[question] for the chemistry types- making chicken soup. Why did lemon juice turn the light brown chicken stock almost white?
[question] for the chemistry types- making chicken soup. Why did lemon juice turn the light brown chicken stock almost white?
Okay, so I was making chicken soup from stock I had made using a (lightly,) browned carcus and neck. just before dumping the the dumplings into it, the stock's color was a nice light brown. I added about 1/4 cup of lemon juice, turned my back for 30 seconds after a stir and it turned it an almost milky-off white. Eventually it deepened to this:
It's delicious, and tastes as expected, I'm just curious as to what happened in the broth's chemistry?
Seasoned with salt (duh), a sprig of thyme, some ginger and garlic, (just a hint of ginger,) black pepper, lemon zest (which was added with the torn chicken,) and white wine deglazed the pot from browning the dark meat.
The stock was from garlic, onion, celery, carrot and maybe ginger scraps cooked with the chicken carcass..
The citric acid in lemon juice is both a bleach and it denatures collagen and protein, which is probably the cloudiness.
The bleaching comes from the ascorbic acid (aka vitamin C), not the citric acid. Plenty carbohydrates get brown when oxidised; ascorbic acid is a good reducing agent so it reverts them back to their non-oxidised and lighter-coloured form.
I'm not sure but I don't think that denaturation plays a big role, since vinegar would also do it, and it doesn't seem to make stock clearer for me. I might be wrong though.
Thanks for the details!
Hmm interesting.
I wonder if the collagen is setting up now that some of the leftovers are in the fridge? Ah well that’ll be matter for later.
Thank you for the response,
America's test kitchen adds baking soda to lower the pH of meat to get it to brown more. Perhaps you did the opposite and the acid lightened and/or prevented browning?
apparently the citric acid interacted with the collagen and protien, from another comment, bleaching protiens and the collagen.
I'm not worried about the color... it's just... one of those "oh, that happened. that's fascinating" moments.
Baking soda raises the pH. (Low pH = acid; high pH = alkaline. Yes, they're switched.)
Alkalinity catalyses caramelisation and the Maillard reaction, that's why meat gets to brown more. However in acid environment both processes happen mostly the same as if they were in a neutral environment, acidity doesn't really prevent this sort of browning. (I'm glad for this, otherwise my Sunday roast would be really sad. I often leave the pork marinading in lemon juice for a day, and it still browns just fine.)