Food Guide: Thickening Agents


Thickening Agents – Roux

Roux has been used in the Culinary industry for a long period of time up to date. Not only it’s practical to its usage, roux is also very useful in terms adding flavor to soups or sauces. There are many stipulations to Roux as there is with politics today, as this long-time French thing is found so useful that many practice this product, use it differently and sometimes, perceive it differently.

What roux can bring to you today is its basic understanding and use. Nothing could be further from roux-truth than to practice this concept of using roux:

Warm Liquid —-> Hot Roux
Warm Roux —-> Hot Liquid

Typically, what Chefs need to understand in the kitchen is that, Roux isn’t just one type of thickening agent or emulsifier, if you want to put it that way. There are many other alternatives to roux also, such as potato starch, tapioca starch, corn flour, etc. These starches have their own strengths and weaknesses, therefore increasing the likelihood of a particular menu to ‘vary’ of a thickening agent or an emulsifier’s usage.

Other thickening agents such as corn, potato, arrowroot, tapioca, and wheat are particularly special themselves, and the below explains their properties.

Thickening Agents’ Properties

There are many sorts of thickening agents out there in the market – Food Central uses only a few by far, due to costing and practicality factors. For certain kitchens, it’s advisable to use certain things, and also, depending on its properties, thickening agents can work well under certain conditions and vice versa.

  1. Stability
    How stable is that particular thickening agent when it’s mixed into the liquid – Whether the liquid will be thick when it’s hot, or will be thin when it’s cold, or vice versa. Temperature is the core of your thickening agent’s stability. Also, it also covers thick, long cooking process. Will long cooking thin out (separation of molecules) your thick liquid?
  2. Consistency
    Consistency as in when starch is incorporated into the liquid, what would probably be the texture of the soup? Use a spoon, scoop up some liquid and pour it back in – Does it have a smooth flow, or does it come close to a stringy-like texture or is it forming lump-like texture of sorts?
  3. Flour-flavor
    Will the thickening agent I use contaminate the soup or sauce that I’m using with its uncooked flour smell, or will my strong flavored soup cover the uncooked flour-smell? Take into consideration volume and thickening agent strength when you’re deciding which thickening agent to use.
  4. Holding Strength
    How much of the mixture of flour and water do I need to incorporate into my liquid before it thickens out to the consistency that I’m looking for? Do I need two tablespoons of corn starch for this amount of liquid to get there or two tablespoons of potato starch?
  5. Transparency, Opacity and Color
    After the thickening has been mixed into a liquid, will it be transparent or will it yield a little sight of cloudy, opaque-like color over the liquid?


Roux is the one best thing to add when you’re cooking it for small dishes or soup. They come in powdered formats now, and you can get them if they are available in your local store.

  • Medium-weak holding power. Cooking the roux too long will weaken its holding power.
  • Stability – The good part about roux is that it holds (after being incorporated well) the sauce at its thickening point even after the liquid is cooled off. Certain starches like tapioca and corn does not hold very well when it’s cooled down.
  • Robust flavor – Roux has a very complex flavor of its own, especially when it comes to the kind of ‘fats’ you want to add in. Choose ‘fats’ that have higher heating point. E.g. Sunflower Seed oil or Peanut. Butter is commonly used, but animal fats are also fine, if you want a more robust flavor.
  • Color – Varies. If you’re looking for the traditional dark roux, cook the flour a little longer before incorporating your fats. If you’re looking for a white roux which needs little color influence, don’t burn your flour.
  • Consistency – Like the potato starch, it should be running in a very streamlined position and springing back up a little.

Potato Starch

Potato starch is known to be one of the most expensive among other flours here in Malaysia. It has:

  • Great strength and holding power – Use only a bit to yield a thick sauce.
  • Stability: Quite weak. When you’re heating up a sauce that requires thickening, consider bringing it to a close boil, add this and turn off the fire as soon as possible. Overheating will cause the molecules in potato starch to break and this will result in a thin liquid.
  • Semi-light flavor – Not very powering to the tongue when you thicken your liquid. Since its strength is good, you do not need to add too much, this will leave the liquid clear of its flour-like favor.
  • Potato starch has no color influence when it’s added to your liquid. Don’t ask for trouble by cross-contaminating it.
  • Consistency – Silky and stringy. When you scoop some up and pour it back down, it should be in a very steady stream, with little silky strings dropping off like a calm waterfall, then when it goes back up, the stream will slightly bounce back up to the spoon.
Potato starches are great for quick thin sauces that requires only a small amount of cooking time or remaking of it. Keep in mind that in order to get a consistent thickening agent, ensure that your ratio of flour to water is at least 1:5. Mix them well – Because after leaving it for long, the starch will fall off and you’ll see water on top of the flour.

Corn Starch

Corn flour is known to be one of the most important flours to have in a kitchen other than just the regular cake and bread flour, or superfine and Rex Milano (flour mixed with seasoning and herbs, used for Pizza dough). Not only used as coating or flour mixture in the hot kitchen, it also has its uses in the Pastry kitchen, for example; Pavlova.
  • Medium strength – Corn starch is not very strong compared to Tapioca or Potato starch. Due to its natural properties, corn flour is used more for stabalizing rather than thickening. (Although we don’t deny that there are a lot of us who use corn flour as a thickening agent)
  • Medium-weak stability – Corn starch also has the potential to break down if you cook it too long, or when your temperature is not high enough (medium-high simmer). Always bring your liquid to a close boil before attempting to add corn starch into it.
  • Very strong flavor – Apprentices usually make a mistake here: They replace roux with cornstarch which is totally acceptable, but only at a certain degree/extent and depending on what we’re thickening. Be sure that for a 1 quart pot of water, you have no more than 4 tbsps of this.
  • Color – Cloudy, medium high in opacity.
  • Consistency – Smooth. Your liquid should be streaming in a very straight line, thick but not lumpy. It should not bounce back up to the spoon. Too much will result in lumps.

Tapioca Starch

Tapioca starch holds stronger than corn starch, and is particularly used as an alternative choice in the kitchen or to bake breads and pastries. Also, tapioca starch smoothens clothes (used by old-timers) during washing by soaking clothes into the tapioca starch solution first before hand-washing them.
  • Medium-strong thickening agent – In cooking when there are small amount of sauces (in a dish), tapioca flour is used to thicken its ‘juices’, mainly for the purpose of creating a thicker sauce rather than a thin one.
  • Weak stability – The bad thing about tapioca starch is that it breaks down a little quicker than corn starch. Especially when you’re on a very high temperature, they have the tendency to ‘thin-out’ faster than potato or corn starch.
  • No flavor – That’s the best part of tapioca starch.
  • Clear, low opacity and almost transparent in color.
  • Stringy consistency – You should see a smooth flow when you scoop it up and pour it back to the soup, while it slightly springs back up when it finishes.
Although it has no odour, care must be taken as too much of it will result in a jelly-like lump – Avoid that at all costs.
Always keep in mind that thickening agents are useful tools to help you thicken your sauce. However, it’s always advisable to bring your liquid to a near boil to achieve any thickening at all. Simply adding it in the sauce when it’s warm or cold will not yield results – But they will when it’s hot. And that’s when everything will spoil.

One Response to “Food Guide: Thickening Agents”

  1. I am a keen cook but have always used Starch based thickeners in my soups etc, never tried Roux, will have to give it a try from now on

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