Source: OHIO STATE UNIVERSITY submitted to
DEVELOPMENT OF BPA FREE COATINGS FOR EXTENDED SHEF LIFE OF CANNED FOODS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
AFRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
1011847
Grant No.
2017-67017-26469
Project No.
OHO03015-CG
Proposal No.
2016-09540
Multistate No.
(N/A)
Program Code
A1361
Project Start Date
Jun 1, 2017
Project End Date
May 31, 2021
Grant Year
2017
Project Director
Pascall, M. A.
Recipient Organization
OHIO STATE UNIVERSITY
1680 MADISON AVENUE
WOOSTER,OH 44691
Performing Department
Food Science & Technology
Non Technical Summary
Canned foods are a main feature of the human diet globally. However, since many foods contain ingredients that are corrosive to metal cans, it is necessary to coat the material with a protective lining. Since the early 1960's an FDA approved bisphenol A (BPA) epoxy resin was used to coat food cans. This tough and strong coating adheres well to metallic surfaces, resists attacks from aggressive food ingredients, and is unaffected by heat, moisture and oxygen associated with food processing. However, recent published reports highlighted adverse health effects associated with the consumption of low level BPA from canned foods and plastics used for baby bottles. As a result, some countries have banned the use of BPA in food packaging, and others are considering the same. For example, FDA has not approved packaging with BPA for infant food, and California Proposition 65 will shortly require food processors to indicate on the labels if packages contain BPA. In response, food packaging manufacturers developed new BPA-free coatings. Unfortunately, cans with BPA-free coatings in grocery stores are showing corrosion within a short time and only provide the food with limited shelf life, unlike what was provided by BPA-epoxide coatings. This creates a need to develop new BPA-free coatings with the same thermal, chemical and mechanical stabilities as BPA epoxide coatings. This proposal seeks to investigate the problem of corrosion in food cans and develop and characterize new coatings that will increase the shelf life of canned foods without compromising safety and quality.
Animal Health Component
0%
Research Effort Categories
Basic
15%
Applied
60%
Developmental
25%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
7117410202050%
5017299200050%
Knowledge Area
711 - Ensure Food Products Free of Harmful Chemicals, Including Residues from Agricultural and Other Sources; 501 - New and Improved Food Processing Technologies;

Subject Of Investigation
7410 - General technology; 7299 - Research equipment and methods, general/other;

