I mentioned gum syrup (also known by its French name of gomme syrup) in my post on the Pisco Punch. You see gomme syrup called for a fair bit in older cocktail recipes, and people will generally tell you to substitute simple syrup. Simple syrup is an acceptable substitute for gum syrup, but despite what people may say it is not one and the same. While you certainly can substitute simple syrup for gum syrup, if you want to drink certain old style drinks they way they were intended to be drunk you probably need to make yourself some real gum syrup.
Gum syrup is simple syrup with the addition of gum arabic (or gum acacia), an edible gum produced from the acacia tree. Gum arabic alters viscosity in liquids and can act as a stabilizer. The special textural properties of gum arabic meant that historically had quite a range of uses, from photography and printing through to food manufacturing. While gum arabic has been superseded in many applications by cheaper alternatives, it is still used in confectionary and soft drinks. Therefore, while gum arabic can be hard to track down, the best place to find it is in a specialist baking supplies store.
Added to simple syrup, gum arabic does several things: first, it prevents the syrup from crystallizing (a problem as syrups become more concentrated); second, it alters the consistency of the syrup and imparts an interesting ‘silky’ texture; third, it provides a very subtle ‘warm’ aroma. Some may disagree with this last point, but I think there is something there.
The production of gum syrup by adding gum arabic to simple syrup may originally have simply been a means of preventing crystallization. However, the textural properties were surely also appreciated.
Making your own gum syrup is extremely straightforward. You need to bear in mind though that gum arabic has a reputation as an inconsistent substance in terms of its chemical properties. Gum arabic from different sources may vary, so treat the following as a guide for experimentation. Don’t be nervous though. There is no room for real error. So long as your gum syrup contains gum arabic it will have some degree of the properties of gum arabic. It will merely be a matter of how noticeable those properties are, which will depend on the nature of your gum arabic and how much you add. Play around until you get a result you like.
I’ve been making my gum syrup as follows:
Take ½ oz of gum arabic and place in a bowl. Add 1 oz of hot water, stir together, and leave to stand for a while until ‘dissolved’. The gum arabic will gradually soak up the water and turn into a kind of a sticky paste. Some recommend leaving overnight but I think a few hours is long enough.
For the next step make a 3:1 simple syrup in a saucepan, using 6 oz sugar and 2 oz water. Heat while stirring until dissolved, bring to the boil, add the gum arabic mixture, bring to the boil again, use a spoon to remove the scum that will have appeared on the surface, cool (placing saucepan bottom in a sink of cold water will speed up this step if you are in a hurry), strain through cheesecloth or a sieve, and bottle.
Stored in the fridge or freezer it should keep for a long time. The high concentration of sugar means it shouldn’t freeze solid unless your freezer is particularly cold.
Now that your syrup is ready your only problem is what drink to use it in. The gum syrup texture really shines in drinks that fit the classic 19th century definition of a ‘cocktail’ (i.e. spirit, sweetener and bitters, diluted with a little ice). You will find that the drink comes across as mellower, but without any loss of flavor. An Old Fashioned makes a good place to start playing around with this stuff, and of course you also need to try a Pisco Punch. A Sazerac may be my favorite gum syrup cocktail though, pretty much to the point where I no longer want a Sazerac made any other way. Since a Sazerac contains no ice the gum syrup texture remains undiluted right through to the final sip, and there is just something about the way the gum syrup works with the robust old-worldly flavors in a Sazerac – especially the anise and lemon oil. I never experimented with gum syrup too much in long drinks (Tom Collinses and suchlike). I think that the more diluted the drink the less you are going to notice the difference from regular syrup. However, gum arabic is supposedly still used in manufacturing coke and other sodas, so perhaps this could be an area to experiment with.