All About Cornstarch (Use Cornstarch To Thicken A Soup)

About Cornstarch
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About Cornstarch

If you have ever made soup, and especially when you are new to the process, there is always the possibility that it will be lighter than the desired consistency. The first remedy for this and which most people have in their homes is flour, wheat flour. Modern kitchen use cornstarch, which is fine flour obtained from the heart of the corn kernel. To some people, it does not make a difference what is used provided that you get the soup to thicken up as needed.

Well, the fact is that these two items are flours and when put side by side, one could pass off as the other. Actually, since both are flours, they are carbohydrates and therefore starch-based but flour contains gluten which has been proven to lower the thickening power of regular flour. Ever wondered why you had to add a lot of flour in a soup to achieve even a hint of thickness? It is the gluten! Since it lacks gluten, a little cornstarch goes a long way, not to mention that soups thickened with cornstarch are clear while those thickened with flour are milky and lumpy.

All about Cornstarch

How to use cornstarch to thicken a soup

Cornstarch lacks gluten and will, therefore, thicken better than the same amount of flour. The golden rule with using cornstarch is to half the amount of flour thickener called for in recipes. For instance, if a recipe requires a quarter cup of flour, using 2 tablespoons of cornstarch will have the same effect. It is almost impossible to identify foods that have been thickened using cornstarch because of the glossy and smooth appearance plus the fact that it does not alter the taste of food. Soups that have been thickened using flour appear cloudy and dull. The process of introducing cornstarch to food is quite easy because the blending happens faster and easier.

On the other hand, using flour means that you blend in water into the flour as the flour first absorbs the liquid part of the soup. If you are looking for best results with cornstarch, stir cold liquids gradually onto cornstarch until smooth then cook over low medium heat. In about a minute of gentle stirring, the starch granules will have swelled to full capacity and the soup is ready to serve.

How to use cornstarch as a thickener

You have decided that your soup requires a bit of help with thickening and you even have cornstarch with you. What now? Mix slurry of cornstarch and about a quarter cup of cold water, wine, stock or other that is not acidic, until smoothly incorporated. Acidic liquids like fruit juices cut the thickening power of cornstarch by up to 50%. What if the cornstarch thickened soup was to be left over? Eat it cold because boiling it will cause it to thin out.

For medium thick consistency, a tablespoon of cornstarch should be used in a pot with an equivalent 2 cups of liquid. Wait till the food is almost coked and when it is about 10 minutes before removing the food from the fire, stir in the cornstarch liquid mix and allow cooking at a temperature of at least 203°F (95°C). Care should be taken not to stir vigorously, or cook too long after thickening begins.

FlourCorn Starch
If recipe calls for this much flourUse this much cornstarch
1 tablespoon1/2 tablespoon (1 ½ teaspoons)
2 tablespoons1 tablespoon
3 tablespoons1-1/2 tablespoons
1/4 cup (4 tablespoons)2 tablespoons
1/3 cup (5-1/3 tablespoons)2 tablespoons plus 2 teaspoons
½ cup (8 tablespoons)¼ cup (4 tablespoons)

Miss Vickie’s Cornstarch Table

Problems you might experience when using cornstarch

One of the greatest disappointments with cornstarch mixes is that some do not thicken at all while others do achieve consistency but thin out when the food gets cold. This is not natural and luckily the causes for such happenings are known;

  1. Inadequate amount of liquid – if the amount of liquid (juice, milk or water) used to constitute the cornstarch mixture is not enough, the starch granules will be unable to fully swell and maintain thickness when the liquid is cold. You can correct this by adding more liquid to the mixture.
  2. Excess sugar ratio – if the proportion of sugar in a cornstarch mixture is high, this can cause irregular swelling of the cornstarch granules. This leads to failed thickening attempt or thinning of soup when cold. The problem in this case can be solved by adding more liquid.
  3. Excess fat ratio – if the mixture you are trying to thicken has a high proportion of egg proteins or fat, the swelling of cornstarch granules might be inhibited or even if the soup thickens, it might become thin once it cools. Adding more liquid to the mixture is the solution to this problem.
  4. Excess acid – as we had mentioned before, acid with reducing the cornstarch ability to thicken. Acidic ingredients that should never be used to mix cornstarch are lime juice, vinegar, and lemon juice. Since the problem is that the power of cornstarch has been diminished, the solution is to double the amount of cornstarch required for the recipe. The alternative would be to add in the acidic ingredients after the thickening has taken place.
  5. Excess stirring – avoid rough or too much stirring as this vigorous action might cause the starch to break down and this thins out the soup.
  6. Prolonged cooking time – if you are cooking a meal that requires long cooking times, add the cornstarch mixture towards the end of that time. If the cornstarch is allowed to cook for too long, the starch cells will rapture and this will cause the soup to become thin.
  7. Freezing – a soup that has been thickened with cornstarch will become thin if frozen because the extreme cold causes the cornstarch cells to rupture.

How does thickening happen?

When added to food that is still cooking, the heat causes the binding of starch to water, causing swelling of the starch and hence thickening. One starch granule grows to about 10 times its size if the temperature is more than 205°F. Larger starch granules at these temperatures will deflate causing the soup to thin out.

Oriental cuisines that include clear and lighter gravies make the most use of cornstarch. You too can use corn starch at home to prevent curdling of eggs when making egg-based dishes. Other uses of cornstarch are in adding crispiness when used to coat pieces of meat and making sauces or custards.

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