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Facts and fiction about food and cooking, by Peter Aitken
All thickening agents are created equal
March 30, 2011Posted by on
A common technique in cooking is to use a starch to thicken a liquid such as a gravy or sauce. Wheat starch (flour) and corn starch are perhaps the most common, but potato starch, arrowroot, and tapioca are also used. Does it matter which one you use? Most definitely. These agents differ in five ways.
- Flavor: does the thickening agent add its own flavor to the sauce or is it neutral in taste?
- Thickening power: just how thick can you go?
- Consistency: the molecular structure of some starches results in long strands that can give the sauce a stringy texture.
- Stability: will the sauce remain thick with long cooking or will it thin out?
- Appearance: is the resulting sauce clear or opaque?
Now let’s look at how the various thickening agents stack up:
- Wheat (flour): smooth consistency, low maximum thickness, good stability, strong flavor (which can be greatly reduced by cooking the flour in fat before adding to the liquid), and opaque appearance.
- Corn starch: smooth consistency, moderate maximum thickness, moderate stability, strong flavor, and opaque appearance.
- Potato starch: stringy consistency, very high maximum thickness, poor stability, mild flavor, and clear appearance.
- Tapioca flour: stringy consistency, high maximum thickness, poor stability, no flavor, and clear appearance.
- Arrowroot: stringy consistency, high maximum thickness, good stability, no flavor, and clear appearance.
What you need to add here is that using cornstarch as a thickener in combination with milk or cream (and some other dairy products) can cause a texture that can be a bit slimy. Better to use arrowroot in these sauces and soups.
One should also consider the pH of the food to which the thickener is being added. Recently, I was making sauced fillings from muscadines and scuppanongs (the native American grapes) for use in fried pies. At the lower pH (more acidic) of these sauces, corn starch did not work well at all and failed to yield a sufficiently thickened product.
I switched to arrowroot with vastly improved results. Though it is a bit hard to find in some grocery stores as stock clerks are generally clueless and when found is quite expensive in those miniature spice jars (arrowroot is not a spice), it is readily available in international or asian markets in quantity at reasonable prices. Tapioca may also be found in these same markets. In a pinch, one could purchase arrowroot noodles and simply use them, though it would take a bit longer for them to dissolve and disperse. But the dried noodles are easily ground in a spice mill.
The arrowroot gave a much higher viscosity product with a wonderful glossy sheen in my fried pies. I would recommend it for any fruit based pie filling over the more ubiquitous corn starch.
Thanks for that wonderful tip.
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