Originally Posted by siduri
That's reassuring, wurzel. The trans sounded like some transgenetic experiment, and long chemical words are offputting. I still think it's weird to be gluing meat - with something that produces ammonia and smells like wet dog, albeit for a little time. I had never heard of the stuff from media or anywhere else, i just like food to be made of food. I'm put off by the fake meat made with soy protein, "soy milk" and other stuff that's "natural" but the result of some elaborate process.
Ahh, another chance for the friendly neighbourhood biochemist to come for the rescue...
Ok, glutamine is a natural amino acid - every protein has some. Most will know it in form of its salt, glutamate. That's why glutamate actually carries the savoury umami flavor- it is a mechanism of our body to tell us "look, there, protein rich food, I need that right now". Incidentally, the reason why I do not like to flavor with MSG - it is cheating exactly this system, and such things never go too well.
Anyway, glutamine has a free carboxy-amide group, looking like this Glu-(CO)-NH2. Now, there are other amino acids with free amino groups, such as lysine. It's terminal amino group looks like this: H2N-Lys
Transglutaminase does the following, hence the "trans" part of the name which has nothing to do with transgenics:
It takes the glutamine and for example the lysin: Glu-(CO)-NH2. + H2N-Lys and exchanges the NH2 groups between the both, so we end up with Glu-(CO)-NH-Lys. The two are now cross-linked, as we call it. Essentially, if the both amino acids were on different proteins, those proteins are now glued together. Of course, that leaves us with one amino group NH2 and a proton H, which recombine to make NH3 - which would be ammonia, hence the wet dog smell.
This is a perfectly natural thing, happening in your body all the time, tightly regulated, of course. However, if you drop huge amounts of it on meats, it'll efficiently glue them together.
I have no problem with applying that in the kitchen - as long as you do not use it to make crappy ingredients appear better - such as industrial pseudo-ham...
Now, to the application. Enzymes like transglutaminase are fickle things. They do not like too much heat, they do not like too much cold, they do not like to few or to much salts or acids in their environment. In the lab, we control these parameters very finely - I am seriously surprised that it works in the kitchen at all. Even under lab conditions, I do not expect a certain enzyme to work 100% consistently. So if it doesn't work, just write it off. Probably not even your fault - the little princesses of proteins have a temper ;)