Filtration of Gin that has Fruit Extraction using a Soxhlet Extractor

I am looking at experimenting by using a soxhlet extractor to extract fruit flavours for gin.

  • Gin in boiler > soxhlet > fruit > back in boiler.
  • The fruit will be in some kind of bag - maybe hop bags.
  • The bottom of the soxhlet will have some kind of filter - maybe cotton padding.
  • Now this will have much less fruit particles than maceration I presume but will still require filtration.

At present I use an enolmatic vacuum filler with an inline 1 micron filter.

Does anyone have an opinion on the enolmatic being able to pull this through a filter? And if so what micron filter might be required?

Or is that a silly idea and tank > tank initial filtration will be required? And if so using what? Something like the following stainless steel pad filter?

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Comments

  • edited April 3

    Why do you feel that a Soxhlet extractor is even necessary? Heck, why do you think it's even applicable here?

  • edited April 3

    Frankly, it's a terrible idea. Why on earth would you subject fruit to repeated cycles of hot vapor and reflux? Many, many, many fruit and vegetable flavors are subject to thermal decomposition. Soxhlet extraction is the equivalent of a jackhammer when compared to single pass distillation.

    Not only that, but you are exposing finished gin to extended time at heat? Same issue, thermal decomposition. For example, putting a vapor distilled gin back into the boiler and then heating it to boiling temperature - this is completely counterproductive.

    I feel like you've read something from another still manufacturer that loves to dabble in pseudoscience, that I think knows less than he thinks he does.

  • edited April 3

    Honestly, fruit is very easily extracted by maceration at room temperature, and has none of the issues inherent in Soxhlet extraction (in fact, there are ZERO potential benefits in this scenario).

    Simply placing the fruit in the gin at room temperature (assuming high enough proof), will yield far better results.

  • edited April 3

    An example of an appropriate use of soxhlet extraction in our world would be to produce cinnamon oil - where you want to use a small amount of solvent to extract from a large botanical mass, and you need extended time and temperature to get a reasonable product yield of oil.

    Though, at the end of the soxhlet extraction, you would run the solvent through a rotovap to separate the ethanol solvent from the cinnamon oil, yielding your pure product - which you would then reintroduce into new spirit to yield your finished product (hint, you would do this for product consistency purposes, where your base botanical might have a highly variable oil content).

    I've heard that cocoa nibs do very well using soxhlet as well.

    Keep in mind the common theme here - extraction of oils from what are typically very "stubborn" hard botanicals (roots, barks, seeds, etc). Or, oils from botanicals where a huge amount of botanical mass is required relative to the solvent (flowers).

    Why limit the amount of solvent? So that you can easily put it through a rotovap to remove the solvent. This is the whole point of the thing, extract the most amount of oil into the smallest amount of solvent.

  • edited April 3

    And since I'm already beating a dead horse here.

    If your goal isn't to make a highly concentrated pure oil (for use as a flavoring later), why on earth would you even bother with any of this?

  • A great use of soxhlet extraction in distilling is quality assurance for incoming materials.

    For example, perhaps you would use soxhlet extraction and rotary evaporation to quantify the oil content of a small amount of each of your individual botanicals - and adjust your recipe to account for these variations, ensuring a high level of batch consistency.

  • edited April 3

    And if you want real world validation.

    Why are cold pressed juices so good, and so expensive? Because they aren't heat pasteurized. Heat pasteurized juices don't taste nearly as good as cold pressed, because they aren't subjected to heat pasteurization, and they are less stable (short shelf life). Temperature is the enemy of fruit.

    Just peruse the literature on fruit juice pasteurization and you'll see everything you need on why subjecting fruit to high temperatures for high amounts of time is generally bad.

  • oh dear, maybe I shouldn't have already commissioned the build :-) it wasn't much money though. I would never pay commercial prices for such equipment.

    The goal is to make a flavoured gin with fruit that has a natural colour, lets say raspberries. Flavour doesn't carry through with distillation. Masceration takes time, space and so i am told is inefficient. I know a raspberry flavoured gin based in the uk takes a month or more to macerate and in my opinion isn't very flavourful. I know a sloe gin producer that used to macerate for 6 weeks and the process isn't efficient.

