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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.

caveman
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    Cheap where? Costs of ingredients are not the same everywhere. – L.Dutch Feb 15 '23 at 06:11
  • @L.Dutch - Feel free to pick any common reference that you're familiar with. E.g. USA, Europe, etc. This usually works for my region. Plus, it serves as a starting point for me (and other readers) to adopt the candidates thickening agents for their region. – caveman Feb 15 '23 at 06:45
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    What's already in the soup will determine how much more [if at all] it might need thickening. tbh, I've never made a soup [& I make a lot] that needed any added thickener. – Tetsujin Feb 15 '23 at 08:06
  • @Tetsujin - Which ingredient is it in your soup that thickens it? In massly produced packet instant soup powders, some of them add flour as the thickening agent. It's about saving cost, as adding more of vegetables and noodles raises the cost. I think they reduce the vegetables, and to avoid it being too liquidy, they add a thickening agent. – caveman Feb 15 '23 at 08:27
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    You cannot compare packet soup to real soup, on any level, ingredient or cost. A packet of soup to serve 4 will be $£€ 1. The same made from fresh will cost a fraction of that, even if you buy a supermarket 'fresh soup' pack where all the work has been done. You don't need fresh soup to have that gelatinous feel you get from dried. Add a potato if you want more 'density' in a fresh soup. It will thicken but in a different way. Also - not all soups should be thick. – Tetsujin Feb 15 '23 at 08:35
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    This isn't as simple a question as you think. Thickeners like roux are a great way to add flavor and depth, but you wouldn't want that in every soup. Are you looking for only flavorless thickeners? – GdD Feb 15 '23 at 08:39
  • @GdD - I'm looking at it the other way around: find the cheapest thickening agent, then make a soup that works with it. So, if we pick the roux case, is it the cheapest thickening agent to begin with? I'm not sure, as roux [seems to contain flour and fat](https://en.wikipedia.org/wiki/Roux), and I guess requires cooking which is an added preparation step. So, I'm totally open to the type of the thickening agent (be it flavourless or flavoured), because I'll be building the right soup that goes with it. – caveman Feb 15 '23 at 08:46
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    @caveman that makes no culinary sense. It's like choosing a carpet and building the house that goes with it :) But if you absolutely want to go that way, then the answer is trivial: Don't use any thickening. Soups don't need to be thickened, and if you make a recipe where you don't use any, the cost will be zero. – rumtscho Feb 15 '23 at 09:48
  • @rumtscho - You make no sense. Explain why can't one build a food backwards? It really depends on what the eater wants. Some people want a given taste, and adopt the texture for that taste. But some people want a given consistency, and choose any taste that goes with it as they like a lot of soup varieties. It is not a common approach (I know), but doesn't mean that it is wrong. Also, I know that a thickener is not required, but it's off-topic, as it's part of my requirement to not be too runny. – caveman Feb 15 '23 at 10:05
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    You can't build it backwards, because everything in the food affects the texture. If you were to first make the "perfect" texture from just a thickener and water, then the moment you add something else, that texture will be changed. The thickener is the last element that adjusts the texture without changing the rest. – rumtscho Feb 15 '23 at 10:40
  • @rumtscho - You're misunderstanding me. The cooking procedure is not backwards. The cooking is normal. The _search_ to identify the recipe is backwards. Once I identify the recipe, cooking goes as normal. – caveman Feb 15 '23 at 10:52
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    @caveman yes, my last comment was about the recipe creation process, not about the cooking process. – rumtscho Feb 15 '23 at 11:00
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    And also, my comment about the trivial solution stands. If your criteria are just thickness and thickener cost, then you can simply choose to make a soup which has the desired thickness, then you don't need to add any thickener, and the cost of the thickener is again zero. – rumtscho Feb 15 '23 at 11:06
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    I'm still wondering what you're doing to your soup for it to need thickening. Ultra-econo soup... Kilo of carrots 50p, an onion, 20p, potato 10p if that. A handful of fresh coriander [cilantro] & a stock cube if you can afford it. Will make at least 2L of fabulous soup, no thickener required. Tomato soup too, no thickener required, just a lot more expensive than carrots & requires sieving, extra step. – Tetsujin Feb 15 '23 at 11:33
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    (@Tetsujin) or lentils. Red lentils are cheap and cooked slowly will thicken the soup nicely, while also making it very satisfying (so you won't need to fill up so much on something like bread) – Chris H Feb 15 '23 at 11:48
  • @ChrisH - are lentils cheaper than wheat flour thickeners? – caveman Feb 15 '23 at 13:10
  • @Tetsujin - are you fundamentally against adding thickening agents to soups? – caveman Feb 15 '23 at 13:17
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    I've just never needed to, in 30 years of making them. – Tetsujin Feb 15 '23 at 13:20
  • @Tetsujin - even in the context of achieving lowest price? My problem with not using thickening agents is that I think one would have to use more vegetables and other ingredients, which I guess are going to raise the prise. I guess a thickening agent allows for less ingredients, yet a thick soup at a lower price. – caveman Feb 15 '23 at 13:52
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    If your veg:water ratio is too low, thickness won't be your primary issue, flavour will. Rough rule of thumb for a veg soup, 500g veg to 1L water/stock. I always simmer a good hour to develop some flavour, no matter what a recipe might say - they usually only allow 20 mins, which I don't think is enough. I usually use a soup make which does only take 20 mins, but the last carrot & coriander I made in a stock pot, 3.5L or so, was far better for an hour & a half. Cost under £1, even with the considerably more expensive coriander & good stock. Carrots were cheap mis-shapes. – Tetsujin Feb 15 '23 at 14:00
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    @caveman no, they're more expensive as pure thickeners, but they're a good part of a cheap diet that happens to provide thickening to soup. In general, considering how to save money on one small aspect of cooking isn't the best idea. Taken to extremes you'd just have slightly thickened water with no flavour and next to no calories. That's not much use – Chris H Feb 15 '23 at 14:15

