Apple pie filling is a delicious component of many classic apple pies. The filling consists of tender cooked apples that are lightly sweetened and thickened. The thickener is essential for giving the filling the perfect texture – thick enough to hold its shape when sliced, but not overly gummy or gluey. The two most common thickeners used are flour and cornstarch. But which one is better suited for apple pie filling? Here is an in-depth comparison of how flour and cornstarch perform as thickeners in apple pie fillings.
Thickening Properties of Flour vs Cornstarch
Flour and cornstarch thicken through different mechanisms. Flour thickens liquids through gelatinization. When flour is heated in a liquid, the starch granules absorb water and swell up. The swollen starch granules form a network that increases viscosity and provides structure. Cornstarch uses a different process called gelation to thicken liquids. The cornstarch particles dispersed throughout the liquid form junction zones that restrict movement of water molecules. These junction zones cause the liquid to set into a gel.
The different thickening processes of flour and cornstarch mean they perform slightly differently:
- Flour begins thickening at a lower temperature than cornstarch. Flour-thickened mixtures will start to thicken around 140°F, while cornstarch requires 185°F.
- Cornstarch thickens more quickly than flour. Once heated to its activation temperature, cornstarch will thicken a liquid rapidly.
- Cornstarch makes a clearer, more translucent mixture than flour. Flour has a tendency to turn liquids cloudy.
- Flour-thickened liquids continue thickening over time. Meanwhile, cornstarch thickens then levels off.
- Acidic ingredients like lemon juice can cause cornstarch mixtures to thin out. Flour is more stable in acidic ingredients.
For thickening pie fillings, both flour and cornstarch perform well. But cornstarch’s clarity and rapid thickening make it more convenient for apple pie fillings.
Flavor Impacts
In addition to differences in thickening capability, flour and cornstarch also impact flavor differently:
- Cornstarch is tasteless and does not impact flavor.
- Flour has a distinctive wheaty, doughy flavor. Even small amounts of flour can influence the flavor of a mixture.
- Overcooked flour develops a starchy, unpleasant taste.
- Cornstarch produces clear, bright flavors. Flour has a tendency to make flavors seem muted.
For apple pie fillings, cornstarch is the better choice in terms of preserving fruity apple flavors. Flour would add an undesirable doughy taste and dull the fresh apple flavors.
Texture
The texture of the thickened filling also differs between flour and cornstarch:
- Flour produces a thick, dense texture. It can tend towards gluey if overused.
- Cornstarch gives a lighter, more delicate texture. The filling is still thick, but not gummy.
- Overcooked flour fillings continue thickening into a heavy, stubborn gel. Cornstarch fillings remain smooth and tender.
- Acidic ingredients like lemon juice can cause cornstarch fillings to thin out too much. Flour is not affected.
While both thickeners can produce a pleasant texture for apple pie fillings, cornstarch tends to result in a more desirable tender yet thick texture that slices cleanly. Flour is more likely to create a dense, gluey filling if overused.
Moisture Retention
When used in baking applications, flour and cornstarch differ in how much moisture they retain:
- Flour absorbs liquid and moisture. Excess flour can result in dry, tough fillings.
- Cornstarch contains very little protein and does not absorb significant moisture. Fillings thickened with cornstarch retain moisture better.
For apple pie fillings, cornstarch results in a more moist, tender texture. Flour absorbs juices released from the apple during baking, leading to a drier filling.
Storage and Freezing
The final thickened texture of flour and cornstarch holds up differently during storage and freezing:
- Cooked flour mixtures continue thickening over time. Stored flour-based fillings will thicken progressively more.
- Cooked cornstarch mixtures are stable over time. The thickness remains consistent during storage.
- Frozen and thawed cornstarch mixtures retain their texture well. Flour mixtures tend to weep liquid and become watery.
For convenience and optimal texture, cornstarch is a better choice for apple pie fillings. The thickness will remain consistent without becoming gluey during storage. Cornstarch also holds up better to freezing compared to flour.
Nutritional Value
Here is a comparison of the nutritional profiles of flour and cornstarch:
| Nutrient | 1 tbsp all-purpose flour | 1 tbsp cornstarch |
|---|---|---|
| Calories | 23 | 25 |
| Fat | 0.2g | 0g |
| Carbs | 4.5g | 5.8g |
| Fiber | 0.3g | 0g |
| Protein | 0.8g | 0g |
As the table shows, flour contains gluten protein while cornstarch does not. Flour also provides a small amount of fiber. From a nutritional standpoint, the differences are minor for the small amounts used to thicken a pie filling. Both can fit into a balanced diet when enjoyed in moderation.
Cost Differences
Flour and cornstarch are both budget-friendly ingredients. Here is a comparison of their typical costs:
- All-purpose flour: $0.15 per ounce
- Cornstarch: $0.09 per ounce
Based on typical retail pricing, cornstarch is the more affordable option. Cost savings may not be significant for a single pie, but could add up when baking pies frequently.
Ease of Use
Both flour and cornstarch are easy to use for thickening pie fillings:
- Flour: Whisk the flour into cold pie filling ingredients until no lumps remain before cooking.
- Cornstarch: Dissolve the cornstarch in a bit of cold water or juice before adding to fruit mixture.
Properly incorporated, both thickeners will smoothly gel the filling without clumping. Cornstarch requires an extra step of dissolving before adding. But overall, ease of use is comparable between the two options.
Suitability for Diets
Here is how flour and cornstarch fit into various dietary needs:
- Gluten-free: Cornstarch is naturally gluten-free. Flour contains gluten.
- Paleo: Neither flour nor cornstarch are allowed on the paleo diet.
- Keto: Small amounts of cornstarch can fit into a keto diet. Flour does not align with keto macronutrient ratios.
- Vegetarian/Vegan: Both ingredients are suitable for vegetarian and vegan diets.
- Low-carb/Low-calorie: Cornstarch is slightly better aligned with low-carb or low-calorie needs.
For individuals following a gluten-free, paleo, or keto diet, cornstarch is the better choice. Both ingredients can suit vegetarian, vegan, and some low-carb diets in moderation.
Ease of Digestion
Flour contains gluten proteins and cornstarch does not. This results in differences in digestibility:
- Flour: The gluten in flour can be difficult for some people to properly digest. Gluten is the culprit in digestive conditions like celiac disease and non-celiac gluten sensitivity.
- Cornstarch: Since it is free of gluten proteins, cornstarch is typically easier to digest. People with sensitivities or allergies to corn also need to avoid cornstarch.
Due to the presence of gluten, flour can cause digestive issues for some people with gluten sensitivities or celiac disease. Cornstarch is better tolerated by most. Those with corn allergies also need to avoid cornstarch.
Conclusion
For thickening apple pie filling, cornstarch has several advantages over flour:
- Cornstarch thickens fillings quickly without altering flavors.
- It produces a tender, smooth texture without becoming dense or gummy.
- The thickness remains consistent without over-gelling, even after freezing.
- Cornstarch has neutral flavor and color, allowing the fresh apple taste to shine.
- It is affordable, gluten-free, and suitable for most diets.
While both cornstarch and flour can adequately thicken a pie filling, cornstarch is best suited for the job. Cornstarch allows the fresh fruit flavors to come through and gives the perfect smooth, thick yet tender texture. Flour would add an undesirably strong flavor and be more likely to produce a gluey, dense filling. For the optimal apple pie filling texture with bright fruit flavor, cornstarch is the clear winner over flour.