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Now that the sun has started to shine in the frozen north I can start thinking on using my espresso machine for some cold drinks. I was thinking of a banana iced coffee. But I would like a more natural flavour than most of the syrups I can buy in my local coffee shop. Do I was wondering if it would be possible to extract the flavour from a banana, without getting the texture/consistency from the fruit?

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You'll need an appropriate solvent for this. The main flavor component in banana, isoamyl acetate, is not water soluble, so you will probably have to use alcohol. As a banana fruit doesn't have much flavor, I guess that you will need a large amount of your banana extract to bring enough flavor into the coffee, giving you the problem of turning the coffee into an alcoholic drink - more like a cocktail of banana liqeur and coffee than like a flavored coffee. Unless you can find some good method for concentrating the liqeur without losing heat-sensitive aroma compunds. –  rumtscho May 21 '12 at 14:36
    
Isoamyl acetate should be solvable in more than alcohol as far as I know. Perhaps the oil in milk and or coffee could be of help. Although it sounds like a good starting point for a drink. "Chimpanzee Coffee" –  daramarak May 21 '12 at 15:43
    
Banana milkshake syrup is probably the simplest way of achieving this. –  ElendilTheTall May 21 '12 at 15:58
    
@daramarak even assuming that it is fat-soluble (but be aware that most of the flavors of bananas probably aren't), you would have to create your flavoring by destillation, not infusion. And banana essential oil isn't common - there must be a reason for this. –  rumtscho May 21 '12 at 17:46
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4 Answers

Consider making a banana consomme via gelatin filtration. As described in Harold McGee's 2007 NYT article, this technique produces liquids with the taste of all sorts of foodstuffs that are otherwise full of texture and color. A tomato consomme, for example, is clear and watery, rather than red and pulpy, while retaining the flavor of a tomato juice. The same technique can be (and has been) done with breads, meats, vegetables, fish, etc.

The process is to make a loose banana gel by mixing a banana with water, adding gelatin, and heating until the gelatin is dissolved. The mixture is then frozen until solid, then suspended in a strainer over a bowl in the refrigerator for a couple of days until the liquid essence distills out and the solids are left in the strainer trapped in a gelatin net.

The particular advantage I believe gelatin filtration will give you in this case is that it will give your coffee a full banana flavor without making it thick, pulpy, or cloudy.

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This assumes that the flavors he wants are soluble in water - and the main one, the abovementioned isoamyl acetate, is not water-soluble. Others will evaporate or be destroyed when heated for the gelling. The technique sounds interesting, but I think that it will work with other stuff better than with a banana. Still, worth a try and an upvote. –  rumtscho May 21 '12 at 22:11
    
Definitely worth an upvote. Could try a vodka-banana gel, to trap that isoamyl acetate also. –  daramarak May 21 '12 at 22:22
    
@rumtscho, I'm not sure of all the mechanics here, but by experience, the flavor does come through regardless of solubility. As you're aware, a substance need not dissolve in another in order to be transported along with it. –  Ray May 21 '12 at 22:27
    
@daramarak, that might work, but I'd be a hesitant as the alcohol will counteract the gelatin. Perhaps simply increasing the gelatin concentration will make up for that effect. –  Ray May 21 '12 at 22:28
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Also, if you start with super ripe bananas and cook them sous vide for about 2 hours at around 74 C, a delicious though cooked flavored liquid will extract itself right into the bag. Tastes like the purest banana bread ever. More here: chefsteps.com/activities/simple-banana-custard –  Michael at Herbivoracious Aug 14 '13 at 15:13
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Although isoamyl acetate is the most commonly used bannana flavoring commercially, this is usually produced artificially (like banana milkshake powder) and so isn't what you want. I would make a 'natural' bannana syrup to flavour the coffee. I would try layering halved bannanas with sugar and leave it for a few day to let the water be drawn out. Then I would discard the bananas and add enough water to make a syrup and heat it to dissolve. Having not tried it I don't know if it would produce a strong enough flavour; I don't know if anyone else has any other ideas...

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Interesting, I'll give it a try. But you are right in the fact that I don't want the artificial flavour. –  daramarak May 21 '12 at 22:07
    
Using barely-soft-enough-to-eat bananas (green at ends) gives fruitiest flavor. Counter-intuitive but that's what banana chips are made from. –  Pat Sommer May 23 '12 at 6:08
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Let the bananas turn as brown and spotty as you dare. The banana flavor improves as they ripen and over-ripen. Then freeze them and thaw them again. This will bust up the cell walls and turn them into a gloppy mess. Use a colander or something to separate the liquid.

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Will this not add some sort of texture? I know you're straining it but won't it still have a certain texture? –  Sebiddychef May 22 '12 at 18:58
    
done that to use up over-ripe B's for bananabread. Does indeed weep clearish liquid. Very golden flavor –  Pat Sommer May 23 '12 at 6:06
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I would try steeping the banana peels in alcohol. The peels actually contain quite a bit of flavor but aren't generally usable, and they should impart minimal texture to the final infusion.

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That might be interesting. I have tried to infuse the bananas in alcohol, but never the peels. I would need organic bananas then I guess. –  daramarak Aug 15 '13 at 6:20
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