When making fruit fillings with a large quantity of sugar, when should part of the sugar be added?

When preparing fruit fillings that contain a large amount of sugar, it's essential to add part of the sugar after the starch has completed its thickening process. This method allows the starch to gel effectively without interference from the sugars, which could lead to an overly fluid mixture.

By adding some sugar after thickening, you ensure that the filling achieves the correct consistency and maintains a desirable texture. If all the sugar were added at the start, it could potentially inhibit the gelling of the starch due to the high concentration of sugar, which might lead to a runny filling instead of the desired thickened result.

Additionally, this technique can enhance the flavor profile of the filling, allowing the natural taste of the fruit to shine through, as it avoids over-sweetening early in the cooking process. The delayed addition of sugar contributes to a balanced flavor in the final product, aligning well with the natural acidity and sweetness of the fruits used.