Hey guys? Help me brainstorm how to make a new drink I'm kicking around.

[xiphias]

It's called the "Boba Libre".

See, the "Cuba Libre" is the official bartender name for a rum and coke. "Boba" are those tapioca pearls that you get in bubble tea.

And it's not quite working yet. I can't get the texture of the boba right. I may just need to practice with normal boba for a while.

So, you boil the tapioca pearls for, like, 25 minutes, then you let them cool for half an hour, and they'll supposedly stay appropriately chewy for several hours after that.

I've been doing the boiling in rum instead of water, and then putting the rum-soaked boba into a glass and pouring Coke over it.

It's almost working. But the texture is just a little off.

Any thoughts? The pot the boba boil in is sealed tightly to keep any alcohol vapors from escaping, and to keep oxygen out, so that the whole thing doesn't just catch on fire -- and it's a glass lid, so I can watch the alcohol condense on the top of the pot and drip back down in.

Should I be boiling the boba longer, assuming that the mixture is boiling at, say, 200 degrees F (93 C), instead of 212 F / 100 C? (Alcohol has a boiling point of 173 F/ 78.3 C, and distilled liquors are usually 40% alcohol, 60% water, so would that mean that it's boiling at about 200 degrees? Or would it mean that the alcohol is floating around as a vapor, and that then the water boils normally?)

Does anyone know anything about the specific chemistry of tapioca?

Comments

[brooksmoses]

Alcohol has a boiling point of 173 F/ 78.3 C, and distilled liquors are usually 40% alcohol, 60% water, so would that mean that it's boiling at about 200 degrees? Or would it mean that the alcohol is floating around as a vapor, and that then the water boils normally?

Mixtures are considerably more interesting than either of those two options. :)

The canonical graph looks like this, if I'm remembering my materials science correctly: Take a horizontal axis of mixture fraction, from 100% water to 100% alcohol, and a vertical axis of temperature. Put dots at 100% water and 212 F, and 100% alcohol and 173F. Then, draw two curved lines between the dots -- one line is concave upwards, one is concave downwards.

Normally, both lines will have a monotonic slope from one side to the other -- that is, when going from the "water" point to the "alcohol" point, they're both always sloping downwards -- but IIRC this isn't always true; there are cases where mixtures can boil when either compound alone won't. (Also, IIRC, alcohol and water do this slightly, which is why you can't get pure alcohol by distillation alone.)

Now, for stuff in thermodynamic equilibrium, anything below the bottom line is liquid, and anything above the top line is vapor. Anything between the two lines does not exist.

So, if you've got a mixture that's partly liquid and partly vapor at, say, 200F, to figure out what's in it you draw a horizontal line across the graph at 200F. The horizontal position where that intersects the top line gives you the composition of the vapor; the position where it intersects the bottom line gives you the composition of the liquid.

Alternately, if you want to find the boiling point of your distilled liquor, you can draw a vertical line at that concentration, and where it intersects the bottom line gives you the boiling temperature of that mixture. Draw a horizontal line through that intersection, and where that intersects the top line then tells you the concentration ratio of alcohol and water in the vapors that are boiling off. (That ratio will have more alcohol than water, which is why the mixture will loose alcohol faster than water when it's boiling in open air, but it is losing some of both even though the boiling point is notably less than that for pure water.)

Since the line is concave-upwards, that means the boiling point is less than 200F; I have no idea how much less.

I have no idea what this means for the boba, but it probably will need to boil at least somewhat longer.

[solipsistnation.livejournal.com]

Hm, ok.

From my high school chemistry, I suspect that if you are boiling stuff with alcohol in it, you're going to be cooking the alcohol off first and then boiling just the water. This is how fractional distillation works-- the solution will first boil at 173F until all the alcohol is gone, and then heat up to 212F. So, you will probably end up with rum-flavored boba with little or no alcohol content. (Yeah, less science than the first reply, but there you go...)

[xiphias.livejournal.com]

Except that the alcohol is condensing on the pot lid and dripping back down in -- as the lid is glass, I can see it happening, and I can tell it's alcohol and not just water steam because, well, it LOOKS like alcohol and not water. You know, legs and tears and all that stuff. Condensing alcohol looks . . . shiner, smoother, oilier than condensing water.

There's alcohol in them boba. I nibbled on a couple. There's alcohol in them.

[solipsistnation.livejournal.com]

Cool. I didn't think about it condensing and dripping back in. That's neat.

Alcoholic boba is a brilliant idea...

[sinboy.livejournal.com]

Boba Libre? Boba Libre? Donde?

