Thank you this is all really helpful. And what about if you want to replace the type of sugar? For example if the recipe says use Demerera and you use caster or granulated white sugar instead? Can it be a 1-1 substitution?
I have all kinds of questions like these which I will need to ask.
Yes you can substitute 1:1 BUT you need to understand the difference between sugars to understand the flavor and texture difference that they will make and baked goods.
When sugar is refined, juice is extracted from the cane, boiled, then centrifuged to remove the liquid (molasses). The more times it is centrifuged, the whiter the sugar since less molasses is in the sugar.
Now sugar starts to get complicated.
Any sugar that is labelled organic cane sugar is not the same as granulated sugar. It is a single crystallized sugar. This means the sugar cane is crushed; solids are removed; the cane juice heated to concentrate into a syrup; it’s then centrifuged once to separate the sugar from the molasses. But some molasses remains in the sugar.
After centrifugation, the sugar syrup is then crystallized. This less refined sugar has more minerals and some molasses in. It has larger and irregular shaped crystal than conventional granulated sugar. This sugar will be darker and coarser than conventional granulated sugar.
Since there is some molasses in the sugar, it will have some flavor of molasses. Molasses is an invert sugar. And since molasses has some water molecules, it will cook and bake differently than conventional granulated sugar. The water molecules will create a softer texture and weaker dough/batter structure.
And since there are trace amounts of molasses in the sugar, it will not caramelize as well as conventional granulated sugar.
Molasses is also acidic, so the ph of organic cane sugar is slightly acidic.
It is not to say organic cane sugar is bad to bake with, only that it will perform differently because of the way it is refined.
Conventional granulated sugar that most of us are familiar with differs in that it is made by re-melting conventional single crystallization sugar and processing it a second time to remove all traces of molasses and minerals. It is then recrystallized a second time. Since there is no molasses it will not impart any molasses flavor or additional moisture. Since there is no moisture, it caramelizes beautifully.
Brown sugar is made by mixing molasses back into conventional granulated sugar.
By contrast, sugar beet sugar will not caramelize well at all. And the molasses from sugar beet sugar is so inferior, that it is not used for human consumption. It is used for animal feed, and other industrial uses.
A true Demerara sugar is made from sugar cane and is a partially refined sugar. It is not a brown sugar in that molasses it’s not added back in. The sugar crystals still contain the molasses, where brown sugar had the molasses removed and put back in.
So when you replace demerara sugar with granulated sugar, you lose the moisture from the molasses and the flavor from the molasses. And if you use sugar beat granulated sugar, you potentially run into problems performance with caramelization.
If you are going to substitute Demerara sugar, it would be better to substitute with brown sugar.