Kombucha is fermented tea. Tea and sugar are fermented using a SCOBY (Symbiotic Culture of Bacteria and Yeast) for a period of time to achieve a tangy, naturally effervescent beverage with a host of health properties. Like all fermented foods, Kombucha also produces trace amounts of alcohol from .1-2% ABV depending on several factors such as fermentation time, temperature, flavorings added, and the like.
Alcoholic Beverages Defined
According to Title 27 United States Code Chapter 8 – Federal Alcohol Administration Act Section 214, “The term “alcoholic beverage” includes any beverage in liquid form which contains not less than one-half of one percent of alcohol by volume and is intended for human consumption.” Since Kombucha may contain more than .5% alcohol by volume (ABV), some Kombucha breweries have elected to brew their Kombucha under a state beer or wine license – the designation of which varies by location. Many have chosen to tightly control their production processes to remain non-alcoholic beverages. Others are producing offerings in both categories.
Current Alcohol Testing Methods
The current methods for testing the alcohol levels in Kombucha are borrowed and adapted from the beer and wine industries, ferments that have been intensively studied for hundreds of years and offered commercially for thousands. The tools used for testing alcohol work very well with those ferments.The hydrometer was invented by the female mathematician Hypatia in the 5th Century BC, and measures the specific gravity, or density, of a liquid (how much solid is dissolved in the liquid to be exact). This is helpful in determining the creaminess of milk, for example, or more relatedly in this case, the alcohol content of beer and wine, based on different scales that have been created for each specific substance.
Hydrometers are by no means exact in their measurements, however. The potential alcohol reading they provide is determined by applying a mathematical formula to specific gravity measurements taken prior to and directly following fermentation, which gives an estimate of the conversion of denser sugar into lighter alcohol. Applying the currently available scales for wine and beer to Kombucha tests using this tool leads to inaccurate readings unless additional computations are taken, for reasons we will cover below.
Another common tool used in the wine and beer industry is the refractometer, which can be digital or analog, and measures the angle of refraction of light when passed through the solution. That light reading is translated to sugar content via the Brix scale, which has an equivalent in terms of specific gravity. Like the hydrometer, the Brix is then measured pre and post fermentation and the rate of change determines the potential alcohol content present.
Both of these are inexpensive and easy to use pieces of equipment and every Kombucha brewer could benefit from the approximate alcohol readings they can provide for in house testing and quality control. The first problem with them is that due to the very low alcohol limits, our industry requires finer controls and testing results to ensure compliance, and these tools are not intended to be finely attenuated enough, even if Kombucha specific scales are produced, to provide our members with confidence that their product will be in compliance.
Anton Paar – Near Infared Technology
One of the testing mechanisms that gained favor following the temporary withdrawal of 2010 is the Alcolyzer Beer Analyzing System manufactured by Anton Paar, a world leader in analyzing equipment. The Alcolyzer relies on Near Infrared Technology (NIR), another testing protocol that is not currently approved by the TTB as an officially acceptable method.
NIR uses light waves at a known oscillation to pass through a particular substance. When it passes through at a specific frequency, it bounces back wavelengths that correspond to levels of potential alcohol. While this technology has been shown to be accurate for higher alcohol concentration products such as wine and beer, the amount of dissolved solids and the low amount of ethanol in Kombucha complicates the reading and often leads to higher readings than what is actually present.
This topic is addressed in their patent; here is an excerpt.
“The spectroscopic determination of low alcohol concentrations, particularly ethanol, in liquid probes is widespread. With so-called near-infrared-spectroscopy (NIR), it is possible to qualitatively and/or quantitatively determine a variety of parameters. NIR-spectroscopy typically takes place in a wave length range of between about 700 nm to about 2500 nm. Superimposed or combination oscillations, rather than base oscillations, are normally measured. In this wavelength range, however, the absorption capacities of the substances under investigation [i.e. ethanol] are relatively low, and the absorption bands are wider and frequently overlap or are superimposed. This complicates the interpretation of the measurements and can even prevent one from obtaining unambiguous and reproducible measurements. Yet, the increasing demand and opportunities for spectroscopic analysis in this wavelength range and the availability of inexpensive components, such as fiberoptics, semiconductor detectors and new light sources, create a need for the fast and quick analysis of probes by means of NIR-spectroscopy with the help of simple instruments.”
The Board engaged in numerous conversations with Anton Paar sales representatives to gain a clearer understanding of their machine and how it works. They estimate the margin of error for Kombucha to be +/- .02% ABV (two hundreths) which would indicate a high level of accuracy and one that would serve the Kombucha industry’s needs. However, this level of accuracy is not what others have experienced when comparing GC test results with AP results. One company reported about a tenth of a percent difference between the two with AP skewing higher. Yet another company requested that AP test a variety of substances with the machine, including sugar water. Every result indicated the presence of alcohol, even where none could be present. When pressed, one Anton Paar sales representative did concede that the error of margin may be more like +/- 1% ABV, an error rate that would make the results questionable for any Kombucha test. With the legal ABV limit for non-alcoholic beverages set at .5%, a plus or minus of 1% is the difference between compliance and being in violation.
