Guest Posting: Kombucha In Aluminium Cans Time Bomb Is Ticking. Industry Must Act, by Gary Leigh
This article is re-posted from the GO Kombucha blog, February 28, 2025. It follows on from another post by Gary on The Risks of Packaging Kombucha in Aluminium Cans (February 3, 2024). On February 4, 2024 we posted The Case for Cans featuring a reprint of an article from the Fall 2021 edition of SYMBIOSIS Magazine, listing a few of the many brands who have chosen to sell canned kombucha. Over the past year we have added to that content with a total (to date) of 22 Comments detailing the reasons many brands have chosen cans over glass bottles. We are interested in hearing the views of other companies that sell their kombucha in cans and encourage them to post comments (below) or submit a Guest Posting explaining their position.
Lactic And Acetic Acids In Sour Beer Promote Corrosion During Aluminium Beverage Can Storage is the alarming heading of a landmark study into the corrosive effect of volatile, bacterially active soda beer in aluminium cans, published in October 2024.
The study is funded by the US Brewers Association and the USDA National Institute of Food and Agriculture as “a step towards evidence-based determination of factors causing corrosion in other canned beverages with high levels of volatile organic acids”, like kombucha.
Its findings are consistent with the following:
- Active organic acids in plastic and epoxy resin-lined aluminium cans are far more corrosive than sodas and colas.
- The dominant acid in kombucha, acetic acid, is more corrosive than lactic acid, the main acid found in sour beer.
- Heat-treating kombucha in sealed cans or storing ambiently vastly increases the potential for aluminium contamination.
Active acids increase corrosion
Its findings will concern regular consumers of commercially produced drinks containing active organic acids packed in aluminium cans regardless of the type of inner liner – acrylic, epoxy resins or porous polymer plastic pouches – which are supposed to provide a complete barrier between the aluminium and the can’s contents.
A similar 2023 study into the corrosive effect of inert, low pH/acidic drinks like Green Coke and Red Bull found relatively small amounts of aluminium in test samples across all liner types, varying in volume depending on factors such as the number of cans consumed daily, length of time in can/sell by date and storage temperature.
In summing up, the new study — the first to be carried out on sour beer, which is similar in active microbial acidity and pH to kombucha — concluded that all can liner types failed to prevent varying amounts of aluminium corrosion and leakage, and significantly more than found in Green Cola and Red Bull in the 2023 study…
More corrosive than Coca Cola
Phosphoric acid in colas and sodas is stronger than the acetic and lactic acids found in sour beer and kombucha. It gives these popular drinks their tart flavour and sharpness while also preventing bacteria and mould growth. However, sour beer, kombucha and variants thereof contain potentially billions of active organic acid molecules per can that increase aluminium corrosion via all types of can linings compared to standard canned drinks. The level of corrosion is correlated with the concentrations of total (titratable) acidity present. pH alone was not a good predictor of can corrosion, further suggesting that organic acids (and not free protons) are involved in the corrosion of lined beverage cans.
The lower the pH and higher the total acidity (a complex correlation) in a test sample, the higher the level of corrosion was found to be, eventually placing outward pressure on the can due to active microorganisms producing CO2/gas, leading to signs of swelling – including buckling at the top and base of the can – and, potentially, explosions
Aluminium corrosion increased in all the sour beers tested in a time-dependent manner, with measurable increases in dissolved aluminium occurring in all between six to 24 weeks. After week 24, sour beer in the acrylic-lined cans made by one manufacturer had twice the amount of leeched aluminium compared to the acrylic-lined cans made by another manufacturer and the epoxy-coated cans, which performed similarly to each other.
W.H.O. recommended aluminium intake
Aluminium concentrations in one 48-week-old can were found to be as high as 58mg/L – 100-fold greater than in concentrations found in non-sour beers and far exceeding the World Health Organization (W.H.O.) recommended total weekly intake of <2mg of aluminium per kg body weight, or <150mg for a 75kg person.
[Note: 1000mg = approximately 1ml. This particular batch of sour beer was not commercially released due to its high acetic acid content].