Field Of Science
2020 - Engineering; 2000 - Chemistry;
Goals / Objectives
To perform a comprehensive investigation to determine food groups associated with corrosion in sealed canned food.To obtain a comprehensive understanding of the corrosion mechanisms initiated by these foods.To use our understanding of the corrosion mechanisms to create alternative coatings that are resistant to the corrosion initiation currently taking place within non-BPA coated food cans.To verify the efficacy of the alternative coatings with simulated and actual tomato based foods currently in grocery stores.To increase the shelf life of tomato-based foods canned in containers with non-BPA coatings in collaboration with a can coating manufacturer, a can making company, and a food processor to ensure that this BPA problem is solved.
Project Methods
Perform a comprehensive review of canned food groups and categorize them according to high acid, high salt (NaCl, KCl), high moisture and high sulfur containing ingredients. To also determine if other volatile compounds should be added to this group. To further categorize these food groups into - meats, fish, fruits, vegetables, soups, preserves, and dairy products. We will specially focus on tomato-based foods later on in the project. This will address objective #1.To analyze each food group to determine the ingredients responsible for breaching the coatings of the cans. A second step would be to analyze the ingredients that are responsible for initiating the corrosion process and to investigate chemical changes taking place in the food samples during heat treatment and storage. These tests will be done using Selected Ion Flow Tube Mass Spectrometry (SIFT-MS), LC/MS, and ICP-MS. The ionic strength and salt content of the samples will be investigated using Ion Chromatography (IC), Ion-Selective Electrodes (ISEs), and conductivity. This will address objective #1.To investigate how aggressive compounds in the ingredients in tomato-based food groups interact with the coating materials, create breaches and initiate corrosion. This will be done on soup samplesstored in sealed cans at 25 degree C (room temperature) and 45 degrees C (accelarated temperature). This information will help us avoid pitfalls responsible for corrosion in currently used cans when working to develop new coatings. This will be done using Scanning Kelvin Probe (SKP), Electrochemical Impedance Spectroscopy (EIS), and Fourier Transform Infrared (FTIR) spectroscopy. This will address objective #2.The synthesis ofnew coating polymers using the information obtained from the previous sections. Based on section 3 above, PPG will redesign polymers/coatings(with a focus on US FDA.175.300 thermoset acrylic polymer) using novel technologies that will block or impede tomato-based food related chemicals from penetrating the coating and therefore prevent or retard corrosion.Tests conducted on new coatings technologies will utilize the latest computer models for design of experiments for polymer development at PPG in conjunction with testing on state of the art application equipment.The results of these studies will allow for new understandings of food coatings interactions which will make significant inroads in can coatings for the future. This will address objective #3.Characterization of the new coatings to determine their mechanical, thermal, and chemical stability in harsh environments of high moisture, temperature, salt, pressure, acidity, alkalinity, and oxygen concentrations. Mechanical testing will be done by dynamic mechanical analysis (DMA) and tensile testing to determine the resilience of the new coatings. Thermal stability testing will be done by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and x-ray diffraction. Chemical stability will be investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to determine the nature and location of bond breaking within the polymeric structure and to understand which ingredients in the food are responsible for such molecular changes. This will address objective #4.To test the mass transfer potential of chemical additives from the polymer towards the food (this will involve migration studies on chemicals such as plasticizers, unreacted monomers, stabilizers, cross-linking agents, and catalysts used in the polymerization process). This will be done using fatty, acidic, aqueous and alcoholic food simulants at room and accelerated temperatures. Analyses will be done using GC-MS, LC-MS and ICPMS. This will address objective #4.To test the long term stability of the new coatings to resist corrosion when exposed to harsh conditions of high temperature, acidity, oxygen, moisture, pressure and in the presence of tomato-based food ingredients known to be aggressive to previously used coating materials.This will be done using the analytical techniques mentioned in ii above. This will address objective #5.To perform this project in collaboration with a coating manufacturer (PPG Industries). Can manufacturer (Silgan Corporation) and Campbell Soup (food processor) have expressed support for this study. This will address objective #5.

