Boil lactose, hard as a rock?

[dendron8]

I had always read to boil lactose with some water before adding it to secondary/keg.. but ive done it twice now, and once it cools it becomes as hard as a rock! Am i doing something wrong?

 

[RPh_Guy]

Details.

How much lactose?
How much water?
How long are you boiling?
Does the solution become clear after it's heated?

 

[dendron8]

1lb lactose
1cup water
Brought to a boil, then cooled. It did not turn clear. Im going to infer im not boiling it long enough?

 

[RPh_Guy]

Sugar (and many other things) have a solubility limit.

I recommend at least an equal amount of water as the sugar, so in your case you need at least 2 cups water.

Also, you don't really need to boil it either. Bring it to about 150-180°F, which will sanitize it and should be hot enough to dissolve the sugar. You'll know it's fully dissolved when it's clear.

Cheers

 

[bucketnative]

Simple syrup is usually 1 part water to 1 part sugar. That will stay liquid after boiling/cooling. This is the ratio that I typically use to add sugars to beer (priming sugar, for one). Your ratio is more along the line of making hard candy.

 

[RPh_Guy]

Would pure lactose candy be any good? With a little flavoring?

 

[bucketnative]

Not a fan of lactose in any quantity in beer, so I can't say that I'd be a fan of it in candy either.

 

[bucketnative]

Actually, I just double-checked the solubility of lactose in water; it's only 195 g/L at 25 °C. For reference, glucose (dextrose) is 905 g/L, and sucrose (table sugar) is about 2000 g/L.

So, if you put 454 g of lactose into 0.24 L of water, you're way over the saturation point at room temperature. Obviously, the solubility will go up with temperature, but I am not sure you can even dissolve 454 g lactose in 0.24 L water.

 

[RPh_Guy]

Hah, thanks for looking that up! Didn't realize it's solubility was so low.

1lb = 454g
454g / 195g/L = 2.3L = 10 cups, the minimum amount of water needed to fully dissolve the lactose.