Advice on forming a 10% solution of Maltol

Question

I’m having great trouble forming a 10% solution of Maltol. Specifically, I’m trying to dissolve 3 grams of Maltol in 27 grams of solvent.

I’ve tried everything from Propylene Glycol, to Deionized Water, to Ethanol, including some mixtures of these few solvents, but none of them can work to fully dissolve all the Maltol.

The best one so far appears to be hot Deionized Water, which appears to dissolve the most Maltol. Adding a small amount of Ethanol helps dissolve the Maltol further, but not completely.

Here I’ve attached a photo of the result. The entire mixture was immersed in a hot water bath. As you can see, the Maltol appears to form fluffy clumps that float to the surface, and are really stubborn to dissolve.

If anyone could advise me on how to achieve a complete dissolution of the Maltol, that would be very much appreciated!

Thank you!

Answer 1

Maltol (3-Hydroxy-2-methyl-4-pyrone) appears to be most soluble in ethanol.
https://pubchem.ncbi.nlm.nih.gov/compound/maltol#section=Melting-Point gives solubility as 1 to 10 mg/mL at 72° F in water, 10900 mg/L at 15 deg C (about 1%); one gram dissolves in 82 mL water, 80 mL glycerin, 21 mL alcohol, 28 mL propylene glycol; Freely soluble in hot water, chloroform; sparingly soluble in benzene, ether, petroleum ether; soluble in alkali hydroxides giving yellow solutions

Your fluffy floating clumps suggest something like water, which would reduce the solubility of maltol and could clump it up. or maybe there is some other impurity that complicates things.

You could try is to make a 5% solution in warm dry ethanol (apparently no problem...) and then evaporate off excess solvent. If you can get 10% when hot, but the solution drops crystals on cooling, you will have a saturated solution. But maybe it won't precipitate...

Answer 2

Only just come across this. This (maltol) is a common material used in flavourings. As a Flavourist, I am very aware the maltol has a maximum solubility in propylene glycol and ethanol of about 2.5-3.0%. Higher levels may be achieved if trying to dissolve in something like lactic acid. Sometimes if using heat to dissolve the maltol you may think you can dissolve more than 2.5% however when the solution cools down, the excess maltol will crystalise out. My advice would be to use a weaker solution, as mentioned above 2.5% is a good level.