Kombucha with a kick: Ethanol content in retail brews
Kombucha is a fermented beverage that is produced by incubating sweetened tea and other flavorings with a symbiotic culture of bacteria and yeast (or “SCOBY”). During the fermentation process, yeasts convert sugar to glucose and fructose, and then into ethanol and carbon dioxide, at which point the bacteria oxidize the ethanol to acetic acid. After approximately 14 days, this process produces a beverage that is fizzy, slightly sweet, and acidic, but typically with very little residual alcohol (<1%). As a non-alcoholic beverage, kombucha is widely available in retail stores, restaurants, farmers’ markets, and other settings.
Living cultures with a little extra zing
Consumers are drawn to kombucha because it is a “raw” product containing living microorganisms, which are believed to promote gut health and provide other health benefits. However, the presence of a living culture within the finished product creates the potential for ethanol production even after the product has been bottled. In fact, kombucha tea that is not subject to additional processing or that is not kept refrigerated can show increases in alcohol content that exceed legal thresholds for alcoholic beverages. Although there are a number of ways to halt or slow these processes, including pasteurization and microfiltration, many of the techniques available kill off or reduce those highly desirable living cultures.
How common is elevated alcohol content?
A recent BCCDC report found that 32% of 684 kombucha products collected and tested in BC contained more than 1% alcohol by volume (ABV), the legal threshold for an alcoholic beverage. The highest alcohol content exceeded 3% ABV. Interestingly, a greater proportion of BC producers (over 70%) had potential or definite problems with alcohol content in their products, whereas only 33% of non-BC producers were flagged. The causes of alcohol exceedances are difficult to pinpoint, but the study noted that temperature abuse (lack of refrigeration) through manufacturing and distribution appears to be an important factor.
Why does it matter?
A small or occasional increase in the alcohol content of one’s favorite kombucha beverage may not be a concern for most adult consumers. However, there are a number of personal, medical, religious or other reasons why a person might wish to avoid or abstain from consuming any amount of alcohol. As identified by the BCCDC report, people who are pregnant or are trying to get pregnant should avoid kombucha products, as there is no safe threshold for alcohol consumption during gestation.
Similarly, parents who may wish to serve kombucha to their children as a substitute for sugary drinks should be aware that even very low amounts of alcohol could be harmful to children, with the greatest harm posed to the smallest children due to their underdeveloped livers and lack of liver enzymes. A risk assessment, presented within the BCCDC report, demonstrates how a small child (10 kg or less) could be at risk of serious harm after consuming only 150 mL of kombucha tea with 2.5% ABV. Parents should be particularly cautious of home brews, which are not subject to the same standardized process controls as commercial producers, and are thus at greatest risk of unpredictable alcohol levels.
What can be done to help processors and home brewers alike?
Food safety professionals can help processors and consumers alike to create a safer kombucha tea product. Some of the recommendations for processors highlighted by the report include:
- Encouraging processors to include alcohol as a hazard in their food safety plan.
- Educating processors and retailers on temperature control, especially in atypical retail environments, like gyms and farmers markets, where temperature abuse might be more common.
- Improving labeling practices to ensure that the need for refrigeration is clearly indicated and that the container includes a clearly printed best before date and manufacturer information.
- Encouraging kombucha processors to use precautionary labeling statements regarding alcohol content, such as “This product may contain alcohol.”
- Processors can reduce alcohol content by slowing or limiting yeast growth by removing them through microfiltration; applying low heat; non-heat distillation; increasing the surface area for fermentation; pasteurization; adding antifungal preservatives, and sourcing yeasts that do not grow at low temperatures.
- Processors should also analyze and document alcohol and pH levels during fermentation, at the time of bottling and until the end of its shelf, to understand whether and when alcohol limits might be exceeded.
The BCCDC report also provides some useful tips for consumers and home brewers:
- Kombucha teas need to be kept refrigerated and consumers should avoid products where temperature control is in doubt.
- Be aware that containers under pressure may have continued to ferment and could contain more alcohol than expected.
- Home brewers can reduce the alcohol content in their kombucha by brewing at a lower temperature, making sure the brew is exposed to oxygen until fermentation is complete, filtering to remove the majority of microorganisms, and limiting flavorings or additional sources of sugar that can be converted into ethanol.
- There is no quick and easy way to test alcohol in kombucha tea (i.e., breast milk strips will not work). Home brewers should follow the advice on safe kombucha production from the BCCDC and other sources.
Kombucha teas, whether produced commercially or at home, can be safely enjoyed by most adults. However, due to the presence of a living culture, kombucha teas may contain varying levels of alcohol. Consumers deserve to know what foods contain alcohol and how much alcohol is in their food. For processors, it’s important to analyze, document, and communicate alcohol content through labeling and other means. For consumers, it’s important to be aware that alcohol may be present and to make informed decisions regarding consumption. To read the full report, including a description of the chemical analyses (alcohol content, presence of E. coli, pH, etc.) and a survey of labeling practices, please visit the BCCDC website.
If you wish to hear more about this project, please join us on September 30th, 2020, when Lorraine McIntyre (BCCDC Food Safety Specialist) will present this work at our NCCEH Environmental Health Seminar series.
Eykelbosh A. Kombucha with a kick: Ethanol content in retail brews [blog]. Vancouver, BC: National Collaborating Centre for Environmental Health; 2020 Aug 13. Available from: https://ncceh.ca/content/blog/kombucha-kick-ethanol-content-retail-brews.