Progress 06/01/17 to 05/31/21

Outputs
Target Audience:The target audiences reached during the reporting period were graduate students, regulatory personnel, academics and food and packaging industry technical individuals. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?One student (Kuo-Hsiang Chang) graduated with a Ph.D. in Material Science Engineering in 2021, and a second student graduated with a master's degree in Food Science in 2019. How have the results been disseminated to communities of interest?During the 2020/2021 reporting period, one paper was presented at the 2020 IFT annual conference. Threeresearch papers havebeen published in a peer reviewed journal.This conference was attended virtually by students, academics, regulatory personnel and individuals from the food and pharmaceutical industries. During the 2020/2021reporting period, oneface-to-face and two virtual meetings were kept with our industrial partner, PPG Industries and Silgan Inc, respectively. During that time, update reports on the progress of the project were presented to the company and feedback on commercial trials of modified can coatings were noted. Our research was guided by feedback from PPG Industries. The reports that were presented to thiscompany focused on data that characterized the degradation of BPA-free can coatings and how it was used to predict the integrity of food cans. In our study, the corrosion of tinplate cans with a BPA-free coating exposed to different solutions was studied using electrochemical impedance spectroscopy (EIS). To accelerate the corrosion process, the cans were stored at 49 °C for varying times prior to testing in various solutions. EIS was performed in the original storage environment and then in 3.5 wt% NaCl to investigate the performance of the can coatings. Separately, EIS was also used to investigate degradation of the coating in the headspace region of sealed sample cans. The EIS results provide insights to the degradation of the coating and the corrosion of cans by different food chemicals. The following is a comprehensive summary of our research, objectives, methods used, results and conclusions made on the packages tested. The study was divided into four segments. These represented the four research papers that we submitted for publications in peer review journals. Summary of study #1. Selected ion flow tube mass spectrometry (SIFT-MS) and ion chromatography (IC-MS) were used to investigate the presence of volatile and non-volatile compounds in canned tomatoes and the polymeric lining before and after retorting the cans which contributes to corrosion and the migration of iron and tin compounds to the tomatoes. Diced Roma tomatoes and other simulant treatment groups were sealed in two-piece tinplated cans (controls in glass jars), retorted at 121°C for 30 minutes, then stored at 49°C for 50 days. Results showed that thermal degradation of amino acids in the tomatoes gave rise to volatile methyl sulfides and non-volatile nitrogenous compounds which were subsequently sorbed by the can lining. SIFT-MS showed a 20-fold increase in dimethyl sulfide concentration. Inductively coupled plasma (ICP-MS) results showed 4-fold and 16-fold increases in iron and tin compounds, respectively, that migrated from the metal to the tomatoes as a result of acid and electrolyte interactions. Summary of study #2. This study investigated how heat-induced changes to compounds in tomatoes initiated morphological changes to the lining in metal cans. X-ray diffraction, Fourier transform near-infrared spectroscopy, and scanning electron microscopy characterized these morphological changes and we investigated the elemental composition of the lining in the cans before and after heat processing. All tomato-filled cans were sealed, retorted (121°C, 30 min), then stored at 49°C for 50 days. Selected-ion flow-tube mass spectrometry then measured the concentrations of volatile compounds in the polymeric linings of unprocessed and processed cans. Results showed that thermal degradation of amino acids in the tomatoes gave rise to volatile methyl sulfides that were subsequently sorbed by the can linings. This process caused breaches in the lining, moisture uptake by the polymer, delamination, and exposure of the base-metal in the cans. These effects allowed electrolytes in the tomatoes to initiate corrosion in the wall of the cans. Summary of study #3. Tinplate cans with polymeric coatings are commonly used for food storage. Due to health concerns related to bisphenol A (BPA), coatings with BPA not intentionally added (commonly referred to as BPA-NI) coatings are currently being considered. Thus, understanding the degradation of BPA-NI coatings is critical for predicting can integrity. In this study, the corrosion of tinplate cans with a BPA-NI coatingexposed to different solutions was studied using electrochemical impedance spectroscopy (EIS). To accelerate the corrosion process, cans were stored at 49°C for varying times prior to testing in various solutions. EIS was performed first in the original storage environment and then in 3.5 wt% NaCl to investigate the performance of the can coatings. Separately, EIS was also used to investigate degradation of the coating in the headspace region. The EIS results provide insights into the degradation of the BPA-NI coating and the corrosion of cans arising from the exposure to different food chemicals. Summary of study #4. Corrosion phenomena associated with tinplate cans were investigated with aqueous solutions of different compounds commonly found incanned tomato products. After only a few weeks of storage at 49°C, cans lined with a coating with bisphenol A (BPA) not intentionally added(BPA-NI) displayed degradation of the coating. Storage of solutions containing chloride, nitrate, and thiosulfate ions in the BPA-NI coatedcans resulted in extensive formation of blisters. Additionally, headspace blackening, which is sometimes found in packaged protein-containingfoods, was also observed. Volatile sulfur-containing compounds produced during the sterilization process might be the origin of headspaceblackening. In this study, the corrosion of tinplate cans exposed to different solutions at 49°C for varying storage times was studied via opticalmicroscopy, optical profilometry, x-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The results showed a strongcorrelation between the presence of cysteine, an amino acid, and/or nitrate, and the degradation of the coating. Furthermore, cysteine wasfound to be a source of headspace blackening. What do you plan to do during the next reporting period to accomplish the goals?This project ended on May 31, 2021. We plan to continue investigations into corrosion in food cans caused by heat treatment of selected foods. We plan to continue our collaboration with food companies that are engaged in can making, metal coatings and food process and packaging.

