I am baking a fancy cake recipe for the first time, and have trouble with it.
Basically, the cake has three layers. The first one is a flourless bisquit. Then there comes a guar thickened puree made of fresh mangoes and grand marnier , and above them JI am supposed to smear a thick wallop of a mascarpone-sour cream combination.
I have all three ready (not yet combined), only the puree is quite runny. I expected it to get as hard as starch-based custard does when it cools (frankly, I have never yet tried to achieve something actually stiff with guar). But I have already put three times as much guar as the recipe called for, and it is a very viscous liquid – when you pull the spoon out of it, you see ridges which slowly run back to smoothness. It is yummy, but there is no way it will carry a thick layer of the dairy stuff (which is not quite hard itself). There is a lot of puree, about 750 ml for a 28 cm cake, so the layer is supposed to be thick.
The best solution I can think of is to mix some gelatin into the mango stuff. But I have never used gelatin and guar together, so I am not quite sure what the result will be. First, will the taste suffer (I know that thickening agents shouldn't have an impact on taste, but I've actually had too much gelatin ruin the taste of the thing). And second, will some weird physical effect caused by the guar prevent the gelatin from setting?
And if you have any better idea than the gelatin, I'd be happy to hear it.
Best Answer
To me, the definitive guide to all these gelling agents is "Texture", the free e-book at khymos.org (which I know about because of this site, by the way). It says that mango is an inhibitor to the working of gelatin, so gelatin won't help as much as you might hope. Having said that, some of the example recipes do use gelatin, so it might still help enough.
About guar gum, it says that acidity (low pH) is an inhibitor; are there any acids in your mango puree? It also says that guar gum leads to high viscosity when warm and low when colder, so cooling it down should definitely make things more solid. You could also try some of the other agents; maybe xanthan gum will help.