Vegetables – Yellowish turnip

To address your points in order:

• If you only cooked your soup for ten minutes, you didn't give it enough time for the flavours to 'marry'. A gentle simmer for half an hour would give you better results. A night in the fridge to really let everything blend would be even better.

• You will not get crispy potatoes in a soup - the liquid will see to that. The only way you will achieve a crispy potato is by cooking and sauteeing them entirely separately and adding them at the end as a kind of crouton

• Green beans don't need much cooking at all - they should still have some bite. If you really want to keep the colour specifically, blanch them separately, plunge them into ice water, then drain and add to the soup for the final 5 minutes of cooking or heating.

• Tomatoes help counteract this by lending some acidity and fruitiness. If you don't want to use tomatoes, try a little white wine or cider vinegar to give a bit of zing.

What you are describing is what we call a food that has "soured". (This is what I was taught growing up.) The food looks and feels perfect but has that awful sour odor.

In my experience it is from improper storage, usually from foods being kept too warm or not getting enough air circulation. (Not necessarily by you, but somewhere along the transport chain.)

I have found it in both Brussels sprouts and broccoli. I have even bought broccoli, used some of it, and later taken the rest out only to find it soured. Or bought Brussels sprouts and kept them for a couple of days before using and found that they had soured. This says to me that the souring process had already started.

Additionally, I have had it happen with fresh corn that was left on my porch in warm weather.

I have also found it in bagged salads and spinach. With those, a good washing and fresh air sometimes gets rid of the odor - but not always.

Unfortunately, we don't always know how foods have been handled and stored before we buy them.

I have searched extensively to find out more about this, to no avail. I can find information about how to tell if food is going bad or rotting, but this is a totally different thing. You have no way of knowing that this souring process is happening. That is, until you smell it.