Lactic fermentation products

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General characteristics and classification. 

Lactic fermentation is one of the oldest and most widespread methods of milk preservation in the world. In the past, this method was exclusively used in households to stabilize the milk of various mammals (cow, sheep, goat, mare), and the ability to produce fermented products has been passed down from generation to generation. Although knowledge of the production of milky fermented beverages consisting primarily of the souring of milk has been known for millennia, knowledge of microbiological and biochemical changes occurring during fermentation has been established in the last several decades. Significant changes in the method of production of fermented milk beverages occurred at the time of the development of industrialization in many countries at the beginning of the 20th century. There are more than 300 different products in the world that can be classified as fermented milk beverages. Such a large diversity complicates their classification. 

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Milk fermented beverages are produced in various forms, such as gels, beverages, strips, crisps, or fixed by freezing and drying by various methods. The basic division criterion is the type of basic microflora used for the production of fermented milk beverages, which due to the optimal temperature of development is divided into thermophilic and mesophilic. The type of microflora used to produce particular dairy fermented beverages has its traditions resulting from natural, lasting for centuries selection of microflora dependent primarily on climatic conditions. In countries with a warm climate, thermophilic microflora was used, and in countries with moderate or cold climate milk was made with mesophilic lactic acid bacteria. In the group of fermented milk fermented with temophilic bacteria, the typical microflora are L.delbrueckii ssp. Bulgaricus and S.salivarius ssp. Thermophilus. Due to climatic conditions, these two species of bacteria contributed to the creation of traditional fermented beverages in the countries of southern Europe, the Middle East and some areas of Asia and Africa. These beverages can be produced from the milk of various sheep, goats, cows, and also camels, mare, donkeys and zebras. Traditionally, in a warm climate, fermented milk drinks contain, in addition to the two mentioned species, other homo- and heterofermentative lactic acid bacteria, acetic fermentation bacteria, yeasts and molds. In this group of milky fermented beverages, the most popular in the world is yogurt, for which the bacteria L.delbrueckii ssp. Bulgaricus and S.salivarius ssp. Thermophilus are used. The next group is milk fermented by selected intestinal microflora L.acidophilus, Bifidobacterium, as well as Propionibacterium and L.casei, which are used to produce products characterized by beneficial therapeutic values. The typified representatives of milk fermented with monocultures include acidophilus milk. The few attractive taste traits of acidophilic milk meant that this product did not find a wider recognition among consumers, although there is an increasing interest in this product in Poland recently. In some highly industrialized countries, pasteurized milk is produced to which a suspension of living cells of L.acidophilus in the number of 106 / cm3 is added. There is also known milk, made only by bifidobacteria, but it has not gained popularity. 

More and more often in many countries of the world, a mixed microflora consisting of traditional bacteria and bacteria of intestinal origin is used to produce milk fermented beverages. Such milk carries different names depending on the composition of pure cultures. Often abbreviation names are used, e.g. BAT and, more recently, also ABT. Beverages fermented with the use of these sourdoughs is a blogurt containing L.acidophilus, S.salivarius ssp. Thermophilus and sometimes L.delbrueckii ssp. Bulgaricus; biogarde and bifigurt containing L.acidophilus, S.salivarius ssp. thermophilius, Bifidobacterium. In addition, in some countries the use of BAP fermented sourdough is used for the production of fermented milk beverages. Their microflora includes Bifidobacterium, L.acidophilus and Pediococcus acidilactici. To enrich milk fermented with vitamin B12 and folic acid, propionic bacteria are proposed in addition to lactic acid bacteria. The intermediate product between dairy fermented beverages for general consumption and for medical purposes is humanized milk with a chemical composition similar to breast milk, fermented with one of the following species Bifidobacterium bifidium, L.acidophilus or L.delbrueckii ssp. Bulgaricus. Humanized milk is usually produced in small amounts for the treatment of infants. 

Milk fermented beverages having their roots in the European tradition are acidified by mesophilic homo- and heterofermentative lactic acid bacteria. Very often mesophilic bacteria are accompanied by yeast, and then the production of fermented fermented beverages takes place thanks to the lactic-alcohol mixed fermentation. Products with exclusive lactic fermentation are characterized by a pure acidic taste, imparted by lactic acid, enriched with the main components of the aroma, i.e. diacetyl, and acetaldehyde. In the case of using mixed sourdoughs, such as, for example, kephir, additional ethyl alcohol and carbon dioxide formed give a specific slightly spicy aftertaste. 

In the Nordic countries, malleable milk fermented by streptococcus producing mucous substances that give a ductile consistency to ready products has become widespread. In the countries of Central and Eastern Europe, traditional fermented milk is obtained thanks to the use of mainly homo- and also heterofermentative streptococci of lactic fermentation. In Poland, a typical representative of this group is sour milk, as well as the acidified buttermilk maintained as a by-product in the production of butter. In some countries, mainly the US, buttermilk is produced as a milky beverage fermented directly from skimmed milk. There are also fermented beverages with an increased content of dry matter or protein. They can be obtained by taking whey, for example Polish polkrem, adding milk powder or using modern membrane techniques (ultrafiltration). 

A typical product obtained as a result of mixed fermentation is kefir, which is traditionally prepared using kefir mushrooms that are a symbiotic creator of lactic acid bacteria and yeasts. Another drink obtained using lactic acid bacteria L.acidophilus and L.delbruecki ssp. Bulgaricus and yeast Torula kumys and Saccharomyces lactis is kumys, traditionally produced from mare’s milk. After fermentation, it contains 0.7-0.8% of lactic acid, 1.7-2.5% of ethanol and carbon dioxide. On an industrial scale, kumis is also made from semi-skimmed cow’s milk enriched with whey proteins. 

The presented classification and review does not exhaust all information about fermented milk beverages produced all over the world, but is only an attempt to show the most typical groups of dairy fermented beverages. 

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You can read also: To drink or not to drink cow’s milk?

Posted on: February 25, 2019

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