Impacts
What was accomplished under these goals? During the 2020/2021 year, the following were accomplished: 1. One student (Kuo-Hsiang Chang) completed his research and graduated with a Ph.D. degree in Material Science Engineering. His dissertation was entitled "Corrosion in Tinplate Cans Used for Food Storage." 2.Kuo-Hsiang Chang also submitted two papers for publication. Both papers were published. 3. Elliot Dhuey, a master's student who worked on this project, submitted two papers for publication. One paper is published and the other is in the review process. 4. Elliot Dhuey also presented a paper at the 2020 IFT conference on the topic of corrosion in food cans.

Publications

  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Kuo-Hsiang Chang, Belinda L. Hurley, Melvin A. Pascall, Gerald S. Frankel. 2021. Corrosion in Tinplate Cans Used for Food Storage. Part 1: EIS Analysis of BPA-NI Coating. Corrosion (2021) 77 (4): 386-401. DOI: https://doi.org/10.5006/3689.
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Kuo-Hsiang Chang, Belinda L. Hurley, Melvin A. Pascall, Gerald S. Frankel. 2021. Corrosion in Tinplate Cans Used for Food Storage. Part 2: Characterization and Corrosion Phenomena in BPA-NI Coated Cans. Corrosion (2021)77 (7): 700-711. https://doi.org/10.5006/3790.
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Dhuey, E., Castada, H., Barringer, S., Joseph, J. Hadad, C., Ruffley, K., Pascall, M.A. 2021. Heat-induced compounds development in processed tomato and their influence on corrosion initiation in metal food cans. Food Science and Nutrition. (2021) 00:112. https://doi.org/10.1002/fsn3.2376.
  • Type: Journal Articles Status: Accepted Year Published: 2021 Citation: Dhuey, E., Ruffley, K., Pascall, M.A. 2021. Characterization of morphological changes to an epoxy-based polymer used as a corrosion preventative lining in retorted canned tomatoes. Journal of Food Engineering.
  • Type: Theses/Dissertations Status: Published Year Published: 2021 Citation: Corrosion in Tinplate Cans Used for Food Storage. Kuo-Hsiang Chang. As partial requirement for his Ph.D. degree in Material Science Engineering. The Ohio State University.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Dhuey, E., Pascall, M.A., Frankel, G., Hadad, C., Joseph, J., Castada, H.Z. 2020. Compounds that develop in processed tomato products and the method by which these compounds initiate corrosion in metal cans. Presented at 2020 IFT 80th Annual Meeting, Chicago, IL.


Progress 06/01/19 to 05/31/20

Outputs
Target Audience:The target audiences reached during the reporting period were graduate students, regulatory personnel, academics and food and packaging industry technical individuals. Changes/Problems:During the 2019/2020 reporting period, twoface-to-face meetings were kept with our industrial partner, PPG Industries. During that time, update reports on the progress of the project were presented to the company and feedback on commercial trials of modified can coatingswere noted. Our research was guided by feedback from PPG Industries.The reports that were presented to the company focused on data that characterized the degradation of BPA-free can coatings and how it was used to predict the integrity of food cans. In ourstudy, the corrosion of tinplate cans with a BPA-free coating exposed to different solutions was studied using electrochemical impedance spectroscopy (EIS). To accelerate the corrosion process, the cans were stored at 49 °C for varying times prior to testing in various solutions. EIS was performed in the original storage environment and then in 3.5 wt% NaCl to investigate the performance of the can coatings. Separately, EIS was also used to investigate degradation of the coating in the headspace region of sealed sample cans. The EIS results provide insights to the degradation of the coating and the corrosion of cans by different food chemicals. What opportunities for training and professional development has the project provided?One student has graduated with a MS degree in Food Science and Technology. Asecond student is completing his data collection and is preparing for his graduation with a Ph.D. in Material Science Engineering. How have the results been disseminated to communities of interest?During the 2019/2020 one paper was presented at the 2020 IFT annual conference. This conference was attended virtually by students, academics, regulatory personnel and individuals from the food and pharmaceutical industries. One research paper was submitted to the Corrosion Journal for publication. This isa peer review scientific journal. What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, the plan is that the second student will graduate with a Ph.D. in Material Science Engineering from Ohio State University. At lease two research papers will be published in scientific journals from data collected from this research. The research project will also end in May 2021 and a final report will be sent to USDA-NIFA.

