Science of Cooking: Ask the Inquisitive Cooks! (2024)

" How does cornstarch work ? " Dear Anne and Sue, OK, so what's the deal with cornstarch? Why, when it's supposed to thicken, does it sometimes seem to go the opposite way and make stuff runnier? How does cornstarch work? Thank you, Dallas R. Calgary, AB Still have more questions? You'll find more answers in our archived monthly feature articles by the Inquisitive Cooks. ( Meet the Inquisitive Cooks ) Hi Dallas, As you've discovered, starches are sometimes noted for their idiosyncrasies! Cornstarch is one of the most commonly used thickeners, but it has some unique traits. So thanks for the good question! Cornstarch must be cooked to 95°C (203°F) before thickening begins. At that point, it usually thickens fairly quickly and the sauce turns from opaque to transparent. When cornstarch thins after it's thickened, it's usually due to continued stirring. Once the thickening network forms, any agitation interferes with the setting process. The sauce thins when the starch network that sets and traps the liquid is broken. Liquid is released and thins the sauce. While cornstarch thickens as it heats, it also sets as it cools, so it's particularly useful as a gelling agent for desserts that must hold their shape such as lemon pie filling. Also, as cornstarch becomes clear when thick, while flour remains somewhat opaque, the color of fruit sauces is deeper and more appealing when those sauces are thickened with cornstarch. Cornstarch also sometimes appears to thin as it stands. This is due to a process called syneresis (commonly referred to as weeping). What you'll see is a fluid seeping from the gel. This problem is more evident if the gel (often a pudding or pie filling) also contains eggs or has a high sugar concentration. People often wonder what the difference is between cornstarch and flour. Both are cereal starches, but cornstarch is pure starch while flour contains gluten. The gluten reduces the thickening power of flour. One tablespoon of cornstarch thickens one cup (250 mL) of liquid to a medium consistency. It takes two tablespoons of flour—twice as much—to thicken the same amount of liquid. Your query really brings up the point that there's a lot to learn about the thickeners that cooks use every day. Wishing you successful sauces! Anne & Sue

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Certainly! I'm an avid enthusiast and expert in the field of culinary science, with a deep understanding of various cooking techniques and ingredients. I have extensively studied the principles behind food chemistry, particularly the role of thickeners like cornstarch in enhancing the texture and consistency of dishes.

Now, let's delve into the concepts mentioned in the article "How does cornstarch work?"

1. Starch Gelatinization Temperature: The article mentions that cornstarch must be cooked to 95°C (203°F) before thickening begins. This is because starches undergo a process called gelatinization, where starch granules absorb water and swell, leading to the thickening of the mixture. The specific temperature mentioned is crucial for cornstarch to achieve its thickening properties.

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2. Thickening Process and Network Formation: Cornstarch thickens fairly quickly after reaching the gelatinization temperature, and the sauce turns from opaque to transparent. The thickening process involves the formation of a starch network that sets and traps the liquid. Any continued stirring after this point can interfere with the setting process, causing the sauce to thin.

3. Cooling and Setting: The article highlights that cornstarch not only thickens when heated but also sets as it cools. This property makes it useful as a gelling agent for desserts that need to hold their shape, such as lemon pie filling.

4. Syneresis (Weeping): Cornstarch may appear to thin as it stands due to a process called syneresis, commonly referred to as weeping. This occurs when fluid seeps from the gel, particularly in mixtures containing eggs or with a high sugar concentration, like pudding or pie fillings.

5. Comparison with Flour: The article draws a distinction between cornstarch and flour, both being cereal starches. Cornstarch is highlighted as pure starch, while flour contains gluten. The presence of gluten in flour reduces its thickening power compared to cornstarch. This is valuable information for understanding the differences in their applications in cooking.

6. Thickening Power: The article provides a practical insight into the thickening power of cornstarch, stating that one tablespoon of cornstarch can thicken one cup (250 mL) of liquid to a medium consistency. In contrast, it takes two tablespoons of flour—twice as much—to achieve a similar thickening effect.

In conclusion, understanding the science behind cornstarch's behavior during cooking is essential for achieving successful sauces and desired textures in various culinary applications. If you have any further questions or need additional information, feel free to ask!