I want to replace sugar with fresh fruit when baking. What fruit would produce the most sweetness? The fruit should not produce an undesirable flavor and be easy enough to buy in Florida.
Edit: Kiwis caused me to think this.
You cannot simply replace sugar with fresh fruit in baking recipes. Sugar is, well, 100% sugar.
Fruit is mostly water, on the order of 70-90% depending on the particular fruit in question. The remainder is usually sugars, starches and pectins for the most part.
Any recipe not specifically designed to be sweetened with fruit is going to fail spectacularly if you try to substitute. To do so, you would have to calculate the water weight in the added fruit and remove it form elsewhere in the recipe (if there is enough liquid elsewhere in the recipe to do so) at the very least.
Sugar is also extremely important to the structure and moisture retention of baked goods (with the notable exception of yeast raised breads), and simply substituting it out is going to have a deleterious effect on the texture.
Instead, you should search out recipes that are sweetened in a manner that meets whatever requirements you have. Applesauce and cooked down pears, as well as bananas might be suitable, but it would depend on the specific application.
In any case, almost no sugar will be lost during baking; all fruits will retain essentially all of their sugar.
Except at the very edge of the baked good, where browning occurs (indicating caramelization and the Maillard reaction are taking place), the sugar will be unchanged by the baking process. The amount of sugar lost to browning in the crust is vanishingly small.
I love to use raisins because they are so, so sweet when backing! Now, of course it depends on the product you're trying to create... but believe me that raisins are really sweet and tasty when baked!
It was just the kiwis. Peaches benefit from heat.
Experiment: 4 fruit each sliced 4 ways for tasting at fresh, heated, slightly browned and half burnt. Some mount of cooked left over to compare when cooled again.
Fresh; mandarin sweetest then yellow mango, and kiwi & peach tied. Heated; peach strongly improves to almost mango sweetness. kiwi tastes slightly less sweet. mandarin becomes bitter. Slightly browned; all fruit same relative sweetness as 'heated' but sweetness clearly reduced. Burned; I guess the black bubbles are caused by sugar burning. Peach and orange had most big black bubbles per weight with kiwi having some and mango almost none. The mango probably did not burn enough. Microwaving mango did not cause such bubbling, only dried it more. Everything tasted much less sweet.
Ree-cooled: burned clearly least sweet. forgot to keep enough not cooked fruit pieces. Kiwi; browned tastes sweeter Mandarin; tie Peach; browned tastes sweeter Mango; tie Heated; mandarin mango peach kiwi Browned; mandarin mango peach kiwi