Cooking slow-roasted pork to 190F?
I got a recipe from America's Test Kitchen for "slow-roasted pork" using a bone-in pork shoulder. They say to cook it at 325F until it's 190F internal temperature.
However: you normally need to cook pork only until 160F to kill microorganisms. Wouldn't cooking it until 190F dry it out? Why would they say to cook it until 190F if 160F is normally sufficient?
They say to cook until 190F because that's the temperature at which the stuff that actually makes your slow-roasted pork moist, the collagen, fat, etc. is breaking down and coating the meat. Less than that and you'll have all those bits still intact in your shoulder, which you don't want.
ATK explains this in their footnote on the recipe:
Just like in a pot roast, cooking the pork low and slow (325 degrees for 5 to 6 hours) pushes the meat well beyond its “done” mark into the 190-degree range, encouraging intramuscular fat to melt, collagen to break down and tenderize the meat, and the fat cap to render and crisp.
ATK's foot and header notes have taught me a lot over the years and I highly recommend them.
It's not the fat (it melts much earlier, and would break down at above 150°C). But you are correct about the collagen, it needs a long time at 68°C and above. A thing neither you not DHayes mentioned: The muscles will indeed dry out, so this method is only suited for certain cuts, rich in collagen. Dried out muscle fibres lubricated by melted collagen feel good in the mouth.
Also, why is 325 considered a "low oven" -- it's not that low. When I make ribs in the oven, I cook them at 250 for 4 hours. 250 is definitely low. Why not cook the pork roast at 250 for a longer period of time?
@Paul - most ATK meat recipes that aren't for slow roasting cook at more like 450-500.