What are the cheapest options for a thickening agent for making soups?

Question

I'm trying to make soups (e.g. tomato soups, with some veggies, chillies, etc) and would like to make its cost lowest possible.

One problem that I have to solve is choosing the right thickening agent in order to make the soup cheapest possible.

Flour seems a common choice, but there is also xanthan gum. Xanthan gum is more expensive per gram, but looking at the cost per gram is misleading as different amounts in grams are required to thicken a given volume. For example, only a few grams of xanthan gum are required to thicken a serving.

To be more specific, suppose that I have 500ml of hot water that I'd like to thicken, what's the cheapest way to thicken it with a soup-like consistency?

There are many more thickening agents than the two that I have mentioned so far, and this complicates the problem for me as I'm not experienced with thickening agents nor soups. Therefore, experts' opinions here would be really helpful, specially that this question seems not answered here, and my search attempts failed to find any website that answers it.

Answer 1

An absolutely definitive answer would be based on a formula that takes into account the thickening power per weight of different thickeners as well as the cost per weight of the thickening agent.

That's completely unnecessary however because I can tell you without a doubt that the cheapest thickener is wheat flour. I don't have to do any of that work because food companies have done that for me: they keep their prices competitive by getting the most effect out of the least price, and they use wheat flour and cornstarch for soup thickening almost exclusively. Xanthan gum may be used in some gluten free recipes, but it's rare. If it was cost effective they'd be using it everywhere.

Of the two most frequently used, cornstarch is double the thickening power of flour, but is far more expensive. The quick checks I did showed anywhere between 10-20 time the price of flour, so at least 5 times the cost for equivalent thickening power.

Cornstarch has distinct advantages over flour as a thickener: it doesn't need to be cooked before it's added and it adds a nice gloss, however purely on a cost basis you won't get cheaper than flour.

Answer 2

While you can't go in general cheaper than wheat flour, two of your example soups might even work without any thickener.

Rice, bread, potatoes and beans are great for natural thickeners. If you don't count them as extra since they are already in the soup, this would be the cheapest option since you don't add anything.

Answer 3

How's this for cheap: Save the water you boil your pasta in. Not much thickening power, but you could reduce it too.

Answer 4

Possibly the cheapest thickener is simply the soup itself. Remove a portion of your soup, liquids and solids together, and puree using a blender. Return the puree to the pot of soup and check the texture - if you want it thicker, just repeat with another portion of soup.

The ingredient cost is zero. The energy cost of running a blender for a minute or two should also be very small. However, the up-front cost of buying a blender (if you don't already own one) may be a barrier, even though the price per pot of soup over its lifetime will be tiny.

Answer 5

Essentially, you're describing an industrial question. Interesting. That said, why not take the solutions from the soup powder industry?

To that end, I would suggest a two part approach. Like using a coarse and then a fine sand paper to smooth a piece of wood.

Part 1 is the higher-volume part: Starch. Cornstarch or potato starch are probably the cheapest and most easily accessible. Note that it is best to dissolve the starch in some water before adding it to the soup. This just helps avoid lumping.

Part 2 is a low-volume, fine texture additive: Maltodextrin. This isn't as trivially easy to come by, but it should be possible. It's also not expensive at all, and you'll only need less than 1 Tbsp for a big pot of soup. Note that Maltodextrin has quite a high glycemic index, even higher than starch or sugar.