts
What was accomplished under these goals? We designedlab exercises for the course FSHN 595 Food Materials Science. This is anew course for which all teaching materials were specifically developed. The course consists of lecture/discussion sessions based on assigned readings and a series of demonstrations of specialized instruments includingthe atomic force microscope, the nanoindenter, the dynamic light scattering particle sizer, the ARES rheometer, the dymanic scanning calorimeter, and the texture analyzer. After instrument demonstrations, students conduct short research experiments.

Publications

Type: Book Chapters Status: Published Year Published: 2014 Citation: Moran, L.L, Yin, Y., Cadwallader, K.R. and Padua, G.W. Testing Tools and Physical, Chemical, and Microbiological Characterization of Microencapsulated Systems. In: Microencapsulation in the Food Industry: A Practical Implementation Guide. Eds. Gaonkar, A.G., Vasisht, N., Khare, A.R. and Sobel, R. Academic Press Ltd-Elsevier Science Ltd, London. Pages: 323-352.
Type: Book Chapters Status: Awaiting Publication Year Published: 2015 Citation: Padua, G.W. and Nonthanum, P. Bi-Continuous Delivery systems. In: Nanotechnology and Functional Foods: Effective Delivery of Bioactive Ingredients. Eds. Sabiov, C., Chen, H. and Yan, R. Wiley-Blackwell Publishing.
Type: Book Chapters Status: Awaiting Publication Year Published: 2015 Citation: Padua, G.W. and Guardiola, L. Microcapsules Produced From Zein. In: Microencapsulation and Microspheres for Food Applications. Ed. Sagis, L.M.C. Elsevier.

Progress 01/01/13 to 09/30/13

Outputs
Target Audience: Industry and academic food science researchers and professionals engaged in the development of methods and processes to improve the safety and quality of foods. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Several undergraduate students had the opportunity to have a research experience. The graduate student had the opportunity to mentor undergraduates who in turn were exposed to the scientific method and laboratory techniques. How have the results been disseminated to communities of interest? Industry- academia relations were strengthened facilitating the dissemination of best practices for enhanceing food safety and quality. Several meetings took place between the lab and industry representatives. Graduate and undergraduate students attended to enhance their communcation skills. What do you plan to do during the next reporting period to accomplish the goals? Continue the work with a new group of students in the design of methods and processes to enhance food quality and safety.

Impacts
What was accomplished under these goals? A doctoral dissertation was completed with the collaboration of industry groups. New information on the behavior of proteins as structural polymers was generated. Results are expected to have a direct impact on food quality.

Publications

Type: Theses/Dissertations Status: Other Year Published: 2013 Citation: Nonthanum, P. Rheological characterization and applications of zein and whey protein gels. PhD Dissertation. University of Illinois.

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

Outputs
OUTPUTS: Outputs of this project include mentoring of undergraduate students through research internships. Technical results include two technical publications (listed below) and new materials for undergraduate and graduate courses. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
New flavor encapsulation processes were developed by industry groups based on the results of this project. These new methods use natural flavors obtained from the concentration of fruit juices.

Publications

Wang, Y. and Padua G.W. 2012. Nanoscale characterization of zein self-assembly. Langmuir 28 (5)2429-2435.
Wang, Y. and Padua G.W. 2012. Characterization of core-shell structures formed by zein. Food Hydrocolloids 30 (2013) 487-494.

Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: Editing a book entitled "Methods in Nanoscale Research in Foods and Bioproducts". Table of Contents: 1. Introduction and Overview. a. Opportunities in food nanotechnology. b.Tools for the food nanotechnologist. Part A: Material Components. 2. Material Components for Nanostructures. 3. Types of Nanostructures. 4. Nanocomposites. 5. Nanostructures for Functional Foods. Part B: Characterization of Nanostructures - Microscopy. 6. Scanning Electron Microscopy. 7. Transmission Electron Microscopy. Part C: Characterization of Nanostructures - Other Technologies. 8. X-ray Diffraction. 9. Focussed Ion Beam. 10. Dynamic Light Scattering. 11. Micro-Computer Tomography. 12. QCM-D. PARTICIPANTS: Graciela Padua, University of Illinois, Urbana, IL. Qin Wang, University of Maryland, College Park, MD. Paul Takhistov, Rutgers University, New Brunswick, NJ. Vania Petrova, University of Illinois, Urbana, IL. Yi Wang, University of Illinois, Urbana, IL. Chang Hui Lei, University of Illinois, Urbana, IL. Phillip Geil, University of Illinois, Urbana, IL. Leilei Yin, Beckman Institute, University of Illinois, Urbana-Champaign, IL. TARGET AUDIENCES: The intended audience includes researchers dealing with new projects (nutrition, health, materials, surfaces, biosensors) in industry and academia, regulatory agencies dealing with food and biological nanoparticles and nanostructured materials, and students in food and bioproducts nanotechnology. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
The rapid implementation of nanotechnology concepts in industry and academia creates the need for information on instruments and methods among researchers and product development teams. This book is addressed to workers new in the field of nanotechnology. Food nanotechnology is an expanding field. This expansion is based on the advent of new technologies for nanostructure characterization, visualization, and construction. This book focuses on state-of-the-art equipment; thus, it contains a description of the tool kit of a nanotechnologist. The purpose of this book is to introduce new researchers and product development teams in food and bioproducts nanotechnology to the most widely used experimental technologies in the field. This book will present widely used techniques in characterization, visualization, and construction of nanostructures, including electron microscopy and other characterization technologies. The book will provide concise explanations for the technical basis of the methods being described, will highlight research opportunities, and will point out methods pitfalls and limitations.

Publications

Padua,G.W. and Wang, Q. (eds) 2012. Methods in Nano Science and Technology Research in Foods and Bioproducts. Wiley-Blackwell Publishing. (In Press).

Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: Zein, a major protein of corn, has an amphiphilic character. Zein molecules contains sharply defined hydrophobic and hydrophilic domains at its surface. Amphiphilicity is one of the main driving forces for self-assembly. Self assembly is the spontaneous formation of organized phases from disordered phases. It is mediated by weak interactions (e.g. Van der Waals, capillary, π-π, hydrogen bonds) rather than covalent, ionic or metallic bonds. Self assembly gives rise to lyotropic ordered phases, such as cubic, hexagonal, gyroid and lamellar phases. Zein was observed to form spheres, hexagonal, sponge and lamellar phases in aqueous ethanol solutions. In this work, the formation, stabilization and characterization of protein self-assembled nanostructures and their applications to food and biomaterials were studied. Of special interest are the lyotropic and thermotropic development of mesophases in protein solutions. applications. PARTICIPANTS: Yi Wang - Post-doctoral research associate. TARGET AUDIENCES: Researchers in academia, industry, and government as well as students at undergraduate and graduate levels. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Zein self-assembles layer-by-layer by an adsorption process resulting in the formation of soft spheres which further aggregate into ever more complex structures. Such structures may serve in the formation of core-and-shell micro encapsulation systems, lamellar films for coating and protecting foods from degradation, or sponges and gels for novel food matrices. Similar structures may also be useful in tissue scaffolding and design of novel biomaterials useful in regenerative medicine.

Publications

Wang, Y. and Padua, G.W. 2010. Self-assembly of zein into nanoscale soft spheres. ACS 239th National Meeting. San Francisco, CA March 24, 2010.
Wang, Y. and Padua, G.W. 2010. Zein microphases in ethanol-water. IFT Annual Meeting. July 17-20, 2010. Chicago, IL.

Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: The development of nanocomposites is a new strategy to improve physical properties of polymers, including mechanical strength, thermal stability, and gas barrier properties. In food packaging, a major emphasis is on the development of high barrier properties against the migration of oxygen, carbon dioxide, flavor compounds, and water vapor. Decreasing water vapor permeability is a critical issue in the development of biopolymers as sustainable packaging materials. In this work, a review of current literature on nanotechnology applications to decrease increase barrier properties of polymers was undertaken. This review will serve as the basis for future research on improvement of biopolymers as food packaging materials. PARTICIPANTS: Graciela W. Padua, Research Associate Professor, Department of Food Science and Human Nutrition, University of Illinois. Amit Arora, Post-doctoral Research Associate, Department of Food Science and Human Nutrition, University of Illinois. TARGET AUDIENCES: Academic and industrial researchers and students interested in the improvement of food packaging materials. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
This review illustrated the potential of nanocomposites in food packaging. The main driver is the need for better barrier properties from polymeric materials. Better barriers against the migration of oxygen, CO2, water vapor, and flavor compounds would have a major impact on the shelf-life of fresh and processed foods. For the case of biopolymers, improving water and gas barrier properties is a critical issue. Nanocomposites technology is still in its early stages. Montmorillonite and kaolinite clays have shown good potential for improving the properties of polymeric materials. Graphene nanoplates are novel and highly promising carbon-based nanosized fillers. Best effects are generally observed at low loads (~5 wt%). Good compatibility between filler and polymer is essential, thus the importance of chemically modified clays. With respect to processing, although exfoliation is recognized as a processing goal, an orderly array of platelets in the polymer matrix, which would maximize effectiveness, is still largely unachieved. Improvements in barrier properties are often reported at 50% that of the neat polymer. Thus, polymers of intrinsically better barrier properties will render even better products as nanocomposites. Further improvements could be expected from the development of more compatible filler-polymer systems, better processing technologies, and a systems approach to the design of polymer-plasticizer-filler.

Publications

Arora, A. and Padua G.W. 2009. Review: Nanocomposites in Food Packaging. J. Food Sci. (In Press).

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

Outputs
OUTPUTS: Activities: 1) Collaborating with Louisiana Station in the imaging of biopolymers. 2) Collaborating with Tennessee Station in writing a grant proposal to USDA/NRI. 3) Collaborating with Tennessee Station in the analysis of rheological data for biopolymer solutions. Events: 1) Attending the NC-1023 meeting in Knoxville, TN. Oct. 12-14, 2008. 2) The NC-1023 project will organize the 2009 Conference of Food Engineering, in Columbus OH, April 5-8, 2009. This conference has a main goal of promoting academy-industry interactions. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Interaction among stations has resulted in the creation of a network of interconnected labs that share equipment and expertise. Projects include a study of the rheology of protein dispersions and application of food nanotechnology in microencapsulation of bioactive compounds and in food safety.

