Acids and Sweet mousses

[jctrs]

Im faced with a PBL in class that I can't seem to find online anywhere. I was hoping someone could help me on here, the question is...What are the acids in fruits such as kiwi and pineapple called that make it hard to use them to make mousses? Also why do they make it hard to use them in mousses? As well as how do you fix this problem? If anyone could help me out I'd appreciate it.

[Suzanne]

I don't know about kiwis, but fresh pineapple contains enzymes that prevent gelatin from gelling. The same kind of stuff that's in papaya, that "digests" proteins (hence chemical meat tenderizer is basically papain). So if your mousse relies on gelatin to set up, fresh pineapple will prevent that.

I'm moving this to the Pastry board, because the chefs there know a lot more about your problem than I do!

[madgoose]

if you just use canned pineapple or kiwi instead of fresh it had already been processed so it will not interfere with the gelatin or you could also try using a different stabilizer

[Nicholas]

The enzyme contained in pineapples, and kiwis that prevents the gelatin from setting up is bromelin.
And what Suzanne said. It breaks down the protein, preventing the gelatine from setting up.

Bromelin is destroyed by heating however, so like what madgoose already said, tinned pineapple or pasteurized pineapple juice can be used with gelatin.

*PS: I'm no chef, I just so happened to know about bromelin!

[Mangilao30]

I've made lime mousse with great success before and limes are really acidic.

[Zukerig]

A+ for Nicholas’s identification of bromelain! Gelatin increases the viscosity of a liquid because when the granules in gelatin are moistened, they swell to approximately ten times their original size, thereby trapping molecules in the process. It’s a phenomenon somewhat similar to the thickening action of starches, however the final results are different – a gelatin-thickened preparation will be finer-textured and will retain its stability under a broader temperature range. For a fuller exposition of the science of gelatinization, refer to ch. 7 of Harold McGee’s On Food & Cooking.

Some ingredients, including sugar in excess, inhibit gelatinization. Fresh pineapple is particularly difficult: The bromelain enzyme compound severely impedes thickening. If you want to include fresh pineapple in your mousse mixture, debilitate the hindering enzymes by simmering the fruit in water for several minutes. Alternatively, if you choose canned pineapple, you can omit the parboiling step because the enzymes have already been deactivated. I’d suggest that the way to go is with tinned pineapple, preferably an organic brand such as Native Forest.

Concurring with Mangilao30, above, lime mousses can indeed be successfully prepared using gelatin; yet my preference is to prepare gelatin-free mango-lime mousses.

Incidentally, classic French mousses are made without gelatin, although many cooks today add a small amount to ensure that the mousse holds its shape. A cold or iced “soufflé” is a gelatin-mousse poured into a mold with a paper-ring collar that helps the mixture to stand dramatically above the rim; then it’s frozen until firmly set.