Let’s clarify this, humans cannot smell sweetness. That’s right, Shakespeare got it wrong all those years ago.
Sweetness, along with saltiness, acidity, bitterness, umami (a savoury taste) and fat, are six of the basic tastes that a human can detect via taste receptor cells primarily located on the tongue and palate in the mouth.
So why is it that often we smell things and could swear that they smell sweet? It's all to do with experience and expectation. Over the course of your life you will have eaten many sweet foods and your memory will have stored information each time about the items you have tried. When you are faced with that item again, or an item that smells similar, your brain essentially looks up the memory of it like using a reference library and reminds you that it was sweet to the taste when you consumed it.
Take the example of a strawberry fruit tea, that when prepared smells intensely ‘sweet’ or candied but when tasted has little to no sweetness at all. The aroma we are picking up is likely a fruity ester, and we are likely pulling up a memory of other items with that same aroma that were in fact sweet when tasted, such as strawberry jam.
When we smell something we are not just reminded of how we expect it to taste but may also be transported back to a memory of where we were last time we smelled it, who we were with, how we were feeling and much more. This is because our olfactory receptors are directly connected to the limbic system of the brain which is associated with emotion and memory.
Try this at home
The concept that we cannot smell sweetness is a difficult one for many to accept. Rather than just take my word for it, here is a simple activity you can do for yourself to test the theory:
Stir half a teaspoon of white sugar into a plastic cup of water until it is completely dissolved.
Pour plain water into a number of other identical plastic cups (around 5-6 will do).
Ask someone to shuffle the position of the cups so that you dont know which has the sugar in it.
Now smell each cup and try to identify the one that contains the sugar. If you get it right first time, ask someone to shuffle the cups again as there is an element of chance that you could guess the correct cup first time.
Have you ever experienced smelling something that seems 'sweet' only to have it not taste so?