History & yogurt facts

In days gone by

Yogurt is one of the oldest, best known foods. Thousands of years ago milk was kept in hide sacks. In the Middle East in particular it was very hot and so the milk quickly soured. Often the end result wasn’t very tasty, but now and again a light, tangy, thick pulp appeared. Once the sack was empty and refilled with milk this soured even quicker. As this process was repeated in quick succession eventually a light, tangy, thick pulp was created:  yogurt. This could be kept for far longer than milk and moreover, it tasted better.

Yogurt soon became popular the world over. As yogurt making methods varied considerably, different types of yoghurt arose. People had no idea how it was made but they had discovered that if ‘old’ yogurt was left in a pitcher, sack or bottle, the new milk soured far more quickly. 

Bacteria

Nowadays we know that yogurt is made with two bacteria types. These were discovered at the start of the previous century by a worker at the Pasteur Institute in Paris. He discovered that people in Bulgaria who ate a lot of yogurt lived for longer. He decided to research yogurt and subsequently discovered two bacteria.

The two bacteria he discovered varied greatly. One was rod-shaped, the other spherical. The rod-shaped bacteria was called Lactobacillus bulgaricus (rod-shaped bacteria = bacillus, lacto = milk, bulgaricus = Bulgarian). The spherical bacteria was called Streptococcus thermophillus (coccus = spherical, strepto = in a strand, thermophillus = heat seeking).

Both bacteria are necessary when making yogurt, otherwise it won’t work. Together these bacteria are called yogurt culture.

Now

Yogurt is a fermented milk product, obtained through the incorporation of two lactic bacterium types. Yogurt is pretty much made today in the same way as it has always been, but with a modern twist. Milk is no longer soured using old yogurt, but with freeze-dried yogurt powder. The freeze-dried yogurt powder is called starter or starter culture.

Production

Yogurt is made with milk, with the fat content first being raised to the desired level. This varies from 0.5% for low fat yogurt to 4.4% for full fat yogurt. The milk is sometimes also condensed. The milk is purified of superfluous bacteria:  this is called pasteurisation. The fat is also spread evenly over the milk; this is called homogenisation.

Now the bacteria are added. Once this has happened the milk is placed in large tanks where the product is kept for around ten hours at a temperature of 30 degrees Celsius. This is the ideal temperature for the bacteria to multiply. The yogurt is now ready. If everything has gone according to plan the yogurt should now also be thickened. Yogurt is tangy because of its very low pH level, which is between 4.0 and 4.5. This is why yogurt can be kept for longer but it does have to be kept in the fridge though as otherwise it becomes too sour.

For true ‘yogurt’ both lactic bacterium have to be live and present in considerable quantities, right up to the point of consumption.

Low fat, medium fat and full fat

Just as with milk yogurt comes in low, medium and full fat versions. Full fat yogurt has at least 3% fat content, medium fat yogurt contains 1 to 3% and low fat yogurt mustn’t exceed 1%.

Stirred and set yogurt

Moreover, differentiation can be made between stirred yogurt (which is stirred during fermentation) and set yogurt (which ferments in the packaging without having first been stirred and is as a result somewhat more granular in consistency).

‘New’ types and flavours

Nowadays many other similar ‘world dairy products’ can be found alongside natural yogurt  at countless supermarkets and retailers, such as:

Greek yogurt

This is prepared from sheep’s and/or cow’s milk. There are scant differences between natural yogurt and its Greek counterpart. The most obvious being that Greek yogurt is enriched with cream. A fat content of 10% typifies this yogurt.

Greek yogurt is produced in the same way as natural yogurt. The yogurt is thick in consistency and the whey is strained off. As such the yogurt doesn’t curdle when heated up and is highly suitable for use in sauces and hot dishes.

Bulgarian yogurt

This is made using milk which is firstly condensed. This makes it thicker than natural yogurt and provides it with a smoother, creamier taste. The fat content of Bulgarian yogurt is 5%, but fuller and lower fat varieties do exist. Bulgarain sour milk is an authentic national product. In Bulgaria yogurt is known as Airan, but this product has also earned a reputation outside of Bulgaria too.

Turkish yogurt

Authentic Turkish yogurt is made using sheep’s, goat’s or cow’s milk. The yogurt is drunk as ‘ayran’ (a type of cool yogurt drink which sometimes has salt added to it), eaten as ‘cacik’ (a thicker yogurt soup with cucumber), and ice cream which can be served as an appetizer. It is incorporated into everything and anything, including sauces and tarts. Kanlica, a city district of the Asian part of Istanbul, is famed for its quality yogurt. This yogurt is particularly nice with podra (castor sugar) mixed through it. Two types can be found at the markets: sivi tas (a runny yogurt from which ayran and cacik are made) and süzme (a thicker, filtered yogurt with10% fat content). Less tangy is the popular kaymak, an ultra-thick cream, thicker than whipped cream and neutral in taste.