I’ve made Candi Sugar several times. All you’re basically doing is inverting the sugar molecules to make it easier for the yeast to break down. (Converting Sucrose into Glucose and Fructose.)
Most yeast will produce “invertase” which is an enzyme that will invert the sugar before “digesting it”.
For instance, when Unibroue started, they only used white table sugar since their yeast would digest properly. Traditional use of candi sugar was for adding colour and more fermentables.
The recipe I used was just as simple as “cooking” table sugar into a syrup, heating it to a certain temperature and keeping it there until I achieved the colour I wanted (amber to dark). Then cooling it.
I’m pasting the article I used below with an addendum to my process I incorporated back in 2017:
Making Belgian Candi Sugar
Belgian brewers often use sugar in beer making to produce high alcohol beers without a thick body. They normally will use what is called Candi Sugar, but this stuff is pretty expensive, costing homebrewers around $4-5 per pound. Basically, candi sugar is ordinary white cane/beet sugar (sucrose) that has been modified by an ‘inversion’ process, producing ‘invert sugar’.
You can make your own ‘invert sugar’ from ordinary table sugar with just a few simple items. Sucrose is made up of two simpler sugars (glucose and fructose) joined together. Yeast must spend time and effort breaking the joining bonds to allow them to get at the simple sugars they need for metabolism. This can be done chemically in an acid environment with heat. You will need a candy thermometer that goes up to about 350°F and a 2 qt saucepan. The ingredients are sugar, water, and citric acid to provide the acidic environment needed.
There are certain temperatures that relate to the process of candy making as shown in the table below. The terms refer to how the sugar will behave on cooling.
Term Used Temperature
Soft Ball 240°F – 155.55°C
Hard Ball 260°F – 126.66°C
Soft Crack 275°F – 135.00°C
Hard Crack 300°F – 148.89°C
To make a pound of Candi Sugar, measure a pound of sugar into the 2 qt saucepan. Add just enough water to make a thick syrup, and mix in a pinch of citric acid. Now bring to a boil and keep the temperature between hard ball and soft crack (260°-275°F). As you boil, evaporation will cause the temperature to begin rising, so have a small amount of water on hand and add a tablespoon whenever the temperature gets above 275°F.
The color will gradually change from clear to light amber to deep red as the boil proceeds. Light candi sugar is a very light amber-yellow. This can take as little as 15 minutes. Dark candi sugar is very deep red. This can take several hours. Once you are at the color you desire, you stop adding water and let the temperature rise to hard crack (300°F). Once it hits hard crack, turn off the heat and pour it into a shallow pan (like a cake pan) lined with a sheet of waxed paper. As it cools it will go rock hard, and you can break it into ‘rocks’, bag in a ziplock bag and store in the freezer until you are ready to use it.
1 lb sugar to ½ cup of water and 1/8 tsp of Cream of Tartar
Boil to 260F-275F until desired colour
Bring to 300F and pour into pan lined with parchment paper