Question from Blair: I’ve noticed a phenomenon when I’m making bitters. After I macerate this that or the other in the alcohol, I filter it to remove any sediment, twigs, etc. I then add cooled caramel syrup to lower the proof and give it a nice texture/colour. After adding and blending the syrup, I start to get some flaky fallout... looks like old fish food or something. It seems like something falls out of solution? I’m partly curious to know why this happens, partly want to stop it from happening.
Answer: You are experiencing solubility issues. Many organic molecules in the herbs and spices used for bitters are highly soluble in ethanol, but not water. When you dilute the alcohol, with water or caramel, after macerating, the concentration of alcohol decreases. These organic compounds will come out of solution and either form a haze, precipitate or sediment. The same principle applies to the louching of absinthe and pastis. The fish flake thing, it’s called flocculation, where the suspended precipitates decide to get together and have a party in big flakes.
It is possible that this could actually be sugars in the caramel coming out of solution, and not the bitter components. Sugar is very soluble in water, but not in ethanol, so the ethanol may be interfering here. In chemistry there is a term called "like in like" and it means to put things together that are similar. Basically, you need to find something that is like water and ethanol, to bridge the solubility issues.
- For sugar issues, add corn syrup to help prevent re-crystallization (probably won’t be potent enough to completely help in this case).
- Phosphoric Acid, good enough for Coke, good enough for me. Actually, you use the salts of the acid (Tripotassium phosphate or sodium phosphate) or a more easily available acid is Tartaric Acid ("cream of tartar"). These may or may not help.
- Glycerol is probably the best starting point. It is a carbohydrate alcohol which works with hydrophilic (water liking) and hydrophobic (water disliking) molecules. Glycerol works because it is soluble in both ethanol (alcohol) and water. It’s also a natural type of sugar (sugar alcohol), which means its "like" the sugars in the caramel syrup.
- Glycerol combined with citric acid can help also. It’s a combination solution that can help if the precipitate is partially caused by the pH of the solution.
- Mannitol, Xylitol or Sorbitol are sugar alcohols that might help keep sugar in ethanol. Sorbitol is probably the best choice as it is more soluble in alcohol than the other two sugar alcohols (polyols).
- And if you are feeling really synthetic Polysorbate is an option. It’s what everyone else is doing.
Depending on your batch size, I’d make up a couple of stock samples and try different mixtures of the above. For 100ml (~3oz) sample size you could add 5 to 10 ml (2 teaspoons) of the emulsifiers (total for any combination). The acids you would use in much smaller quantities, 1 gram (1/4 teaspoon) would be more than enough, probably use less to start.
For most of these emulsifiers, they should be added at 2% to 10% for sugar alcohols, 1% for acids and 0.1% for Polysorbate. You can use more, but if you need an excess amount (i.e. 20% glycerol) than you might need to look at other options or combination solutions.
For those that want "natural" products, sugar alcohols are natural. They are found in fruits. Polysorbate 80 or 60 (known as Tween 80 / 60) are semi-synthetic, so if that’s not your thing, don’t use them. But many foods contain Polysorbate including ice cream, oral medicine, etc. Pick what works for you.