Hello. Given that the title of this blog is Soup and Stuff I felt that there was a lack of actual soups being discussed. Well honestly there is a lack of anything being discussed but for now I decided to make a soup using what little items I had left in my cupboard. I am trying to avoid going shopping as it is raining and I don’t like Tesco when it is busy. As it has been mentioned before myself and Claire are scientists, and so while I was making this several sciency things came to mind and I decided to include them. I think this makes the blog a bit more interesting (I think I should make it our USP !).
A quick Google search suggested that red cabbage soup could be something worth cooking. I bought the cabbage about 2 weeks ago and I haven’t really had any inspiration for it. For this soup I looked at these recipes and then decided to pretty much ignore both of them. Mainly due to a lack of ingredients, what I took from these is that red cabbage and acid (Lemon juice or red wine) seem to go well together.
Materials and Methods
So first I assembled the stuff I needed. For this soup I used
- 1 red cabbage
- 2 small onions
- 4 cloves garlic
- 1 beef stock pot
- 1 small quantity of clover light
- 2 tablespoons Balsamic vinegar
- 1 tablespoon Lea and Perrins
- Then for seasoning : Salt, Pepper, and Thyme
The actual method like any soup is really simple. First I chopped the onions, and garlic and softened them with some clover. Then I chopped up the cabbage into smallish bits, this is when the first sciencey thing came to mind.
Science interlude 1
When I sliced it down the middle, the way the leaves of the cabbage were coloured reminded me of structures found inside every cell in our body, the Golgi apparatus. The Golgi apparatus was named by its discoverer Camillo Golgi, in the late 1800′s. In our cells it functions to process and modify proteins before they are released into the cell. The image in the panel shows a cross section of a Golgi from a thin slice of a human cell, which has been frozen and then imaged with an electron microscope. The actual Golgi Apparatus is a big system of vesicles (membranous sacs), and according to Wikipedia your average cell has about 70 of them. Newly synthesised proteins make their way through these stacks and different enzymes modify the new protein for instance adding sugar groups or phosphoryl groups a protein. The individual cells in the Cabbage would have hundreds of Golgis (Golgii ?) in them too and I thought it was quite interesting how similar looking features can be found on a macro and molecular scale.
Back to the food
When the aromatics became slightly translucent, I added the chopped cabbage and mixed to ensure that the clover covered the cabbage. I then cooked until the cabbage became soft, stirring often to ensure bits of it didn’t stick to the pan (I was trying not to use too much butter, If you add more I don’t think you would need to stir it so much – for the lazy). The colour of the cabbage seems to intensify as the water inside evaporates.
Once it was nice and soft, I added the stock pot and topped up with water from the kettle until the cabbage was submerged. I added about 1 teaspoon of dried thyme at this point. Then I added the balsamic vinegar and the Worcester sauce. I then let the mixture come to the boil and turned the heat down to simmer for 10 mins. When I returned I noticed that the colour of the cabbage had changed from purple to a more red colour. Finally I seasoned the soup with some salt and pepper and at this point I tasted it and decided it was finished. The cogs turned and I realised at this point that the cabbage was purple and not red initially… why wasn’t it called purple cabbage ? This led me to science interlude 2.
Science interlude 2
When I thought about why the cabbage would change colour when I cooked it I remembered an experiment I did during my A-levels. We took beetroot, homogenised the tissue and diluted it out to use the extract as a pH indicator (pH is a measure of how acidic, or alkaline a solution is). I realised that the cabbage must contain the same or similar molecule as beetroot and that something must have changed the pH of the food as I cooked it. Obviously this was the vinegar, which almost everyone knows is acidic.
I decided to test this and took the base of the cabbage and poured a little bit of white wine vinegar on it, sure enough I saw the purple containing pigment begin to change to a pinky red.
I looked again to wikipedia and found that the molecule which gives beetroot and cabbage (and many other vegetables) the deep purple colour is an anthocyanin. You may have heard of anthocyanins as they are regularly paraded in the media as being super anti-oxidants. In plants they are thought to act as attractors for insects, and as a “sunscreen” protecting leaves from UV light. The figure below shows the general “skeletal” structure of an anthocyanin, the R groups indicate where different chemical groups or atoms can be present.
As I noticed, anthocyanins can also change colour depending on the pH. The colour changes from red in acidic pH, to blue at neutral pH, and finally to yellow and then colourless at high pH. The colour change due to pH change is driven by an equilibrium of a hydrated or “open” form, which is colourless and the “closed” or dehydrated form. Low pH favours the closed and coloured form, and high pH the opposite. This research article titled “The effect of light, temperature, ph on stability of anthocyanin pigments in Musa acuminata bract” contains more information on the chromatic shift in anthocynanin molecules in different conditions.
I ate the soup with some rye bread, it was very good. I think for some it might have been quite acidic, so I would maybe recommend using 1 tablespoon of vinegar. I am a vinegar fiend though and thought it was lovely. One smallish cabbage made enough soup for 2 generous servings so I have some to take to the lab with me tomorrow.
Overall I was impressed with this soup, despite it having hardly any ingredients, it was really tasty and it made me think how much of a weird person I am for thinking about science all the time.