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Bacteria/Mold/Whatever Growth in 49% ABV Rum?

I just found a bottled of Scarlet Ibis (49% ABV) in the back of my liquor cabinet that I'd opened up, removed a few ounces of, and forgotten about -- maybe a year ago. There are a number of little off-white blobs floating around in the bottle, which certainly weren't there before. I Googled around and most of the information is not only contradictory but also not at all authoritative (it's tough to trust anything found on Yahoo Answers).

Anyone here have any idea what could be going on? Were there a bit of particulate matter in the rum I would expect sediment at the bottom of the bottle, not floating around. Is it possible for any kind of organism to survive in such a high ABV environment? And if so, is it still safe to drink the stuff? Obviously I'd rather not send it down the drain!

Thanks all.

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  1. You don't trust Yahoo Answers but you trust the yahoos on Chowhound? ;)

    You might try Darcy O'Neil at Art of Drink (http://www.artofdrink.com/). While he is a chemist and not a biologist, he might well have an answer.

    Absent another answer (JMF???), I'd filter it with a coffee filter. Make sure your guest drinks first. ;


    www.kindredcocktails.com | Craft + Collect + Concoct + Categorize + Community

    2 Replies
    1. re: EvergreenDan

      Your comment about Darcy O'Neil reminded me that one of my friends is a microbiologist. Just e-mailed her. I'll report back on what she has to say on the topic...

      1. re: davis_sq_pro

        And my friend agrees with the wisdom of Yarm:

        "At that concentration bacterial membranes and such are totally messed up and destroyed. Although there are extremophiles that can survive environments like high temperatures or salinity, I am unaware of anything that can grow in that high a concentration of alcohol. It should be safe to drink..."

    2. I have a degree or two in biology, biochemistry, and microbiology. 70% is what is considered fungicidal and bactericidal when sterilizing tools and equipment for tissue culture and animal surgery. Living fungus is more sensitive than the spores (bacteria is the most sensitive of the bunch). I have seen this range written as 60-90% (100% is less effective for some water actually helps to kill spores which can be rather shielded from harsh environments).

      I have heard of mold growing in 20% ABV liqueurs. It grows slowly and doesn't amount to too much (often a brown fluffy haze or precipitate at the bottom). But here there is a lot of sugar for energy source and often nutrients from the infusions.

      Will fungus grow in 49% ABV spirits with no sugar added? Doubtful since it is rather close to what would kill them (besides the lower amount that will just stop their growth) plus there is little to use as energy and nutrients. I cannot think of any 40% liquors that have grown microbes. I have heard of precipitates from poor filtration, cork disintegration, oils coming out of solution, or other though.


      6 Replies
      1. re: yarm

        Thanks, Yarm. Sounds like application of a coffee filter is all I need to be on my way to sipping a bit of rum punch.

        1. re: davis_sq_pro

          If it smells good and tastes good, drink it.

          I had a bottle of St. Germain get a brown precipitate. I was told that it was mold by JMF. I figured it was botanical precipitate. Regardless, I finished the bottle (although I did not use the last 1/2 oz) and I was no worse for wear.

          A lot of the fungicidal alcohol percentages are to kill fungus so it doesn't grow once introduced into a happy environment (tissue culture medium, surgical incision, etc.). Fungus doesn't like to grow in many harsh conditions that will not kill it. And spores can be resistant as I mentioned before. Alcohol and liqueurs probably have a fraction of microbial growth than practically everything else you eat and drink.

          1. re: yarm

            Really, I said that the St. Germain had mold? It could because it is only 20% abv. but I think that the brown precipitate in early bottles of SG are from organics settling out.

            1. re: JMF

              Might not have been you but I remember someone telling me that. The reps went from saying that it had an infinite shelf life down to 6 months. When we compared the dregs of our old bottle (close to 2 years old) to the fresh one, it wasn't that different. A degree of brightness in the new one, but the old one wasn't skunked or anything. Brown precipitate and all. I remember declaring that it was botanical matter coming out but someone was insistent that it was mold.

              1. re: JMF

                It was in this thread: http://chowhound.chow.com/topics/750509

                "Even if the alcohol didn't evaporate, mold can grow in alcohol, there are some very alcohol resistant strains. Even up to 40% abv., many time particulates in spirits and liqueurs are mold."

