Use of Copper as Food Contact Surfaces for Alcoholic Beverages within Retail Food Establishments
Amanda J. Garvin, MPH-PHA, REHS, MLS(ASCP)cm
Food Safety Specialist, Michigan Department of Agriculture and Rural Development
Abstract
Copper as a food contact surface for acidic alcoholic beverages is prohibited for use according to the 2017 Food and Drug Administration (FDA) Model Food Code. However, there are two common instances where copper is used in contact with alcoholic beverages within retail food establishments. It is used for single drink mugs for alcoholic beverages such as mule cocktails, and during distillation process in food contact surfaces of a still in craft distilleries. Foodborne illness due to the use of copper in contact with alcoholic beverages is unknown. This study includes a survey of retail food safety regulators, a survey of restaurants and retail distilleries, and research on copper related illnesses through the American Association of Poison Control Centers (AAPCC). Eighty-eight responses were returned out of 573 regulator surveys distributed. Of the respondents, 36% allow copper mugs in retail food establishments for alcoholic beverages although 7% of respondents stated their law differed from the 2017 FDA Model Food Code regarding copper as a food contact surface. Of the respondents, 52% stated they inspect craft distilleries under their retail food safety program of which 58% allow copper in contact with the alcohol during distillation. Due to the constraints of a pandemic occurring, results were not obtained from restaurants or retail craft distilleries. The AAPCC returned a statement stating copper toxicity is very rare in their database therefore it would not be a helpful resource. Recommendations include more research on outbreaks, identifying safe levels of copper in liquor, and matching regulations and current allowable practices with each other.
Key words: copper, copper mugs, food contact surface, craft distillery, retail food
Use of Copper as Food Contact Surfaces for Alcoholic Beverages within Retail Food Establishments
Background
The 2017 FDA Model Food Code is guidance backed by science and available for states to adopt in part or in whole. The 2017 FDA Model Food Code does not allow copper in contact with foods with a pH below 6.0, except for the pre-fermentation and fermentation steps of beer brewing. The Food Code Annex discusses yeast for brewing. The yeast uses low levels of copper as a metabolite, which is necessary for fermentation. However, copper levels above 0.2 mg/L inhibit yeast growth, and thus incapacitate fermentation (Food Code: 2017 Recommendations of the United States Public Health Service Food and Drug Administration, 2018). Therefore, the product would be ruined which makes the problem self-limiting. Outside of the use of copper surfaces during fermentation, 2017 FDA Model Food Code prohibits the use of copper for distilling and serving alcoholic beverages. Copper mugs for use to serve alcoholic beverages, such as mule cocktails, was addressed at the Conference for Food Protection (CFP) in 2018, issue 2018 III-030 (Conference for Food Protection, 2018). One example of a mule cocktail is a Moscow Mule which traditionally contains vodka (pH 4.0), ginger beer (pH 4.0), and lime (pH 2.0); both vodka and ginger beer are either distilled or fermented in copper and have a pH below 6.0.
Copperware is desirable as a food contact surface due to the thermal conductivity, aesthetic appearance, antimicrobial properties, and enhancement of flavor (Koontz et al., 2020). In the case of mule cocktails the copper is believed to change the flavor of the beverage as people drink it. The importance of copper in distilling liquors such as scotch whisky, cognac, Irish whisky (Garnham, 2018), other grain whisky, vodka, and gin, (Notman, 2017) has long been established. Distillation using copper has an important effect on whisky aroma. Copper reduces sulfur aromas due to the removal of dimethyl trisulfide (DMTS) and other yet unknown compounds (Harrison et al., 2011). Copper also is critical to the production of fine brandy as it is a required catalyst for the complex flavor and browning of brandy (Garnham, 2018). Copper levels in liquor are related to liquor type, manufacturing process, soil type, and agricultural practices (Navarro-Alarcon et al., 2007).
