S.V. Ice cream

So, I've been reading through a few sous vide ice cream recipes, (sous vide for the home cook, under pressure, and volt/ink) and nearly all of the recipes say to cook the base for approximately 20 min. The temperatures range from 185 to 174. One of the recipes in under pressure calls for setting the bath to 179, then turning it down to 174 and putting the base into the bath. Isn't the amount of base in the bag important? It seems that the amount of base and size of the bag don't matter. If you were to sandwich the bag between 2 cooling racks, the thickness would be even throughout. If you were to toss the bag straight into the bath, the shape would be irregular. Why aren't these topics addressed? Does it not matter? If so, why??

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trev_teich

Any suggestions on ice cream machines for home?

trev_teich

Ha, I've read some reviews that mention this, but if it makes good ice cream I will deal with the noise as I don't have a basement. Which one do you have?

dpietranczyk_49940

I've been using my stand mixer and dry ice that I've vita-prepped. Works pretty well. If you eat it right away it has some fizz in it, but if you let it temper in the freezer that goes away. Trying to get liquid nitrogen has been quite the hassle for me. The companies won't sell medical grade over the counter. Only industrial. Maybe Chris could shed some light on this matter while we're at it. Praxair is who I've dealt with and they said that the industrial grade hasn't been tested for anything harmful that would remain after the nitrogen has boiled off. Should this be a concern? I'm not sure what else could be in it.

trev_teich

dpietranczyk you are in Chicago too right? Where are you getting your dry ice?

Chris_Young_80640

I'm actually working on a talk for Seattle's Town Hall tomorrow night and I will be talking about sous vide ice cream. We'll be putting a recipe up for sous vide ice cream in the next couple of days—along with a whole bunch of stuff for module 2. But here is what I'll say for now:

(1) With a liquid in a bag, the temperature can climb fairly quickly since you can get some internal convection inside the bag. If you massage the bag a couple of times for the first 10 minutes or so, you're bag should quickly reach the same temperature as the bath.

(2) In the US, and most other places in the world, the minimum cooking temperature is set to be 149 °F / 65 °C for at least 30 minutes of holding time (plus the required heat to temperature time) because the organism Coxiella burnetii, which is difficult to destroy with heat and can be found in milk.

You'll notice this is a much higher standard—longer cooking time and higher temperature—than we have discussed elsewhere on the forum for meats and other foods where Salmonella is the target pathogenic organism set by food safety authorities.

(3) Higher temperatures are frequently used for ice cream because eggs are mixed into the base, and the pastry chef was trying to get a thicker viscosity. This tends to make it a richer, slower melting style base.

I also tend to think that recipes that start at a higher temperature and then reduce it at some point during cooking are an odd reflection of a particular kitchens setup. The only advantage that I can see is to speed the time it takes to reach pasteurization temperature. I say just massage the bag, it will achieve a similar speed up on the heating time.

(4) I have yet to find a home ice cream machine for less than several thousand dollars that I think does a good job of churning and freezing the base. You get the best results with ice cream the faster you can freeze it. Liquid nitrogen or crushed dry ice in combination with a stand mixer is how I do it at home.

Note, you'll need at least 1.75x the weight of liquid nitrogen to base for the freezing, where as you need at least 0.6x the weight in dry ice to freeze your ice cream base. In practice, you'll want a bit more of either since not all of the cooling power of these ingredients will go into turning liquid water into solid ice. So I would suggest having 2.5x liquid nitrogen or 1x dry ice on hand for the exploit.

Nerd Fact: The reason for this is that water's enthalpy of fusion (the energy required to turn it from a liquid to a solid) is larger (334 kJ/kg) than the energy of vaporization for liquid nitrogen (200 kJ/kg), but less than the enthalpy of vaporization for dry ice (574 kJ/kg).

(5) We buy our liquid nitrogen from Praxair. There is no difference between welding, medical, and food-grade liquid nitrogen. It all comes from the same chilling unit. Dry ice is available at many supermarkets, but sometimes we've had to ask the store manager to bring it out for us—so call around to see who has it and who is selling it cheap.

dpietranczyk_49940

Thanks Chris! This helps very much.

@trevorteich I am in Chicago as well. I live in Chicago city limits, right up against the border of Indiana. Lang Ice (the bag with the penguin on it) is 5 min over the border and has it for $1/lb. I heard someone say that Amazon fresh ships everything with dry ice. I'm not sure if they deliver here though. You might be able to ask for it at someplace like Baskin Robins.

trev_teich

Thanks and Chris I like the nerd fact!

dpietranczyk_49940

Yes. I use the paddle attachment. Blending your dry ice into a powder is the easiest way to crush the dry ice. You could put it in a bag and break it down, but you'll end up with irregularly sized pieces. If someone were to bite into one of these or worse, swallow one... It would be bad news. Turn the mixer on low and rain in the dry ice until it's frozen. I have gone by eye, but Chris provided an amount so I'd go with that. Oh, and be sure that you do add it bit by bit otherwise you'll have ice cream base all over your counter top.

Brendan_Lee_56950

@dpietranczyk how long do you let it temper in the freezer before the carbonation goes away?

dpietranczyk_49940

@BeeLee I suppose it depends on the size of the dry ice pieces. I vita-prep mine and then leave it in the freezer over night. Leave room for the ice cream to swell as the CO2 makes it's way out.

tonybatty_36486

Chris, when I first looked at the ratios of liquid nitrogen and dry ice I thought you'd got them the wrong way round but understand the issue of latent heat but do the ratios also take into account the large difference in temperature between liquid nitrogen and dry ice?

Shannon_Barnes_68642

I have a cuisinart and agree that it is so loud! I have a very small house, there is NO escaping the noise. But totally worth it for homemade ice cream. I have the MC recipe in my to-make list.

Chris_Young_80640

@tonybatty – the energy required to raise the temperature difference of liquid nitrogen to the freezing point of water, or raise the temperature of dry ice to the freezing point of water is totally dwarfed by the energy required to cause the phase change. Latent heat is really all that matters.

michaeltran

I have a cuisinart and agree that it is so loud! I have a very small house, there is NO escaping the noise. But totally worth it for homemade ice cream. I have the MC recipe in my to-make list.

Some of the best Ice Creams I've ever made were from my Cuisinart ICE-21. See attached for several ice creams I made from Jeni's Splendid Ice Creams.

(1) Sweet Corn w/ Blackberry

(2) Maple Ice Cream w/ Salted Buttered Pecans

(3) Roasted Strawberry

michaelnatkin

Love that corn + blackberry combo!

susan_fox_33805

I've been making Jeni's Splendid Ice Creams of late too. Sometimes adding my own twist. No pix but: roasted pear ginger, meyer lemon (my favorite), eggnog, and moca. Looking forward to getting into it SV style.

Chris_Young_80640

First time I remember seeing sweet corn ice cream served with black berries was at Gramercy Tavern years ago when the amazing Claudia Fleming was the pastry chef. She had a recipe in her book "The Last Course", which is a phenomenal book. All of her recipes are great.

susan_fox_33805

Made Jeni's Kona Stout ice cream yesterday. Knocked my socks off.

Terry_17511

Hello My Name is Ice Cream says sous vide at 160F for 30 to 60 minutes. Any thoughts? I'm going to give it a whirl. I made ice cream almost every week in summer. If I can sous vide the base it would make it so easy