Make amazing yogurt in your Smart Hub

Start by filling a jar with whole milk. I prefer the full-fat yogurt that I get from whole milk, but you can also use 2%, 1%, or skim if you prefer yogurt with less fat. Some 1% and skim milk will yield a thicker yogurt because of extra milk protein added to the milk by the manufacturer to try to approximate the mouthfeel of full-fat milk.

The first step is to heat the milk to a temperature to between 180ºF and 195ºF. The hotter you get it, the less time it needs to spend there. Harold McGee, in On Food and Cooking, says 185ºF for 30 minutes or 195ºF for 10 minutes. This step accomplishes two things: it kills any bacteria in the milk that could compete with your culture and it denatures some of the whey proteins which allows them to bind with the other milk protein, casein. It is possible to make yogurt without this step, but it won’t be as thick as it would if the whey had been denatured by the heat.

With the Smart Hub, this is easy.  Simply fill it with water, set it to your temperature of choice, wait for it to quickly get up to the set temperature, and then lower in your jar of milk.  In a few minutes the milk will reach equilibrium with the surrounding water, and then you can wait for the amount of time that McGee suggests.  In this batch, we’ve done 185ºF for 30 minutes. 

Once 30 minutes have passed, remove the milk from the Smart Hub and wait for the temperature to fall to around 115ºF, which take 20 minutes or so.  At this point, we’re ready to inoculate the milk with our yogurt culture. 

At bare minimum, the starter culture must have a viable population of two bacteria, Lactobacillus Bulgaricus and Streptococcus thermophilus. These two bacteria work together to consume the lactose and produce the acid that sets the yogurt, as well as the compounds that give yogurt its myriad of tangy, sour, and tart flavors. The lactobacilli bacteria are responsible for most of the acidity, while the streptococci and other strains make some of the more interesting, delicate flavors. A starter heavy in lactobacilli strains will produce an acidic yogurt that will be sure to set, but it may lack the grassy and cheese-like flavors you can get from more diverse cultures.

You can get your starter population from a variety of places, the easiest being a container of store-bought yogurt – just make sure to choose a yogurt that you like with no added flavors or sweeteners. You can also use a specially formulated yogurt starter, which usually comes in the form of a freeze dried (or lyophilized) powder. Most of the ones that you are likely to find at your grocery store are going to be heavy in lactobacillus and will give you a very tart yogurt. There are also a number of websites selling traditional or heirloom cultures that contain a more diverse population of bacteria.

The amount of starter that you use can have a big effect on the result, especially if your starter is from your previous batch. Some of the bacteria involved in the fermentation become inactive after a certain level of acidity is reached, so if you use too much starter then the mixture might be too acidic to give those bacteria a chance to make their contribution. In The Art of Fermentation, Sandor Ellix Katz explains that sometime he gets a thicker yogurt when using less starter, probably for the reason I described above. He recommends about a tablespoon per quart, or around 5% by volume, but notes that some references say you can go as low as 2%.

 You can add herbs, fruit, or spices to flavor your yogurt before fermentation.  We’ve experimented with lavender, mint, and rosemary so far, and of those, lavender has been the winner.  Some additives will interact with some bacterial strains and lots of plants will have some bacteria already living on them, so know that you won’t always get the same results as you would without the pre-fermentation additions.

 Now you’re ready to ferment! Yogurt bacteria are thermophilic, meaning that they are more active at warmer temperatures. But different strains do best at different temperatures, and different rates of acidification produce different results. McGee says, “Rapid gelling produces a relatively coarse protein network whose few thick strands give it firmness but also readily leak whey; slow gelling produces a finer, more delicate, more intricately branched network whose individual strands are weaker but whose smaller pores are better at retaining the whey.”

I like a very thick, Greek style yogurt, so I strain it after fermentation with a cheese cloth.  I’ve found that the effect that McGee describes actually gives me the reversed results when straining.  The coarser network that results from fast gelling more readily releases the whey when straining, so I end up with thicker yogurt from faster sets.  Slower setting yogurt doesn’t drain as quickly or as thoroughly, so the resulting yogurt is creamier and runnier.   

After you’ve fermented your yogurt, it’s ready to eat, store, or strain.  I line a colander with some cheese cloth and leave it to drain for a few hours, usually in the fridge so that it doesn’t continue to ferment at room temperature.  Then I return it to the jar I made it in and store it in the fridge, where it will keep for around two weeks.

You can also make a delicious parfait with your favorite fruit, sweetener, and granola.  Start with a layer of fruit or honey, followed by a layer of yogurt, and then keep layering until you get to the top!