If an aliment should ever be elected as the legitimate representative of the country of Bulgaria, it will certainly be yogurt. The legend tells that once upon a time, Bulgarian horsemen carried milk as a food ratio in leather bags that eventually gave a home to a lactobacillus bulgaricus — more precisely lactobacillus delbrueckii subspecies bulgaricus. The bacterium subsequently returned the favor by metabolizing good Bulgarian milk into the first Bulgarian yogurt in history.
Albeit serving as an essential feature of Bulgarian culture and the country's identity, the internationalism established as the name of this dairy product is not of Bulgarian origin. The word yogurt stems from the Turkish yoǧurt that roughly translates to thick milk. In Bulgaria, yogurt is simply referred to as кисело мляко (kiselo mlyako) translating to sour milk. The fact that the word milk is rarely used alone but almost always in the combination of sour milk for yogurt or fresh milk for ordinary milk bears eloquent testimony of the omnipresence of yogurt in Bulgarian everyday life.
The production of yogurt is akin to that of soured milk. While the bacteria that are responsible for the fermentation of soured milk, are a natural constituent of milk — see Home-Made Soured Milk — the lactobacillus bulgaricus needed for making yogurt has to be added manually to the milk. It also requires higher temperatures for optimal development.
Many Bulgarians take it for granted that lactobacillus bulgaricus is a Bulgarian discovery. However, the currently proven state of scientific research credits it to the Danish bacteriologist Sigurd Orla-Jensen who first described the microorganism after finding it in Bulgarian Yogurt.
Besides, there is no shortage of other kinds of bacteria that soccur in the home-making of yogurt, usually yielding a different flavor (for example
mild yogurt) or different microbiological features (probiotic yogurt, yogurt with dextrorotary respectively clockwise rotating lactic acid and so on) of the resulting yogurt.
Since yogurt bacteria are not a natural constituent of milk, leave alone pasteurized milk, you have to add them manually.
A quick-start to yogurt-making is to buy a pot of yogurt from your local grocery store, mix two tablespoons of it into half a liter of milk and ferment it for a little bit more than 6 hours at 40 to 45 °C (104 to 113 °F). You will receive some kind of yogurt, however, you will usually not know which bacteria are inside because the species used does not have to be declared for yogurt. Decide yourself whether that is an issue for you or not.
This will only work if the bacteria culture in the yogurt you have bought is still alive but this is usually the case.
You can also find Lactobacillus bulgaricus (and many more) on the internet. The company Bacillus bulgaricus ships worldwide. Compared to yogurt as a starter culture, these bacteria are a little bit on the expensive side but you only need them for the first batch of yogurt you make. The next time you just use four tablespoons of your last batch to add to the next liter of milk.
No matter whether you start with a package of bacteria or yogurt from the store, you can use the remainder of the last yogurt as the starter for the next batch. However, sooner or later you will notice that the quality is deteriorating, most probably because in addition to the benign lactobacillus bulgaricus, other unwanted bacteria start proliferating in your homemade dairy product.
Then it is about time to find a new bacteria culture, either from a pot of bought yogurt or from new, fresh bacteria.
It is common in Bulgaria to produce yogurt from sheep's milk. Goat's milk and buffalo milk are equally usable for yogurt which will, of course, have a very different taste. As a matter of fact, all milk of animal origin should be fermentable to yogurt.
It is said that vegan milk like oat, almond, or soya milk can also be processed into yogurt, although I have never tried that myself. Honestly, I would probably test first with some ready yogurt from a store as a starter so that I have more confidence that the bacteria contained are usable for the base product.
You have two ways of adjusting the fat content of your yogurt.
On the one hand, conventional yogurt has the exact same fat content as the base product. If you make yogurt from skimmed milk with a fat content of 1.5 %, the yogurt will also have a fat content of 1.5 %, neglecting evaporation.
Not only in Bulgaria but also in many other countries, yogurt is often drained after fermentation. Just fill yogurt into a clean cloth wrapped around a wooden spoon, hang it into a bucket or other vessel and wait three to four hours (or even shorter or overnight). The result is that most of the water has vanished from the yogurt, and hence the amount in fat and proteins of the remaining creamy substance increases accordingly. The liquid that drips off has a sour and refreshing taste and does not have to be thrown away.