    The goal could be achieved using particular method, if gin in the boiler is a bad idea - and it sounds like it is then using ethanol to produce a concentrate that can be saved for compounding with gin may be better.

    I heard from the person/company I think you are referring to about one example where they increased the extraction efficiency of a berry by a significant amount, I do have contacts at the end producer so I will reach out and confirm their real world experience. I have tasted the product and it is very nice, well to my palate anyway.

    On your points,

    The use of gin - as said above maybe not the best then. Maybe just ethanol to produce the concentrated extract. Then compound with the gin.

    The temperature - I would presume the vapour would go for the path of least resistance - the condensor/dephleg and get condensed into a warm distillate, not a very hot liquid. I have a thermo port in the liquid path so i can monitor this and can hopefully influence this temp with power and coolant control. I have had an opinion that 57c is a good liquid temp.

    Maceration - more time, more mess, if I am to believe said person less efficient.

    as my wife says, "you are just bored" maybe true but this craft is surely about experimentation. Have you had bad experiences from soxhlet extraction? or is this just your opinion. Which I truly value if the latter.

    And yes - I hate pasteurized orange juice ;-)

  • @needmorstuff. Looks like this time you don't need more stuff. Just saying. I agree with @grim but I am not an expert and I don't like fruity gins.

  • You need to read up on anthocyanin stability and browning in fruit juices.

  • I made a gin with hops, really light on the hops as well. And it was clear to start with but about 4 months later it turned brown. It didn't effect the taste that much but it didn't look nice. I gave most of it away.

  • I have spent the last few hours looking at how to stop things going brown, about all i came up with was adding lemon juice! not exactly something i could sell.

    I know of a gin called pinkster in the UK that is subtlety pink, it is mascerated with fresh raspberries. Now they obviously don't go deeply into production methods so i wonder if they use something to stabilise the colour.

  • edited April 3

    And that's how you get @grim going.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • gotta love the passion

  • @needmorstuff, a lot of pink gin use Hibiscus flowers. I tried it and it works. But after about 6 months they turn from pink more into brown.

  • Personally I think you guys have it wrong. There is no hot vapour associated with the Soxhlet but rather warm refluxed distillate ~+53 deg C. This distillate with extracted flavours from Soxhlet is ultimately siphoned back to the kettle for further distillation and reflux. The process is repeated numerous times and ultimately recovered as an extract.

    Any case, you are using it to extract delicate flavours from fruit or whatever that are not possible within the hot kettle as well as hot vapour path.

    Would the above used as an alternate to a Gin basket ?? No but I suppose you could.

    This system I don't see possible with a typical plate column with dephleg but rather a packed LM column that is in total reflux and such distillate drawn off to soxhlet.

    Do I see this as a viable system for doing what it is intended to do ….. Hell yes.

  • @needmorstuff

    You need to fuck this shit off RIGHT NOW.

    I'll tell you how I make mine.

    1. Distill the base gin
    2. Dilute the base gin to "overproof" in my case 45% since I release the final product at 40%
    3. Put the fruit in
    4. Let nature take it's course
    5. MUST temperature control it - maceration is MASSIVELY subject to temperature - invest in temperature control
    6. After 7 days I filter all the fruit bits out - takes about 6 hours by gravity through 4 ever finer filters - otherwise my Enolmaster bottle filter clogs up in no time
    7. Analyse the gin and proof down to bottle strength (40% in my case)

    Do it properly, and you'll have a gin that tastes - and looks - great.
    It will be diametrically opposite the pink gins in your local supermarket.

    My gin is 100% natural - I don't do anything other than wait patiently for the ethanol to extract flavour and colour from the fruit.

  • Only thing I would recommend for that is to be purging tanks, and bottles, with an inert gas to eliminate as much oxygen contact as possible.

    There are two main drivers of browning of anthocyanins, temperature and oxygen.

    Both will result in your beautiful color turning brown faster.

