[Everybody now!] We all scream for ice cream!
Guess what! Ice cream is primarily made out of a main ingredient in the keto diet–heavy cream! Yay! And now the sad news: to be scoopable, the way ice cream should be, it needs sugar. That’s right, the big no-no. So how to make keto ice cream? This is where I have most read and enjoyed learning about food science. This blog entry should be called, “my mediocre attempts at making keto ice cream that Nora loves anyway.”
Harold McGee’s epic tome, On Food and Cooking, gives my favorite description of the pleasures of cream:
We value cream above all for its feel. Creaminess is a remarkable consistency, perfectly balanced between solidity and fluidity, between persistence and evanescense. It’s substantial, yet smooth and seamless. It lingers in the mouth, yet offers no resistance to teeth or tongue, nor becomes merely greasy. This luxurious sensation results from the crowding of the fat globules, which are far too small for our senses to distinguish, into a small volume of water, whose free movement is thus impeded and slowed. (p. 27-28)
Ice cream is a dish that manages to heighten the already remarkable qualities of cream. By freezing it, we make it possible to taste the birth of creaminess, the tantalizing transition from solidity to fluidity. (p. 39)
Doesn’t that make you want a perfect pint of ice cream? “To taste the birth of creaminess”…it doesn’t get any better than that. And now the science part:
Plain frozen cream is hard as a rock. Sugar makes it softer, but also lowers its freezing point (the dissolved sugar molecules get in the way as the water molecules settle into ordered crystals). (p. 39)
Sadly, I do not own this book (hint hint). I had it on hold at the Corvallis Library for 2 months before I got it, then could not renew it after my time because someone else had it on hold. This is a book originally published in 1984 and updated in 2004. Come on people of Corvallis, you’ve had 8 years to check it out. That says something about this town.
Armed with this knowledge, I moved on to making ice cream with a little help from our friends. Our friend Cora made some keto raspberry ice cream for Nora a few months back and we found out about the “hard as a rock” property. It was tasty, like raspberries and cream, but was solid. I put a butter knife through the side of a plastic container trying to chisel some out. It had a ratio of about 15:1 because she used cream and not many raspberries, so I hoped that the next attempt with many more berries to provide some natural sugar would be a bit softer, Harold’s predictions notwithstanding.
Last month we received an ice cream machine as a gift from our dear neighbors, Connie and Kevin. That gave me my chance to try ice cream for Nora and put some of my food science learning to work.
The first recipe was a raspberry frozen Greek yogurt. I decided that Harold knew best, so trying something less conventional might yield better results. Greek yogurt has lots of protein and a decent amount of fat, but few carbs. Protein is also a key ingredient to finessing the texture of ice cream and I was hoping that enough protein would be a recipe for success.
The result was tangy with the flavor of Greek yogurt and had a lot more raspberries than the original recipe, so it was very tasty. But it still froze fairly solid. If we let it thaw just enough we could give it a quick stir and get an ice cream-like consistency, but thaw too much and it was liquid. Alternatively, I froze it as popsicles. The only problem is weighing the amount of yogurt in each pop and keeping track of each one. But Nora managed to eventually eat the whole batch enthusiastically, about 20 g at a time.
Raspberry Frozen Greek Yogurt
200 grams raspberries (about 1.5 cups)
340 g (1.5 cups) Traditional Plain Greek Yogurt
114 g (0.5 cups) English Double Devon Cream
1/4 tsp cinnamon
1 tsp pure vanilla extract
The nutrition facts are for 22 g, which is about 1 popsicle. You can see that 1.3 carbs is quite a bit at once and it has a 2:1 ratio, so this would have to be paired with other things in a snack to balance it out. It’s not ideal, but yielded fairly good results.
My next attempt was based on a recipe by David Lebovitz, chef and author of The Perfect Scoop. Ice cream expert! I wanted a mint ice cream recipe made with real mint, thinking that I could get great flavor without carbs. This one is the ticket, from his blog: http://www.davidlebovitz.com/2010/05/mint-chip-ice-cream-recipe-chocolate/
I made his version and a Nora-version. Oh my, was it wonderful. It calls for 80 g of mint leaves, which is a lot (believe me, I have a gram scale). I only had about 20 g in my garden that I could harvest, but a little went a long way in this recipe.
It’s a 2-day process, but I was able to follow the recipe once while making 2 versions with a little planning. I used half-and-half instead of whole milk, but otherwise did everything in the recipe EXCEPT adding the sugar: steeped the mint leaves in hot half-and-half and cream, then cooking in the egg yolks according to the recipe (below and at the link). Then I reserved some of the mixture for Nora and added a bit of her Cytra, which is sweetened with saccharine. I then added sugar to the portion for the rest of us while it was still warm so that the sugar would dissolve. Adding the sugar at the end did not affect the quality of the regular version, and I didn’t have to make the recipe twice. Then the mixtures must cool overnight.
The next day, I froze each version in the ice cream machine. Here is where I saw the importance of sugar firsthand. I put Nora’s version in first. The machine has a frozen bowl to chill the mixture and a rotating arm that scrapes it off the side of the bowl and mixes it so that large ice crystals are not able to form. When I make Nora’s ice cream in the machine, a thick icy-cream layer builds up on the side of the bowl that the rotating arm can’t scrape away. The portion in the middle freezes more like regular ice cream, so I stop the machine, scoop out the middle part, and then wash off the inside of the bowl.
