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A few times now I've come across online advice that, when steeping/infusing fruits in liquid to extract their flavours, it helps to add sugar to the solution. As an example this sloe gin Wikipedia page states "sufficient sugar is required while the drupes steep to ensure full extraction of flavour". Some commentators mention that this is obvious, because if you add sugar to strawberries they macerate and become syrupy. Well it seems to me a very big assumption that if sugar crystals draw in liquids/flavours from a high moisture-content source then a largely already liquid sugar solution must do the same thing. Can anyone clarify?


Edit: This SA answer to a related but I think distinct question would seem to suggest that adding sugar to the solution should in fact slow absorption down as it would reduce the difference between sugar concentrations in the solution and fruit..

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    You need to take into account the fundamental difference between sugar and water, compared to sugar and alcohol. That is what gives you the apparent discrepancy between the two statements. My favourite method for sloes and cherries is to prick and steep in alcohol first. Then pour off the liquid and add sugar. Pour the liquid off and add more sugar. Repeat about three times in total. At the end I have a really luscious colour, maximum flavour and little shrivelled up fruits which are just skin and stones. That is "total juice" and maximum extraction in my book!
    – user28908
    Commented Nov 18, 2014 at 22:46
  • Thanks Piglet. Your method sounds like what I think would work better. I think the Wikipedia statement still needs to be addressed. I haven't found anything other than what sounds like culinary myth and pseudo-science, so I remain skeptical :)
    – geotheory
    Commented Nov 19, 2014 at 10:44

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In sum: YES, sugar DOES really help to extract fruit flavors.

The answer quoted in the edit does NOT imply that "absorption is slowed down" in general. It merely states that in a sugar solution, sugar will generally not move out of fruit; it doesn't say anything about what else happens.

Osmosis is simply a process by which the stuff on both sides of a barrier tries to come to equilibrium. Increasing sugar content in a solution will only decrease the amount of sugar that comes out of the fruit, but it will often simultaneously increase the water that diffuses out (along with many things dissolved in that water, like fruit flavors).

In other words, in a plain water solution, sugar will diffuse out of fruit to raise the water's sugar concentration. However, in most cases when a sugar solution is used, it is deliberately higher in concentration than the sugar content within the fruit cells (as in the strawberry example mentioned in the question, where there is basically no water at first outside the fruit, so water is forced out to bring the system into better equilibrium).

Sugar is very hydrophilic, which basically means it attracts water. If the sugar solution has a higher sugar content than the moisture within the fruit cells (as is true in most recipes using this technique), water will diffuse out of the fruit. Anything that is water-soluble, such as various flavor components, will come along with it to some extent. Meanwhile, sugar will also be forced into the fruit, changing its texture -- when done in excess over a period of time, such a process can actually preserve the fruit by lowering the water content substantially (driving it out into the solution) while raising the internal sugar content of the fruit, resulting in candied fruit.

You may note that candied fruit generally lacks many of the flavors of fresh fruit. This is because many flavor components were extracted along with the water by the sugar solution.

Regarding questions that were raised in comments, the same process occurs with alcohol in a solution. There's almost no alcohol inside the fruit, so alcohol's presence outside the fruit will force water out of the fruit, carrying flavors along with it. Alcohol also tends to dissolve certain flavor components that water doesn't dissolve as well, so it will gather different sets of flavors than water alone. Note also that different flavor components will come out of the interaction of this osmosis process with the cell membrane compared to, say, simply crushing the fruit, again partly because some flavor molecules are more soluble in alcohol.

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  • This sounds very reasonable, thanks for the contribution! But going by this logic I wonder about the relative benefit of adding sugar in the case of sloe gin. The solution's water concentration is a relatively low 60% (vs berry's typical 85%) so water extraction is presumably very efficient already. And sugar absorption is also going to be optimised by not adding sugar to the solution, meaning better extraction of any sugar-related flavours. So I still can't see any benefit of adding sugar in this case. How does this sound to you?
    – geotheory
    Commented Dec 1, 2014 at 12:32
  • As I said in the answer, both sugar and alcohol have a tendency to draw water (and flavor) out of fruit. I've looked around a bit in food science books, and I don't see much explanation about interactions in solutions which contain BOTH sugar AND alcohol. While the general tendency of osmosis is to try to equalize things, there may be interactions here that still justify the sugar addition in some cases. (I rather like the idea of Piglet's method, which would pull different components from the fruit at different stages.)
    – Athanasius
    Commented Dec 1, 2014 at 13:36
  • Also, for the record, I'm not sure that "sugar-related flavors" really exist; flavors are not generally "dissolved" in sugar as they are in water. Increasing sugar output from the fruit won't actually increase flavor extraction to a significant degree; it will just bring out small amounts of sugar.
    – Athanasius
    Commented Dec 1, 2014 at 13:41
  • I like Piglet's method too. Also the notion I'm being advised by a friend of Winnie the Pooh.
    – geotheory
    Commented Dec 1, 2014 at 13:43
  • Not sure I agree on that. Sugar is a taste too, and different ones must have different flavours. Yeasts would certainly agree as many varieties consume some sugars but not others.
    – geotheory
    Commented Dec 1, 2014 at 13:47
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MY OBSERVATIONS SO FAR: I once left sloes with intact skins (not pricked) in water overnight to clean them. Nearly all the bigger ones split their skins so I disposed of them in case they made the gin cloudy. After adding gin (37.5% ABV) to just cover the remaining small hard sloes, the colour is a beautiful clear red after 2 weeks. The sloes are still intact and I usually leave it longer for a darker colour - no shaking. I add the sugar at the very end, after removing the sloes and diluting the sloe gin with more gin to give me the colour I want. I use 125gm/700ml bottle (approx 18% sugar by weight). The result of this method is a sloe gin of superb colour and flavour, and a slightly reduced ABV of 34% due to the added sugar.

CONCLUSIONS: (1) Sugar is not needed at the start to get a good flavour. (2) Sloes in plain water appear to absorb the water by osmosis through intact skins. (3) Pricking and shaking the sloes is unecessary, and could lead to sediment making the sloe gin cloudy - if the skins of riper sloes split. (4) The skin of the sloes seems far more important than the flesh in making sloe gin. Is extracting juice from the flesh really necessary?

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  • Useful thanks for sharing. I don't think I share your concern about split skins. I find it's better to freeze berries instead of prick - all the skins split regularly and speed up diffusion. The result isn't cloudy - just leave it a couple of days and slowly pour clear gin off the sediment :)
    – geotheory
    Commented Oct 26, 2015 at 16:45

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