Yogurt

Fairwind Farms goat milk, about to become yogurtMy ideal yogurt is Greek yogurt, which is thick, rich, flavourful, and made of sheep’s milk. Unable to find whole sheep’s milk, I’m experimenting with goat’s milk from Fairwinds Farm of Fort Macleod, Alberta, as it is fattier (and just more Greek) than cow’s milk.

There are two ways to make yogurt at home. The first is to add a small amount of commercial yogurt containing active cultures to milk. The second is to use pure bacterial cultures. Regardless of which method you use, the process is basically the same.

Danlac Starter Kit

I eventually want to make cheese with pure bacterial cultures. I contacted Danlac in Airdrie, and ordered a starter kit containing several doses of rennet and cultures for yogurt, mozzarella, and feta.

The rennet and cultures were put in an envelope and mailed to me. The recipes for yogurt, feta, and mozzarella were e-mailed. Danlac’s motto is “Serving the food industry,” not “Serving the interested individual,” and the recipes reflect that fact: they’re more like industrial specifications than recipes. There are values measured in pounds per square inch, and mention of back pressure valves and plant conditions. All the relevant temperatures and times are listed, but to understand exactly how the process might be done in a kitchen, I consulted a few of the several hundred sources on the internet.

Yogurt: A First Attempt

Mise en Place

First, in my kitchen sinks, I set up an ice bath and a 45°C warm water bath. The first is for cooling the hot milk, the second is for holding the milk at the bacteria’s incubation temperature.

Water baths for controlling milk temperature while making yogurt

Next I measured out the yogurt cultures. The YO-MIX 601 packet I received contains freeze-dried pellets of the two most common cultures used in yogurt production: Lactobacillus bulgaricus, and Streptococcus thermophilus. The problem is that the packet is designed to inoculate 500 L of milk, and only weighs 7 g. I wanted to inoculate 4 L of milk, which means that I would need 0.0056 g of yogurt cultures. Unfortunately, my weigh-scale is not that precise.

4 L divided by 500 L is 0.008.

I poured the bacteria onto a cutting board. Using a butter knife, I roughly divided the contents into five piles, then split one of the those piles into ten. I continued eye-balling smaller and smaller divisions until I had approximately eight thousandths of the original pile balanced on the end of my knife. It was about a pinch. Go figure. This is sure to be a huge source of inconsistencies between batches. I slid the rest of the pellets into a small ziploc and put them in the freezer, as per storage instructions on the packet.

Measuring bacterial culture for making yogurt



Heat the Milk

The first step in making yogurt is heating the milk and holding it at 85°C for five minutes. Besides killing any micro-organisms in the milk (which is completely redundant if you’re using pasteurized dairy), the heat induces a mysterious change in the milk proteins that helps them set properly once coagulated. I heated my milk plain and simple on my stove top.

Heating the milk to make yogurt


Cool the Milk to Incubation Temperature

Next the milk is cooled to around 42°C, which is the ideal temperature for the bacterial cultures. I transferred my pot to the ice bath. After a couple minutes of stirring, it had dropped to 45°C.

Cooling the milk to inoculation temperature



Pitch Cultures and Incubate

With my milk temperature hovering around 42°C, I pitched my yogurt cultures. The milk now had to be held very close to this temperature for the next several hours.

There are lots of ideas on the internet for holding your milk at this awkward temperature, which too warm for room temperature, and too cool for an oven. I tried a simple system of thermal isolation. I tightly covered my stainless steel pot of milk, put it in the warm water bath at 45°, and covered the whole bath with plastic, and then with a thick towel. It made for a surprisingly closed system. My water bath lost a little more than 2°C every hour, at which time I would replace a few cups of water from the bath with hot water. Setting up the warm water bath in a large plastic cooler would probably work even better.

Incubating the milk to make yogurt



Length of Incubation

In industry, fermentation is stopped when the pH of the milk is around 4.50. I don’t have any titration tools, but my Danlac recipe provided the following rough time-line: if your milk is held at 42°C, it should take six hours to reach 4.50pH, and if your milk is held at 38°C, it should take eight and a half. Though you don’t want lose heat or disturb the fermentation by opening the pot too often, thickness and taste are the best indicators of when to stop the process. I ended up letting mine incubate for a little over twelve hours. This was maybe because of the inaccuracy of my yogurt culture measurement, but also because my incubation temperature slipped into the cooler end of the acceptable spectrum for a few hours.

Stir

Next was by far the most ambiguous step in the recipe: “Treatment of coagulum according to desired consistency by: stirring, using back pressure valve for improving structure, homogenizing.” I ignored the second and third options, as they didn’t sound like tasks I could perform in my kitchen. I stirred my yogurt, mixing the loose curd structures and whey together.

Let the Yogurt Set

Finally I left the yogurt in the fridge for twenty four hours to cool and “form a solid network”.