Kombucha is a newer industry and Anton Paar may see an opportunity here to develop equipment that is Kombucha specific. How long or when they start the process remains to be seen and KBI has already offered to supply samples whenever they decide to engage in that process in Austria, where the company is headquartered.
Kombucha-Specific Issues with Available Alcohol Testing Tools
The other and more pressing issue is that none of these tools are capable at this time to successfully interpret potential alcohol levels of Kombucha due to the important role bacteria plays in Kombucha fermentation.
Unlike beer and wine, where in most cases yeast are doing the fermenting, Kombucha fermentation is two-fold. First, the yeast convert sugar into ethanol and carbon dioxide. Then the bacteria feed on the ethanol, converting it to healthy organic acids. These acids can have a similar lightness as alcohol, thus confounding the readings of “yeast only” attenuated equipment.
Moreover, traditionally fermented Kombucha is self-limiting in terms of the amount of alcohol it can create to about 2% ABV. This number is similar to other traditional herbal ferments known as small beers i.e. root beer, ginger ale, and water kefir, to name a few. This category may be thought of as “healthy, low alcohol” and many countries considered peers of the United States have alcohol laws that reflect a higher tolerance for beverages in this low range, due to their lack of intoxicating properties.
Hybrid Kombucha beers require other types of yeast that yield higher alcohol levels in order to meet the alcohol standards for those products (4-14% ABV).
Traditional raw Kombuchas, which dominate the market, also contain more particulate than most beers and wines, which tend to be pasteurized and filtered, potentially confounding readings by causing light waves to refract incorrectly or shifting the gravity of the brew. With so many pitfalls, the commercial Kombucha brewer is left wondering what type of testing protocol will accurately detect the lower levels of alcohol present.
Testing of Kombucha tea for alcohol levels for brands sold as non-alcoholic beverages is crucial for quality control and compliance. Any testing method with a variance of +/- 1% can mean a violation of labeling laws and trouble with state inspectors.
One example of the potentially devastating results of not creating accurate, consistent testing methods is the voluntary withdrawal of all Kombucha brands off the shelves of Whole Foods and other stores in 2010.
As a result of that action taken by Whole Foods, the Kombucha industry lost millions of dollars in product and continues to spend that much and more to reformulate products, change labels, and institute tighter alcohol monitoring protocols. KBI is working with all of its members to prevent future incidences of non-compliance from occurring.
Headspace Gas Chromatography
So what methods are available to the commercial Kombucha brewer to confirm that their product is in compliance? According to the TTB (Alcohol and Tobacco Tax Trade Bureau), there are 3 acceptable methods of measuring ethanol content in alcoholic beverages: distillation, densitometry and gas chromatography. Headspace Gas Chromatography is the methodology used in the law enforcement field to determine blood alcohol levels as low as .01%, accuracy required for forensics that makes it the preferred choice for the regulatory agency.
In Headspace Gas Chromatography, the headspace (air volume) of a pure product creates an equilibirum when pressure is applied. Only a minute amount of sample, a tenth of a gram, is required to obtain test results. The sample is pressurized with helium then purged to remove all other volatile substances from the sample and captures them on a trap made of carbonaceous material. The trap is then desorbed or heated rapidly onto a Gas Chromatograph and then mass spectrometry is used to detect the alcohol level. This method eliminates suspended and dissolved solids and removes any enzymes and bacteria that might interfere with the ‘gravity’ of the sample.
Mass Spectrometry utilizes a fingerprint of known origin by establishing a calibration curve (5 point) using ethanol in water. A long established sound scientific technique, this process produces results with 99% confidence level.
The difficulty for the Kombucha brewer is that GC requires trained technicians in order to obtain accurate results. The sample must be handled according to strict protocols to prevent any contamination from creating misreadings. As such, samples must be sent to a lab in order to determine accurate alcohol levels which can be costly and time consuming.
Even when submitted to a lab, various techniques for preparing the sample may cause issues when working with Kombucha, and technicians not specifically experienced with Kombucha have been known to inadvertently introduce error.
KBI Recommendations for Alcohol Testing
The KBI Board of Directors current recommendation is that those seeking alcohol testing to demonstrate compliance utilize Headspace Gas Chromatography combined with Mass Spectrometry from third party lab for official alcohol testing. When selecting a lab, question them thoroughly to gain an understanding of how the sample is handled to ensure the highest quality results. Providing the lab with the handling protocol linked above and insisting on higher level technicians completing the test are also recommended steps to ensure accuracy. The Board agrees that the Anton Paar Alcolyzer Beer Analyzing System, hydrometer and refractometer can provide data for in-house tracking with the caveat that there is a significant margin of error that must be taken into account.
AOAC & KBI – Working Together to Create a New Standard for Testing Ethanol in Kombucha
KBI is working with AOAC to establish a new testing method for the low levels of ethanol present in Kombucha. Here are some of the updates on that process.
These recommendations are subject to change pending new information or technological developments. Updated June 1, 2016