              2. re: yarm

                Mold can grow on the SURFACE of a high abv. sweetened spirit if the bottle is left undisturbed for a long period of time. Small amounts of sugar can collect on the surface, acting like a barrier, and the mold can grow on that, then as it gets heavy enough, or is slightly disturbed, it can sink into the spirit. So this may be the case.

                But it is probably colloids flocculating out of suspension. Exactly what is hard to tell, but a combination of sugars, organics and botanicals, esters, glycerol (glycerin), etc. I would think that it's most probably glycerol, or the fatty acids esters of glycerol. Glycerol naturally occurs in spirits, and is added to many for smoothness and a rounder mouth feel.

          2. I agree with others that it is almost impossible to grow any microorganism in 49% ethanol.

            Keep in mind when folks are talking about higher percentages for killing, 60-90% ethanol is what it takes to guarantee to kill 100% of a living culture.

            The amount to INHIBIT new growth should in theory be much lower.

            That said, there are some fungi that NEED a small amount of alcohol to live. Even they would not likely survive in 49% ethanol:


            Heck we could always try to culture it here in the lab for you...

            My guess is that you have some precipitate which happens to float. Uncommon, but not unheard of. Thus as the precipitate forms, it floats to the top.

            1. It coud be throwing off sugar crystals. Very little will grow in 49% alcohol. This from a guy who just fished a dead spider out of his single malt scotch and kept on drinking.

              9 Replies
              1. re: kagemusha49

                it wasn't Octomore Scotch by any chance was it?

                1. re: kagemusha49

                  Which reminds me of the glass of Jim Beam I was once served FULL of fruit flies, like dozens, which I did not drink...

                  That said, one spider, fish it out, forge ahead. Heck I see a new beverage category. Spider venom infused single malt.

                  1. re: StriperGuy

                    Yechh on the fruit flies. That's like the time many years ago when I learned why you don't leave speed pour spouts in bottles for long stretches. I was given a bunch of half-full bottles of various liquor by some roommates who were moving. The bottles had been sitting on a shelf with the uncapped speed pours probably for months. I had made a drink and was just starting to take a sip when I noticed all the black dots in the bottom of the bottle, "hey, are those...?" Spit, then dumped all the bottles in the sink immediately.

                    1. re: nickls

                      That's exactly the scenario at the dive bar where I had my fruit fly cocktail.

                      1. re: StriperGuy

                        My fruit fly experience was a glass of Appleton 21 at a supposedly upscale bar in the Boston area. Not fun, especially given the reaction from the bar: the bartender just kind of shrugged when I showed it to him, removed the half-filled bottle from the shelf, and took it into a back room. He returned and poured me another drink. Later, some other guy emerged from the back carrying a "new" bottle of Appleton 21 that they put on the shelf -- but it was tough for me to miss the fact that it too was only half full...

                        I'm sure that straining the dead flies out of liquor is a fairly common practice at a lot of places, but I really wish they'd done it after I was out of sight. I'll never return to that bar. (A comp on the drink, or at least an apology, wouldn't have hurt either.)

                        1. re: davis_sq_pro


                          I totally agree that a few fruit flies likely do no harm, but noone wants to see that.

                          In the dive bar they dumped the bottle, cracked a new one in front of us, and comped ALL of us a round even though only I had order the Jim Beam to begin with.

                    2. re: StriperGuy

                      That could turn you into a superhero.

                        1. re: phantomdoc

                          Could be - it WAS a loxosceles (brown recluse) - they are common around here.

                    3. is the Scarlet Ibis chill-filtered? I read that sediment can form in non-chillfiltered Whisky if it is kept in a cool place. I would think if the fatty acids were congealing they would float.

                      1 Reply
                      1. re: ncyankee101

                        It is specifically labeled as NOT chill filtered. But it was not kept in an especially cool place -- in the back of a cabinet in my kitchen.

                      2. Hey science people, could these be fatty acids?

                        20 Replies
                        1. re: ellaystingray

                          No fats in rum. I'm still thinking sugar crystals.

                          1. re: kagemusha49

                            Rum has fatty acids, the highest among several types of liquor tested here. I would expect pot stilled rums such as Scarlet Ibis to have more than others.


                            1. re: ncyankee101

                              Thanks for having my back ncyankee101. Sort of makes me look like I might have any idea what I am talking about...