Copper became popular to use in stills in Britain and France once metallurgy improved, probably around the fifteenth century, and continues to be used today (Strengell, 2014). The still is made up of four distinct parts, any or all of which may be made of copper: the pot, distillation column, lyne arm, and condenser (Gurstelle, 2020). The first distillation takes approximately four to seven hours at 173oF, which is the evaporation point of ethanol. The second distillation typically takes eight hours at approximately 158oF (Luening, 2020). The first portion distilled off, otherwise called the foreshot, and the last portion, called the tail, are discarded. The middle portion, or heart, is kept making the finished product. During this process, most of the copper becomes copper salts and is removed, though some copper, in the soluble form, does remain (Professor, 2016). One study by Carreon-Alvarez et al. (2008) found 7 mg/L of copper on average in tequila. Another study by Carreon-Alvarez et al. (2008) found mean copper levels in the following beverages: whisky contained 1.01 mg/L, rum contained 2.34 mg/L, brandy contained 8.01 mg/L, and beer contained 0.40 mg/L. The levels of copper in the aforementioned beverages raises the question of what is a “safe” copper level in alcohol?
Although copper is essential for life, too much is harmful especially for people who have certain childhood diseases, or an adult disease called Wilson disease (National Research Council, 2000). Copper release increases with a lower pH and/or higher temperatures (Koontz et al., 2020) which is why there is concern that drinking a beverage of a pH below 6.0, although served with ice or cold, may cause copper toxicity. The U.S. Environmental Protection Agency (EPA) maximum contaminant level goal (MCLG) for drinking water is 1.3 mg/L copper (National Research Council, 2000), whereas the World Health Organization (WHO) and Health Canada recommend a limit of 2.0 mg/L (Koontz et al., 2020).
One published study showed that gastrointestinal effects occurred following acute exposure at and above 3 mg/L which were mild, non-life-threatening effects to humans. Data from another study of 60 participants found 3.0 mg/L caused a 12% increase in minor gastrointestinal symptoms over control participants (National Research Council, 2000). High oral intake of copper salts may be toxic, however, since their effect is emetic, the body has difficulty retaining enough copper to produce fatal results. Intake of up to 0.5 mg/kg body weight/day, and an occasional intake of up to 10 mg/day, are considered safe for adults (Reilly, 2002). The effects of copper as a cause for renal failure have been observed with chronic exposure in sensitive populations. Sensitive populations include those with Wilson disease, heterozygote carriers to the gene for Wilson disease, and several other childhood diseases. Since this research examines consumption of alcoholic beverages in the United States, which has a legal drinking age of 21, this research only addresses Wilson disease (estimated 9,000 cases in the U.S.) and heterozygote carriers of Wilson disease as they are the only diseases noted that affect adults (National Organization for Rare Disorders, 2018).
The only instances of acute copper toxicosis associated with food or beverages found during the research were a possible exposure to a cocktail shaker contaminated with copper, faulty check valves on vending machines causing carbon dioxide backflow, beverages contaminated with copper over 30 mg/L with etiology unlisted, increased copper level in tap water, and soft drinks causing illnesses (National Organization for Rare Disorders, 2018). Since 1950, there were also two instances of copper poisoning which were due to the acidic beverage sitting in a copper carafe overnight (National Organization for Rare Disorders, 2018).
Liquor for alcoholic beverages generally has an acidity level below 6.0 pH which is below the allowable level in the 2017 FDA Model Food Code for copper in contact with food. Copper is a very desirable surface for use in single beverage immediate service cups and when distilling liquors due to its ability to change flavor profiles and its thermal conductivity. Due to this, copper has been used in the making of stills for centuries. During distillation, copper may be in contact with the liquor for periods of 12 hours or more at extremely high temperatures. Higher temperatures have been known to leach out copper more quickly than lower temperatures. The copper levels that are appropriately set for drinking water may not be applicable to alcoholic beverages since the diseases associated with elevated copper levels are mostly childhood diseases. Lastly, the historical associations with copper poisoning seem to be reported from carbonators, soft drinks, drinking water, and the use of copper for storing.
