The trick involves floating an uncooked egg, in its shell, in your sorbet mixture to determine if you have the right amount of sugar. When you get too much sugar in your sorbet it won't freeze properly, no matter how long you process it. We just got a new commercial ice cream maker at my current job, and this week I made several gallons of sour cherry, and red currant sorbet. We're getting the most amazing fruit from Southeast Minnesota Food Network right now, and it's making delicious sorbet.
I kept trying to find good recipes for both the sour cherry and red current sorbet, but most of what I found was coming from British or German websites where everything was in metric. I've found a good website for converting recipes, but I was still never sure they were going to work. I had several huge orders for sorbet coming up, all within one week, so I had to be sure I had it right. That's where the egg test came in.
Most sorbet recipes will have you puree and strain the fruit, and then add simple syrup, which is just equal parts sugar and water, boiled until the sugar dissolves. The problem is that you can never be totally certain how much sugar is in the fruit itself, and how much simple syrup you should add. So to be completely accurate, you add simple syrup, one cup at a time to the fruit puree and put a whole egg in the mixture. If the egg floats enough so that it's exposed surface is the size of a dime, the sorbet will freeze properly. If the egg sinks, you need more simple syrup. If the exposed area of the egg is larger then a dime, you need more fruit, or a bit of water to reduce the amount of sugar.
The trick came in most handy the other day when I was racing to freeze the sour cherry sorbet before I had to leave. I had used the last 4 cups of white sugar in the house to make my simple syrup. I had it in the sink, cooling in an ice bath, but when I turned to use it, it was gone.
"Where the hell is my simple syrup?" I yelled. No one knew what I was talking about, but pretty soon, we figured out that one of our dishwashers, thinking it was just a pan of old water, had dumped it out and run it through the dishwasher. So after a few minutes of swearing to myself in the back storeroom, I pulled it together, and grabbed a box of sugar in the raw. Sugar in the raw is also called turbinado sugar, and has a coarse grain and light brown color. I made a simple syrup with it, in the usual one to one, sugar to water ratio, cooled it down, and began adding it cup by cup to the pureed cherries. I got out an egg, and it immediately sank to the bottom of the bowl. So I added more simple syrup, until I had used the whole 6 cups, and after pushing aside the cherry foam, there it was, the dime-sized portion of egg sticking out of the mixture. I put it in the ice cream maker, churned it for 30 minutes, and tasted. Perfect! We served it the next day with a flourless chocolate cake, and the contrast between rick, dark, creamy chocolate, and cold, tart sour cherry was delicious.
Sour Cherry, or Red Currant Sorbet
Makes about 1 1/2 quarts
2 1/2 pounds, sour cherries, pitted, or red currants, stems removed
1 cup sugar
1 cup water
Puree the pitted cherries, or red currants in a food processer, and press the pulp through a medium sieve.
To make the simple syrup, combine the sugar and water in a small saucepan. Bring to a boil for one minute, until the sugar is disolved. Cool the simple syrup in an ice bath, or the refrigerator.
Pour the simple syrup into the cherry puree. Take an egg and gently drop it into the mixture. The egg should rise to the surface, with a dime sized portion of it exposed. If the egg sinks, add more simple syrup. If too much of the egg is exposed, add a few tablespoons of water, until the egg sinks down slightly. When you've achieved the correct ratio, put the mixture in the freezer for 20 minutes to chill.
Process the chilled mixture in an ice cream maker, according to the manufacturers directions. Once frozen, transfer the sorbet to a different container and store in the freezer.
