cooking gelatin

On Sat, 5 Feb 2005, Ryuji Suzuki wrote:

> Gelatin is a partially degraded collagen, which is the tough stuff
> found in the cheap cuts of meat, skin and bone. Collagen can be
> degraded by heat treatment, which requires many minutes of heating at
> about 95C. This is why people can make delicious stew out of tough
> cuts, and the liquid part of the stew makes stiff jelly when
> refrigerated. Equally delicious stew can be made at about 1/3 of the
> time by using a good pressure cooker capable of twice the atomospheric
> pressure, which makes the boiling point of water to be about 120C.
> (Crappy pressure cookers can't reach that high.) That is, gelatin
> itself is viable at these temperatures and duration of heating.

I make a pea soup with smoked ham hocks that gets boiled for 4 hours. I
roast a ham for an hour and a half, barbecue for 2 hours, soup with pork
sausage cooks for 3 hours. Some things get cooked for a day. So what?
These materials don't make very good size for gum printing.

> Commercial manufacturing of gelatin use strong acid or base to degrade
> collagen. Food gelatin is usually made by acid process of pigskin,
> and photographic gelatin by lime (base) process of cow bones.

Again, so what? How it's made is beside the point. How it's used is the
point. Powdered gelatin as an ingredient in cooking has to be handled
carefully -- in fact instructions on the jello box of old (I don't know
what they are today, or even if it's still made) were to dissolve in hot,
not boiling water. Recipes for chiffon pie, etc., mix in other ingredients
before cooking. Which, I will add, is merely illustrative, not necessarily
definitive. Experiences with sizing for gum printing, however, are
definitive.

> Gelatins do get broken down in harsh conditions, but not that easily.
> Bacterial growth is probably the most common cause of gelatin
> breakdown.

Oh my. "The most common cause of gelatin breakdown" ! Clearly then, you
have made a survey. So sorry, it has gone wrong somehow. Or let's say that
on the topic of sizing for gum printing you speak past your area of
expertise. Gelatin that has been scalded or overcooked will spoil a gum
print. Not that some styles of printing might not get away with it --
perhaps by scrubbing, or scouring, or whatever -- but that's not this
discussion. And I daresay it's not what the questioner had in mind.

J.S.
Received on Sun Feb 6 01:45:11 2005