Impacts
What was accomplished under these goals? During the 2019/2020year the following were accomplished: 1. One student completed his research and graduated with a MS degree in Food Science and Technology. His thesis was entitled "Investigation of Corrosion in Canned Diced Tomatoes with BPA-Free Lining." 2. The MS student mentioned above also presented data from his research at the annual 2020 IFT conference. He is in the process of preparing a reseach paper for pubication. 3. One Ph.D. student has completed his data collection and is preparing for graduation. However, his data collection was hindered by the pandemic and the resultant shutdown of his research laboratory at Ohio State University. In the mean time, he has submitted a reseach paper for publication with the data he has collected to date.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Three papers were presented at scientific meetings. These were: 1. A progress report on the project at the Principal Investigators' annual reporting meeting with NIFA in Boston. 2. Kuo-Hsiang Chang, Gerald S. Frankel, Elliot P. Dhuey, Melvin Pascall. March 24-28, 2018. Poster presentation entitled Corrosion in Tinplate Cans used for Food Storage. National Association of Corrosion Engineers. Nashville, TN.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Kuo-Hsiang Chang, Gerald S. Frankel, Elliot P. Dhuey, Melvin Pascall. Sept. 29-Oct. 3, 2019. Oral presentation entitled Corrosion in Tinplate Cans for Food Storage. Materials Science & Technology Conference. Portland, OR.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Dhuey, E., Pascall, M.A., Frankel, G., Hadad, C., Joseph, J., Castada, H.Z. 2020. Presented at 2013 IFT 73rd Annual Meeting, Chicago, IL.
  • Type: Journal Articles Status: Submitted Year Published: 2020 Citation: Kuo-Hsiang Chang, Belinda L. Hurley, Melvin A. Pascall, Gerald S. Frankel. 2020. Corrosion in Tinplate Cans Used for Food Storage. Corrosion Journal.


Progress 06/01/18 to 05/31/19

Outputs
Target Audience:The target audiences reached during the reporting period were graduate students, regulatory personned, academics and food and packaging industry technical individuals. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Currently we have trainied one masters, one Ph.D. and one post-doctoral fellow on the techniques of can corrosion testing. How have the results been disseminated to communities of interest?So far two papers were presented at scientific meetings. These were: Kuo-Hsiang Chang, Gerald S. Frankel, Elliot P. Dhuey, Melvin Pascall. March 24-28, 2018. Poster presentation entitled "Corrosion in Tinplate Cans used for Food Storage." National Association of Corrosion Engineers. Nashville, TN. Kuo-Hsiang Chang, Gerald S. Frankel, Elliot P. Dhuey, Melvin Pascall. Sept. 29-Oct. 3, 2019. Oral presentation entitled "Corrosion in Tinplate Cans for Food Storage." Materials Science & Technology Conference. Portland, OR.e expect to publish at least a peer review paper by this time next year. What do you plan to do during the next reporting period to accomplish the goals?Our goal is to graduate one masters and one Ph.D. student who were funded from this project. We also plan to publish at least two but we may publish more peer review journal papers.

