Unsure why foam sauce doesn't hold
I experimented for with xanthan gum for the first time tonight. I made a sauce which was about half roasted peppers, half savory stuff (lamb stock, beef broth, balsamic vinegar and a bit of chili powder). I added about 0.9% of xanthan gum, strained through a fine sieve and poured in an iSi whipper with 2 shots of nitrous oxide.
I served it at 50°C, the sauce was nice and so was the foam, but it took only a couple of seconds until the foam melted and it became a sauce with big gas bubbles in it. I somehow expected the foam to hold.
Anything I missed?
Best Answer
I suspect your first problem is using the iSi whipper. It does create foams, particularly whipped cream, but both Khymos and Texturas advise using an immersion blender or electric eggbeaters in a broad vessel (so there is room for the bubbles to pile up without interfering with your making more). Besides, xanthan is shear-thinning, meaning that it is viscous only while at rest, becoming fluid when stirred or sprayed.
The second possible problem: while xanthan is used in some air recipes and is used to stabilize whipped cream and mousses, I find it is more effective as a thickener than a foaming agent. Next time you make a foam, try using lecithin. Lecithin is mainly used as an emulsifier, but it also dramatically alters surface tension, making bubbles more stable. Very little lecithin is needed to keep foams stable, though the exact amount will depend on the proportion of oil and water. For a fat-free sauce like the one you describe, I would suggest trying 0.5% lecithin by weight (i.e., for 200g liquid, use 1g lecithin).
If you really want to use the xanthan, you can try adding methyl cellulose to it. I saw a recipe for an eggwhite-free "marshmallow foam" that called for 1.5g xanthan, 1.5g methyl cellulose, and 250ml water, plus vanilla, salt, and powdered sugar.
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How do you stabilize foam?
The main ingredients for foam are air and water. Surfactants, which are similar to detergents, are then traditionally added to stabilize foams. Another traditional way to stabilize foam is to add microscopic particles, like talc powder.How do I make my sauce foamy?
To create frothy xanthan-only foam, try 0.5% to 0.8% scaling with a strongly-flavored fruit juice, like pineapple or watermelon. After combining the xanthan with the juice, allow to rest for 5 minutes (the mixture will thicken slightly with time) then dispense with a whipping siphon.How do you make xanthan gum foam?
By weight soya lecithin should be used in a concentration of 0.3-0.8% for foam and 0.5 to 1% for emulsions. As an emulsifier, it can be whisked into the chosen liquid; while for foams or mousses, a stick blender held just below the liquid's surface creates maximum yield.3 Ways To Make CULINARY FOAM with Siphon (MUST-HAVE kitchen tool)
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