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A good sauce doesn’t just depend on its flavor. The consistency of that sauce is just as important. Is it runny and thin, or thick and gloopy?
To control consistency, cooks all over the world have developed a wide range of techniques. One of them, popular in for instance Indian cuisine, is to use ground cashews. Cashews thicken sauces, making them rich and creamy. Cashew’s high fat content, and low moisture content come into play here.
What do we need to thicken a sauce?
Compare a glass of water, to a thick, velvety butter chicken sauce. The difference in consistency is striking. Something happened while making that sauce, that caused the texture to become very different. Nevertheless, the main ingredient of the sauce still is water. So what happened?
Water itself consists of water molecules. These small water molecules move around freely and easily as you’ll see in a glass of water, a lake, or the ocean. In order to thicken a sauce, we have to limit the freedom of movement of these molecules. This is a delicate balance. Reduce their freedom too much, and you’ll end up with a gel, or a thick dry paste. Don’t reduce it enough, and you’ll have a watery consistency.
Cashews bind water
And that’s where cashews can come in. As with any nuts, cashews are quite dry. They contain just a small amount of water. Instead, they’re mostly made up of fat (over 40%), carbohydrates (≈30%) and proteins (a little under 20%).
A whole cashew is crunchy and firm, thanks to the internal cellular structures. However, when you cook a cashew, the internal structure will soften. If you then also grind the cashew, it will completely fall apart into a paste. This paste contains all those fats, carbohydrates and proteins.
Several of the ingredients that have now been set free love being in water. They are hydrophilic. If you mix ground cashew paste with water these carbohydrates will start to bind water. The large molecules surround themselves with water. As a result, those water molecules can’t move as freely anymore. This causes the liquid to thicken.
Particles thicken too
But it’s not just those water binding molecules in cashews that can thicken water. If you add a lot of small particles into a little bit of liquid, that liquid will thicken as well. All those little particles spread throughout limit the movement of water. They’re kind of in the way.
The smaller you grind a paste and the small those particles are, the thicker the liquid. This is because the total surface area of small particles is a lot larger than that of large particles. As a thought experiment, imagine adding one very large marble to a glass of water. There are still a lot of big empty spaces where the water can sit and float freely. Now, add the same weight of marbles, but add a thousand tiny ones. These can pack very efficiently, and the water will be forces to sit in between all these particles. It doesn’t have as big a space anymore to move freely.
Why cashews make a creamy sauce
Cashews are very commonly used to thicken sauces, more so than many other nuts. One reason must have been the availability of nuts in the region where those dishes were developed. Cashews were likely more prevalent in regions where people thicken sauces with cashews.
But, cashews also have two very practical advantages. First, cashews are relatively neutral in flavor. Just try adding ground pecans to a sauce. They have a big impact on flavor, which may or may not be desirable. Cashews on the other hand add more of a muted undertone than an “in-your-face” additional flavor.
The other major advantage though is their high fat content. Cashews are a very fatty, thus creamy nut. When you grind cashews into a paste, this fat gets released into the sauce, resulting in a very creamy, rich sauce.
How to thicken with cashews
To optimally use cashews to thicken your sauces, they have to be grind down into a smooth paste. The finer, the better. If you have very strong blenders, or grinders, you can grind down cashews as is. However, for most of us, it’s a lot easier if we give the cashews a slight pre-treatment before attempting to grind them down.
If you’re using the cashews in a hot dish, as part of a sauce, it’s easiest to add the cashews to the dish and cook them along with the other ingredients. Once they’ve softened. Add the sauce into a blender and blend away.
If you can’t cook the cashews on forehand, or if you don’t want to grind the entire sauce, you can also soak the cashews in hot water. They’ll start to absorb some of that water, making it easier to grind them down.
You do still need to control water content
Do keep in mind that there’s a limit to the ‘power’ of cashews, just like there is a limit to any thickening agent. If there’s too much water, your sauce will still be watery, regardless of how well you’ve blended your cashews.
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USDA, Food Data Central, FDC ID: 170162, link; Used to find cashew nut composition