Originally Posted by mckallidon
True story. But that is only for roasted bones. If you did that with any raw carcass, you'd get all sorts of nasties in there. A pressure cooker would increase the rate of this process. As you increase pressure, you need more energy (heat) to get the same effect on the liquid (boiling), because the pressure keeps the water molecules from escaping off the surface as steam. You need more energy to overcome this. This increase in energy creates more motion of the water molecules which increases the rate that they dissolve the bones.
I highlighted this post because by the time you've made a few stocks--both at home and at work, you'll realize what utter b*llocks this highlighted post is.
Both open pot simmering and pressure cooking are methods to extract flavour. BUT neither method will work if you don't have flavour to extract. Before I can elaborate any further I have to take you back to cooking 101.
Lets say you cooking a chop or a steak. After the item is cooked, you remove it from the pan, pour off any oil and you deglaze the pan. What you are de glazing is the fond, or carmelized juices. It is these juices that have all the flavour.
Like spoiled Broth said in the above post, bones don't have much flavour. Why do we use them? Because untill about 20 years ago, most kitchens would butcher their own meat, bones come with the meat whether you like it or not. Rather than toss them out, you might as well coax the little flavour that they do have out of them. You can't saute or fry a bone, it has diddly-squat for water content so it won't fry, but you can roast them. When you roast, you are caremelizing the surface of the bone. This doesn't offer the same amount of flavour as real meat, but it does have some flavour. The smaller the bones, the more surface area you have, and therefor more caramelization, it is also faster to extract flalvour from smaller bones. You need to roast so the bones have a nice pale golden colour, then you add your nirepoix, roast untill this has good colour, add your tomato puree, and roast again untill the puree is mahogany coloured. When you roast mirepox you are also caramelizing the natural sugars and concentrating the flavour. Then you drain off all fat, put it in a pot and add cold water unitl it cover 2/3 of the bones--the mess will settle and be submerged under the water. Don't throw out the roasting pan, you can deglaze this with water, wine, or remmoulage. Bring to a boil, lower the heat to a bare simmer, and skim off any scum, then add your aromatics like bayleaf, peppercorns, and single clove.
Now I should explain about fat. Fat is a thief. It robs liquids of flavour and coour. You need to remove this as quickly as possible when it forms. Bones and meat trimmings will release fat slowly, so you have to be on guard.
Not all bones are suitble for stock, marrow bones offer little in way of flavour, and you need to extract the marrow--which is fat, if you want to use this type of bone.
Again, as spolied broth wrote, you need bones with cartilage, connective tissue, gristle and bits of tough-as-nails-meat attatched to it to roast. Cartialge provides natural gelatin, which gives your stock(and resulting sauce) body, suaveness, and smooth mouthfeel. Many cooks augment this with the addition of split and blanched calves feet--or more commonly pigs trotters, turkey wings or chicken wings.
I can't comment on using a pressure cooker for stockmaking--in my 35 years of cooking, I've never used it. Most palces I've worked in, we need to do 40-80 liters (U.S. 1 quart) once or twice a week, a mickey-mouse pressure cooker isn't gong to handle that kind of volume.
Like others have written, good stock takes time to make--as with most other things in life too, I guess. Dedicate one day to fooling around in the kitchen at home: Some nice tunes, some choice beverages, and take your time to make stockaybe do some baking or other prepwork for the week. Stock freezes beautifully, take advantage of this fact.