                              Scientists! I am talking to you. Sound off.

                              1. re: ellaystingray

                                Actually I had my own back as I had mentioned fatty acids a little further up the thread - but you're welcome ;-)

                                1. re: ncyankee101

                                  My mistake - rum DOES have fatty acids. However, acids like acetic acid and propionic acid are NOT going to solidify at room temperarature and are more likely to evaporate. Fatty acids are NOT fatty as in like fat. I still think we are seeing sugar being thrown off.

                                  1. re: kagemusha49

                                    But there's not much sugar around; Scarlet Ibis is not a sweet rum and I doubt they've added sugar after distillation except for what might have been extracted from the wood during the aging process. And what would be the mechanism for crystallization? There was no major temperature change or anything along those lines...

                                    1. re: davis_sq_pro

                                      Be curious what the residual sugar is in the rum.

                                      1. re: StriperGuy

                                        After distillation? Should be 0%, right? Unless I'm mistaken and sugars can vaporize and then re-condense? I would think the only "residual" sugar is whatever is collected from the wood in the barrels.

                                        1. re: davis_sq_pro

                                          I'm not sure how they get in there, but some rums are obviously quite sweet.

                                          Most whisky, rum, and many spirits have quite a bit of sugar in them. Do they make it through distillation?

                                          Can't imagine it all comes from the barrel.

                                          With some rums, the distinct molasses notes are perhaps blended in after distillation... where is JMF when you need him?

                                          1. re: StriperGuy

                                            Some dark rums do definitely add some molasses back after distillation, and some of the well-known top rums (such as Zaya) are suspected by many of being doctored. Rum is not regulated nearly as much as Bourbon or scotch, they can pretty much do what they want other than the AoCs - though the West Indies Rum Producers Assn. has been making some effort to set standards for producers belonging to their group.

                                      2. re: davis_sq_pro

                                        Plus I wouldn't think sugars would float. In wines and unfiltered beers priming charges sit at the bottom of the bottle.

                                        1. re: davis_sq_pro

                                          Practically every rum on the market has an appreciable amount of added sugar. if you tasted my rums which I don't add any sugar to at all, you would instantly see how much sugar is added to rums. There are really no laws governing how most rum is made. Sugar, spices, caramel coloring, etc. are all used extensively. (Also many brandies have sugar added. It is legal in the US to add up to 2.5% sugar by weight to brandy.)

                                          1. re: JMF

                                            I haven't tasted your rums but I have had severall top-notch rums that I believe are unadulterated - Seales 10 yr, Doorley's XO, El Dorado 12 and 15 - and some that are most likely doctored, such as Zaya - and though Zaya is very good I much prefer the EDs.

                                            1. re: ncyankee101

                                              Any rum with a sweet taste has been sweetened. The whole El Dorado line definitely has. I haven't had Seales or Dorleys so I can't comment.

                                              Mine won't be on the market for about 1.5-2 years.

                                              1. re: JMF

                                                Richard Seales is adamant about using no additives in his rums, and his age statements are minimum unlike many. Here is an interesting story about him.


                                                so what are some examples of rums that you don't consider to have been altered? What about Pusser's? Flor de Cana 18 yr doesn't taste very sweet to me, though I don't like it nearly as much as the EDs.

                                                in any event I don't consider the sweetness to be as out of balance with the rest of the flavor profile in the EDs as I have noticed in the Zaya and Zacapa 23. The main thing I like about the ED 12 and 15 are the deep chest-warming notes of leather and tobacco I get, as well as the smoky sweetness. i don't get that same chest-warming feeling from the Zacapa.

                                        2. re: kagemusha49

                                          I wouldn't call acetic or proprionic acids as fatty acids. The fatty acids in question are longer chain or chains with cyclic groups that impart those funky, interesting, and unusual flavors that aren't found in stripped down rums like Bacardi. Acetic acid would definitely be in the heads and should be cut out -- these fatty acids are coming off in the later parts of the distillation.

                                          I have seen rum reviews that have attributed sediments to spices (not the case here) and fatty acid flocculation while aging. It is common enough that I have read about it a few times and I don't frequent rum websites all that often.


                                        3. re: ncyankee101

                                          Not a scientist and can't read. Just saw you said the exact same thing before I did.

