If you are anything like me, then you love ice cream. There is nothing like making your own, but the problem is, it just takes too long to freeze the machine in order to make more! However, very recently The New York Academy of Sciences posted a cool podcast where Kent Kirschenbaum talks about using liquid nitrogen to make ice cream; and the liquid nitrogen making the ice cream super creamy.
Great! I thought when I read this, just what I need to have my dream of multiple foryo creations on one sitting!
But first: What is liquid nitrogen? In plain English, it’s cold.* Most of the air we breathe is actually nitrogen (about 78%). In order to to liquify nitrogen gas, you have to cool it down. A lot. Liquid nitrogen is -320°F (or -196°C, if you prefer). While liquid nitrogen is used for many temperature-related applications, it’s particularly useful for freezing foods because nitrogen is odorless, colorless, and tasteless.
Now to make the ice cream base. There are hundreds and hundreds of recipes for ice cream and froyo (my all time favorite), with different compositions and styles. I like frozen yogurt the most, and am a complete sucker for soft serve texture. According to that podcast, liquid nitrogen gives you just that kind of super creamy texture in ice cream. But how about frozen yogurt? Turns out the fat from milk generally makes up between 0.5-6% of the ingredients in frozen yogurt, but 10-16% of the ingredients in ice cream.
Would liquid nitrogen have the same effect on froyo as it did on ice cream, or would the different fat content change the texture dramatically?
One of the benefits of making ice cream using liquid nitrogen is that you can test the batch in just a few minutes, and make more as many times as you want! So let’s find out. I decided to try two different compositions of frozen concoctions: a strictly yogurt-based froyo, and a mix of cream and yogurt. For added deliciousness, I flavored them with seasonal fruit: figs and raspberries. In-season fruit is the best ingredient for sweet and refreshing concoctions, and it is finally fig season so I couldn’t resist. The ones I used were a bit over-ripe, but as sweet as they could be! I made a compote of the figs and raspberries, adding a little sugar and Cointreau**, and mixing some of this with dairy for each experimental frozen treat as follows:
Batch #1 (fattier, more like ice cream): Half-and-half, lowfat kefir, goat cream cheese.
Batch #2 (less fatty, true frozen yogurt): 2% Greek yogurt, lowfat kefir.
And now it’s time for the fun part: making the ice cream. I slowly poured the liquid nitrogen into the bowl of ice cream / froyo mix, while trying to stir constantly with a wooden spoon. That’s the key: the ultimate fine-textured ice cream happens when ice crystals are really tiny, so keep stirrin’! Essentially, the extreme temperature of liquid nitrogen plus rapid stirring do not allow enough time for large ice crystals to form, making the end product creamier.
So did it taste any different? Both mixes produced a dense, custard-like mouthfeel; what I imagine pudding would taste like were it frozen.
As expected, the fattier ice cream (Batch 1) had a soft and rich texture. But to my delight, the more traditional froyo (Batch 2) also tasted like normal frozen yogurt – maybe even creamier and better! It appears the liquid nitrogen has a similar effect for both ice cream and frozen yogurt, which is good news for me and my froyo addiction!
But would both freshly made frozen concoctions hold up after storage in the freezer? The consistency of fresh-made froyo depends on the fat content making it feel smooth, and small ice particles making it melt at a slow rate. If these small ice crystals melt and re-freeze into larger ones, you lose that creamy texture. (This can happen during freezing, like when you leave froyo or sorbet in the freezer for too long, and it gets covered with a furry layer of ice crystals.)
My froyo had less fat, but it turns out the fig compote served as great antifreeze. Together with the freezing power of liquid nitrogen, both of the mixtures were amazingly soft and creamy, even after 24, when I tasted them again.
So, victory! Liquid nitrogen works its creamy magic on both ice cream AND frozen yogurt, making them even better. Better froyo, faster, made with a totally awesome method? I love it!
*Have you ever seen someone on TV stick a rose into a vat of mysteriously steaming liquid, pull it out, and shatter it into millions of pieces with a hammer? That’s liquid nitrogen. It’s that cold.
**To really take advantage of liquid nitrogen’s freezing power, the liquor cabinet comes in handy. The low freezing point of alcohol ensures that your frozen concoction stays nice and soft once you store it in the freezer for later enjoyment.