Publications

No publications reported this period

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

Outputs
OUTPUTS: 1. Improving Food Safety and Quality of Fresh and Fresh-Cut Fruits and Vegetables: A flow-through chamber was designed and used to wash produce samples for microbial reduction tests. This was the first effort to examine the efficacy of sanitizers with a continuous flow set-up. A biphasic microbial inactivation was found in washing of fresh produce with and without a sanitizer. For the first time, kinetic models were used to describe the microbial removal kinetics during produce washing operations. 2. Acoustic Energy as a Practical Juice Safety Intervention for Inactivation of Acid Tolerant Pathogenic Microorganism: For the first time, a complete set of TS, MS and MTS inactivation data for a microorganism were obtained at sublethal and lethal temperatures. The population reduction of E. coli K12 treated with TS, MS, and MTS followed dual-phasic inactivation kinetics, which includes a fast reduction phase in the first few minutes followed by a slow one for remaining minutes. Within 2 minutes, a 5-log reduction of E. coli K12 in phosphate buffer (0.01M, pH 7) was achieved by MS, TS, and MTS. Especially at 61C, a 5-log reduction was achieved within 30 s by TS and MTS. In SEM observation, disrupted cells and debris of cells were observed in MTS-treated cell at 61C and 400 kPa for 30 seconds. 3. Interactive Virtual Experiments for Food Processing Education: One virtual lab module has been developed that was demonstrated in a presentation at the 2007 IFT meeting. The E. coli population reduction data during thermo-sonication treatments have been collected as a function of treatment time and temperature. The inactivation data were fitted to different kinetic models. It was found that the inactivation of E. coli K 12 with power ultrasound in the thermo-sonication mode can be best described by the Weibull model. This is a joint effort among four institutions: Purdue University, The Ohio State University, University of California, Davis, and UIUC with the support of a USDA Higher Education Challenge Grant. Dr. Morgan (Purdue) leads the effort and Dr. Singh at UC Davis provides important technical support in the development of the simulators. 4. Characterization of zein nano and microscale structures: Zein-solvent-surfactant mixtures of varying HLB were characterized by SEM, DLS, AFM, and FIB techniques. Such structures may find application in microencapsulation processes. PARTICIPANTS: Graciela W. Padua, Department of Food Science and Human Nutrition, University of Illinois. Hao Feng, Department of Food Science and Human Nutrition, University of Illinois. TARGET AUDIENCES: 1. Food Engineering researchers at universities, government agencies, and industry. 2. Food industry professionals. 3. Food Science students.

Impacts
1. Improving Food Safety and Quality of Fresh and Fresh-cut Fruits and Vegetables: Washing produce with sanitizing solutions is an important step in reducing microbial population during postharvest handling. Little information exists regarding the effects of washing solution flow conditions on the efficacy of pathogen reduction during washing. The research findings reported here may be useful in designing produce wash systems for achieving enhanced pathogen reduction and improved produce quality and safety. The biphasic microbial inactivation behavior during produce washing provides an important guideline for the design of a commercial washing procedure, as washing in phase II is ineffective and should be avoided. 2. Acoustic Energy as a Practical Juice Safety Intervention for Inactivation of Acid Tolerant Pathogenic Microorganism: The results demonstrate that MTS may be used as an alternative to inactivate foodborne pathogens in liquid foods (orange and apple juice). The relatively short treatment time (30 seconds) and low temperature compared to commercial thermal pasteurization (71.1 C) may ensure the production of orange and apple juice with an improved product quality. 3. Interactive Virtual Experiments for Food Processing Education: The virtual lab module(s) developed in this study may provide a useful tool for students to deepen the understanding of food processing principles taught in the classroom. It allows students to explore the effect of operational conditions on the rate of heat, mass and momentum transport, as well as quality changes, during a unit operation process. It also provides access for students to emerging food processing technologies (High pressure processing, Pulsed electric field, Ultrasound, etc.) that are normally not available in classroom settings for most food processing course instructors. 4. Characterization of zein nano and microscale structures: Corn proteins will become more readily available as the corn ethanol industry intensifies production. Zein, a major kernel protein, offers the possibility of becoming a building block for novel food structures and biomaterials. Of particular interest for this research, zein microspheres can be easily produced. Microspheres may be used to improvwe the quality of foods by carrying, protecting, and delivering a number of health functional compounds and flavoring agents.

