YOGURT FERMENTATION

(The picture is taken from iati.blogsome.com)
If you go to a modern supermarket or a hypermarket, you are bound to see stacks and stacks of yogurt cream and drinks in the dairy section. Yogurt is now a very popular and nutritious food drink which most of the health conscious population will vow to its nutritional goodness and even to anti cancer properties.

For the general information, yogurt is not a new food product. It is a fermented milk derived from cows and goats and have a long history stretching hundreds or thousands of years ago.

The remarkable thing is that yogurt was not that well or popularly known in Malaysia. This is probably attributed to its sour taste, boring whitish curd appearance and are taken only by very few people. Nowadays with the advent of powerful marketing, food technology and re branding and repackaging yogurt is becoming very popular indeed.

Now we have yogurt in all sorts of beautiful containers and in various fruity and sweet flavours. The old yogurt now is spiced up with all kinds of goodies making it so appealing to all. Even children love yogurt now!!

In this blog we will be discussing in detail about yogurt fermentation and how it is made or manufactured





Yogurt is actually a fermented milk product. The milk are fermented using bacteria such as Lactobacillus bulgaricus. In some yogurt production it might involved more than one type of bacteria such as Streptococcus thermophilus.

The Lactobacillus bacteria are fermentative bacteria which convert sugar into lactic acids. They can tolerate the presence of oxygen

The milk sugar or lactose is fermented by these bacteria to lactic acid which causes the characteristic curd to form. The acid also restricts the growth of food poisoning bacteria.

During the yogurt fermentation some flavours are produced, which give yogurt its characteristic acetaldehyde flavour.


Yogurt is a fermented food derived from the fermentation of milk. A commercially produced yogurt is made up of milk, sugars, stabilizers, fruits and flavors, and a bacterial culture Lactobacillus bulgaricus.

The fermentation of yogurt is approximately about 4 hours. A completely fermented yogurt has about ph 4.4 value of acid range

CONTROLLING YOGURT FERMENTATION
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The most important component in controlling the quality of yogurt fermentation is temperature. Temperature affects the yogurt fermentation by:
1 Controlling the growth rate of the microorganisms
If the temperature is too low, the culture grows too slowly to adequately acidify milk and to achieve a good texture. The commercial starter is a mixed culture of thermophilus and L. bulgaricus.
If the temperature is too high it might end up killing the cultures

Temperature will affect the taste of the yogurt produced a the formation and secretion of metabolites which contribute to the overall taste are dependent on the growth rate.

The temperature range of proper yogurt fermentation is quite small, i.e. from 42 ºC to 44 ºC.
Higher temperature tends to give a sweeter yogurt as the rate of metabolism is higher. It will also makes the yogurt set faster.

It is very important that once the desired acidity is reached the fermentation is halted by low temperature. This cooling step is of most importance in the industrial production of yogurt, if not the taste of yogurt will be affected