Impacts
What was accomplished under these goals? During the 2018/2019 year the following were accomplished: 1. A comprehensive investigation was performed and the food groups associated with corrosion in tin-plated steel two piece cans were identified. We initially focused on chicken-based canned products and after looking at the following types of items: Chicken Broth - (code 123),Chicken with Rice -(code 234),Chicken with Rice-Healthy Request - (code 345),Cream of Chicken - (code 456),Cream of Chicken-Healthy Request - (code 567),Home Style Chicken Noodles-Healthy Request - (code 678) and Healthy Kids 6-Souper Shapes - (789). 2. A correlation made between the volatile compounds in these canned and retorted recipies showed that products with concentrations of dimethyl sulfides, propyl mercaptan, dimethyl trisulfide, cysteine and several organic acids were associated with the corrosion. We also focused our investigation on Chicken Noodle soup since this showed the highest correlation. 3. To understand the corrosion mechanism cause by these products, we found that the ingredients responsible for the corrosion were chicken, carrots, celery, potassium chloride, sodium chloride, chicken broth, water. To confirm it, we tested the polymeric coating in the processed cans and found open channels for the inorganic potassium chloride, sodium chloride and organic acids to initiate the corrosion. 4. We then turned our attention to tomato-based products to reproduce this technique. So far, the data we collected have shown that methionine and nitrates in the tomato products are responsible for the corrosion.Corrosion in the cans with BPA-free coating was studied using electrochemical impedance spectroscopy (EIS), X-Ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). EIS was also used to investigate degradation of the coating in the headspace region. XRD, SEM and XPS were used to investigate blackened stains that immerged in the headspace of the cans. These were precursors of corrosion. 5. Results of the corrosion studies showed that the impedance of the cans dropped quickly in the first week due to water uptake. The presence of the chloride or nitrate ions strongly affected the degradation of the BPA-free coating. Blisters likely formed by cathodic delamination were observed in solutions containing chloride, nitrate or thiosulfate. Decreased coating adhesion led to breakdown of the coating. Pitting was also found in the cans containing low pH solutions with aggressive chloride and nitrate ions. The blisters and pitting lead to catastrophic failures of the cans. Thus, the adhesion of the BPA-free coating played an important role in the corrosion in the food cans. A strong correlation was found between the cysteine and nitrate and the degradation of the coating. Furthermore, sulfur-containing chemicals were found to impact the headspace blackening. 6. We are now in the process of testing alternative coatings and will be comparing them with BPA-based coatings. The intent is to develop coatings with the corrosion resistance of BPA epoxy but without BPA.

Publications


    Progress 06/01/17 to 05/31/18

    Outputs
    Target Audience:The target audience would be students, academics, regulatory personnel and industry food scientists. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project will train two graduate students and provide the food canning industry with information that could be used to reduce the incidence of corrosion in food cans filled with tomato-based products. One master's and one Ph.D. student will be trained from this project. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period we expect to have data on the names and mass transfer potential of organic compounds found in tomatoes with the ability to cause corrosionin food cans. This will allow us to develop and modify existing can coating polymers to better protect these cans against corrosion. We will also initiate an investigation into the nature of the corrosions since this information will also be important in the polymer development process.

    Impacts
    What was accomplished under these goals? Since this project was initiated, work has started on identifying the different types of tomato products that are commerically on the market in food cans and documenting the ones that are most likely to induce corrosion in food cans. Testing hasalso began on the tomato variety typesthat seem to have aggressive tendancies to cause corrosionand we have recorded the volatile organic and acid compounds found in them. So far, the student has learned the technique of removing the coatingfrom previously sealed food canswithout damaging the polymer. Thishas allowed him to extract samples that could be tested with minimum errors. This is important, especially for the mechanical and physical testing of the coating samples. The student has also learned the methodology of sample preparation and the identification and quantification of volatile compoundsby the use of selected-ion flow-tube mass spectrometry (SIFT-MS). Higher molecular weight compounds were similarly tested, but using an ion chromatograph method (IC). The coatings of the retorted cans were removed and were analyzed similar to that of the tomato products. Results obtained showed that volatile sulfur containing compounds developed during the retorting of the tomatoes and penetrated and plasticized the coating of cans. This created channels for oxygen, water, organic acids and dissolved sodium salts to permeate the coating and initiate corrosion in the metal parts of the cans. The next phase of our study will focus on an understanding of the types of corrosions caused by these foods and how to prevent them with appropriate polymeric coatings.

    Publications