Grapefruit Syrup & Soda

Grapefruit soda is one of the most requested topics I've had, and this method is slightly different from the traditional methods out there, but the results are really good. This formula has a stronger flavour than most commercial versions, mostly thanks to the grapefruit mercaptan, and if you find anything too strong (flavour, acidity, etc.), you can easily cut the amounts back. As usual here, these recipes are a guide for you to make the perfect beverage for your personal tastes, and the recipes are just a starting point to save you time. I dump a lot of syrup down the drain so you don't have to.

Grapefruit Syrup Formula

900 mL Base Syrup
11.0 g Grapefruit Oil Emulsion
1-3 drops Grapefruit Mercaptan Dilution
0.1 g Nootkatone
3 drops Ethyl Butyrate
1 drop Guavante (optional)
40 g Citric Acid
Water, to make 1000 mL

Base Syrup

625 grams Sugar
Water to make 900 mL

This is a 1:1 ratio, and I recommend leaving about 100 mL of space because we will be adding other ingredients to this. Once everything is added, you can top it off with water to the 1000 mL mark.

Grapefruit Emulsion

The emulsion is made using the same technique used in the Crystal Clear Soda Science video, except this one is more concentrated, so you end up using less emulsifier and the foaming and taste issues are much better.

4.0 g Polysorbate 60
0.4 g Span 40 (optional)*
4.0 g Grapefruit Oil
7.2 g Water
~37 g Propylene Glycol

Create the emulsion using the technique in this video.

*Span 40 can be used as a co-emulsifier to improve the stability of the emulsion. It is discussed in the Pepsi patent. Span 40 has a lower HLB value, meaning it is more soluble in oil, so it is mixed with the essential oil first, then added to the emulsifier.

Grapefruit Mercaptan

For that true grapefruit flavour, grapefruit mercaptan (GM) is key. As noted in the video, the amount used is in parts per trillion, so millionths of a milligram. To measure these amounts, use dilutions, and here is the calculation for the sample I bought at Perfumer's Apprentice, which comes in a 1% solution.

1. A 15 mL bottle weighs about 12 grams, meaning a 1% solution has 120 mg of GM

2. If you take 1.0 grams, which equals 10 mg of GM and dilute it to 250 grams using a solvent (alcohol, limonene or triethyl citrate) then 1 gram of the diluted mixture will have 0.04 mg of GM.

3. A typical drop, if you use alcohol as the solvent, is about 25 mg, which means there are 40 drops per gram. This means one drop will have 0.001 mg of GM

4. Since our syrup makes 8L of finished beverage, a single drop works out to 0.000125 mg of GM in a litre (0.000125 ppm or 125 parts per trillion (ppt)). The math is 0.001 mg divided by 8L.

5. The EU usage limit is 0.001 mg (1 part per billion or 1000 ppt), and FEMA gives an average usage of 0.000150 (150 ppt).

In our case, 1 drop is probably sufficient, but 3 drops will give a little extra punch and still only be half of the EU limit. If you want to use less, or have more precise control of your drops, you can simply dilute the 1.0 grams of GM to 500 grams and then everything will be half the amount per drop. For even more precision, dilute 1.0 grams to a litre and every drop with be 1/4 the amount, so a single drop added to 1L of syrup will result in roughly 30 ppt of GM when the syrup is turned into 8L of soda. This is also effective if you feel that the source material may be at a 2% concentration instead of 1%, but at these tiny levels, it can be hard to get exact dosing. Luckily, using this method, the flavour is never overpowering.

Other Flavour Compounds

Grapefruit is a relatively simple flavour once the essential oil and grapefruit mercaptan are combined. Beyond that, there are other flavours you can add to improve the flavour.

Nootkatone: This is a compound found in the peel of grapefruit and has a characteristic grapefruit aroma, making it a great addition. Use at 0.1 grams per 8L. (Source)

Ethyl Butyrate: To give a fruitiness to the flavour, the addition of esters is common. They are used at low levels and help enhance the fruit flavour. You can add many different esters, and typical usage is a few drops per litre of syrup.

Guavanate: This is a compound that resembles guava, but it finds use in grapefruit flavours and can help give depth to your grapefruit flavour. Use a single drop per litre.

Octanal and Decanal: Grapefruit are closely related to sweet oranges; in fact, the parents of the grapefruit are a sweet orange crossed with a pomelo. If you look at the GC/MS analysis of grapefruit oil, you will see the aldehydes octanal and decanal at about 0.5% in the oil. These can be used in a drop or two per litre of syrup to enhance the citrus flavour.

Naringin: This is a bitter compound found in the peel of grapefruits and can help round at the flavour, especially if you appreciate the bitterness of grapefruit. Can be used up to 300 ppm in a beverage, which would be 2.4 grams added to the syrup. This is a bit high and I've found 0.5 grams added to the syrup to impart a decent flavour. Feel free to experiment, but do note that the naringin dissolves slowly and may cause some haze in the final beverage.

Acidity

Grapefruits are quite acidic, and the juice is up to 2% acid, mostly citric acid. This can make them unpleasant to drink, so for most grapefruit beverages, the acidity is reduced significantly. In this formula, it has been reduced to 0.5% which still creates a tangy beverage and may still be too acidic for some people, but if you like a Daiquiri made with freshly squeezed lime juice, you will like this acid level.

40 g Citric Acid to 1L of syrup

You can also add malic acid or any acid. And you can also temper the acidity using some sodium citrate, which will increase the pH, giving the beverage a less puckery flavour.

Zero Calorie Version?

Yes, you can substitute the Zero Calorie Syrup formula for the syrup in this formula. Do note that you may want to reduce the amount of acid as high intensity sweeteners work slightly differently than sugar when mixed with high a proportion of acid.

As usual, if you have any questions, please post them below.