If I am as quick as possible, the bowl is cold enough to make the sugared version immediately after, but just barely. When ice cream made with sugar goes in the machine, it is soft as it freezes and the machine can easily scrape the sides. It takes a lot longer to freeze, as you would expect from the additional sugar which lowers the freezing point of the mixture. Having 2 portions of the same recipe with and without sugar really demonstrated the point.
The grand finale of this recipe is the “chocolate chips.” I would have never thought of this if not for the Lebovitz recipe. I used a Green & Blacks 80% cocoa dark chocolate bar. Higher cocoa content means less sugar, hence fewer carbs, in the chocolate. Measure out the amount you will put in the keto ice cream (it only takes a few grams, at 0.28 carbs per gram of chocolate in those bars). It melts nicely in a small silicone pinch bowl in the microwave. While the ice cream is in the machine stirring, drizzle in a stream of melted chocolate. It freezes in tiny threads as it hits the cold ice cream. Mmmm, that’s something special. I did the same on some of Nora’s raspberry ice cream another time to give her a little chocolate on top. What a treat.
This ice cream was fabulous. The infusion of real mint leaves gave it an herbal minty quality. Next time I will try to use even more mint. I held back on the sugar so it was not overly sweet. I will definitely make this again, for all of us, when my mint patch recovers.
Keto Mint Chocolate Chip Ice Cream
240 g (1 cup) Organic Valley Half and Half
480 g (2 cups) Organic Valley Heavy Whipping Cream
Pinch of salt
85 g (5 large) egg yolks
80 g (2 cups packed) mint leaves
In a medium saucepan, warm the half-and-half, 240 g (1 cup) heavy cream, salt, and mint. Once the mixture is hot and steaming, remove from heat, cover, and let stand for an hour to infuse the mint flavor.
Remove the mint with a strainer, then press down with a spatula firmly to extract as much mint flavor and color as possible. Once the flavor is squeezed out, discard the mint.
Rewarm the infused milk. In a separate bowl, whisk together the egg yolks, then slowly pour some of the warm mint mixture into the yolks, whisking constantly, then scrape the warmed yolks back into the saucepan.
Cook the custard, stirring constantly with a heatproof spatula, until the mixture thickens and coats the spatula. If using an instant read thermometer, it should read around 170ºF (77ºC). Immediately stir the mixture into the remaining 240 g (1 cup) cream, then place over an ice bath until cool.
Refrigerate the mixture thoroughly, preferably overnight, then freeze it in your ice cream maker according to the manufacturer’s instructions.
The nutrition information above is ONLY for the mint ice cream. The ice cream alone has a ratio of about 7:1, and only 0.7 carbs in a 50 g serving! You can add enough chocolate to reduce the ratio to the desired level. In the future, I will calculate the amount of chocolate I want to add per serving, measure that amount, then melt the chocolate in a silicone pinch bowl (be sure that your bowl is completely dry, as any water in the melted chocolate will cause it to seize and ruin the pourability). Pour the chocolate in threads on the serving of ice cream, stirring as you go. Wa-la, you have chocolate chips in your ice cream!
The last ice cream experiment was of the blueberry variety. It was a simple recipe, but turned out quite different than the rest.
Blueberry Ice Cream
405 g (2.8 cups) fresh or frozen blueberries
720 g (3 cups) Organic Valley Heavy Whipping Cream
305 g (1.25 cups) whole milk
In addition to these ingredients, I again used Cytra to sweeten the mixture a bit, but you can use any no-carb sweetener you choose. Mix the sweetener in while you crush the berries. Then mix well with the cream and milk (I used a food processor). Then freeze in the ice cream machine.
Like the mint ice cream, I made it side-by-side with a sugar version and it turned out very differently. First, when I crushed the blueberries with sugar for the traditional recipe, the blueberries turned that keep purple-blue that I would expect from the blueberry skins. When I made Nora’s version, the Cytra did not extract the color from the blueberry skins in the same way. The mashed berries looked more green-gray with flecks of dark skin. I have not looked up the food science interaction that causes the color change in the presence of sugar, but I would love to know the secret.
As with the mint ice cream recipe, Nora’s non-sugar version formed a thick frozen layer on the outside of the ice cream machine bowl. The sugared version did not do that. And the final product was quite different. Nora’s version froze absolutely solid. I have to chisel it out of the bowl to measure it, or melt it enough. If I chisel it out and mash it up, it has a very dry crystal quality about it, not at all creamy. It’s not unpleasant, but it is not like ice cream either. If you click on the picture to get a larger version, you can see that texture. It also melts quickly, so getting it in as fast as possible is key, although Nora takes care of that herself and licks the bowl clean!
Thus far, I’ve learned that cream alone does not make ice cream. Harold is right–how could I ever have doubted him. Taking sugar off the table, the recipes that included more protein were far more successful than the blueberry ice cream recipe, which was mostly cream and berries. I added whole milk there in order to get some of the milk protein, sugars and solids, but it was not enough to make a difference in the texture.
The custard-type ice creams that include egg yolks are a better bet, but also require a 2-day process because the egg yolks have to cook, then cool down enough to make the ice cream. It’s a plan-ahead endeavor, but the quality of the final product makes it worth it. I will also experiment more with Greek yogurt to see if I can get some better results. But this is all academic to Nora. If it’s called ice cream, she’s thrilled to have it.