I was this past weekend experimenting a little bit with Transglutaminase (TG). TG, also known as “Meat Glue” is used to bond food together. A transglutaminase is an enzyme that catalyzes the formation of a covalent bond between a free amine group (e.g., protein- or peptide-bound lysine) and the gamma-carboxamide group of protein- or peptide-bound glutamine.
More specifically I was using Activa® GS (from the manufacture Ajinomoto), which is a mixture of transglutaminase, maltodextrin, and gelatin, with the addition of polyphosphate salts and oil. Activa GS is known to be able to bond relatively large food pieces.
The preparation is recommended to be combined with water to make a slurry, which is alkaline or basic due to the polyphosphates. Since the TG enzyme is inactive at high pH, the slurry remains stable until it is applied to the meat. At that point, the pH drops, activating the enzymes, and the bonding begins. Unlike other TG preparations, Activa GS has the advantage that it can be left out on the counter all day without degrading.
I wanted to test a couple of things today:
1) I opened the bag with TG almost nine months ago and all sources highlights that the TG enzymes degrades quickly once exposed to oxygen (and the TG package itself, even if unopened, is said the hold for not more than two years). So I wanted to see if it still was working properly. That said, once opened (nine months ago) I vacuum sealed it and I have most of the time after that kept the bag in the freezer, so I have basically taken care of the TG to my best knowledge once opened.
2) It is recommended to make a slurry with 4 parts water, by weight (e.g. 10 gram TG and 40 grams of water) or make a dry addition to a mixed- or tumble-marinated product. It is supposedly NOT recommended for an application using a sprinkle coating (which is fine for a lot of other Transglutaminases). Consequently, I wanted to use my (“old”) Activa GS and use the sprinkle coating method to see if this works or not.
To make a long story short; it worked fine using the old Activa GS together with the sprinkle coating method!
Here are the details:
I bought two filets of Atlantic wolffish (Anarhichas lupus), also known as the seawolf, Atlantic catfish, ocean catfish, devil fish, wolf eel (the common name for its Pacific relative), or sea cat, is a marine fish, the largest of the wolffish family Anarhichadidae.
I sprinkled both “contact” sides of the filets.
After that I mounted the two filets together. As maybe can be seen on the pictures, the two pieces are not shaped like boxes but on the other hand they are approximately symmetric to each other, each piece having a “slope” (thinner) side. The thing here is to match the thin side of one the fish filets with thick side of the other fish filet.
I continued the forming by wrapping the fish filets in cling film (plastic/glad wrap) pretty tight.
After that I placed the wrapped fish in a sous-vide bag and vacuum packed it.
After forming, products are generally left under refrigeration for 4 to 24 hours to allow bonding to become complete. After the reaction is complete the products can be frozen, tempered and portioned. I left the bag in the fridge for about 4.5 hours. After this I opened the bag and removed the plastic wrap and put the now bounded fish back in the bag together with some butter and virgin olive oil (and again vacuum packed it)
The picture below shows the “bonded” side of the two fish pieces. You can hardly trace that it is constituted of two different sections.
Below is a picture of the “top” (maybe less interesting) side of the mounted fish.
I then cooked the seawolf sous-vide in a tempered water bath set to 50 degrees Celsius (120 degrees Fahrenheit) but I took the bag out of the bath when the core temperature reached 46 C (115 F).
Finally I quickly seared the wolffish in a hot frying pan to get the Maillard reaction.
I served a puree of broccoli to the fish (I cooked the broccoli sous-vide at 83 degrees C (181.4 F) for an hour and then run it in Vita-Prep 3 together with some cream, lemon, cream cheese, peeper and salt. My initial intention was to make a super smooth puree but I managed to destroy my homogenizer…).
To summarize: I am very pleased with the result and there is not any problem I have noticed to sprinkle the Activa GS. Some may see this as a play with food but I don’t think thats the case though, for instance, a restaurant can save a lot of potential food waste by using this method. I personally also think that (in a lot of cases) the end result looks more appealing (and you also “eat” with your eyes…). Moreover, it is easier to get a more even and consistent cooking with a more uniform piece of meat which of course also improves the end result.