Open cola

The recipe for Open Cola, an open-source recipe for a Coke-type drink, came out in 2001. I've always wondered what was in Coke so thought I'd have a go at making some with Ash and Pete.

Here's what happened.

First of all we got all ingredients together. This was no mean feat in itself, and cost about £40 - but this is enough to make several batches. We sort of followed the recipes on Wikipedia and Cube-Cola. Most of the essential oils came from an online supplier, with everything else coming from eBay (I love eBay).

Flavouring formula

• 3.50 mL orange oil
• 2.75 mL lime oil
• 1.25 mL cassia oil
• 1.00 mL lemon oil
• 1.00 mL nutmeg oil
• 0.25 mL coriander oil
• 0.25 mL neroli oil
• 0.25 mL lavender oil
• 10.0 g food-grade gum arabic powder
• 40 mL water (the Wikipedia recipe says 3ml but this really didn't work for us)

Put on some gloves and goggles, the essential oils are pretty fierce. Measure out the oils and mix together, as shown below left. Mix the gum arabic powder with the water until it forms a cloudy liquid, and then add the oils.

You'll need to blend these together into an emulsion, which can take several minutes in a food processor or with a whizzy stick. Eventually it will form a cloudy emulsion as shown in the bottom right. You can tell it's an emulsion because if you put a drop into a glass of water, it won't separate into a oil layer on the top of the water. Don't leave it in the food processor too long because the oils start to attack the plastic.

We (okay, I) made a right mess of this step because we didn't dilute the gum arabic with enough water, so we wasted quite a lot of the mixture. We ended up with 30g of the emulsion when it should have been nearer 60g.

The mixture smelled absolutely incredible but it didn't taste too great - very very bitter.

Concentrate

The two recipes we were following deviated quite widely here, so we made a new middle path.

• 1.5kg plain granulated white table sugar
• 750mL water
• 30.0 mL caramel colour
• 17.5 mL 75% phosphoric acid (particularly nasty, watch out)
• 30.0 mL flavouring formula
• 1g caffeine tablets, crushed up, diluted with 10ml of water and passed through a coffee filter

Put the sugar and water in a pan and heat, making sure it doesn't boil. Add the caramel, phosphoric acid (carefully!) and caffeine solution to the flavouring formula and stir carefully.

My pH sticks said that the mixture was about pH 1, so don't drink it.

Once the sugar has all dissolved in the water, adding the flavouring and stir, then allow it to cool. We made just over two litres of the concentrate, enough to make 14 litres of cola. This is what the concentrate looked like.

Drinkies

We diluted the mixture 7:1 with sparkling mineral water and tried it - absolutely delicious! We had a bottle of Coke to compare it with, and to be honest after our magical open source cola, the "real thing" tasted dull and lifeless.

I've since tried it with soda water (also nice) and with straight tap water and it's still great! I've had really good feedback from everyone who's tried it, although almost nobody has guessed what flavour it's supposed to be - especially since it's not brown.

So it's a winner in terms of taste, how about cost? If we hadn't messed up the first stage we would have had more like 28 litres of cola and enough ingredients left over to make another 2-3 batches. That's about 70 litres of cola for £40, which is about half the cost of buying it.

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