Problem Statement
The risk of using copper as a surface in contact with alcoholic beverages by industry in retail food establishments is unknown.
Research Questions
1. How commonly is copper used in contact with alcoholic beverages by industry?
2. How do Local, Tribal, and State regulations differ from the 2017 FDA Model Food Code regarding allowing the use of copper in contact with alcoholic beverages?
3. How many foodborne illness outbreaks, associated with the use of copper as a food contact surface are known to have occurred?
Methodology
The target population included regulators and operators of retail establishments that serve alcoholic beverages which may use copper either as a serving mug or as part of the distillation process.
There were three methods of data collection. First, a survey was sent to Association of Food and Drug Officials (AFDO) retail regulatory officials listed on “AFDO’s Directory of State and Local Officials,” CFP retail regulatory members through the CFP Membership List as of September 19, 2020, and FDA state, local, and tribal inspection training officers of each state from the “State, Local, Tribal and Federal Inspection/Training Officers Certified by the FDA” list. The survey asked each respondent how their respective state or local regulators handle copper as a food contact surface to alcoholic beverages. The results were then assessed against the 2017 FDA Model Food Code, including both copper mugs and distilleries which use copper as part of the distillation process.
Second, the Manager of Program Compliance with the National Restaurant Association (NRA) was asked to send a survey to its retail food establishment members and contacts. The survey asked if NRA contacts use copper mugs or copper as a food contact surface within their distillery or food establishment.
Finally, data was collected from illnesses related to copper which were reported to the American Association of Poison Control Centers (AAPCC) and available on the National Poison Data System (NPDS) to see if copper as a food contact surface for alcoholic beverages could be associated with any illness.
Results
The retail regulator survey was sent to a total of 573 contacts. Eighty-eight respondents returned the survey, covering 36 states. Eighty-three of the surveys were counted, as five respondents stated they did not regulate retail establishments. Table 1 shows the breakdown of agency type and how many of them follow some version of the FDA Food Code. As Table 1 shows, 96% of respondents stated they follow a version of the FDA Food Code, but 36% of respondents do allow copper mugs in retail establishments for service only. Of the respondents, 7% stated their law differed from the 2017 FDA Model Food Code regarding copper as a food contact surface. Also, six jurisdictions allow variances to their regulations for the use of copper mugs and eleven other jurisdictions would be open to variances if retail establishments submitted a request for variance and had sound science to back up their request.
Table 1
Results of Regulatory Authority Survey: Type of Agency Respondent, Authority to Regulate Retail, and Regulation Based on FDA Food Code
Regulators were asked if they inspected craft distilleries under their retail food safety program, to which 52% responded affirmatively. Of those respondents, 58% allow copper in contact with alcohol during distillation. Graph 1 breaks down the responses of those which allow copper as part of the distillation process that operate under retail regulations.
Graph 1
Jurisdiction Allows Copper as Part of the Distillation Process Under Retail
Finally, retail regulators were asked if they had any additional comments or other food contact surfaces of concern. The main comments concerned a lack of guidance regarding copper mugs and admissions that some regulators never previously looked for copper in contact with alcohol during distillation or service.
The NRA was asked to send a survey to its retail food establishment members and contacts in December 2020. Unfortunately, due to the constraints of a pandemic occurring, the survey was not disseminated. NRA indicated that they would be willing to distribute the survey once retail food establishments were not under the burden of the pandemic.
Data was collected on illnesses related to copper which were reported to AAPCC and on the NPDS to see if copper as a food contact surface for alcoholic beverages could be associated with illness. The AAPCC returned an email stating “according to a senior member of the AAPCC, in their opinion, copper toxicity in general is very rare in the NPDS data”; therefore, they believed what little data they did have on copper toxicity would not be helpful.
