Fermentation, chemical process by which molecules such as glucose are broken down anaerobically. More broadly, fermentation is the foaming that occurs during the manufacture of wine and beer, a process at least 10,000 years old. The frothing results from the evolution of carbon dioxide gas, though this was not recognized until the 17th century. French chemist and microbiologist Louis Pasteur in the 19th century used the term fermentation in a narrow sense to describe the changes brought about by yeasts and other microorganisms growing in the absence of air (anaerobically); he also recognized that ethyl alcohol and carbon dioxide are not the only products of fermentation.(Agrilearner)
Fermented product of milk
(Agrilearner) Fermented milk products are produced from homogenised or pasteurized milk or cream with the help of starters containing lactic acid bacteria. Some of these products have been enriched with different types of dairy products (whey powder, milk powder, buttermilk powder) before fermentation.
The use of different starters in manufacturing various types of products gives each product a specific texture and a characteristic taste. Fermentation temperature and time vary by product.(Agrilearner)
In manufacturing kefir, sour milk, sour cream and fermented buttermilk, lower fermentation temperatures (24–30 °C) are used. The manufacturing of yogurt requires higher fermentation temperatures (38–42 °C). All fermented dairy products are cooled before packaging in order to hinder the growth of the lactic acid bacteria in the products.
The content of living lactic acid bacteria in fresh fermented dairy products should be ≥107 CFU/g. Fermented milk products should be stored at 2–6 °C.
Kefir is a fermented milk product that was traditionally made with kefir fungi. Today, a starter made from kefir fungi is used. In addition to lactic acid bacteria, the kefir microflora also contains yeasts. Yeasts give kefir its characteristic, slightly sharp taste and effervescent texture. The yeast content of kefir should be 104 CFU/g.
Besides lactic acid fermentation, some alcohol and CO2 are produced in kefir as a result of the effect of yeasts. Today, most kefir is produced with a 2.5% fat content.
Buttermilk is a liquid left behind after churning butter out of cream. Buttermilk may be marketed as a fresh or a fermented product, but the latter is more common. A mixture of buttermilk and skimmed milk is used as a raw material for making buttermilk to which mesophilic starter is added. Fermented buttermilk is a slightly sour and effervescent product, the fat content of which doesn’t exceed 0.5%.
Sour milk is a standardised fermented milk product. Mesophilic lactic acid bacteria are used for fermentation, and various fruit and berry ingredients may be added to the final product.(Agrilearner)
Sour cream is manufactured by adding mesophilic lactic acid bacteria to standardised cream. Sour creams with a 10% or 20% fat content are most common. Sour cream is a highly viscous and slightly sour dairy product.
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