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Why Does Watercress Soup Become Bitter?

My friend, Jo, asked me this question about making watercress soup.

She says that her watercress soup turned out bitter. When it comes out bitter, it is really a waste of time and money (and appetite too) as no one will touch the soup.

UPDATE: Alan Bergo left me an interesting comment about bitter watercress. Please see his comment below this post. 

Naturally I have come across this "bitter watercress soup" puzzle once. Yes, even I - I who profess to know my soups. Actually I am still learning. I am curious about soups and so this question by Jo niggled me to no end.

Many years ago, I made a pot of watercress soup and strangely, it didn't taste good at all. It had hints of bitterness. I never really got around to investigating why until Jo asked me this question again.

Now that I am a lot better at making Chinese soups, I started to think of whom I could ask.

Two people come to mind.

The woman who sells vegetables at the market. She's a friendly matronly type, a grandmotherly soul. She would know.

And then there was my balding and ever cheerful Chinese uncle herbalist at the very same market. (Gosh I love this market. I was just remarking to Nic how lucky we are to live in this area where the market people are truly helpful and lovely.)

Anyway - I asked the daughter-in-law of my favourite vegetable seller (the woman wasn't around today, unfortunately). Now she tells me that the cardinal rule of making 'sai yeong choi' or watercress soup is this - your pot of water MUST BE BOILING before you add watercress.

If you add watercress into the water which is warming up or even cold water, your soup will turn out bitter.

That's it.

That's the thing you have to remember.

In all my soup-making days, I always bring water to boil first. I never add ingredients to cold water in a pot.

I will verify this again with her mom-in-law when I do see her in the market but this daughter-in-law of hers is also an experienced cook and she has been helping her mother-in-law sell vegetables for a long time.

Now you know why your pot of water must be boiling before you add your soup ingredients.

Note: She also mentioned that if you are making soup with matrimony vine leaves, you cannot overboil the leaves. If you do overboil them at high heat, the soup will also end up bitter and nasty.


Comments

Anonymous said…
Yes, but don't you kill all the nutrient value of the Watercress by boiling it? Though, i'm in search of having watercress without such bitterness, I may just give this a shot.
Alan Bergo said…
Whether your water is boiling or cold has nothing to do with bitterness, sorry. It could be due to when and where the watercress is harvested, as older water cress is higher in sun-induced flavonoids that increase the hot flavor as the plant matures and attempts to flower/go to seed. Typically store-purchased watercress, if it is truly Nasturtium officionale, as opposed to an upland cress (Barbarea spp and others) is harvested quite old and spicy hot.
Krista Goon said…
HI Alan - Thanks for your comment. I stand corrected then.
Krista Goon said…
Hi Anonymous: Please see Alan Bergo's comment below this. He says it has nothing to do with boiling but when and where the watercress is harvested.
Anonymous said…
Dog simple and plain as a significant majority of nutrients 50 to 70 percent will be lost stop sugarcoating the truth, Its still better than raw watercress flavor, but if you want the full nutritional content of a food without bitterness you must dry them into a powder, if it still taste bitter mix it into a smoothie.
I made 2 pots of soup with 1 bunch of watercress, 3 days apart. Day 1 soup wasn't bitter but day 3 soup was. Same method both times, inside a pressure cooker for 40min. Except day 3 soup,i did not saute it after releasing the pressure and adding salt. Day 3 soup was bitter. Day 1 soup was delicious. Could the post-pressure sauteing make a difference?

No idea...
Krista Goon said…
Hi there! I have not used a pressure cooker for making watercress soups so I can't say if there's any difference sauteing or not. Interesting outcome though and I really want to figure out why sometimes watercress soups get intensely bitter. Did you let the soup come to a boil first with the pork bones before you added the watercress?