SUMMER FRUIT PIES

SUMMER FRUIT PIES TRADITIONALLY RELY ON flour or cornstarch to thicken the fresh blueberry, cherry, peach, or strawberry-rhubarb filling. However, we find these thickeners to be problematic.

Cornstarch thickens well, but at a price: in our tests, it yielded dull fruit, lacking in bright flavor and noticeably less acid. As a result, the mixture tasted sweeter and heavier. The flour resulted in fruit that was similarly unsatisfying in appearance and taste, and it also had another failing: two tablespoons was not enough to firm up the fruit well. To give flour another chance, we ran a test using four tablespoons. This time, the fruit was gummy and almost inedible. As it turns out, this is because flour, unlike the other thickeners, contains proteins and other components as well as starch. As a result, it takes at least twice as much flour by volume to create the same degree of thickening as cornstarch. This amount of flour will adversely affect your pie—you can taste it.

By contrast, the samples of fruit that we thickened with the root starches arrowroot and tapioca were clear and bright in appearance, and the flavor of the fruit was fresh and clean. Of the two, tapioca thickens a little better and is much cheaper, so it is our favorite.

Tapioca comes from the root of the cassava plant. Also called manioc, this plant is grown throughout most of the tropical world and is harvested when its roots are about 6 to 12 inches long. The starchy root can be boiled and eaten, and in many countries it takes the place of rice or potatoes in the diet.

To make what we know as tapioca, the starch is separated from the plant and cellulose material in the root. Pearl tapioca is made from tapioca starch that is heated to form pearls. To create quick-cooking tapioca, the starch is partially gelatinized and then pasted together into pellets to improve its thickening powers. While we don't necessarily think of processing food as a good thing, in the case of tapioca, it results in a much more usable product.

During additional testing we found that the amount of tapioca should be varied depending on the juiciness of the berries. If you like a juicier pie, three tablespoons of tapioca is an adequate amount for six cups of fresh blueberries. If you like a really firm pie with no juices, five tablespoons is the correct amount.

Mixing the fruit and tapioca together works fine when a regular top crust is placed on the pie. However, when we made a lattice-top pie, we found that the tapioca on top of the fruit baked into hard bits that once in our mouths felt like Tic-Tacs. For an open or lattice-top pie, we suggest mixing all of the tapioca with three-quarters of the fruit filling, filling the pie, and then adding the balance of the fruit on top.