by Peter Thomson, bakery application specialist
Tests with fat reduction have found a way to keep filled pastries dry and crisp
A soggy pastry crust can take all the pleasure out of eating a savoury tart. So, with many bake-off quiches, pies and flans on display in the chilled and frozen counters of today’s supermarkets, it only makes sense to look into strategies for keeping the pastry crisp.
Here at DuPont, we work with two such strategies: migration-resistant fillings that keep pastry dry, and pastry formulations for delayed moisture absorption from the filling. For the pastry, the solution we like best actually came to light during trials with a reduced fat shortcrust pastry.
A useful fibre
Our initial objective was to reduce the fat content by 25%. At the same time, we added 2.5% polydextrose. A recognised dietary fibre with prebiotic and satiety-inducing effect, polydextrose is also widely used as a bulking agent, highly suitable for food and beverage products that are lower in fat, sugar and calories.
The addition of polydextrose gives the reduced fat shortcrust pastry the same eating quality as a standard full-fat recipe. We have also found that it improves pastry texture and crispness.
Theories about the mechanism
How this works, we are not entirely sure. A couple of theories are that the polydextrose interacts with the protein, starch or fat in the pastry or that, being soluble, it interrupts the development of flour gluten simply by absorbing water. There’s a possibility that both theories apply. Either way, polydextrose is an effective shortening agent.
On baking, the fibre turns into a syrup, which then solidifies into a glass on cooling. This is the characteristic that gives improved pastry crispness. When a filling is added, the polydextrose only very slowly transforms from its glassy state back into the syrup. In this way, moisture absorption is delayed, and the pastry keeps its crisp, short bite for longer.
Tarts in the chilled counter benefit in particular from this delayed migration, which secures a freshly-made eating experience after the final baking. In frozen tarts, the polydextrose ensures any moisture present in the pastry is frozen in small molecules, which are less damaging to the pastry system during defrosting.
The speed of water migration will always vary according to the type and quality of the fats and flour used. So, even though our trials were based on a textbook formula, the results are only a guideline. The optimum polydextrose level must be determined for each pastry recipe.
We tested Litesse® polydextrose from the DuPont™ Danisco® range.