Should you use cane sugar or beet sugar for marmalade? Also Can I mix preserving sugar and granulated sugar?
The sugar derived from both sugar beet and sugar cane is chemically identical - it is sucrose. Therefore it should not matter which source the sugar comes from. Some confectioners claim that cane sugar is better for complicated sugar work and that beet sugar will tend to crystallize too easily when making a caramel. However we have not noticed any difference in day to day cooking between the two and either should be fine for marmalade. In addition, it can be difficult to tell the origin of the sugar. In the UK Tate & Lyle is cane sugar and Silver Spoon is beet sugar, but brands in other countries will vary and quite a lot of sugar will be a mixture of the two. Also the packaging may not identify the source.
You do want to use a refined white sugar for marmalade and jams. Some people prefer to use caster sugar as it dissolves quickly, some prefer granulated sugar. There is also preserving sugar that has even larger crystals which dissolve slowly, produce less froth and can give a clearer preserve. We feel it is better to use one type of sugar only, rather than mixing them, as they all dissolve at different rates.
There is another type of sugar called jam sugar. This is different to preserving sugar as it has had pectin added to it. You do not need to use jam sugar for marmalade as the Seville oranges are high in natural pectin. Jam sugar is good for fruits that are low in pectin, such as strawberries.