Before I get to your specific questions, I should note that there are lots of other threads on the site that address the question of espumas/foams and the tools used to make them. For example,
here and
here, and that's just for starters.
So, my CDC just bought me a spuma canister thingy to use for making amuse and no one in the kitchen is really experience with using one, so I was wondering about all the little things I should know about using one and what I can do with it. So far all I've made have been cream based foams from root veg purees or cheeses. What else can I do with this thing?
It depends on the specific model you have, but you can make lots of different types of foams. If you speak any Spanish, you'll find a great PDF file explaining lots of different types of foams here:
http://www.cookingco...mas_elBulli.pdf (though, as I write this, I can't get the link to work).
You may also be able to use the canister to make carbonated fruit by using the CO2 capsules instead of the N2O ones, though this usage may not be condoned by the manufacturer.
A few specific questions:
- Can I make water/fruit based foams from purees? Would that require an emulsifier/stabilizer such as an oil, gelatin or lecithin?
Yes and yes. Gelatin seems to be the easiest and most common stabilizer. If you want to make any hot foams, you'll need a heat-resistant stabilizer; agar and egg white seem to be the most common for that application.
- What are some proper ratios for the question above?
It depends on the starting consistency of the puree and the desired consistency of the end product. Experimentation here is the key. I'm sure I'm not giving away any trade secrets to say that the PDF I mentioned above contains a recipe using 300g sweetened raspberry puree + 100g water and 2 sheets (at 2g each) of gelatin. That might give you a good starting point.
- Is there a way to change the amount of air injected into the foam? Would that be affected by how many chargers I use?
Exactly! Consult your product manual, though. I don't know what make or model you're using, but I have a pint-sized iSi Thermo Whip and the manual clearly states never to use more than 2 chargers.
- How smooth does a mixture have to be to pass through the spuma nozzle without clogging?
Every foam recipe I've ever read has you pass the foam base through a chinois at least once, and sometimes more.
- How full can I fill the canister for use?
Again, this should be indicated in the manual. The Thermo Whip has a maximum fill line indicated on the inside of the bottle. In general, though, the iSi products appear to come in one-pint and one-quart versions.
- When I charge the canister, does the charger foam up everything inside at that moment, or does it only add air to the mixture as it's being dispensed?
The way I understand it, the gas dissolves into the liquid, and when you release it from the pressurized canister, it comes out of solution, thereby foaming as it's being dispensed. But don't quote me on that.
