I have a 6 gallon aluminum pot that I wired an electrical heating element into. It appears in my first post on this blog, Homebrewing on a Potbelly Stove in 2015. I’ve used it with success to boil maple sap into syrup.
This year I went to lend it to a friend for syrup making and they expressed concern that the aluminum pot might contribute off-flavors to the final product. A quick search confirmed that indeed, this belief is widespread in maple syrup-making posts online – they say an aluminum pot is inadvisable due to the syrup’s acidity.
As a longtime beer brewer, this claim seemed questionable. Citation needed! Off I plunged into a rabbit hole. In short, here’s why I don’t think this risk can be real:
- Hundreds of thousands of homebrewers make beer in aluminum pots with no metallic off-flavors. This is a settled issue in homebrewing: back in 2007, HomeBrewTalk created an FAQ addressing concerns about the suitability of aluminum pots for homebrewing. (The HBT thread suggests boiling water in your pot to build up an oxide layer before using it for the first time. I’m not sure that’s needed).
- Brewing involves boiling wort (sweet, not-yet-fermented beer) for 60+ minutes. Wort typically has a pH around 5.0.
- Finished maple syrup has a pH around 6.0 or higher; from a little reading it seems that the less-concentrated sap likely has a similar pH. That is, maple syrup is less acidic than wort.
- It seems that cooking strongly acidic liquids like tomato sauce in an aluminum pot for a long time can give a metallic flavor to the food. I haven’t experienced this but will concede the possibility. With tomato sauce, we are talking a pH around 4.
What would be the chemical mechanism by which aluminum pots could affect the flavor of homemade maple syrup but not harm homebrewed beer?
That aluminum pots wouldn’t affect the flavor of maple syrup makes sense to me. Aluminum cookware is ubiquitous in home kitchens and restaurants around the world, but we don’t experience metallic flavors when we go out to eat.
So what gives?
I think it’s what irked me enough to write this up. When I started homebrewing around 2007, the homebrewing community was an echo chamber of canned advice. Someone would post a question on HomeBrewTalk forum and folks would respond by repeating something they’d read previously on HomeBrewTalk.
As the hobby grew, curious and scientific brewers put some common claims to the test. For instance, an early “exBEERiment” from Brulosophy tested the impact of racking a beer from a primary fermentor to a secondary vessel. This was seen as necessary practice in early homebrewing. Eventually, the community came to accept that it is fine to leave a beer on the trub for months.
It bugged me how posters in homebrewing forums would authoritatively repeat what they’d heard without ever questioning the science behind it or experimenting.
And that’s why it pains me to search up this question and see:
- Facebook and forum posts suggesting the syrup taste will be affected
- AI slop posts that repackage these concerns for clicks
- Bonus: fearmongering that cooking in aluminum pots will increase your risk of Alzheimer’s disease
The frequency with which the statements “it will make your syrup taste metallic” and “it will give you Alzheimer’s” co-occur should give one pause. The Alzheimer’s claim is unfounded: “No convincing relationship between aluminium and the development of Alzheimer’s disease has been established.”
If you are reading this because you want to boil maple sap into syrup using an aluminum pot: go for it! If the pot is brand new and you want to be extra careful, boil some water in the pot first.
If you are reading this and think I’m wrong: please describe the mechanism by which an aluminum pot could change the flavor of maple sap/syrup when it doesn’t affect more-acidic beer wort.
I would love for chemists or food scientists to chime in with some citations or explanations, one way or the other. I’m not 100% confident and am open to being proven wrong – but the evidence I can find points to aluminum pots being perfectly suitable for syrupmaking.