It’s a relatively new form of sugar. Until the granulation process was developed, sugar came in loaves, and you scraped what you needed off with a knife blade, a rather time-consuming process, I’d imagine. So how do sugar manufacturers produce all those uniformly tiny crystals without the whole mess sticking together?
This British Sugar site hints that screening for size is involved but not how they get the crystals to screen in the first place. Growing large crystals, then breaking them up seems inefficient, and wouldn’t get you a neat, five-pound sack of tiny little perfect cubes. Spraying a saturated solution to let the (presumably) water evaporate in mid-air might do it, but as anyone who’s left the lid off the sugar jar on a damp day could tell you, the stuff better be bone dry before it hits anything else (including itself).
Searching for ‘granulate(ed) sugar’ on Howstuffworks.com and Google come up with all sorts of recipes and where to buy it, but not how it’s made. Any Dopers work in a sugar mill?
Yeah, I’d imagine putting any relatively brittle, crystalline substance (solid salt and sugar would both qualify) into a big drum with some heavy iron shapes and spinning the drum around for a while would do it. You can take it out, sift it to remove the stuff that’s been pounded into grains small enough and add some more large crystals every so often.
Salt and sugar aren’t as regular as they seem… I’d imagine there’s some pieces that are almost as large as the desirable ‘cutoff’ is and there are grains that are much, much smaller.
This is just a wild guess of course, but it might not be too far off.
Generically, you have a big rotating drum with liquid solution coming in one end and granulated product coming out the other.
Air flow, liquid flowrate, temperature, speed of rotation, texture of the drum, concentration of solution, humidity, etc. are all factors in the final average granule size… depending on what you’re granulating. The conditions that produce nicely sized salt granules will probably not work for sugar and vice versa due to their different properties.
Here’s an interesting slide-show about how they get from sugar beets on a truck to various types of sugar: Monitor Sugar. Not much detail on the granulation step, though.
Crystal size is determined controlling time, temperature, and agitaion of the holding vessels. If the vessels cool quickly, you’ll get lots of small crystals, or just a horrible amorphous goo. If the vessel cools slowly, you’ll get fewer, larger crystals.
Don’t know much about fudge, but I assume this falls under the heading of ‘irony’, as in that trying to make fudge the thing you want to have happen LEAST is for the sugar to crystalize?
Sugar is seeded with a suspension of fine sugar particles in butanol. This is made by putting about 1 kilo of sugar into a small ball mill with butanol, letting the mill run for a couple of hours and decanting off the suspension. The operater used this to seed the pan.
As water is removed under heat and vacuum the crystals precipitate out.
The sugar crystals (collected as mentioned in earlier posts) are graded in screen mesh to give you finer crystals, such as caster sugar.
Thanks for the answers. I wasn’t thinking of anything as complicated as rotating drums. Guess that’s why it took the manufacturers a while to come up with the process.
Funny, that happens to me when I try stuffing the piping hot fudge pan in the freezer every time, but when I let it cool naturally, it doesn’t crystallize. Maybe your prof was exaggerating about the “bit of care” part?
Just a guess, but are you in a hurry those times you put the fudge in the freezer to cool? Like, in a hury enough to have been a little sloppy with the sugar measuring or stirring?
Fudge gets crystals when the sugar solution over saturates. That is, the idea fudge is the maximum number of disolved sugar molecules that will hang out between the fat molecules without being complicated crystal structures. You can get an awful lot of sugar molecules to separate and hang out between the fat molecules. But if there’s a little sugar hanging on the side of your pan, or on your spoon, or on your sleeve and it falls in to the perfectly saturated fudge, it will over saturate. That is, the sugar molecules, excited to see just a few more of their kind, stop playing well with the fat molecules and form roving gangs of sugar molecules. They grow a penchant for sharp spiky shapes and hang out near corner bars making a nuisance of themselves. In short, they form crystals, and suddenly your fudge is grainy. The difference in sugar between perfect fudge and grainy fudge can be less than a quarter teaspoon of sugar. Certainly little enough that rushing the process can lead to sub-par fudge.
