Unless you are prepared to build some industrial strength equipment of your own design and then move everyone in the neighborhood away while you experiment with this, I fear you are taking your life in your hands.
Normal pressure cookers add a maximum 15 PSI to achieve a water boiling point of 121 C or 250 F. Autoclaves, used for surgical sterilization, go to 30 PSI. You are talking about going more than twice that.
There is no reason, based on the science of Maillard reaction, to believe that it would not occur at a high enough temperature. The presence of excess water would normally inhibit the process because of temperature reduction, but your "super duper pressure cooker" would keep the temperature at a high enough level to allow the chemical breakdown to occur. You might, in fact, discover that it occurs a bit earlier, as water tends to facilitate many reactions. Caramel making comes to mind as an indicator of what might be achieved, as sugar syrup (OK, most of the water is gone, but in principal) browns when you get in the above 330F-165C degree range.
As to crisping based on quick pressure reduction (perhaps when your device explodes?) That seems less likely as most crisping comes at the loss of water, and you are, in effect, keeping water in contact with your food both in liquid and superheated steam form. It would, most likely, be similar to a braised food surface, than a fried one.
Interesting thought. Please don't try this.
From a culinary viewpoint, there is little to no reason to use bones more than once in making stock. Even the author of the article you reference indicates the first go is the one that tastes best.
To maximize the quality of your stock:
- Use good clean or filtered water; add hot water as the stock reduces over time to keep the level above that of the bones
- Use good bones, chopped with a cleaver to reasonable sizes (a few inches)
- Optionally roast the bones prior to stock making for a deeper, browner flavor
- Skim the scum in the first part of the stock making process (obviously not an option in a pressure cooker)
- For a more clear stock, don't allow it it boil, but rather than let it go at a slow simmer (again, not in your control with a pressure cooker)
- Simmer it long enough for reasonably full extraction, which will leave the bones either bendy (more in the case of poultry or long bones) or somewhat fragile
- Include good quality vegetables for flavor
- Don't salt the stock, as during reduction it can concentrate and become overwhelming
In other words, apply basic cooking common sense and you will have a good outcome.
Best Answer
Like @Greybeard, I've had a great deal of success using a pressure cooker to make stocks and broths quickly. Pressure cooking is, by definition, at a higher temperature than normal simmering or boiling. In those methods, the upper temperature is limited to the boiling point of the liquid (212 degrees F, 100 degrees C for pure water, a bit higher for solutions with dissolved solids such as salt). The pressure buildup inside a sealed pressure cooker actually raises this boiling point; it's the opposite of why water boils at a lower temperature at higher altitudes, and a higher temperature means generally faster cooking.
In the case of stocks and broths, this higher temperature increases the rate at which collagen hydrolyzes; basically, it untangles from its original tough, tightly-woven state and forms free-floating strands which then tangle and interconnect as the solution cools, producing the characteristic texture of gelatin.
So: a pressure cooker is good, in that it reduces the amount of time that this process takes. Rather than 8 hours of simmering, you can use a pressure cooker and get a similar amount of collagen extraction in perhaps 3-4 hours of cooking.
If you're like me, you'll take a look at this result and wonder: if I can make a great chicken stock in 3 hours, what happens if I let it cook for 12? The answer, unfortunately, is disappointing. Bones will crumble will barely any effort, but the resulting stock won't be any more viscous or tasty than a stock cooked for a shorter amount of time. What gives?
Howard McGee's classic tome On Food and Cooking offers a hint: gelatin isn't impervious; those long strands are delicate, and they can be denatured or damaged by acids or enzymes. McGee also notes what a lot of people seem to miss: at higher temperatures, collagen strands on their way to becoming a tightly-bonded network of gelatin can become damaged, or "cut" partway down their length. Instead of a dense network of long strands, you get fewer bonds between shorter strands, and we perceive this as a less "gelatinous" broth.
In other words, using a pressure cooker raises the temperature so much that it can actually damage the collagen you're trying to extract over a longer cooking time, even as it takes less time to extract in the first place. This happens much less with an extended simmer, even one measured in days, because the temperature isn't high enough cause much damage - indeed, it can't be, because it's limited by the boiling point.
There's a balance point here: a pressure cooker will allow you to produce stock comparatively quickly, but it introduces the risk of overcooking (in the sense of destroying some of the collagen you've worked to extract). 3-4 hours under pressure seems to be the sweet spot for chicken stock; turkey can go a little longer, maybe 6 hours. For a beef or pork stock, where there is much more collagen to be extracted, using a pressure cooker is still faster but almost counter-productive; you can't fully extract all the collagen you might want without damaging some. If you really want a full extraction of all the collagen present, a traditional simmer is the way to go, even though it takes longer.
That said, you may decide that the advantage of speed for a commercial enterprise is more important, and opt for something like a 6-8 hour pressure cook for pork or beef bones; I wouldn't go much more than 12 hours, personally. You might even decide on an initial extraction in a pressure cooker, followed by simmering the already-cooked bones in the traditional manner until you've extracted everything that's left. You'll want to experiment a bit as you try to make this a viable business, but I'd definitely advise being aware of this limitation before you run into some less-than-optimal batches of stock like I did. (Don't get me wrong - the end result was still good, just not any better than stock pressure-cooked for a shorter period of time.)
EDIT: Somehow I made it through this entire long-winded answer without noting that many modern electric pressure cookers are also designed to be used as slow cookers, holding a sub-boiling temperature for an extended period of time without pressure. This is great - you can safely maintain a lower-temperature extraction for an extended period of time (though you need to make sure you use the "high" setting to get above the hydrolyzation point of collagen). They can also be programmed to switch from one mode to another. I've started successfully experimenting with hybrid methods: pressure cooking for an hour to jump-start the extraction, letting the pressure release, then slow-cooking overnight before straining in the morning. If you're going to consider pressure-cooking at all, this may be a way to get the best of both worlds.