Results

The end product was acceptable, though a little thin. After straining with cheesecloth it was much closer to my thick, creamy Greek-style yogurt. It has a very pleasing, mild acidity that is rarely found in commercial products, which tend to be a little harsh.

I think next time I’m going to use 1/8 tsp of the yogurt cultures, about double what I added this time. Hopefully that will make the process run a bit quicker, and result in a thicker product.

The final yogurt: a little runny, but tasty

Crème Fraîche

A spoonful of crème fraîcheCrème fraîche is similar to sour cream. In fact, they are made by the same process: inoculating dairy with a bacterial culture that converts lactose to lactic acid, which in turn coagulates the proteins in the dairy and thickens the mixture.

The main difference between the two products is that crème fraîche is cultured whole cream (about 30% milk fat) while sour cream is made from leaner dairy products (usually about 15% fat). The added fat in crème fraîche gives it two advantages over sour cream. First, it has a more luxurious texture. Second, the fat tempers the acidity, making for a subtler and more rounded flavour.

Making Crème Fraîche at Home

Fresh dairy naturally contains the bacteria that would, over time, turn cream into crème fraîche. The traditional method of production would be to simply incubate that bacteria, and let nature take care of the rest. In the age of pasteurization, we must reintroduce this bacterial strain to the cream. There are several supermarket products that contain this strain. Buttermilk is one.

To make crème fraîche at home, you need only stir one tablespoon of buttermilk into one cup of cream. Cover the mixture and leave it at room temperature for two days.  The cream will become quite thick, but as soon as you stir it it will become runny, like double cream.  Somehow it develops a nutty flavour, almost like brown butter.

Crème fraîche is perfect for finishing cream soups, as it adds a very mild, pleasing acidity to cut the richness. It being the end of May, with Edgar Farms enjoying its brief few weeks at the Strathcona market, cream of asparagus soup seemed appropriate.

Cream of asparagus soup with crème fraîche

Butter and Buttermilk

I think as children most of us were taken to historical sites like Fort Edmonton to learn how the settlers made wool and horseshoes and butter. Even so, I’ll start at the beginning.

You make butter by agitating cream.

It works like this. The fat in cream is in tiny globs, each covered with a membrane that prevents the fat globs from joining together. When you agitate cream, you break these coverings, releasing the fat globs, which all rush out to join their fatty brethren and form a solid mass of butter.

To commence butter-production, fill your container half way with heavy cream. Add a pinch of salt, secure the lid, and start shaking. You don’t have to strain yourself, just use a gentle shake that you can sustain for maybe ten minutes. After a while the cream will thicken: the contents will be noticeably less fluid, and there will be less sloshing. At this point you’ve simply made whipped cream:

The cream, thickened by agitation
Once whipped cream has formed, it’s a little more difficult to keep the cream moving in the jar. Perform a couple minutes of aggressive shaking, which will separate the butterfat and buttermilk:

The separated butterfat and buttermilk


Buttermilk: A Digression

While the resulting liquid is technically buttermilk, it does not have the tanginess that we usually associate with buttermilk. Why do we think of buttermilk as sour?

An old-timey counter-top butter churn.When my mom was growing up in northern Ontario, they kept dairy cows.  They had a butter churn. Not the tall wooden ones you see at historical villages, but a large glass jar with a crank that spun paddles within.  Once the day’s cream had turned sour, they would pour it in the jar.  Once the jar was full they would make butter.

Whoa. Hold on. “Once the day’s cream was sour?”

I know.  In the age of pasteurization “sour milk” means “spoiled milk,” ie. a putrid mess of mold and coaguluum.  But before milk is pasteurized it contains a community of friendly bacteria called lactobacillus that are able to get a strong foothold on the milk before any other microbe. In my mother’s day sour milk was exactly that: sour. It wasn’t harmful, but if incubated too long could be too strong tasting.  This is what they used to make butter.  Both the butter and the buttermilk would have had the tangy taste of culture milk.

These days commercial buttermilk is made from pasteurized whole or partly-skimmed milk that has been inoculated with lactobacillus and incubated.

 

Back to the Butter…

The butterfat that has clumped together must now be worked to remove small pockets of buttermilk that remain within. When making such a small amount of butter, you can just use your hands. Knead the butter. You should see droplets of buttermilk come out.

At this point the butter is usually pressed into a mold to form the familiar bricks. Or in my case, hockey pucks:

The finished butter in a round ramekin

My finished butter was made with store-bought cream, so it has little to distinguish itself from store-bought butter, besides a slightly richer dairy flavour. It’s very good, but the benefits aren’t great enough to convince me to start churning cream for my daily supply of butter. (Maybe once I have my own cow…) It’s still a good experiment to try once, if only for general knowledge and appreciation of this rich but humble staple.