                                          1. re: ellaystingray

                                            I do not believe that all the sugar in the molasses used to make rum is consumed in the process. Crystals would likely form as the liquid evaporated on the junction between the surface of the liquid and the bottle. These crystals could then propagate across the surface and remain afloat due to surface tension. They would be unikely to look particularly crystalline due to impurities also being precipitated simultaneously. Incidentally, it is quite clear that black rum is not a pure distillate as the dissolved solids that provide the color would not be distilled - these dissolved and suspended solids are added back.

                                            1. re: kagemusha49

                                              Kagemusha, are you suggesting that the sugar is carried out of the solution into vapor and over the still? Most sugar in rums is added after the distillation -- generally, there's only sugar added in flavored and spiced rums.

                                              My best guess is that Scarlet Ibis is not a sweetened rum especially given that it was formulated by request of the owners of Death & Company in Manhattan.

                                              Darker rums are from the barrel's wood (often charred or toasted) as well as what was in the barrel before (including whiskey, sherry, and wine). Some of the darker ones do use caramel or black strap molasses. Many white rums are actually stripped of the color from aging (some white rum is unaged though).

                                              1. re: yarm

                                                No - if you read my previous reply carefully I am saying precisely that this is impossible. But black rums contain color and flavor that cannot be provided by distillation and that means that those elements (including sugar) must be added by recombining something like molasses with the distillate.

                                2. So, now that you've filtered it out, consumed some, and still have 10 toes, what's it taste like? Any similarity to Smith & Cross? I've recently seen it in Boston (but, oh where, Porter Sq maybe?) and was tempted. That you pushed it to the back of your cabinet is not exactly high praise.

                                  For reference, I absolutely love Smith & Cross. Particularly fond of Bitter Mai Tai (is that plural already?).

                                  6 Replies
                                  1. re: EvergreenDan

                                    I haven't filtered and tasted the extra-chunky version yet. But I did taste it before, and it bears little similarity to S&C. Whereas S&C has that deep Jamaican-style molasses-y funk, Trinidad rums have more of a turpentine kind of funk (in the BEST possible way). I liked the Scarlet Ibis quite a bit when I first tried it, but I still had two bottles of Plantation Trinidad--a very similar rum--and I wanted to use them up first. So I shoved the SI at the back of my cabinet, drank way too many Plantation Trinidad Planter's Punches, and ... here we are!

                                    1. re: EvergreenDan

                                      It is a good rum, but I couldn't bring myself to spend $30-32 on it. It is no Smith & Cross in power, but it is a flavorful rum. DSP's recommendation to look into the various Plantation rums at the same price point is a good one.

                                      1. re: yarm

                                        The Plantation rums are great. I was hanging out at an event yesterday for a few hours with the NY/NJ manager for Ferrand Cognac/Plantation rum and worked my way through the whole line of 6-7. They have a new one hitting the market Dec. first. An overproof, aged, Barbados rum, 73% abv. / 146 proof that is a huge, tasty, flavor bomb. (This is the first of the Plantation rums that isn't finished with 6 months to 1 1/2 years in a Ferrand cask.)

                                        1. re: JMF

                                          I found a store around here that has some of the older bottlings, like the Panama that I had been searching for for 2+ years. We just got their Barbados 5 and I have a nip of their Barbados 20. Nice that they're offering an interesting almost 151 (besides Lemonhart, there aren't that many with a ton of character, well, I guess Inner Circle could count if we could find it).

                                          1. re: yarm

                                            The Panama is easily my favorite rum. I hope you picked up a bottle? What did you think of it?

                                            There was a store in the area selling Inner Circle as recently as last year. I bought some on the basis of Wondrich's poetic descriptions about the stuff in "Imbibe." Perhaps it was built up too much; I was thoroughly underwhelmed. It was an okay mixing rum, kind of like a Demerara stripped of much of its character.

                                            Definitely looking forward to some more overproof options. Have you ever seen the Bounty or Fiji rums awarded Gold by the Ministry of Rum in its 2011 competition? (http://www.ministryofrum.com/tc/2011.php) ...

                                            1. re: davis_sq_pro

                                              I picked up a bottle last Sunday but I have not had a chance to open it yet. It and two older ones are still at Blanchard's on Centre Street in Jamiaca Plain, MA.

                                              There are 3 varieties of Inner Circle so I wonder if one is better than the others. I haven't seen Bounty or Fiji around.