Optimizing Sugar Paste Consistency with Vacuum-Assisted Heating

[maria1]

TL;DR Summary

I'm trying to understand how to achieve a good consistency of my mix of sugar, water and citric acid without getting a burnt color

Hello,

I'm in the process of developing a sugar paste for hair removal and trying to find a good ratio between sugar, water and acid in order to get a gewy consistency. I currently use 8 tbs sugar, 4 tbs water and 2 citric acid and let it reach a temperature around 128 degrees Celsius (262.4 degrees F) on the stove to have a nice and firm consistency. However it takes too long time and gets a burnt color. On a chemistry level - what is causing this? What changes do I need to make in order to lower the time it takes to get a similar consistency (and therefore also not burning it and having a lighter color)?

Thank you

 

[Borek]

Color is due to the sugar decomposition (caramelization) that occurs at elevated temperatures,. not much that can be done about it.

Elevated temperature is typically used to speed up the dissolution, in this case it can be also required to allow some hydrolysis of the sugar (sucrose gets split into glucose and fructose). Both processes will take place even at room temperature, albeit much more slowly. Could be leaving the mixture for much, much longer would produce the same consistency without the color (not that it has to happen, thing are not as simple as I signaled above), but having it ready fast and without color doesn't sound likely to me.

 

[Tom.G]

If the heating is just to reduce the water content you could heat the water under a vacuum. The vacuum lowers the boiling point of the water, keeping the temperature down. (at least until it all boils away!)

One way to implement this is to use a Pressure Cooker as the vacuum chamber, and draw a vacuum in it with whatever vacuum pump you can obtain for experimenting.

Please let us know how it turns out.

Cheers,
Tom