Thursday, June 27, 2013

Powdered Raw Sugar

Our wonderful hand-crank grain mill advertises on the side of the box that it can be used for wheat, rice, oats, barley, rye, peppercorns, spices...and more!  We've been focusing mostly on the 'and more' part because, well, what's the fun of an experiment if we know it's going to work?  Anyway, the other day, we found ourselves asking the question, 'what's the fastest way to counteract the enjoyment of eating a dessert dusted with powdered sugar?'  The answer, of course, is accidentally inhaling just before taking a bite and having the powdered sugar lift off the surface of the treat and fly directly into our sinuses or lungs.

'Why does powdered sugar have to be so fine, anyway?' we asked ourselves.  We understand that for some things, like frosting, the particle size affects the texture of the product, and some folks don't like even a hint of graininess on their confections.  (They are confection perfectionists.)  Then we thought, 'wait a minute, we don't mind a little graininess (maybe we won't even be able to tell!), and we have a tool to fix this!'  Since we can change how finely ground things come out of the grain mill, we can make powdered sugar that isn't quite so finely powdered!  Then Katie can make some lemon bars and we can sprinkle our not-quite-so-powdery sugar on them and see if we still accidentally snort the stuff.  (Katie's lemon bars alone would be worth the experiment.)

Additionally, one of the drawbacks of using raw sugar, which is like a strange combination of brown sugar and white sugar with large, brown transparent crystals that take forever to dissolve in anything, is that the crystals are too darn large.  We could probably cut the crystals in half and make them into a much more usable form.  So, let's see what the grain mill can do!

We're going to try to grind a half cup of the raw sugar into powdered sugar, and half cup into the same size as standard granulated white sugar.  First up, the powdered sugar!
Off to a good start!  It looks like powdered sugar, but not quite as fine.
The problem with the very fine grind is that it takes forever.  So we loosened up the mill a little bit.  Now it still makes a pretty fine powder, but it goes faster.  You can see that it's not quite as fine as the first stuff, since it's a little more brown-colored (and the particles look larger).
One of the reasons it takes a long time is because of a phenomenon called 'bridging.'  As some of the particles fall into the mill, the ones above readjust, and hopefully fall in, too.  But sometimes the particles on top can form a structure that won't fall in on it's own (think like a stone archway on a fireplace).  So it's necessary to keep stirring the hopper to keep things moving.  Since we were only rotating the grinder with one hand, this left the other hand to stir with a wooden spoon.  Clearly, some of the grinding happened even without going through the grinding wheel.  The other reason this is taking a long time is that the grooves in the grinding wheel are getting packed up with the fines (the very small particles).
We opened up the mill a little more, and were still able to get a fine enough powder (the right-hand half), but it went a lot faster.  The first half cup of raw sugar took about an hour to grind into powdered sugar, but more than half of that time was spent trying to find the right setting on the mill.  With more practice, that part will go much faster.
The second half cup of raw sugar we wanted to turn into grains the size of standard white sugar, and it went a lot faster.  The whole half-cup took about 15 minutes.  Clearly, some of the particles are still smaller than the target size, but the main goal of slightly decreasing the particle size was still met.
Here are our four grades of raw sugar.  Regular raw sugar on the far left, most coarsely ground next (approximately white table sugar-sized), and the two finely powdered sugars, which are both still a little coarser than the confectioners sugar you get at the store.
One of the issues with any grinding operation like this is that the product has a certain particle size distribution.  The bowl on the right in the previous picture has all grains that are small enough for what we want to do. The bowl on the left, however, has the unground raw sugar and the coarsely ground stuff, which itself has a range of particle sizes.  So, we can sieve them to separate out the sizes we want.  For now, we're just going to use a set of colanders with different screen sizes.  The biggest one looks like it won't let the raw sugar through but will let the rest pass.
It worked!
The next finest one looks like it will let the powdered stuff pass, but hold back the table sugar-sized stuff that was our second goal.
It worked, too!  The stuff that made it through the second colander still has quite a range of sizes, but we're out of screen sizes to use. (Plus, we've proven the concept and the mix is fine for our own use.)  The four bowls in front are the grades from the grinding (the far left is unground).  The two bowls in the back are the standard white sugar and commercial powdered (confectioners) sugar.  They're in order of grain size, decreasing from left to right.  If you want to know more about the actual standard grain sizes of sugars, check page 42 of this book.
It's easier to see the range in grain sizes on something else, like strawberries!  The far right is the commercial powdered sugar, and the third from the left is the standard white sugar.  Let's make some lemon bars!

One lemon bar down, intentionally inhaled just before biting, and no sugar in lungs or nostrils...that means it worked!  Good job, Katie.  Better eat a second one just to make sure it wasn't a fluke.

We could've probably made the powdered sugar a lot faster with a food processor or blender, but it's good to know that the grain mill will work if we need it to, and that the colanders will work to sieve out the larger particles, which would still be there with the other methods.  In the future, maybe we'll work on a solar-, wind-, or human-powered ball mill to do this kind of work.  Stay tuned for updates on that!

Have you ever accidentally snorted powdered sugar off a lemon bar?  Do you have a different way to make powdered sugar?  Tell us about it in the comments section below!

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