If you’ve studied ice cream making, you’ve probably been told to pay attention to drawing temperature—the final temperature of the ice cream before you remove it from the machine. This marks the end of dynamic freezing, and the transition to an even colder environment (blast chiller, hardening cabinet, chest freezer, or regular kitchen freezer) for static freezing—also known as hardening.

Most sources, including articles on this site, and the authoritative Goff & Hartell textbook¹, suggest a drawing temperature of -5°C to -6°C (23°F to 21.2°F). My old mentor, a Michelin-starred pastry chef, often emphasized that drawing temperature was the only factor to consider when timing your ice cream batches.

What’s so special about -5°C?

We know that if we draw the ice cream too early, it won’t be sufficiently frozen. Too much liquid water will remain, and it will freeze into unnecessarily large ice crystals during static freezing, leading to an icy texture. Likewise, the foam structure won’t have had sufficient time to develop, making it too dense and too hard.

What happens if you draw at a colder temperature?

There are in fact some advantages. All else being equal, you’ll create a structure with a greater number of smaller ice crystals, and since they’ll enter the static freezing stage at a lower starting temperature, there will be less opportunity for the crystals to grow larger during hardening. In short: you’ll get smoother ice cream.

Experiments show that ice crystal size decreases steadily with decreasing draw temperature². I’ve personally observed improved texture at draw temperatures down to -7°C (20°F). Research on ultra low-temperature extrusion* shows that ice crystal size decreases at least down to a draw temperature of -15°C (5°F).³ Air bubble size and fat globule size—other predictors of texture—likewise decrease.

Yes, there’s a catch.

If you use a standard commercial batch freezer, and make ice cream with a standard formulation (one that reaches ideal scooping consistency at around -14°C), the conventional drawing temperature is as cold as you can go. Any colder and you’ll have problems. These machines have a horizontal barrel and dasher, and use the rotation of the dasher to expel the frozen ice cream when the operator opens the chute. If the ice cream gets too firm, either from poor formulation or a too-low draw temperature, then it will get stuck in the machine—the texture might be amazing, but you can’t have any.

That’s where the magic number comes from. If you’ve got a commercial shop with a Carpiggiani, Bravo, Emery-Thompson, Taylor, or other horizontal batch freezer, stick with the conventional advice: draw at -5° to -6°C.

If you’ve got a vertical bowl machine, your choices get more interesting.

Most consumer grade machines, whether they have a compressor or a freezer bowl, are going to have a hard time getting getting a batch colder than -5°C; they just don’t have the freezing power.

But if you’ve got an especially massive freezer bowl (such as the Kitchen Aid mixer attachment) or a powerful compressor machine (including models by Musso Lello, Nemox, Texas Frozentech, Hubert Cloix, or Cattabriga) then you can do some interesting experiments. They might offer a simple way to improve your results.

The limiting factor will typically be the motor that spins the dasher.** If you see or hear or smell signs of the motor straining, shut it off. You’re done. On a good machine, you’ll find that at this point, you’re somewhere below -6°C, and your results will be better because of it.

But don’t push it. Try to stop before you see signs of strain. Even on machines that cost several thousand dollars, the dasher motors are often light-duty. Routinely overloading or stalling a motor (or its geared transmission) will shorten its life, risking repairs that could involve waiting weeks for parts to arrive from Italy. In worst cases, parts won’t be available, or you won’t be able to find service in your corner of the world, or the repair price will exceed the value of the machine.

Fortunately some machines (including the Nemox range) have an automatic shutoff based on a torque detector. You can rely on a system like this without worrying about motor damage. Other machines have an auto shutoff that detects motor overheating. This kind of system is a failsafe that you don’t want to rely on regularly—this would be like timing a roast with your smoke alarm.

In some cases, the limiting factor might be your formula. You’ll know if you find a film of butter inside the bowl or on the dasher blades, or if you find the texture overly dense and flat, with flecks of butter in your mouth or a generally greasy mouthfeel when trying a sample. This can be a symptom of excessive milk fat, excessive levels of emulsifiers, or both.

It could also be mean that the ice cream has just churned too long—but if this happens before you’ve reached your target drawing temperature, it means that your machine lacks the freezing power to get there, and you’ve churned well past the point of it adding any value.

Diminishing returns.

How do you know when to stop when nothing goes wrong? When the machine isn’t straining, the mix isn’t turning to butter, but your white beard is growing ever longer? This means you’ve run out of freezing power. It probably means you’re using a consumer-level machine, either with a freezer bowl or a sub-200-watt compressor. Or it could mean your recipe is unbalanced. Maybe a bit too much anti-freeze? Is it more cocktail than confection?

In these cases you will reach a point where more churning is counterproductive. Research and experience show that a lower draw temperature produces smaller ice crystals and finer texture, when all else is equal. However, a longer residence time fights against you—it produces larger ice crystals and coarser texture². The net result is that increasing residence time is fine, as long as that increased time corresponds with rapid cooling. If you see the rate of cooling beginning to plateau, stop. You’re done.

I keep an instant-read thermocouple thermometer handy. Whenever I want to double-check what’s going on, I pause the machine and poke the probe below the surface. Even without using a thermometer, you’ll get a pretty good idea that the freezing curve is flatlining when the ice cream stops thickening noticeably.

In summary

• If you’re using a commercial horizontal barrel machine and formulating ice cream for normal scooping and serving temperatures, draw at -5°C to -6°C.
• If you’re using a commercial (or pro-sumer) vertical bowl machine, go as cold as you can without straining the machine.
• If you’re using a lower-power consumer machine, go as cold as you can before the temperature plateaus.
• If your ice cream texture breaks from overchurning (buttering etc.) fix your recipe.

*This research was done with novel technology capable of churning and extracting ice cream at extra-cold temperatures. The machines are suited to industrial manufacturing. You probably can’t have one if you don’t have a factory.

**With the KitchenAid mixer attachment, the motor is powerful enough to tear the cheap plastic dasher to bits. Fortunately, the design includes a clutch that slips when overloaded, preventing this from happening. You’ll know you’ve reached the limit when the dasher stalls and you hear the clutch’s loud, irritating clicking.

¹ Goff HD, Hartel RW. (2013) Ice Cream 7th ed. Springer
² Drewett EM. & Hartell RW. (2007) Ice crystallization in a scraped surface freezer
³ Wildmoser J (2004) Impact of low-temperature extrusion processing on disperse microstructure in ice cream systems. (Dissertation)
⁴ Shrivastav A, Goswami TK (2017) Low Temperature Extrusion of Ice Cream: A Review. J Food Nutr Popul Health. Vol. 1 No. 2: 11