Glucose vs. Gelatin

Reader Chana asks:

I was just reading this post on invert sugar (which I have never used). My question: why use gelatin in sorbet, etc. if glucose sugar will do the trick? Do they do the same thing? I’ve never used gelatin, either. It tends to be an animal product (i.e., not kosher), although I suppose synthetic gelatin is readily available. What do vegans use? Is synthetic as good?

Glucose does indeed help inhibit crystallization in sorbets, no question. However the reason I tend not to use it is because it doesn’t perform the added function of thickening the sorbet mix. Glucose molecules are quite small, nowhere near the length of a protein (gelatin) or starch (locust bean gum) molecule. That means that glucose won’t inhibit the flow of the mix like a stabilizer will. Of course a thicker mix isn’t essential for making a sorbet, however because thicker mixtures tend to run less, they give the impression of a slower-melting dessert.

As far as gelatin substitutes go, algae-derived agar-agar is a popular one for many vegetarians. I myself don’t care for it because it produces a more rigid gel with an almost crumbly mouthfeel. Also, it’s my impression that you can’t melt and re-mold it like gelatin, but I could be wrong about that.

UPDATE: Reader Bronwyn comments:

You can melt agar, but it melts at a much higher temperature than it sets at. It’s strange stuff. We use a very pure form of it in the labs for running DNA gels and a slightly less pure form for the gel in petrie dishes for growing bugs on. When you dissolve it you need to heat it pretty much to boiling point before it melts and dissolves properly, but then it doesn’t set until it cools to 40°C or so. Then if you want to melt it again it needs to get back up to near boiling.

The high melting point is what makes it nasty (to my mind) and crumbly feeling when you eat it. I like gels that melt in your mouth.

UPDATE II: Reader Laura adds:

In regards to Chana’s comment, a kosher gelatin product was recently released on the market (made by Glatech). Theoretically, you can get unflavored, although my local kosher market just carries the sweetened/flavored/colored versions.

There is also Diet Kojel (unflavored unsweetened sugar-free jel dessert), which is a kosher/vegan gelatin substitute. Here is the ingredient list: Vegetable Gum, Adipic Acid, Tapioca Dextrin, Calcium Phosphate, Potassium Citrate. I think that the vegetable gum is carrageenan because the French version of the ingredient list is: Carragenane, acide adipic, dextrine de tapioca, calcium phosphate, citrate de potassium.

The thing about Kojel is that it sets up quickly (room temperature or slightly cooler, I think) and it can’t be reset once it sets up.