‘Sous Vide’…Yogurt?

There’s a hot cooking trend lately, a method called sous vide — by which food is cooked in a hot-water bath, after having been sealed in [plastic] packaging. High-end restaurants have been using this technique to deliver perfectly cooked protein, and taking it beyond what’s otherwise practically possible in the kitchen, by completely transforming meats or vegetables by cooking for extended periods of time (as in, 1-3 days). If this is new to you, check out this primer — the immense precision it gives you as a cook makes it perfect nerd-fodder.

Sous vide began getting really popular at home when the cost of easier-to-use devices began to hit the $200-and-below mark. These machines used to look like science projects, or be an all-in-one affair the size of a bread machine, meaning there’s some considerable investment of kitchen real estate in owning one. The device I bought is the Anova Precision Cooker, which is great because it just clips onto the side of any container that can hold water and can handle a temp of around 200F. I think this flexibility is great — and when you’re done, it’s reasonably small enough that you can toss it in a drawer or cabinet.

I’ve done chicken, steak, fish, pork, ribs, beef short ribs (oh man, 36 hours at 135F… what comes out is just unbelievable), hard-boiled eggs, all with great results. What makes this method so great is you’re setting the water-bath at the exact target temperature of the item you’re cooking. You want a mid-rare steak, you set to ~135F. You want a perfectly cooked chicken breast, 145-150F. Hard boiled egg, 165. Hell, you can tune temperature by a tenth of a degree. Because your water temperature isn’t changing, once the food has reached equilibrium with the water, it’s literally impossible to overcook (unless you leave it in several hours too long — not all foods benefit from longer cooking, and their textures can change negatively). The flexibility this affords you means mealtime can be at your convenience — throw your steaks in at 4pm, they’re ready by 5pm, but if you get held up making your sides, no big deal — they’ll stay warm in the bath and you can remove them when you’re ready.

I won’t get into the techniques of sous-vide cookery because it’s been covered extensively by a favorite food writer of mine, J. Kenji Lopez-Alt from Serious Eats. What I want to share is using sous vide to do something that’s much less obvious, but that it’s no less-perfectly suited to accomplish than the traditional means: making homemade yogurt.

Making yogurt at home, if you’ve never tried, is already stupid easy — and leveraging a sous vide cooker makes it even more….stupid? No, easy. The process for yogurt goes like this:

  1. Obtain a milk of a good quality (make your yogurt extra-special by finding a nice organic milk, or one locally produced, or heck even goat or sheep’s milk)
  2. Heat it up to denature the proteins, which means to unwind their tight structures, which improves the texture of your yogurt (more information on denaturation)
  3. Cool the milk down, so you don’t kill your friendly bacteria
  4. Add your bacteria culture, in the form of another yogurt (one that contains “Live Active Cultures”…should say so on the package somewhere, and you’re wasting money if you aren’t buying yogurt with “LAC”, and your yogurt was probably thickened with gums and starches and isn’t yogurt at all.)
  5. “Incubate” the whole thing — set up the milk in a controlled warm environment to allow the culture to innoculate the milk (they make purpose-built “yogurt makers” for this, which is a silly single-purpose contraption just to keep the whole thing warm)
  6. Wait a while…
  7. Stick in the fridge, let it cool, then taste it.
  8. [Optional] If you like Greek yogurt, from this stage you can park the whole thing over a very fine strainer, a cheesecloth, a large coffee filter, and drain for several hours, then what you’re left with is Greek yogurt. The stuff that drains off is whey — and it’s actually useful too. In cheesemaking (like making mozzarella), the whey is saved and cooked again, and you end up with some ricotta cheese. You can feed to your dog. You can add it to pasta sauce. You can put it in a smoothie. You could drink it. It has some yogurt tang, so do whatever you find appropriate, but don’t dump it.

The guidelines for doing sous vide yogurt came from this ChefSteps article. The last time I made yogurt, I had a mass of plastic deli containers carefully laid out on my kitchen table, wrapped in towels, wrapped in an electric blanket, with a thermometer sticking out of the whole mess. Trying to regulate temperature with a get-up like this is like driving with your elbows, so the precision water bath really struck me as a clever idea.

As written, the recipe calls for 800g of milk, 40g starter yogurt. As long as we keep the ratio the same, these amounts can be scaled up/down. If you’re working with a different volume of milk, say you have some specific storage containers you want to make your yogurt in, without having too much/too little, you can fill them with milk, then weigh all the milk together (be sure you’re not weighing the container). The formula would be this:

milk (in grams) x 0.05 = starter yogurt (in grams) 

Here’s what I did:

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800g of milk, weighed. I opted for a 2% local milk from “Sparkman’s Dairy” in south Georgia. A really nice milk will pay off in the end, you will taste any sweet and grassy qualities it has, even as milk. (It was actually on markdown at the store, expiring soon. Great opportunity to score cheap milk for good yogurt.)

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Heat milk to 185F. Some people like to hold at this temperature for a while, so time @ 185F is another variable parameter. (190F is also fine, don’t obsess over 185.0). I actually used the microwave, easier and cleaner than stirring at the stove. Then cool your milk down to 109F or less. Optionally, you can also steep some aromatics in the milk during the heating stage.

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40g of yogurt, weighed out. Add to the cooled milk (@ 109F, take it’s temperature). I’m using a Fage 2% for the culture. Choose a plain yogurt whose taste you like – the culture in it will drive the final taste just as much as the milk you use.

 

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Water bath set for 109F. I’ve clipped the Anova to a stock pot, and I’ve divided my milk between two glass swingtop jars from IKEA. Use whatever. Any glassware works, even an old pasta sauce jar.

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I cover the top with foil and a towel to keep in heat and evaporation, so my machine doesnt have to work so hard. I did two batches — one overnight (8 hours), and another for the minimum time (5 hours). I think the overnight batch was preferred – it seemed less prone to separation.

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Chill in the fridge for a few hours, to slow/halt the innoculation process. Looks like yogurt!

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It’s yogurt! Perfect with nice granola and a drizzle of honey

 

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