The next highest level of aluminium was 3mg per standard-size 355ml can, around a third to almost a half the amount typically ingested via an average daily diet. To reach the total weekly intake of aluminium at that level as defined by the WHO, a 75kg person would need to consume at least 7 x 355ml cans a day.
When also factoring in aluminium intake from non-food sources such as kitchen utensils, tin foil, antacids, beer kegs, antiperspirants, toothpastes, beauty products and vaccinations as well as from the environment, the study infers that consuming several cans of sour beer daily can make a significant contribution to a person quickly reaching the W.H.O.-recommended level.
However, where canned kombucha is concerned, the potential for over-consuming aluminium is potentially significantly higher than sour beer. Excessive acetic acid is usually considered a flaw in sour beers, while it’s a defining characteristic of kombucha. Conversely, compared to standard beers, lactic acid is dominant in sour beers to provide the sour taste, with up to 7.0g/L compared to around only 0.5g/L in kombucha.
And while sour beer’s relatively high titratable acidity concentrations of around 5g/L are similar to traditional kombucha, kombucha’s pH is slightly lower likely due to the dominant acetic acid present which gives kombucha it’s bite and sharpness; 1.0 to 3.0g/L of acetic acid in kombucha compared to 0.3 to 1.4g/L found in sour beer.
Therefore, the considerably higher concentration of acetic acid in kombucha will correlate to far higher levels of aluminium leeching than the already alarming amounts this study found in sour beers.
K.B.I. responsibility/duty of care
An increasing number of kombucha brands have been packaged in cans for almost a decade. Yet none have been publicly or officially tested for consumer safety. Despite a lack of scientific evidence about aluminium toxicity and the body’s ability to flush excess aluminium, the degradation in can linings found in recent studies raises real questions for the kombucha industry.
It is now incumbent on the Kombucha Brewers (K.B.I.) trade association to pursue and assess the levels of aluminium corrosion and product contamination across the broad range of traditional kombucha and variant kombucha drinks its members produce to ensure they fall within levels that the body can manage safely.
Consumers deserve to know which level of daily consumption of traditional kombucha and its variants may cumulatively impact bone development and brain function. Medical science now points to aluminium poisoning as a key driver of Alzheimer’s, Parkinson’s and multiple sclerosis, among other progressive neurological disorders.
Notwithstanding there is still no safety standard to address explosions of kombucha packed in sealed, airtight cans and tightly sealed glass bottles. It will only take a couple more incidents of injuries sustained from ‘kombucha bombs’ to go viral on TikTok for the global tide to turn against commercial kombucha…
Recommendations for brewers
K.B.I. needs to act on those findings and recommend a course of action to both members and non-members globally to ensure consumers’ well-being is prioritised. Recommendations such as:
- Reducing product shelf-life.
- Recommending a daily can limit for consumption on every can.
- Ensuring chilled storage throughout the distribution chain.
- Sourcing manufacturers of more durable and less corrosive inner liner types.
- Ending the practise of pasteurising inside sealed cans (heat considerably exacerbates aluminium leeching).
Or, mitigate all such issues and other potential pitfalls – including contamination by microplastics and chemical residues from the liners, some of which still contain the ‘hormone disruptor’ BPA – by switching to the good old glass bottle with a pressure release cap, as used by GO Kombucha ever since we first paved the way for commercially produced kombucha in the UK in 2003.
Aside from being made from just three natural ingredients – soda ash, limestone and sand – glass is the natural environment for storing kombucha since it preserves the quality and flavour of the drink.
Industry expert Gary Spedding Ph.D warns: “More due diligence is needed!”
GO Kombucha approached the US Brewers Association and K.B.I. but neither responded to our call to action. So we approached Gary Spedding Ph.D, a leading US brewing and distilling analytical chemist and biochemist who has participated in several kombucha test protocol collaboratives and conversations, and this is what he had to say:
In my opinion kombucha has no place in cans whatsoever. Acidity at such levels is just asking for a disaster. The simple fact of the matter is these types of beverages have not been subjected to the necessary testing in cans.
Kombucha producers need education in what they are doing. Just as do craft brewers turning to commercial production. No one is even doing simple force testing of products nor getting them tested for a number of critical quality control points.