  • You're better off using the enolmatic cartridges but getting a proper housing for it so you can run on +pressure with a pump. That way you can just transfer tank to tank and get a decent volume don't.
    I've used them for fruit and spice macerates many times and it has worked well.
    Obviously it will depend what you're working with but 5μm will brighten 80% and 0.2μm will clear up nicely.
    Work your way down the grades for high solids.

    Natural colour stability over extended periods is a problem that I haven't solved yet.
    It's dependent on many factors which makes it challenging.
    I've tried a number of things so far but haven't had great luck.
    Still on the list to trial is gum arabic.

    I don't have experience with a soxhlet extractor but but just from extraction experience I can see how constant washing with fresh solvent would have a big impact if what you're extracting has an extremely low saturation point.

  • You know, a percolator coffee maker is a crude soxhlet... :)

  • edited April 8

    I might be able to contribute a little.

    @needmorstuff said: The goal is to make a flavoured gin with fruit that has a natural colour, lets say raspberries.

    Most fruit colors are phenolic compounds, and many are pH sensitive. I understand that neutral beverage spirits tend toward a pH ~4 (acidic), and certainly mixed-drinks will be acidic, so this generally tends to push the anthocyanin class of colorants toward pink/red and away from blue/purple. You may need to control pH to acheive good color control. You are more likely to get a 'pink' beverage, but you're unlikely to see any natural blue from blueberries, blackberries, juniper berries. at that pH.

    In many fruits the color is tightly attache to the skin. Winemakers use certain 'pectinase' enzymes to extract fruit color and this should help your fruit flavor & color exaction in a lot of ways. Whether these enzymes will function in a high ethanol environment is doubtful. The chemical alternative is a high pH maceration to really degrade the skins, then a pH neutralization.

    @needmorstuff said: Masceration takes time, space and so i am told is inefficient.

    I know a raspberry flavoured gin based in the UK takes a month or more to macerate and in my opinion isn't very flavourful...

    It always pays to understand the specific flavor chemistry involved. Most fruits have organic acids, some sugars for taste & esters, some ketones and often isoprenoid & "essential oils" for flavors. Raspberries have some carotenoid compounds involved in flavor but ..

    So the primary flavor compound is quite soluble in ethanol, not water. That raspberry-ketone has an aroma threshold ~0.01ppm, but is only extractable at ~1 to 4 ppm in raspberries. IOW it takes a lot of raspberries (on the order of 1% by weight to hit threshold). Brewers reportedly use ~1kg of raspberries per 8 l of product (12% by weight), and I suspect you won't be far off that. Also the ketone is quite stable thermally, but you'll certainly lose any aromatic esters at the higher temps you suggested. The essential oils and isoprenoids are likely to be ethanol soluble.

    Side Note that trans-α-ionone is a synthetic flavor ketone similar to raspberry that has been used to 'spike' raspberry juice and wines.

  • @needmorstuff said: I have spent the last few hours looking at how to stop things going brown, about all i came up with was adding lemon juice! not exactly something i could sell.

    The concept is an anti-oxidant. Many of the organic compounds in a fruit are subject to browning reaction - oxidation. No chem lesson, but oxidation can involve sulphur, iron, but in this case most likely atmospheric oxygen. Anti-oxidants are merely chemicals which are more prone to oxidize without bad color or flavor effects and therefore protect the food product quality. Some oxidation reactions in fruit are driven enzymatically, but these aren't, I think, of much concern in a high ethanol solution. Citric acid is a weak anti-oxidant. Raspberries and a lot of fruits contain natural phenolic anti-oxidants like quercetin, but this is bitter in quantity. There are literally hundreds of approved food anti-oxidants, but you'd want advice from a food chemist wrt which one would work in this circumstance (and legal jurisdiction).

    Interestingly ascorbic acid is another weak anti-oxidant present in most fruits, but tends to brown the anthocyanins causing many fruit colors.

    Yeah - avoid oxygen contact. Nitrogen is your friend. O2 is only a little less soluble in ethanol than water, and for both increases with temperature.

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