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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.

GdD
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    I suspect that in manufacturing quantities corn starch is more competitive in price than it is in the supermarket. I'm used to seeing it sold in smaller and more robust containers than wheat flour, as it's expected to be kept for a long time. As corn starch can be added late, you can use as much or as little as you want. Doing that by cooking and adding a roux is possible but takes more heat, and the energy cost will be worth considering – Chris H Feb 15 '23 at 10:18
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    Quick check with my local wholesaler: a kilo package of cornstarch is €2,50, all purpose flour about 90ct. In thickening power I'd think that cornstarch has more than twice the power so in pure cost that might be better for say, a commercial kitchen. But it may well be that when you order by the ton it swings the other way again. – Borgh Feb 15 '23 at 10:26
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    You are right in everything you say @ChrisH. I'm answering the narrow scope of the question. – GdD Feb 15 '23 at 10:32
  • The process for making cornstarch is much more involved than milling grain, flour will still be cheaper than cornstarch, even if you buy it by the ton. – GdD Feb 15 '23 at 10:34
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    Yes, it will probably never quite reach parity in terms of ingredient cost for a given thickening power. – Chris H Feb 15 '23 at 11:46
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    Cornstarch also has the downside of loosing its thickening effect if overheated/reboiled. If you were only making single servings this shouldn't be a problem, but trying to make in bulk for later use it might become a problem. – bob1 Feb 15 '23 at 20:41
  • Is the wheat flower, or even corn flower, cheapest even when considering the procedures followed to use them to thicken soups? For example, does it require cooking? Can we just pour boiling water on it, stir, and call it a day? It would be great if this is possible, as such flour could be used in instant-soup style recipes (e.g. pour powder in little cold water, add boiling water and stir, wait for 5 minutes, then eat). – caveman Feb 15 '23 at 23:32
  • @caveman instant soup isn't really something you can make at home. It most definitely requires all kinds of artificial flavors, because you can't really cook down "real foods" enough to get soup powder. – Esther Feb 16 '23 at 03:48
  • @Esther - my question is limited to the thickening agent aspect, not the full soup. Does wheat flour, corn flour, etc, require cooking? Or would it suffice to just let them sit in a hot water that was previously boiled in a kettle, and let it set there for 5 minutes? – caveman Feb 16 '23 at 04:17
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    Both wheat flour and cornstarch must be cooked. Cornstarch gelatinizes at about 200F, 93C, once at that temperature it thickens pretty fast, then you don't want to cook it anymore. Would it thicken if you poured boiling water on it? Maybe, the problem you could have is the container will absorb heat and cool your water. Potato starch would probably work better as it gelatinizes at a slightly lower temperature. – GdD Feb 16 '23 at 09:03
  • @caveman Starches and other complex carbohydrates cook in a complicated manner that involves volume change of granules and followed by bursting of the granules and the formation of a molecular mesh of individual molecules interweaving with each-other. This is why you can't just chuck some flour into hot water and expect it to dissolve. Instead it forms lumps which almost never break apart as they cook and hydrate forming an insoluble mass. – bob1 Feb 16 '23 at 20:06
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    @caveman the problem seems to be that you lack the understanding that thickening agents come in the context of a whole soup, so speaking of "just the thickening agent" without the rest of the soup makes little sense. – Esther Feb 16 '23 at 20:49
  • @Esther - No. I know that. But the problem seems to be that you lack the understanding that I said that I'm flexible with my selection of the soup. I will pick any soup recipe and I'm happy with any. My only constraint is the pick the cheapest thickening agent. Then, I'll search for soup recipes that go with that thickening agent, and I'll be happy with it. I said this multiple times. I know this is odd, but it does make sense in my case. Kindly comprehend. I don't want to waste time repeating this again and again. – caveman Feb 16 '23 at 20:53
