If you grew up in certain parts of India you probably use bread (e.g. naan or chapati) as a utensil to scoop up sauces. Just imagine how annoying it would be if those sauces are as runny as a soup, it’ll be hard to scoop them up properly for sure!
It’s one of the many reasons we try to optimize texture and in the case of a sauce it’s all about thickening. You can thicken sauces with flour, as is used in a bechamel, but another common method is to use cashews (or other nuts)!
Composition of cashews
Have you ever seen a photo of a cashew nut hanging on the tree? It’s amazing to see that it is only a small nut attached to a fruit which is a few times its size. Cashew nuts grow in various countries around the world, where India is the largest producer.
As with most nuts, cashew nuts contain a high percentage of fat, over 40% (of course, there is variation between harvests and origins). Apart from that, cashews contain a considerable amount of protein, averages of 18% (these nutrition number come from the USDA). What is important though here is the starch content of cashew nuts, it is over 20%.
What happens when you thicken sauces?
When you try to thicken sauces what you’re doing is that you want to make them less flowable. In food scientist terms this can be described using rheology. The field of rheology studies the flow of materials. If a sauce turns thicker, the viscosity of the sauce will go up. So how do you do that?
Generally, you thicken a sauce by reducing the water content since it’s water that makes most sauces liquid to start with. Reducing the amount of water thickens the sauce, think of making a thick sugar syrup or a homemade stock or sauce.
Thickening by binding water
You can reduce the water content by boiling of water, as we described above. However, you don’t necessarily have to get rid of the water to thicken the sauce. Instead, you can also trap the water. By entrapping the water it can’t move as freely, also thickening the sauce.
Flour thickens sauces well thanks to its starches which swell and absorb water. Potatoes work in a very similar way when added to soups, as does corn starch.
Using cashews as thickeners
Let’s look at those cashew again, why do they work well as thickeners? Again, that starch has an important role to play. Cashews contain quite a large amount of starch and this will thicken sauces, just like flour and potatoes do.
An advantage of using cashews over flour for instance is that cashews have a lot of flavour that they contribute to the sauce. Also, the fat content will help improve the consistency of the sauce.
While researching this topic, I had expected to find other reasons as to why cashews are good in thickening, maybe some other molecules in there? However, cashews haven’t been researched that much, except for the cashew apple so it was hard to find other reasons for its thickening power. If you do know of others, let us know in the comments!
On the texture of our food
Whether you’re cooking or manufacturing food, you of course want your food to taste good and be nutritious. However, no matter how good the taste of a curry, if the texture is off people probably still won’t like it. Instead, we try to create interesting and convenient textures. You want a pie crust to be crispy, a jam to be soft and smooth, a muffin to be crumbly and a curry sauce to be slightly thick but not too much.
What that perfect texture looks like depends on a lot of factors, one of them definitely being your cultural background and what you’re used to. Chinese cakes tend to be slightly different from European style ones for instance (if you’re interested in these kinds of things, read the book First Bite).
Also, in some cases you just need those textures. If that pie crust wasn’t crispy, the pie would fall apart. A hard jam would be impossible to eat. And that sauce would be impossible to scoop up. Hence the use of cashews (as well as other nuts) in sauces in a variety of cultures.
Science of cashew’s thickening power
So we use texture to make good food and using cashews as a thickener is just one of many examples. We use cashews when making a variety of Indian dishes, our favorite being butter chicken.
- 400g chicken (best to use chicken thighs without the skin)
- 1 cinnamon stick
- 1 large bay leaf
- 4 cloves
- 5 green whole cardamons
- 1 can of canned tomatoes (approx. 500g)
- approx. 70g tomato puree
- 150 ml milk
- 100-200ml water
- 1 onion (medium sized)
- 50g garlic (this is about half a head of garlic, don't worry though, it's not that garlicy at all)
- 60g cashew nuts
- 1 tsp honey
- 3 tsp ground coriander
- pinch of chili powder (to taste
- 1/2 tsp fenugreek seeds
- 1-2 tsp butter (or to taste, the classic recipes use more)
- Cut the chicken into smaller bitesize pieces.
- Add all ingredients except for the butter into a pressure cooker (we used an InstantPot). Pressure cook for 30 minutes.
- Remove the cinnamon stick, cloves and bay leaf and use a hand held blender (or regular blender) to break up all the particles and create a smooth sauce. You need quite a strong blender to properly break up the cashew nuts.
- Bring the sauce to the boil and cook until the required thickness before adding the other ingredients to the sauce (the Tandoori chicken). Add butter to taste to create the desired richness.