Table 2 below is data pulled from the AAPCC Annual Reports, Table 22A (Demographic profile of SINGLE SUBSTANCE Non-pharmaceuticals exposure cases by generic category). The data shows there are less than 700 reported copper exposures per year for every year of the annual report that could be obtained. Also, of the fewer than 700 cases per year, only a portion of those were in adults that would be within or possibly within the legal drinking age. The exposures at age 20 or older varied from 38% in 2012 of the total number of cases to 50% in 2017. The cases of copper exposure in the AAPCC Annual Report are not specific to ingestion but cover any type of possible copper toxicity exposure. Also of note is the low number of injuries including deaths related to copper poisonings.
Table 2
Demographic profile of copper exposure cases by generic category
Conclusions
During analysis of the data, several conclusions may be determined which represent the key findings of the research:
1. Over one-third of regulators surveyed allow the use of copper mugs and over one-half allow copper as a food contact in distilleries for alcoholic beverages. Many are not enforcing the existing regulations which would not allow the use of copper in contact with alcoholic beverages due to the high acidity level of alcoholic beverages.
2. There is a high consistency of regulatory adoption to prevent copper in contact with acidic beverages, but there does not appear to be consistency between jurisdictions in how they enforce their own regulations, or in how variances are used when allowing for copper food contact surfaces in distilleries or copper mugs for use with alcoholic beverages.
3. Questions remain as to how often foodborne illnesses may occur due to copper ingestion. It is unclear if copper, as a cause for foodborne illness, appears to have minimal risk, if there is a lack of data collection for copper due to ingestion, or if the use of regulations to restrict copper as a food contact surface are important in preventing foodborne illness.
Recommendations
Based on the data collected and the conclusion formulated, the following are the recommendations:
1. Toxicity from copper in contact with alcoholic beverages appears to be a candidate for a thorough risk analysis, including a risk assessment for more scientific data, risk management to harmonize results with necessary regulatory interventions, and risk communication to provide the industry, regulators, and consumers with science-based information to make decisions on the safety of copper as a food contact surface.
2. With the increased popularity of mule cocktails, studies should be conducted to determine a safe level of copper in alcoholic beverages or a maximum safe time an alcoholic beverage may be in contact with copper. This information would be helpful for regulatory agencies to either change their existing regulations and practices, or to safely create a variance template for copper in contact with alcoholic beverages and distillation of liquors.
3. More research needs to be conducted on the low incidence of copper poisonings to see if the low incidence is due to a minimal risk of copper in contact with alcoholic beverages, if there is a lack of data collection for copper due to ingestion, or if the use of regulations to restrict copper as a food contact surface are important in preventing foodborne illness.
Acknowledgments
Throughout the writing of this research project, I have received a great deal of support and assistance. I would first like to thank my supervisor, Sean Dunleavy, and the Michigan Department of Agriculture and Rural Development for the continued support throughout the life of this project. I also would like to acknowledge my coworkers, Becky Vought, Shane Green, Rodney Blanchard, and Steve Czarnecki, and my mentor, Doug Saunders, whose expertise was invaluable in formulating the research questions and methodology. Your insightful feedback pushed me to sharpen my thinking and brought my work to a higher level. A huge thank you to the International Food Protection Training Institute (IFPTI) team and the Cohort IX Fellows. Finally, thank you to the survey respondents who provided such valuable information for this project and the past IFPTI Fellows who contacted me with support.
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Author Note
Amanda Garvin, Food Safety Specialist
Michigan Department of Agriculture and Rural Development (MDARD)
This research was conducted as part of the International Food Protection Training Institute’s Fellowship in Food Protection, Cohort IX
Correspondence concerning this article should be addressed to:
Amanda Garvin, MDARD, 334 66th St, South Haven, MI 49090
garvina1@michigan.gov
*Funding for this statement, publication, press release, etc., was made possible, in part, by the Food and Drug Administration through grant 5U18FD005964 and the Association of Food and Drug Officials. Views expressed in written materials or publications and by speakers and moderators do not necessarily reflect the official policies of the Department of Health and Human Services; nor does any mention of trade names, commercial practices, or organization imply endorsement by the United States Government.