  • @caveman that doesn't make sense either, because, as previously mentioned, most soups *don't need thickening*. Let's say we say flour is cheapest, then you choose a soup that works with flour (lets say a blended vegetable soup). Most such soups don't need thickener, but you are making it "cheaper" so you use half vegetable soup and half water + flour + flavoring. But maybe if you made a different kind of soup, with a different thickener, you would need less ingredient and more (cheap) thickener to get a good taste. – Esther Feb 16 '23 at 20:58
  • @caveman Like someone said, this is like looking for the cheapest carpet and imagining that the house you find it in will also be the cheapest house. No, sometimes expensive houses can have cheap carpets, and sometimes cheap houses have expensive carpets. Sometimes a soup can use a cheap thickener but still be expensive overall, and sometimes the "thickener" is expensive, but you don't need much so the soup is cheap overall. How much thickener depends not just on the strength of the thickener, but also on the rest of the soup. – Esther Feb 16 '23 at 20:59
  • @Esther - You don't make sense. Do you realise that "most" does not mean "all"? My requirement is to have the thickness (3rd or 4th time I'm saying this), but my requirement is _not_ the specific soup recipe (I can pick any that goes with the thickner). Don't add noise to this solved question. I'm going to ignore you onwards. – caveman Feb 16 '23 at 21:10
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    @Esther is making perfect sense. What is quite clear from the comments is that you actually don't understand the problem, so you're struggling with how people are explaining it to you. BTW, you cannot put either cornstarch or flour straight into boiling or near-boiling water, all you will get is lumps of solid which will never break down. if there is no roux process, then you have to add as a cold slurry to below boiling almost finished liquid, then stir briskly until it thickens. Both will lose consistency if over-heated, & cornstarch will gelatinise if allowed to cool. – Tetsujin Feb 17 '23 at 16:32
  • This question has become needlessly argumentative. The question is essentially 'what's the cheapest thickener for a generic soup', and has an answer. Yes, there's a lot of nuance that is missing, but badgering someone about it isn't the way to get that point across. Why don't we let a novice explore cooking in their own way. – GdD Feb 17 '23 at 16:49
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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.

Zibelas
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  • I have to count them as extra, as I'll be adding more of them in order to cause a thickening of the same volume. If I add a cheap thickening agent, I can add lesser of those ingredients, and thicken it separately by an agent. – caveman Feb 15 '23 at 22:01
  • @caveman and what will you do about the loss of flavor that comes from using less of an ingredient? Most of the time, if you use enough ingredient to get decent flavor, you have sufficient thickening. Unless you're using soup powder, in which case it probably comes with its own thickener. – Esther Feb 16 '23 at 03:50
  • @Esther - I will find whatever flavour enhancer that goes with thickener. – caveman Feb 16 '23 at 04:16
  • so you're making a soup powder, not a soup? that is important context. You want to make a "soup" out of water + flavors and thickener, and are looking for the cheapest method? – Esther Feb 16 '23 at 20:48
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How's this for cheap: Save the water you boil your pasta in. Not much thickening power, but you could reduce it too.

jeff
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  • Have you considered the cost of energy and the reduction process? I guess it would nonetheless help the flavour, but not sure how much thickening power it has. – caveman Feb 15 '23 at 21:59
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    Well - a lot of folks cook pasta in very little water, which reduces the amount of thickening needed. – Journeyman Geek Feb 16 '23 at 06:03
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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.

user105870
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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.

Carmi
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