Sour milk products

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Sour milk products are foods made from milk that is acidified by fermentation by naturally occurring or added microorganisms . Due to the metabolic activity of the microorganisms, some of the lactose contained in milk is broken down into lactic acid and characteristic aromatic substances such as acetaldehyde , acetone , butanone and others are formed. As a result of the acidification, putrefactive and pathogens (such as staphylococci ) are suppressed and the milk protein ( casein ) coagulates and falls into a fine flake, which manifests itself in the fact that the milk becomes thick to firmness; The souring of milk is therefore also called curdling . A liquid, drinkable consistency is only aimed for with a few products. The denaturation of the casein also improves digestibility. Overall, the acidification creates a long-lasting, tasty, digestible milk product.

In terms of their merchandise , sour milk products only include products from the white range - sour cream butter and sour milk cheese are also made from sour milk, but are usually considered in terms of butter and cheese. Sour milk products also form the basis for numerous mixed milk products that are created through the addition of flavors , fruit , etc. - for example fruit yoghurt .

properties

Sour milk products differ in the milk used (cow milk or milk from other animals), the microorganisms used, the duration and temperature of the incubation and the fat content. Depending on the acidification culture - often combinations of different types of bacteria - lactic acid fermentation takes place homofermentative or heterofermentative . In homofermentative fermentation only lactic acid is formed , in heterofermentative fermentation alcohol and carbon dioxide are also formed . In addition, the cultures also in the ratio in which differ D and - L -lactic acid are formed.

Some sour milk products have been ascribed health- promoting effects due to the bacteria they contain , which are said to be particularly related to the human intestinal flora . There is a large market for probiotic products, but the health benefits are sometimes controversial. Since acidification occurs through the breakdown of lactose, the lactose content in sour milk products is lower than in other milk products. They are therefore also edible for people with lactose intolerance .

Manufacturing

The starting product of all sour milk products is pasteurized or thermized , often also homogenized milk (also skimmed or low-fat) or cream . This is inoculated with the desired acidification cultures and "incubated" at relatively high temperatures over a period of several hours. Incubation temperature and time are matched to the cultures and the desired degree of acidity and differ from product to product. Incubation is sometimes done in large containers before filling, but sometimes the milk is also filled immediately after inoculation and ferments in the packaging. After the allotted time, the sour milk product is cooled to stop the acidification and protect the product from spoilage - this is how it is then sold. In some cases, further heat treatment after fermentation is common in order to improve the shelf life. For example, this is permissible with fruit yoghurt, but prohibited with pure yoghurt - according to German food law.

Some sour milk products are also stirred before they are packed to give them a thick instead of a firm consistency. It is also possible and permissible to increase the dry matter by adding skimmed milk powder or casein.

history

Sour milk types were probably the first dairy products humans made. In regions of the world with a warm climate, raw milk self-acidifies within a few hours, so that people there enjoyed more sour milk than fresh milk and learned to make it consciously. In this way they got aromatic, digestible and relatively long-lasting products. The industrial production of sour milk, on the other hand, started late: Since around 1880, sour milk products have been manufactured using dairy technology and using pure cultures.

The world is extremely rich in regional or local sour milk specialties. For example, Filmjölk / Ymer / Viili and Rjaschenka come from Europe, Kumys and Yakult from Asia , Omaere and Mursik from Africa ; there are also drinks like Ayran and Dugh .

Market volume

In 2016, sour milk products generated sales of 18,112 million euros in Europe, including 3,572 million euros in Germany. The paragraph was 8,620 million kilograms, the per capita consumption of 16.6 kilograms (Germany: 21.6 kg Austria: 13,0 kg Switzerland 15.3 kg).

Classification

Depending on the type of acidification, a distinction is made between products that are acidified with common lactic acid bacteria, products from special cultures, and products from mixed fermentation, both lactic acid and alcoholic.

Fermentation with common lactic acid bacteria

Among the dairy products, by ordinary mesophilic lactic acid bacteria - Lactococcus lactis including earlier than independently prestigious subspecies cremoris and diacetylactis - in milk acid fermentation are leavened, including sour milk and a number of related species that differ in fat content and consistency. The following are to be mentioned in detail:

The “simplest” product in this category is the well-known thick milk. In principle, it could already be produced by letting freshly milked raw milk stand at sufficiently high temperatures (22–45 ° C): The lactic acid bacteria naturally present in milk multiply quickly, suppress putrefactive agents and allow the milk to thicken quickly. In the case of dairy production, on the other hand, heat-treated milk is inoculated with cultivated cultures, as is common practice.

