Neat as sorbet syrup is in terms of its ability to resist freezing completely, it would still freeze into a (mostly) solid block were it not for the ice cream machine. An ice cream machine performs two crucial roles in the sorbet-making process. Firstly, it freezes the syrup mixture quickly, and that helps create ice crystals that are very small in size. But second, and just as importantly, it provides agitation, which keeps the little ice crystals tumbling. That tumbling action keeps the crystals well dispersed among all the other flotsam and jetsam in the sorbet mix (unfrozen syrup, bits of puréed fruit or cocoa powder granules, etc.). The result is that the small crystals have a difficult time connecting up with one another and growing into big crystals, the kind that are responsible for the “grainy” or “icy” sensations that sometimes occur with sorbets.
I know what you’re thinking: what happens when the agitation stops? Won’t some of those ice crystals find a way to join into larger crystals when you put the sorbet in the freezer to firm? Yes indeed some of them will. However the hope is that by the time the sorbet mix is ready to leave the machine, such a high proportion of the liquid water will be bound up in these tiny, isolated crystals that there’s won’t be enough left over to form lots of big, joined-up ones.
A great deal depends on how cold the refrigerant in your machine is. Since Mrs. Pastry is an absolute ice cream freak, we now own a rather expensive one. It works well, but you need not have an expensive machine to make a great sorbet. Most of the less expensive machines work via a removable refrigerant-filled tub that you put in the freezer the night before you plan to make your frozen whatever-it-is. The idea is that the zero-degree refrigerant plus the chilled mix will lead to fast freezing. It’s a good system, but one that will work even better if you can get the refrigerant in the tub chilled to below zero Fahrenheit, which is the temperature of a typical kitchen freezer. Basement chest freezers get even colder, however. So if you have access to one, use that instead. You’ll notice the difference in the finished product.
Aside from that, the best tip I know for delivering a less-icy sorbet to the dining table is to simply let it soften a bit before serving. Quite a few of us have the expectation that our sorbets and ice creams should be ready-to-eat as soon as we remove them from the freezer, but that’s really not reasonable for most home-made frozen desserts. When I first started fiddling with electric machines, I was constantly frustrated that none of my ice creams were as creamy as the ones I remembered coming out of the old hand-cranked wooden tub ice cream maker that my parents had. I was using richer cream, more sugar and high technology, so why didn’t my modern ice cream match my memory? The one day it struck me: the ice cream we used to eat at those block parties was served a whole lot warmer. Thawed a bit, my machine-made stuff tasted a lot closer to what I remembered.