In Bulgaria this concentrated yogurt is called tsedeno kiselo mlyako (цедено кисело мляко), roughly translating to sieved sour milk or sieved yogurt. Lebanese labneh is essentially the same and greek yogurt with a high content in fat that is available almost everywhere is produced in very much the same manner. If you prefer, you can, of course, also use non-homemade yogurt as a base product for tsedeno kiselo mlyako.
The optimal temperature for the fermentation is said to be 42 °C (107.6 °F). I personally set the temperature to 43 °C because I assume that the real temperature of the milk is slightly lower because of inevitable warmth loss.
But there is a lot of room for improvisation anyway. The bacteria develop in a temperature range at least as wide as 30 to 45 °C (86 to 113 °F). The closer you get to the optimal temperature of 42 °C (107.6 °F), the sourer and the firmer the yogurt will be.
The same holds true for the duration of the fermentation. I set the alarm to 6 hours and 15 minutes after a temperature of 42 °C (107.6 °F) has been reached. I verify the temperature with a roasting thermometer. And again, the longer the fermentation lasts, the sourer and firmer the final product will be.
These settings will certainly do for starters and you can then slowly proceed with little variations to reach your preferences in terms of sourness and firmness. By the way, you should not have the idea of
firm yogurt slipping out of its vessel in whole and being sliceable with a knife. Industrially produced yogurt with such features will almost always contain emulsifying agents and stabilizers such as starch that you have no reason to use at home.
The Lactobacillus bulgaricus is pretty aggressive towards unwanted relatives. That being said, you certainly do not need a germ-free environment for making yogurt at home.
But since you want to use your yogurt as a starter for the next batch of jars, you should have everything reasonably clean, wash all jars, spoons, thermometers, etc. with hot water and avoid sticking your fingers into the milk.
Likewise, at least with the last jar that will be used as a starter for the next generation, you should only use clean spoons and, of course, stop yourself from eating directly from the jar with a used spoon because the bacteria of your oral flora will proliferate in yogurt at least as easily as their relatives from the species lactobacillus bulgaricus.
There is not just one way of doing it. One common aspect is that I would place the jars always in a bain-marie (water bath) because of the higher volume in liquid helping in keeping the temperature stable.
In Bulgaria, you will hear most of the time that you first have to heat the milk to at least 90 °C (90 °F) and letting it cool down then to 45 °C (113 °F). The warm milk is then transferred into loosely closed (not air-tight) jars wrapped into thick towels so that it can ferment at 40 to 45 °C (104 to 113 °F) for about six hours.
Honesty, you can make do without the gratuitous first step of boiling the milk when you use pasteurized milk. Moreover, nowadays you have cheap but way better means for ensuring an optimal environment for fermentation than towels.
You will find all prerequisites for making yogurt in the oven in almost every kitchen. Fill a high baking tin with 43 °C (109.4 °F) warm water, transfer the jars with the milk and the starter into it, and then keep the temperature at 43 °C (109.4 °F). You will find an oven thermometer or roasting thermometer put into the water to be helpful in the process. And you control the temperature not only with the knob of your oven but also by opening the oven door a little. You will certainly find the right settings after a little bit of try and error.
You can also find dedicated yogurt makers. I personally would not use them because they are only good for making yogurt, nothing else.
My favorite device for yogurt making is my sous-vide cooker. Sous-vide cookers come in two makes. One is a closed box very much like a yogurt maker, and they are often advertised as a combination of sous-vide cooker and yogurt maker.
The sous-vide cookers that you hang into a pot filled with water are not only more space-efficient but also cheaper. Beware though that you have to check the combination of the pot, the jars, and the cooker because these devices always have a marker for the minimum and maximum level of water. When hanging the device into the pot, the top of the jars should be somewhere between the min and the max marker so that the jars stand as deep as possible inside the water.
- 500 g organic full-fat milk (3.5 % fat content) or any other milk of your choice
- 2 tbsp yogurt as a starter (alternatively: bacteria according to package instructions)
- Heat the milk and a bain-marie (water bath) to 43 °C (109.4 °F) and ensure that the temperature is kept as close as possible for the rest of the process.
- Mix the starter with the milk, transfer into jars, and close loosely (non-air-tight).
- Let the milk ferment for six hours and 15 minutes.
- Close the jars firmly and keep in the refrigerator. It is not possible to predict how long exactly the yogurt will be good for consumption. But you will know when it has gone bad because it will show mold or develop an unpleasant taste.
|per 100 g||per portion|
|- of which saturates||2||g||4||g|
|- of which sugars||4.7||g||9.4||g|