Publications

Wang, H., Feng, H. and Luo, Y. 2007. Control of browning and microbial growth on fresh-cut apples by sequential treatment of sanitizers and calcium ascorbate. J. Food Science, 72: 1-7.
Lu, S., Luo, Y., Turner, E. and Feng, H. 2007. Efficacy of sodium chlorite as an inhibitor of enzymatic browning in apple slices. Food Chemestry, 104: 824-829.
Wang, H., Feng, H. and Luo, Y. 2007. Modeling of the effect of washing solution flow conditions on Escherichia coli O157:H7 population reduction on fruit surfaces. J. Food Prot. (Forthcoming).
Wang, H., Feng, H., Luo, Y. and Zhang, A. 2007. Produce surface characteristics affect product quality and safety. Acta Horticulturae (Forthcoming).
Wang, H., Feng, H. and Luo, Y. 2006. Inactivation of Escherichia coli O157:H7 with peroxyacetic acid, acidic electrolyzed water, and chlorine on cantaloupes and fresh-cut apples, International Fresh-Cut Produce Association (IFPA) annual meeting, Baltimore, MD, 2006.
Wang, H., Feng, H. and Luo, Y. 2006. Effects of washing conditions on Escherichia coli O157:H7 reduction on fruit surfaces. International Fresh-Cut Produce Association (IFPA) annual meeting, Baltimore, MD, 2006.
Wang, H., Feng, H., MacLaren, S. and Luo, Y. 2006. Examination of cell morphological changes of Escherichia coli treated with acidic electrolyzed water, peroxyacetic acid and chlorine using a MFP-3DTM atomic force microscope. Institute of Food Technologists, 2006 Annual meeting, Orlando, FL, 2006.
Luo, Y., Wang, H. and Feng, H. 2007. Produce surface characteristics and washing conditions affect quality and safety of fresh-cut products. The International Conference on Quality Management of Fresh Cut Produce 2007 (QMFCP2007), Bangkok, Thailand, 6-8 August, 2007.
Zhou, B., Feng, H. and Lou, Y. 2007. The efficacy of sanitizer and ultrasound combined treatments on reduction of Escherichia coli O157:H7 surrogate population on spinach. Institute of Food Technologists, 2007 Annual Meeting, Chicago, IL, 2007.
Feng, H. and Martin, S.E. 2007. Ultrasonic pasteurization of foods. In: Encyclopedia of Agricultural, Food, and Biological Engineering, (ed.) Heldman, D.R. and Dekker, M. New York.
Ugarte, E., Feng, H., Martin, S.E. and Cadwallader, K.R. 2006. Inactivation of Escherichia coli with power ultrasound in apple cider. J. Food Science, 71(2): 102-108.
Ugarte, E., Feng, H. and Martin, S.E. 2007. Inactivation of Shigella boydii 18 IDPH and Listeria monocytogenes Scott A with power ultrasound at different acoustic energy densities and temperatures. J. Food Science, 72: 103-107.
Wambura, P., Yang, W., Williams, L., Feng, H. and Rababah, T.M. 2007. Shelf life extension of roasted peanuts by surface lipid removal. Transactions of ASAE 54: 1315-1321.
Mutamba, A.B.O., Ibrahim, S.A., Yang, H., Seo, C.W. and Feng, H. 2006. Reduction of Escherichia coli 0157:H7 in milk using sonication as influenced by milk fat content. The Annual Biomedical Research Conference for Minority Students, Anaheim, CA, 2006.
Feng, H. and Martin, S.E. 2007. Power ultrasound inactivation of bacteria and food enzymes. ASABE Annual Meeting, Minneapolis MN, June 17-20, 2007.
Yang, W., Yang, R. and Feng, H. 2007. Power ultrasound enhanced extraction of xylan from corncob. Institute of Food Technologists, 2007 Annual meeting, Chicago, IL, 2007.
Feng, H., Morgan, M., Balasubramaniam, V.M. and Singh, R.P. 2007. Virtual laboratory modules for food processing education. Institute of Food Technologist, 2007 Annual Meeting, Chicago, IL, 2007.
Kim, H.J., Feng, H., Kushad, M.M. and Fan, X. 2006. Effects of ultrasound, irradiation, and acidic electrolyzed water on germination of alfalfa and broccoli seeds and Escherichia coli O157:H7. J. Food Science, 71(6): 168-173.
Zhou, B., McEvoy, J.L., Luo, Y., Saftner, R.A., Feng, H. and Beltran, T. 2006. Application of 1- methylcyclopropene reverses the deleterious effect of exogenous ethylene on fresh-cut watermelon and controls microbial growth. J.Food Science 71(6): 180-183.
Wang, H., Feng, H. and Luo, Y. 2006. Dual-phasic inactivation of Escherichia coli O157:H7 with peroxyacetic acid, acidic electrolyzed water, and chlorine on cantaloupes and fresh-cut apples, J. Food Safety, 26: 335-347.

