Making spicy ghost pepper ice pops — how do I calibrate the heat and keep it e...

I'm making ghost pepper ice pops for a kids' popsicle stand. We do this every year and each year we introduce a few weird flavors.

Goal: someone who likes spicy food takes a lick and goes "wow, that's really spicy" — genuinely hot, but not novelty-challenge dangerous, since it's served to the public.

We will of course be very careful to separate this from the other popsicles, only serve it to adults, etc...

The hot sauce is basically the whole flavor. My base is water, a vinegar-based ghost pepper hot sauce, a little sugar, lime juice, and salt. (That is generally how you run the popsicle stand. Each flavor is just that ingredient without much additional stuff.)

Two things I'm trying to get right:

CALIBRATING THE HEAT

• What's the reliable way to calibrate — freeze a test spoonful and taste it fully frozen, rather than tasting the mix warm?

• Any tips on making the heat pleasurable rather than just punishing? I'm assuming sugar/acid/salt balance matters (like hot honey), but I'd love specifics on ratios or what actually shifts "painful" toward "crave-worthy."

• Rough sanity checks on landing "very spicy but safe for a willing adult" would help

— I'd rather build up carefully than overshoot.

KEEPING IT EVENLY SPICY

I have noticed that when I make popsicles, often the ingredients freeze unevenly and all the flavor sinks to the top or the bottom. I am worried that if I make a ghost pepper popsicle all the hotness will concentrate in one place and it will be insanely over hot in one spot.

Is this something to be worried about? Are there ways to address it? I'm considering xanthan gum (~1/4 tsp per cup) to gel the base so nothing migrates. Is this a good idea? Overkill?

I suspect that there will be enough heat retained in the ground chilies to allow you to do this without any major problems. Your biggest difficulty will be keeping the grounds suspended during freezing, which is where @ecnerwal's comment regarding the granita approach is probably the easiest option.

However, to my mind the best approach will be an icecream approach rather than ice-pop. Milk/cream will moderate the heat, so give you better control of the final heat and will allow excellent dispersion of the chili oil in the fats of the cream/milk. The casein in milk will also help keep the capsaicin in suspension.

If you must go with a water approach (and seeing as it is for adults) I would extract the capsaicin (the main heat ingredient in chilies) in ethanol (vodka would be the easiest in terms of flavour and availability) and add to the water-ice - you shouldn't need much capsaicin or ethanol to do this, but you would need to test how much per volume, both for dissolving the capsaicin, and how much to add for taste.

To do this grind your chilies until very fine (blender should work, or a mortar and pestle) in some vodka, allow to steep overnight in a sealed container and then (optionally) filter out the chili grounds using a coffee filter paper. I'd start with about a 1:3 ratio of chili:vodka in terms of weight, but you might need more ethanol than that to be effective at the filtration step.

Of course, vodka will also alter the freezing point of the water, so you can't add too much or the water won't freeze, or your ethanol will freeze fractionate - like when applejack is made. Capsaicin is ethanol soluble, with the ethanol acting to make the capsaicin also soluble in water. You also don't want to add so much as to make people drunk or unable to drive/look after their kids, or run afoul of any liquor sales/supply laws, so be cautious on adding more than a couple of millilitres per icy-pop.

The chemistry behind the solubility is that capsaicin is a non-polar molecule, while water is a polar molecule. "Like dissolves like" is the rule for solutions, so water can dissolve other polar substances, but not non-polar. Ethanol is a non-polar molecule (so can dissolve capscaicin), but has a hydroxyl group which allows solubility in water via dipole interaction, so ethanol can dissolve in water and also dissolve the capsaicin.