Man, it's been a busy week. I had planned to make this ice cream base on Wednesday, but I ended up being so sick that day that I just went to bed when I got home from work. I did finally make the ice cream base on Thursday, and froze it on Friday. Let me tell you about it.
Before starting anything, I decided to do something that I had failed to do so far: actually look at the ingredient list on the stabilizer. It appears to be made from a delightful blend of sugar, gelifying agents, pectin and carob flour. Now, I already knew that sugar helps keep ice crystals small. I'm not sure what was meant by "gelifying agent", but I was ready to guess some sort of gelatin base. And pectin? What would pectin do for ice cream? And carob flour. Yet another mystery.
It decided it was time to consult The Great Book, aka On Food and Cooking: The Science and Lore of the Kitchen by Harold McGee. I also looked at Cookwise: The Secrets of Cooking Revealed, by Shirley Corriher (whom you may recognize as the mad food scientist on Good Eats). These are two books that you need sitting next to all of your cookbooks. It seems to me, reading these two tomes, that pectin is to plants what collagen (from whence gelatin is extracted) is to animals. These are connective tissues, fibers that help mantain the structural integrity of plant walls and muscle fibers, respectively. What's interesting is that by themselves, they're actually kind of hard. But when heated, they loosen up. In the presence of water, they loosen up a lot. When the water is cooled, they form a matrix, trapping some of the water inside. What's truly interesting is that unlike proteins, they can be reheated and cooled over and over again.
I also discovered that fat plays a similar role in ice cream production. It turns out the fat molecules actually coat water molecules, creating sort of an insulator which keeps the water liquid, even at freezing temperatures. This tells me that it's important to have emulsifiers present in the ice cream, to help the water and fat stay together. Also interesting is the role of salt in the ice cream itself. When you add that pinch of salt to the ice cream base, it lowers the freezing temperature of the water. Other chemicals in the milk and cream seem to do that as well. What results from this is a mixture that, even at temperatures of 0F or so, still contains quite a bit of liquid (not solid) water. In fact, about 20% of the water remains liquid. Were it not for this, the ice cream would not be scoopable.
And so, some of the secrets of the stabilizer are unlocked. With this in mind, I sallied forth with a somewhat new ice cream base: Fresh Ginger and Lemongrass Ice Cream. First, I had to decide how much stabilizer to use. The container tells me to add 5 to 10 grams of stabilizer for every 100 grams of sugar. Sadly, even if my kitchen scale was reliable, it doesn't seem to have that fine of a reading. I knew that I was going to use 3/4 cup of sugar. According to the sugar bag, 1 tsp sugar is about 4 grams. So 3/4 cup would be about 144 grams. This gives me a conversion factor of 1.44. That means that I would want between 7.2 and 14.4 grams of stabilizer. Now, looking at the granularity of the stabilizer, I decided it felt like a hard flour. I looked at several of my flours and alternative flours and found that they ranged from 28 to 33 grams per 1/4, with most of them at 30 grams. Since there are 4 tablespoons per 1/4 cup, this tells me that I needed about 1 to 2 tablespoons of stabilizer. Bearing this in mind, I formulated my ingredient list:
1 pint milk
1 cup heavy cream
2 tablespoons fresh ginger, finely grated
3/4 cup sugar
2 tablespoons stabilizer
4 oz cream cheese, softened
6 egg yolks
1 stalk of lemongrass, roughly chopped
No candied ginger on this one. I just wasn't that impressed with it last time. And yes, I know that's a lot of lemongrass. I wanted a lot of lemongrass flavor in this. You could cut back by half if you wanted.
I decided to try the curd method on this one again. However, you should note that there is no lime juice this time. Instead, I decided to use a little heavy cream as my liquid, since I knew the fat would help insulate the egg yolks and help keep them from scrambling. I added the sugar, stablizer, salt, egg yolks and a little of the cream to a double boiler on high heat. I whisked constantly to keep it moving. After a minute or two, I added my ginger and a little more cream. I had about half of the cream in there by this point. At this point, I began to whisk in the cream cheese, just a little chunk at a time, until it was all incorporated. When it began to thicken, I whisked in the rest of the cream and the milk. After a minute, I added the lemongrass. Now, the lemon grass was roughly chopped for two reasons: first, I wanted to increase surface area, for maximum flavor extraction. Second, I wanted to keep the pieces big enough to be able to strain later.
When it was obvious it wasn't going to thicken much more, I moved the bowl to an ice water bath and whisked to cool it down. It was pretty much the same viscosity as my previous ice cream bases. I then moved the mixture to a plastic container and moved it to the fridge to cool overnight. Yes, with the lemongrass still in it. Remember our talk about infusing flavor? This would give the lemongrass plenty of time to get to know the rest of the mixture.
Now, I let this chill overnight, and then checked it in the morning. It had thickened considerably! This was new. The other ice cream bases I had made had kept the same consistency right up until I froze them. Very interesting indeed. I put the mixture back in the fridge and went to work. When I got home, it was pretty much the same thickness still. I strained out the lemongrass and moved the mixture to the ice cream maker and promptly forgot about it for the next 40 minutes. Fortunately, that extra 10 minutes didn't seem to cause any problems. I moved it into containers, and moved those into the freezer. A couple of hours later I checked on them.
Now in the past, a couple of hours wouldn't have been enough time to harden the ice cream. The outside might have been hardened a little, but the inside would still be at softserve consistency. This was not the case! It was almost to the perfect consistency already! I was intrigued. I took a taste and it was smooth, creamy and flavorful. I put it back to let it chill overnight. This morning, I checked up on it. Oh man! It had hardened, but was still very scoopable. The flavor was still dead on. And the texture? Smooth and creamy. Not the least bit grainy. In fact, they reminded me of a certain ice cream smoothie bar that you can buy at the store. Success!
So if you can get your mitts on some ice cream stabilizer, I say do it. Here's the stuff I used. Yes, it's an additive. But it's a darn handy one. My next step is to see if I can simulate it with a few more common ingredients.