According to Appendix 1, Group I, the German Milk Product Ordinance specifies various legally binding sales names for this type of sour milk. Simple sour milk is therefore called sour or drinking sour milk, curdled sour milk is also called curd or set milk. The regulation provides for a minimum fat content of 3.5% for both thick and non-thick sour milk, as well as skimmed milk, low-fat and cream levels.

This results in the following designations:

Fat content Designations Designations (thick)
at least 3.5% Sour milk
Drinking sour milk
Curdled
milk
curdled curdled milk set milk
1.5-1.8% Low-fat sour milk.
Low-fat drinking sour milk
Low-fat
curdled milk Low-fat curdled milk curdled Low-fat
settling milk
Max. 0.5% Sour milk skimmed
drinking
sour milk skimmed sour milk
Sour milk skimmed thick curd Sour milk skimmed
thick skimmed milk
Set
milk skimmed skimmed
milk
at least 10% Auer cream milk
Rahmsauermilch
sour cream
sour cream
Cream
thick
milk
Cream set milk Cream thick milk Cream set milk

There is also crème fraîche with at least 30% fat and buttermilk with a maximum of 1% fat.

Fermentation with special cultures

Various sour milk products are also obtained exclusively through lactic acid fermentation, but with specific, sometimes thermophilic cultures. The best-known product of this type is yogurt, the others are more or less similar to yogurt.

(Names such as "Bioghurt", "Bifighurt" and "Biogarde" are or were registered trademarks of a company, the "international Bioghurt Society".)

According to Appendix 1, Group II, the German Milk Product Ordinance divides yoghurt products into yoghurt and mild yoghurt - the addition “mild” therefore designates products that are acidified with other lactobacilli instead of L. bulgaricus . The ordinance provides for a minimum fat content of 3.5% for all yoghurt products and also provides for skimmed milk, low-fat and cream levels.

This results in the following designations:

Fat content Designations Designations (mild)
at least 3.5% yogurt Mild yogurt
1.5-1.8% Low-fat yoghurt Mild low-fat yogurt
Max. 0.5% Yogurt from skimmed milk and
skimmed milk yoghurt
Mild yogurt, made from skimmed milk
Mild yogurt made from skimmed milk
at least 10% Cream yogurt
Rahmjoghurt

Mild cream yoghurt Mild cream yoghurt

Combination of lactic acid and alcoholic fermentation

Through a combination of lactic acid bacteria and yeast , various products are obtained that are influenced by both lactic acid fermentation and alcoholic fermentation and have a more or less high alcohol content . These include:

  • Kefir , made from kefir grains which contain Saccharomyces yeasts and various lactic acid bacteria, including L. lactis ; also obtained from goat and sheep milk , low alcohol content of 0.2-0.8%
  • Kumys , of Asian origin, made from mare's milk ; strong kumys can contain over 2.5% alcohol.

According to Appendix 1, Group III, the German Milk Product Ordinance distinguishes between kefir and mild kefir . Accordingly, the fermentation cultures for regular kefir must contain all the characteristic microorganisms of the kefir grains, including the yeast, and the end products of the alcoholic fermentation must have formed in the finished kefir, namely carbon dioxide and at least 0.05% (by weight ) alcohol. Mild kefir , on the other hand, can be fermented without yeast and does not need to contain carbon dioxide or alcohol. The regulation provides for a minimum fat content of 3.5% for all kefir products and a low-fat, low-fat and cream level.

Fat content Designations Designations (mild)
at least 3.5% kefir Mild kefir
1.5-1.8% Low fat kefir Mild low-fat kefir
Max. 0.5% Kefir from skimmed milk
Magermilchkefir
Mild kefir made from skimmed milk
Mild kefir made from skimmed milk
at least 10% Cream
kefir Cream kefir
Mild
cream kefir Mild cream kefir

Individual evidence

  1. a b c d Edmund Bauer: Handbuch der Lebensmittelchemie . Ed .: Ludwig Acker u. a. 3: milk, butter, cheese. Springer, Berlin 1968, p. 407 ff .
  2. a b c d Paul Präve (Ed.): Handbuch der Biotechnologie . 3rd, revised edition. Oldenbourg, Munich 1987, ISBN 3-486-20039-9 .
  3. a b c d e Gerald Rimbach, Jennifer Möhring, Helmut F. Erbersdobler: Food and goods knowledge for beginners . Springer, Berlin 2010, ISBN 978-3-642-04485-4 .
  4. Yoghurt and sour milk products , Statista , January 2017.
  5. a b c Annex 1 of the Milk Products Ordinance of July 15, 1970 ( Federal Law Gazette I p. 1150 ), which was last amended by Article 17 of the law of July 25, 2013 ( Federal Law Gazette I p. 2722 ) ( online )
  6. ^ Hans Joachim Klupsch: Sour milk products . Mann, Hildesheim 1968.