I have thought of a funny concept on what makes things taste like this, taste like that, and it kinda looks like this:

  • Sweet = Sugar (C6H12O6)
  • Sour = ?
  • Salty = Salt (NaCl)
  • Bitter = ?

What I'm trying to figure out is what is the simplest substance that makes this taste like that. That's why it clearly defines that sugar is the simplest substance that makes things sweet and salt makes things salty. I wonder what substance makes things sour?

What is the substance makes things sour?

BONUS: Figure out what makes things bitter.

  • 2
    There are many sugars, your model is too simplistic. – GdD Mar 10 at 9:45
  • 1
    Bitter is usually a base. – Wayfaring Stranger Mar 14 at 1:04

Sour flavours come from acids, like citric acid (in lemon juice, for example) or acetic acid (in vinegar). I don't think there's any one acid that qualifies as 'simplest'.

Bitterness is much more complicated; there are lots of different foods (coffee, uncured olives, citrus peel, alcohol, hops quinine) which are bitter to some extent but there isn't an obvious culinary ingredient/chemical that just gives 'bitter' as a taste. Our perception of bitterness is believed to have evolved to signal toxic foods.

It's worth pointing out that your existing examples are an oversimplification: C₆H₁₂O₆ is glucose, which is only one kind of sugar, and there are others which also taste sweet to us (as well as non-sugar sweeteners, some of which taste far sweeter by mass than sugar. There are also other salts, like KCl (potassium chloride). There is much more information in the Wikipedia article if you are interested.

  • 5
    KCl has a salty flavour, but also bitter, just to confuse things; many other salts (in the chemistry sense) taste bitter too, rather than salty (in the culinary sense) – Chris H Mar 10 at 9:40
  • Doesn't bitterness often come from (poisonous to little things like bugs) alkali compounds which plants use as insecticides? – RonJohn Mar 14 at 3:07
  • @RonJohn, Yep, that's what I was referring to in the but about toxic foods, I just wasn't confident enough to be more specific. – dbmag9 Mar 14 at 8:33

what is the simplest substance that makes this taste like that

The problem with this sentence is the definition of "simple". What you are describing in your examples is not "the simplest" substance for a taste, it is the prototypical substance for a taste - the one which we have encountered the most commonly, and our brain associates most strongly with the term for the taste. So, the only sense it is "simple" is from the point of view of gestalt psychology, not any objective quality of the molecule.

That being cleared up, here an explanation of the tastes and what they are meant to denote:

  • the sensation of "sweet" means that your mouth has recognized simple carbohydrates (simple in the chemical sense, typically monomers or dimers as opposed to polymers like starch). The prototypical sweet substance for our culture is sucrose, as you already noted. This is despite there being other substances which have a stronger sweet taste (e.g. saccharine) or being chemically simpler (e.g. glucose).
  • the sensation of "salty" is a recognition of chloride ions. The prototypical substance is indeed table salt.
  • the sensation of "sour" discovers acids, as others have noted. For a typical Western culture, the prototypical acid will be either acetic acid or a mixture of citric and ascorbic acid, depending on whether your family tends to use more vinegar or more lemon juice.
  • the primary purpose for the sensation of "bitter" is to discover alkaloids. There is a huge variety of alkaloids, and humans have been breeding them systematically out of their food plants for centuries. Thus, there is no single prototypical alkaloid which everybody uses as the standard for bitterness. A potential candidate would be quinine (in tonic water), but we encounter many other bitter substances with a similar (low) frequency. Also, we do encounter bitter tastes in other foods, especially when there are metal ions present, but these tend to be perceived as less bitter than alkaloids.
  • the sensation of "umami" discovers glutamates. The prototypical substance is monosodium glutamate, MSG.

For completeness of sensations felt with the tongue (despite not being traditionally counted as "a taste"):

  • hot/spicy is a type of pain produced by capsaicin or mustard-like substances corroding your mucosa
  • astringent is a sensation caused when tannins cross-link proteins on your cell surface and in your saliva, changing the configuration of the cell surface and reducing the saliva lubrication
  • cold is a sensation whose mechanism consists of triggering the TRPM8 receptor. This usually happens by actual coldness (e.g. eating ice cream) but accidentally, it so happens that menthol also activates this receptor.
  • For bitter there's [Bitrex/Denatonium]/(en.wikipedia.org/wiki/Denatonium), which is one of the most bitter substances known to man, but is used routinely in products as a deterrent against consumption and for things like fit-testing for wearing respirators. Chemical formula is C28H34N2O3 – bob1 Mar 10 at 19:39
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    The sour taste of lemon juice is caused mostly by citric acid, not ascorbic acid, isn't it? – Tanner Swett Mar 10 at 22:12
  • 2
    @TannerSwett citric is indeed the large part of the sour taste in citrus - hence the name. Ascorbic is vitamin C; name derived from its anti-scorbutic (anti-scurvy) effects, with the "a" bit meaning "without" or "not". – bob1 Mar 11 at 0:49
  • Indeed, there is also a lot of citric acid in lemons, edited. As for Bitrex, I doubt that it is the prototypical bitter taste to many people; for me, it is an unusual taste. Intensity is not what makes it prototypical, it is frequency of encountering during a learning phase. – rumtscho Mar 13 at 8:52
  • Theanine, a stimulant in tea, also has umami. It's a glutamate analog: duckduckgo.com/… – Wayfaring Stranger Mar 14 at 1:11


Weak organic acids (e.g., the acetic acid in vinegar) taste more sour than mineral acid at the same pH. according to a review at Elsevier's Science Direct topic overview.

So your substances are the culinary acids: citric, acetic (vinegar), malic, tartaric, fumaric. Of those, acetic acid is the simplest molecule.

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