I have suggested to the industry, including K.B.I., for over a decade and a half now that product warning labels need to make it clear that this product can referment/continue fermenting and promote gas build up to explosive levels.
Acidity and pH, while related, are not the same thing in terms of the chemistry that can cause corrosion. Other metal ions and chlorides are also a concern – tea itself can be corrosive! More due diligence on testing, storage/distribution and home storage conditions for such products is needed in the industry on this very explosive topic.
I have just been helping a fellow injured in a keg explosion ten years ago, which was filled with sour beer and housed unrefrigerated in a warehouse – a potential issue with kombucha no matter how packaged.
No compensation so far from the keg company, and he has no money left to his name. He was charged $150,000 for a report by a so-called expert who did not address the corrosivity issues, or examine the remains, or perform a test set up.
Any accident or harm to a customer’s health could financially ruin and finish the business of a kombucha producer. And in the US at least, potentially some jail time.
This article is posted with the express permission of www.gokombucha.co.uk.
Disclaimer
The views and opinions expressed in this guest posting are solely those of the original authors and other contributors. These views and opinions do not necessarily represent those of this publication.
As an industry we should be focussed on building our category, supporting one another (especially during these challenging days), rather than attacking other brands. I don’t care if it’s Remedy or someone else – they’re helping to introduce people to kombucha and we (the industry) should be supporting this.
This would be a very long response if I went through everything Gary has claimed, but a few points:
The article claims kombucha’s acetic acid makes it far more corrosive than sour beer (which contains mostly lactic acid), causing “extreme” aluminium leaching. This is incorrect. Researchers have established that it’s the total amount of dissolved acid (titratable acidity) that drives corrosion risk, not just pH or any specific acid type. Further, there are many acidic beverages with a pH 2.5–3.5 which have been safely canned for decades, so kombucha is not inherently an “extreme” outlier.
The article claims “Aluminium concentrations in one 48-week-old can were found to be as high as 58mg/L – 100-fold greater than in concentrations found in non-sour beers and far exceeding the World Health Organization (W.H.O.)”. I can find no reports supporting this claim. And a minor correction – 58mg/L is equal to 20.6 mg of aluminium in a single (350ml) can, which is actually 10 times what might be found in a normal acidic drink – not 100-fold.
Next. There is no scientific evidence that aluminum leaching leads to diseases like Alzheimer’s. This claim is not grounded in evidence – hypotheses about aluminum causing problems are based on much higher exposure scenarios (e.g. occupational exposure), or outdated studies on patients with kidney failure using aluminum-containing medicines.
Next. There have been multiple studies measuring how much aluminum actually migrates into acidic beverages from cans, and the consensus is that the amounts are very small. One comprehensive test found that even after 12 months in the can, the aluminum in soft drinks (with pH as low as 2.5) contributed at most an estimated 0.8 mg of aluminum per day to the consumer. This is practically negligible – it’s a tiny fraction of what an average person gets from other daily sources of aluminum (our normal diet, which includes aluminum naturally present in foods or added via processing, contributes around 5–10 mg of Aluminium per day). Toxicologists also note, that only a small percentage of ingested aluminum is actually absorbed by the human gut, as much of it passes through.
Further, regulatory authorities have set safe intake limits for aluminum to ensure public health. The World Health Organisation’s provisional tolerable weekly intake is about 2 mg per kg body weight (roughly 150 mg per week for an adult). In the context of beverages: a person would have to chronically consume extremely large quantities of canned kombucha to approach that limit. Even the sour beer study (which the article references) found typical aluminum levels on the order of a few milligrams per can at most, meaning you’d need to drink in the order of a half-dozen very acidic cans every single day to come anywhere near the safe intake threshold.
If I was drinking that many acidic drinks per day – I’d be worried about the damage the acids were doing to my teeth, rather than aluminium leaching.
Even the final claim in the article “glass is the natural environment for storing kombucha since it preserves the quality and flavour of the drink” is patently false.
– Cans have a lower Lifecycle Carbon Footprint.
– Cans have a lower transport emissions footprint.
– Cans have lower Carbon Emissions.
– Cans can be infinitely recycled.
