White Flakes in Spiced Rum After Several Months in Bottle

[DistillingSafari]

We've redesigned a spiced rum for a client and are running into issues with flocculation (white flakes) appearing in the bottle after 3-4 months on the store shelves. Wondering if anyone has seen/solved this issue before.

Fabrication process:
The base is a light rum (3 years in ex-bourbon) that has been used without issue in other products. We added our mixture of natural flavoring, real spice macerations (macerated in the same rum), liquid sugar and blackstrap molasses. Proofed to 35% ABV then rested in stainless for 3 weeks. Filtered through 0.45um before bottling. Product is all clean and clear at this point.

Three months later, we get a call from a distributor saying that 120 caisses have white flakes in them. We checked our inventory and 75% of bottles have the issue as well, to varying degrees. Haven't seen this in any of our products before, or since.

Any ideas?

[Kindred Spirits]

My first question to any client that has any sort of sediment or flaking issue is What kind of proofing water do you use?

Second is what's your filtration process for bottling?

[FaintingGoatSpirits]

what kind of filter are you using? Plate and Frame? do you use any charcoal in the filter?

[Silk City Distillers]

Blackstrap is going to be problematic, it is a concentrate waste product that could contain any number of compounds or minerals likely to floc or settle, including potential clarifying and flocculation agents added during the sugar manufacturing process that end up in the blackstrap.

Macerations can be problematic at low proof, fats or oils can come out of suspension and solidify, flocculate, etc.

Sugars can often have anti-caking agents added to them that, depending on where you live, don't need to be disclosed.  These can fall out over time.  

Even though your filtration is on the high end at .45 micron, we're talking about compounds far smaller than that.  Moving from .45 to .1 would likely have zero impact.

You could consider chill filtration during production, but again, if the issue is high mineral content (calcium or magnesium in blackstrap, your water, liquid sucrose, etc) - .1 micron is big enough to drive a truckload of ion through.

I'd put my money on the blackstrap, because that's essentially a giant wildcard.  I'd say maceration as the second.

[DistillingSafari]

Thank you all for you replies.

The dilution water is demineralized water that we've been using for a few years, so should be ok there.

We're actually using a combination of filters: 5um Pall nylon 30" depth cartridge style, followed by a 0.45um plate, with no charcoal at all. These filters are installed in series, in-line between the tank and bottling machine. They were pre-treated with peroxan and rinsed before passing the rum (first few liters of product are rejected).

The blackstrap does seem a likely culprit, which is unfortunate because it played three roles at once - color, sugar and flavor. The spice maceration was done in rum that had been diluted to the final 35% ABV.