Why did shrimp stock darken?

[JuanaCook]

3 weeks ago I made shrimp a shrimp stock from which about a quart was frozen. Last week we wanted another dish that required a stock, so added the first stock as an ice-block to the new batch then topped up with water. After thawing plus 45 minutes or so, the simmered stock tasted good and ready. I strained it into a container then immersed that container in ice water to quickly cool it down then set it aside for a few minutes until needed. When I collected the chilled stock, I noticed it had changed from the opaque yellowish color I expected to a grayish color. It tasted ok so I used it.

What prompted the color change? How can it be avoided in the future?

Thanks

 

[CraigC]

3 weeks ago I made shrimp a shrimp stock from which about a quart was frozen. Last week we wanted another dish that required a stock, so added the first stock as an ice-block to the new batch then topped up with water. After thawing plus 45 minutes or so, the simmered stock tasted good and ready. I strained it into a container then immersed that container in ice water to quickly cool it down then set it aside for a few minutes until needed. When I collected the chilled stock, I noticed it had changed from the opaque yellowish color I expected to a grayish color. It tasted ok so I used it.

What prompted the color change? How can it be avoided in the future?

Thanks

Probably too many variables to place a finger on it. What went into the stock besides the shrimp?

Craig

 

[JuanaCook]

Shrimp shells and a basic mirepoix with onion, carrot, celery. Sachet d'Épices with whole peppercorns, smashed garlic clove, 4 twigs fresh tyme & 3 bay leaves. Liquid was 5 cups of frozen stock from previous batch topped up with about 5 additional cups of cold water. I skimmed it but avoided stirring, like a beef or chicken stock. The stock tasted ok and was the color I expected until after it was chilled in a plastic container that was immersed in ice water. It still tasted fine, but the color had become a grayish.

 

[Zhizara]

I don't know if this helps, but as I use frozen stock to cook something else, the stock does get darker with each use.

Each time I use the stock I have, I add an equal amount of water, as you do, and and after cooking, I pour off at least another container just to return to the freezer, enriched by whatever I cooked in it.

 

[Sir_Loin_of_Beef]

It's because of the economy, and the volatility of the entire market