On 2004-11-21, Wayne Boatwright > wrote:
>
> You pretty much hit it on the head, notbob. The potential for abruptly
> expanding from the inside out can easily result from quick pressure
> release. I've even seen this difference in a roast.........

Many many years ago when I was still wet behind the ears, I operated a steam
retort in a cannery. This was definitely an issue with cans. Pumping cold
water into the retort would drop the pressure so fast, the cans would, if
not burst, at least bulge, rendering them unsellable. So, pressurized air
was pumped in along with the cold water to contain the heat generated
pressure inside the cans till they cooled. Though I've never seen an
exploded roast or anything I've home pressure cooked, I figure the priciple
is the same. If there's another reason, I'm open to enlightenment.

nb