*knocks Boba Libre into El Pit De Sarlac*

[navrins]

Gracias. Somebody needed to do it, and you did it way better than anything my brain was coming up with.

[mattblum.livejournal.com]

Is the rum still drinkable after being used to boil the boba? If not, aren't you using up a lot of rum doing this?

In any case, my recommendation would be to boil the baba normally, or maybe in a rum/water mixture (maybe 30/70?). Then, after you've boiled them, leave them soaking in rum until you use them. I suspect that the textural difference might be due to the fact that the steam being absorbed is largely alcohol instead of largely water. But, then, I'm no chemist.

[xiphias.livejournal.com]

Is the rum still drinkable after being used to boil the boba? If not, aren't you using up a lot of rum doing this?

Not really, and yes, I am. I'm still in the experimentation phase. If I get this to an implementation phase, I'll work out a more efficient methodology.

[wcg.livejournal.com]

Try boiling the tapioca in water first for about 20 minutes. Then drain the water, put in the rum, and bring to a boil again for 5 minutes. See if that helps.

[adrian-turtle.livejournal.com]

I can't stand either rum or boba, but my experience with cooking grains of stuff (rice, oatmeal, barley) in stuff other than water. Well, including some water, but not JUST water. Broth, milk, juice, etc. They don't have such a drastic boiling point difference as rum, but I've found they're all much better for flavoring grain than for cooking it to the right texture. It's a significant trade-off, and I have not found a way around it by adjusting the cooking time or temperature...the only way I can get good texture is to dilute the flavored liquid or do some pre-cooking in plain water.

[kightp.livejournal.com]

Yes. It's kitchen chemistry; the starch in the tapioca will react differently to different liquids, which also react differently to being boiled. It wouldn't surprise me if the solvent nature of alcohol will react differently with the tapioca starch than plain water would. That could certainly affect the texture of the finished product.

Alas, I don't know enough chemistry to tell you what's going on or how to correct for it. You need a collaborator who's into "molecular" cuisine.

[xiphias.livejournal.com]

That's more or less what I'm hoping for in this brainstorming.

A little secret about the molecular cooking movement and molecular mixology? Y'all are as smart as any of the folks doing it, and smarter than most.

[kightp.livejournal.com]

Yeah, but they get to play with Really Cool Stuff. (-:

[cattitude.livejournal.com]

As an experiment, you might try using vodka, or perhaps everclear and water, instead of rum. The sugars and such in the rum have got to be complicating matters.

[xiphias.livejournal.com]

I doubt it will make that much difference. The amount of non-alcohol non-water stuff in rum is fairly trivial for the level of chemistry we're talking about. Maybe if I was using a dark Jamacan rum, too, that might be significant. But this is just Bacardi, and chemically, I suspect that the difference between Bacardi and vodka is basically a few ppm of aromatic esters.

. . .

Okay, I just had a teaspoon of Bacardi while holding my nose, and there IS a very slight taste difference between Bacardi and vodka, but not a hell of a lot. Without aroma, there's not that much rum-like about Bacardi. It's all in the aroma. So I continue in my suspicion that there won't be that much difference for this level of chemistry.

[trinker.livejournal.com]

What's off about the boba?

And are you adding any sugar to the holding liquid afterward? I seem to recall that that contributes to the gloss.

[sproutntad.livejournal.com]

eeeeewwwwww......

boba is disgusting - why ruin a perfectly good rum a coke? :) But other than that, it sounds like a lot of fun to try it. I'm just not going to be a guinea pig for you!

[arib.livejournal.com]

I don't have much knowledge of kitchen chemistry at all, but I'd love to hear how this turns out (or try one, honestly...)

[wandaphishy.livejournal.com]

It's almost working. But the texture is just a little off.
Any thoughts? The pot the boba boil in is sealed tightly to keep any alcohol vapors from escaping, and to keep oxygen out, so that the whole thing doesn't just catch on fire -- and it's a glass lid, so I can watch the alcohol condense on the top of the pot and drip back down in.

I think the texture problem comes from losing the alcohol during the boiling process; any “sealed” pot has leaks (and it should have, otherwise it will explode) and the alcohol is the first thing that escapes the system since its boiling point is the lowest. You could use a common (http://www.breathalyzercanada.com) to check the alcohol loses.

[xiphias.livejournal.com]

Amazing. This is clearly a spam account, but with an actual human reading and responding. Normally, I delete spam comments, but I'm impressed enough by you that I'm leaving this one up. Congrats!