The percentage of fruit in fruit fillings for pies refers to the proportion of actual fruit content in the filling. The difference between 50% and 70% fruit fillings lies in the fruit-to-sugar ratio. A 70% fruit filling contains a higher proportion of fruit compared to a 50% one, making it fruitier and potentially less sweet.
The choice between 50% and 70% depends on personal preference and the desired sweetness level in the final product. Both percentages can be used for pies, but 70% fruit fillings are often favored for a more pronounced fruit flavor.
For doughnuts, a 15% fruit content might be adequate, but it depends on the specific flavor profile you want. Adjust the fruit percentage based on the desired intensity of the fruit flavor in the doughnut.