Jan Krüger's blog

Creative Engineering and randomness

Making Cola

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Waste of time

I don’t even remember why I started, but I mix my own cola from first principles. It’s a fun hobby and I get to experiment with the flavour components – therefore, in theory, ending up with a cola that’s particularly close to what I like. It’s been taking a fair number of iterations, though. I’m currently on my third batch (two of 45 litres, this one is 22.5 litres). Here’s my journey, including the fine details that some other sources don’t mention. I’ll close with the recipe I used and what I’ll change in the next batch.

Sources and prior art

Here’s what I used for inspiration:

My ingredients are sourced from various German vendors:

All right, let’s get into the fun details. I’m going to skip over some of the details covered in depth in the other sources, and add my own spin and the things I’ve learned that I didn’t see mentioned anywhere else. Still, if you want to make your own cola, too, this should hopefully be detailed enough.

Towards my own recipe

First attempt

I started out trying a slightly tweaked version of Cube-Cola – the main deviations is that I used phosphoric acid instead of citric acid to get closer to the “proper” taste profile of cola. I also made my own caramel colouring because I couldn’t find a good source of the industrial double strength colouring they used. I’ll explain how in a bit.

The other huge deviation is one of the reasons I got into this whole thing: I was drinking a lot of cola and consuming a lot of sugar in the process – probably way too much sugar. However, I never really could get into the sugar-free colas being sold around here, which are typically sweetened using acesulfame potassium, aspartame and sodium cyclamate.

The two options I looked at were rebaudioside A (one of the components of stevia) and sucralose.

Going purely from price – the initial cost for the whole project is quite high, mostly due to the many different essential oils – I ended up choosing sucralose, and I’m quite happy with the result. Obviously sucralose doesn’t taste exactly like sugar, but at least it doesn’t have the typical metallic or bitter aftertaste.

So I mixed what’s mostly Cube-Cola, with those changes, guesstimating the amounts:

Since sucralose is said to be 600x sweeter than sugar, I just divided the amount of sugar for a 45 L batch by 600 and ended up with 8.5 grams.

Phosphoric acid woes

Calculating the amount of phosphoric acid took a lot more time, and I got it wrong in my first batch. I had a 85% solution of phosphoric acid, meaning that it’s 85% phosphoric acid and 15% water (100% phosphoric acid is kind of difficult to get and handle).

The Cube-Cola recipe uses 32.5 mL of citric acid for a 45 L batch, and the OpenCola recipe equates 17.5 mL citric acid with the same volume of 75% phosphoric acid, so I calculated how many grams of phosphoric acid there were in 32.5 mL:

Somehow I got some of this completely wrong and ended up with 38 mL of phosphoric acid. While it probably didn’t destroy my teeth, it did taste a fair bit too tart in the end. Whoops.

Mixing oils

Oils don’t naturally mix with water, so an important part of the process is making an emulsion from the oils. This needs an emulsifier - in the OpenCola/Cube-Cola recipes, gum arabic is dissolved in water and the oils blended into that.

The Cube-Cola folks recommend using a whisk attached to a power drill to really mix up the emulsion, but that seemed unnecessarily complicated. I tried getting a dedicated stirrer but the best I could get was a wimpy little battery-driven hand-held milk frother - which kind of worked okay, but it took quite some time. I added a very small amount of vodka to help stabilize the emulsion (many oils dissolve in alcohol), which I think helped the process along a lot.

Making caramel colouring

Caramel colouring is basically a solution of very strongly caramelized sugar in water. The extreme caramelization turns it a very dark brown and it stops tasting sweet - instead you get a bitter flavour and a rather different smell.

Warning: caramel gets very, very hot – way hotter than boiling water – and can cause terrible burns. You don’t want it on your hands, and you want it in your face even less. Be very, very careful.

The process is not difficult – aside from the risk of serious injury:

Adding the other ingredients

To the oil mixtures, I added (in this order – you don’t want to add the acid first and the water later, it can splash and ruin things, including your eyes):

I ended up with a jar of concentrate and all I needed to do to get a 1.5 L bottle of cola is add one teaspoon (plus a little bit) to a bottle of carbonated water. This first 45 L batch lasted me a few weeks.

The result

Aside from being way too tart, there were a few more issues:

After toiling to consume all of that concentrate, I got ready to make the second batch…

Second attempt

I made these changes:

I also added a bit of vanillin, inspired by the Pemberton recipe. Vanillin is the primary flavour component of vanilla – all the other flavours are missing, so the taste is a lot less complex, but it’s also really cheap and ridiculously strong.

To estimate how much I needed, I consulted a number of sources regarding how much vanillin was contained in typical vanilla extracts, and settled on adding 0.33 grams of vanillin per 45 L batch. This works fairly well.

Finally, I added a few new flavour oils that I thought might complement the taste, notably grapefruit oil and clove oil.

This time, I gave up on the milk frother and got myself a cheapish magnetic stirrer - which is basically a plate you put a container on, and a small magnetic stir bar (coated in PTFE) in the container, and the plate rotates the bar using the magic of magnetism.

I got mixed results (har har) out of this. The bulk of the emulsion settled faster, but it seemed like the stirring process tended to push the oil to the sides of the container, so in the end I had to do a lot of fiddling to get everything caught up in the mix.

The result was quite promising, though this time it wasn’t tart enough due to the low amount of phosphoric acid, and that made it taste rather too sweet and fruity. Specifically:

Third attempt and notes on future changes

I’m getting there! To make this easier to follow, this is the full recipe and guide.

I made an important change to the mixing process: this time I used a double-whisk hand mixer with just one of the whisks installed. This made the emulsion happen a lot faster. Also, I believe it makes for a superior emulsion, as explained by “Blasted Bill Putt” in his Open Soda videos: due to all the shearing forces with the whisk hitting the sides and bottom of the container, the individual oil drops get “cut” a lot more often, resulting in smaller drops (we’re talking about microscopic drops here), which is what a successful emulsion is all about.

This batch also introduces more flavour components, inspired by the list of ingredients on “Red Bull Cola” (available in parts of Europe) which is a rather opinionated take on cola. Here’s what showed up for the first time in this batch:

The recipe (without the changes, see next section!)

Warning: when I say glass, I mean glass (a ceramic mug will do, too, but don’t use plastic – gum arabic sticks to it like mad and oils can dissolve it).

Done! A 1.5 L bottle of carbonated water needs about two teaspoons of concentrate, or roughly 6 mL of concentrate per litre.

Warning: the concentrate is still quite acidic, avoid spills and wash it off generously if comes into contact with anything. Keep face away from any potential splashes.

First tests indicate that this could still use some changes:

Cutting corners

This is a lot of components. If you want to try it yourself but don’t want to get quite as many different ingredients, here are some suggestions:

Making a bottle of cola

The basic idea, of course, is adding the right amount of concentrate to a bottle of carbonated water, e.g. 9 mL for an 1.5 litre bottle. Here are a few things to pay attention to:

Planned changes

Well, there you have it. Experiments will continue until all volunteers have died from cola poisoning.