In Chapter 4, we discussed proteins coagulating when heated. Many proteins dissolve in cold water but solidify into small particles or into froth or scum when heated. It is these particles that make a stock cloudy. Much of the technique of stock-making involves avoiding cloudiness to produce a clear stock.
The purpose of blanching bones is to rid them of some of the impurities that cause cloudiness. The bones ofyoung animals, especially veal and chicken, are highest in blood and other impurities that cloud and discolor stocks.
Chefs disagree on the importance of blanching. Many feel it is needed to produce clear white stocks. Others feel blanching causes valuable flavors to be lost. Fish bones, at any rate, are not blanched because of their short cooking time.
Pr rocedure for Blanching Bones
1. Rinse bones in cold water.
This washes off blood and other impurities from the surface. It is especially important if the bones are not strictly fresh.
2. Place bones in a stockpot or steam-jacketed kettle and cover with cold water. Impurities dissolve more readily in cold water. Hot water retards extraction.
3. Bring the water to a boil.
As the water heats, impurities solidify (coagulate) and rise to the surface as scum.
4. Drain the bones and rinse them well. The bones are now ready for the stockpot.
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