Progress 01/01/06 to 12/31/06

Outputs
Fresh fruits and vegetables are increasingly recognized as causative agents of foodborne illness outbreaks. A recent E. coli O157:H7 outbreak (October 2006) involving fresh spinach affected 199 people in 26 states and caused 3 death cases. Cilantro, Coriandrum sativum, is widely used as seasoning and ingredient. In order to maintain its aroma, cilantro is commonly consumed fresh (uncooked). However, raw consumption of cilantro increases the risk of foodborne disease. Bacterial contamination in cilantro and other leafy vegetables is difficult to eliminate by washing because of the of bacteria's ability to form biofilms. Bacterial biofilms are reported to be more resistant to biocides such as antibiotics and disinfectants than free cells. Food irradiation was proposed as a possible means to control the safety of cilantro. Radiation is able to penetrate tissues and possibly eliminate bacteria in protective biofilms. The objective of this work was to further investigate the effect of gamma irradiation treatment on cilantro quality, including color, texture, and the content of aroma-active compounds. Experiments were conducted where cilantro leaves were irradiated at doses of 0.5, 1.0, 1.5, and 2.0 kGy. Cilantro samples were stored at refrigeration temperature (40 degrees F) for up to 14 days. Texture was measured with the Texture Analyzer, color was evaluated with the Hunter colorimeter, and aroma-active compounds in cilantro extracts were identified and analyzed by a GC-MS system. Irradiation affected the texture of cilantro. Tissues became progressively softer with irradiation dose. Color became slightly darker with irradiation, but green and yellow colors were not significantly affected. Flavor analysis of non-irradiated and irradiated cilantro samples using Gas Chromatography-Mass Spectrometry (GC-MS) indicated that the major volatile constituents in cilantro are (E)-2-tetradecenal, (E)-2-dodecenal, nonane, decanal, (E)-2-tridecenal, dodecanal, and (E)-2-decenal, in agreement with previous reports. Results indicated that there were no significant changes in concentration of major volatile compounds in cilantro upon gamma irradiation. The overall flavor profile of cilantro appeared to remain unchanged after the irradiation treatment. Results suggested that low irradiation treatments (0.5 and 1.0 kGy ) contributed to maintain freshness up to 2 weeks of storage at refrigerated temperatures. Fresh appearance of the product was better maintained for irradiated than for non-irradiated samples, which was attributed to elimination of spoilage bacteria. However, higher radiation dose had an adverse effect on the product. Irradiation treatments at 1.5 and 2.0 kGy appeared to break down tissue structure causing excessive moisture loss.

Impacts
Increased consumption of fresh fruits and vegetables has magnified the impact of safety concerns associated with them. A recent E. coli O157:H7 outbreak (October 2006) involving fresh spinach affected 199 people in 26 states and caused 3 deaths. The highest risk of contamination is observed in leafy vegetables which provide a large surface area for attachment of microorganisms. Soil, irrigation water, animals, and farm workers can serve as potential sources or carriers of microbial pathogens. Bacterial contamination in leafy vegetables is difficult to eliminate by washing because many bacteria have the ability to form biofilms. Bacterial biofilms are reported to be more resistant to biocides such as antibiotics and disinfectants than free cells. Food irradiation is proposed as a possible means to control the safety of uncooked leafy vegetables. Radiation has the ability to penetrate tissues and possibly eliminate bacteria in biofilms. However, radiation may also negatively affect the quality of fresh foods by promoting oxidative reactions and polysaccharide breakdown. This work is aimed at the characterization of radiation induced changes in fresh leaves. Increased knowledge of the impact of irradiation on food quality will permit effective design of safety assurance food processes.

Publications

No publications reported this period