– Cans are 100% light-proof, which prevents degradation of sensitive compounds in kombucha (ginger, turmeric, and other herbs are light sensitive).
– Glass bottles have a higher oxygen exposure risk. This oxygen exposure leads to oxidation, which causes flavour degradation (vinegary or stale taste), a loss of beneficial compounds (like polyphenols and vitamins), and potential overgrowth of unwanted bacteria or yeasts.
Finally, coca cola has a pH of around 2.5. It’s been in cans for well over 50 years without corrosion problems. So, this article is little more than scare mongering, more so than a ticking time bomb.
Now, can we all get back to growing awareness of kombucha and less beating up on kombucha brands who do things differently.
Here are a couple of scientific studies:
– https://pubmed.ncbi.nlm.nih.gov/8197828/#:~:text=of%20dissolution%20of%20Al%20from,toxicity%20for%20the%20human%20body
– https://health.ec.europa.eu/system/files/2018-03/scheer_o_009_0.pdf#:~:text=Experimental%20data%20indicate%20that%20oral,is%20contained%20in%20food
I’m not trying to push cans, but I see so many false and irresponsible claims thrown out. The study is about sour beer, and an actual reading of each portion of the study yields more and more issues with the study and differences to kombucha.
The study starts with two confounding variables, one being the immense outlier of the “#9” product deemed not fit for sale, skewing all of the graphs and data for the commercially available section. Producing the “scary” numbers all on its own, while not even being considered viable for consumption. The second being that most of them contained sulfites and that, per the study: “the component that was best correlated with dissolved aluminum was molecular SO2”. After separating all of the samples containing sulfites, we’re left with only two different TA/Ph ranges, and the study shows one combination within the safe/no corrosion range and the other still around 1.75 (low) BUT with a TA of 16.3 (mostly lactic). My kombucha that I recently sent in for testing had a TA of 3.5). Which brings me to the next point.
The study says that their TA and Ph correlated with corrosion BUT 1) they couldn’t separate the two factors so they can’t definitively tell which one (or both) it is, but brewed acids often have a Ph buffer 2) majority of these samples are STILL below .5 until at least 8 g/l TA. 3) we see in these graphs that AcrylicA is actually performing substantially worse than BPANI. 4) these samples are not brewed and therefore may contain different portions of dissociated acids. 5) But most important is that all of the data points going above .5 in BPANI cans here are going above 8 TA of specific acid concentrations, and we aren’t given data on which are the ones being more corrosive, as well as which might contain sulfites.
They also finish by stating their study had limitations including NOT testing impact of can storage, important, as heat is conductive to corrosiveness and kombucha is stored refrigerated, while these were stored room temperature.
So, all this in mind, if you plotted my kombucha, for example, on their graph by matching its similar statistics and the can I’ve used, it would come in at <0.5. Kombucha does not contain Sulfites, the most correlated component. Kombucha is not predominantly lactic acid (a physically more corrosive acid in other applications). Most kombucha has a lower TA. Every can manufacturer I’ve reached out to is using BPANI2. Raw Kombucha is stored refrigerated. Every leading factor is different. This is not how science works.
Of note, kombucha brewers can control their PH, and is usually the way they gauge fermentation. So in theory a PH adjusted brew (less acidic starter) buffered in time with no sulfites (never seen Sulphites in kombucha) would come in below .5 (their threshold for no/negligible corrosion) according to their plot points. Kombucha brewers could pivot and possibly prevent the issue altogether.
I’m not saying cans are amazing. Local and aged kombucha is still best done in kegs and bottles, and that’s how I’ll do them. But for short term shipping and small businesses in particular, cans are economical and ecological. Scare tactics and distantly related studies won’t help grow our industry. I would LOVE studies on kombucha and cans and I would love for better liners to be produced. This isn’t even touching on the possibility of the liner leaching, which I would see as a bigger issue. But again, microplastics and aluminum are in all parts of our diet. It is a systemic issue, and we shouldn't be getting down on kombucha businesses over false claims. Would you rather them drink coke? Start studies for our industry, yes! But until then it’s safe to say this study does not apply. I will gladly send in my product for corrosion testing where I find it available and report back.