I have a school project. We are to create a recipe of our own and also explain the effects of the ingredients used when cooking.

I would like to know if adding onions to tomato sauce helps to sweeten the sauce and how it helps to sweeten the sauce. Can someone help me?

  • 3
    @xuq01 please don't post answers, or guesses, in comments. If you want to tell others what you think is the right answer, please write it as an answer. If you are so unsure about it that you prefer to avoid the possibility of being downvoted, that's a sign that you shouldn't be posting it at all.
    – rumtscho
    Jul 5, 2018 at 16:16
  • Note that some people are "supertasters" for whom onions taste twice as bitter.
    – Tanath
    Jul 11, 2018 at 4:08

2 Answers 2


Onions contain a good amount of sugar; that is why they brown and burn easily.

The sweetness is more than often hidden behind the sharp onion smell and taste.

Some onions like the vidalia onion varieties are really sweet.

One way to test if an onion will sweeten the tomato sauce would be to prepare two similar batches, one with onion, and one without.

After that sauce is cooked you need to measure the sugar level of the sauce; there are many ways to do it (chemically, mechanically, use Google).

Another less precise test is just to do blind tasting tests from the 2 batches. Use friends and fellow students to taste the 2 sauces and ask them which one is sweeter; statistically, the sauce with the onion should be sweeter.

You could also do multiple batches with different increasing amounts of onions to see how the amount of onion changes the sweetness of the sauce.


If you sautée the onions first, the bitterness will disappear, so:

  • if you add the tomatoes to sautéed onions: Yes
  • if you add the raw onions to the tomatoes: Not so much

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