Pure lactic acid fermentation bacteria – Streptococcus

Streptococcus (Streptococcus). Milk under normal conditions, milked and stored at a temperature above 10 °, will be sour and will sooner or later curl into a uniform curd, not scratched by gases. Souring usually progresses from bottom to top, which testifies, that bacteria that avoid air oxygen are active here. The taste and smell of the milk are pure, pleasant, sometimes resembling fruit, e.g. apples and pears. Sometimes the taste is sterile.
Various types of beneficial bacteria from the group of streptococci are active here, which transform milk sugar into pure lactic acid.. These are mainly the normal sour-milk flora. They come from cow's feces, feed, litter, previously contaminated with stable dust and milking vessels. In milk they usually have an advantage over other bacteria in excess 90%.
You can get an almost pure culture from them by doing the following.
You take milk known to be good, mostly clean and sets to sour, even acidification at a temperature of about 20 ° C per 4 do 5 days. After this time, when we found out, that the curd is clean in taste and smell and without gases, we discard the top layer, as infected with aerobes and transplant the remaining content into pasteurized or boiled milk. We acidify again at 20 ° C. As a result of acidification of the first sourdough, acid-deficient bacteria slowly disappear from it, how alkalizing, decay, etc., while lactic acid streptococci still remain viable. In the past, such raw ones were used, that is, simple sourdoughs for acidifying cream, and in cheese-making they still have some practical significance, because the presence of this group of bacteria in different varieties is necessary to implement the proper maturation of cheeses. Meanwhile, in winter they are often missing.
Long and hard winters in our conditions are not conducive to the spread of lactic acid bacteria, unable to grow at low temperatures. The hostess has been dealing with it for a long time, putting the bowl of milk on a warm stove. Then the favorable heat and the previous contamination of the soaked pot do its job, because "what the shell will soak up with, this in the aftermath of smacks”.
I have been using simple streptococcus cultures for many years in my cheese making, especially in winter. I distinguished them in the described way from random milk samples revealing unusual advantages during souring. I also took them from exceptionally beautiful gl1-gl2 fermentation tests, where the choice is rich and easy. They were usually better suited to acidifying the cheese milk than the laboratory isolated cultures, intended for fermenting cream, which is probably explained by this, that the scope of work of more varieties of bacteria in simple leaven is wider, more adapted to the changing environment in terms of food and temperature fluctuations . However, in an untrained hand, this help can fail.
Lactic acid streptococci, when multiplying, form strings of beads with a diameter of approx 0,8 micron ( = 0,0008 mm). Hence their name. When development is alive, the grains of the beads break off in pairs, that is, they create splits. The grains are slightly elongated in shape and slightly tapered towards the outer ends, like rice grains. Better off without air, but they bear it. Thus they are not strict anaerobes. Fully produce life span from 0,7 do 0,85% pure lactic acid. They develop best at 30 ° C, below 10 ° C and above 40 ° C they develop poorly, and they die at 60 ° C.
The most important in this group are.
Streptococcus lactis i Streptococcus cremoris (cream streptococcus). From the selected cultivars and strains of these bacteria, isolated in laboratories, cultures for sour cream leaven are produced. The same cultures are also used to acidify the cheese milk.
Streptococcus lactis reproduces very quickly under favorable conditions. Its optimal temperature is indeed 30 ° C, however, at 20 ° C it produces as much lactic acid, co and at 30 ° C, although it takes longer. Below 10 ° C and above 40 ° C it does not develop at all, and dies during pasteurization at 60 up to 70 ° C over time 15 minutes.
Streptococcus cremoris binds into even longer strings of beads and coarser grains than the previous. It grows faster at lower temperatures than Streptococcus lactis, at 18 ° C it is very acidic. Some of its strains produce tiny amounts of carbonic anhydride, some dissolve the protein a bit, others again produce a pleasant scent that is also shared by butter. Some varieties grown below 18 ° C form mucus, which usually fades, when the milk coagulates. At temperatures below 10 ° C, and above 35 ° C they stop developing, they die during pasteurization at temperatures above 60 ° C.
Streptococcus holandicus is also included in this group, ductile whey streptococcus, formerly used for leaven in the production of Dutch cheeses.
Streptococcus thermophilus (heat-loving streptococcus). It is most commonly found in low-temperature pasteurized milk and then stored at 40 do 50°C, it is also obtained in large amounts in unpasteurized milk, stored at 44 ° C. Sometimes it can withstand temperatures of up to 80 ° C. It develops slowly at room temperature. It produces slightly more lactic acid than Streptococcus cremoris. It binds into long chains at optimal temperature, however, some strains below 30 ° C occur singly. They are relative anaerobes. In Emmental cheesemaking, they consider them essential for the proper maturation of cheeses, next to Thermobacterium helveticum = Bact, casei epsylon. The lack of them in natural cushion and cheese milk gives negative results. Noticed in Switzerland, that they are often not present in the milk supplied to these cheese dairies, which did not return wholesaled whey to suppliers, or when the suppliers are meticulously confusing the milk cans, which equated to the sterilization of the vessels. Via the returned shurved whey
Streptococcus thermophilus spread depending on more or less careful washing of the watering cans and contaminated the milk to varying degrees. It happened for this reason, that there was a different bacterial flora in the milk of the suppliers, who returned the whey, a inna, where the cheese dairy kept it to itself. From this emerged the issue of the need for constant control of the rennet mortar in terms of its quantitative and qualitative bacterial composition, and the need for a separate culture composed of Streptococcus thermophilus.
In Normandy, in the winter season, milk for the production of Camembert and Livarot cheeses was heated to 55 ° C.. Heat bacteria were spread unknowingly.
The genus Betacoccus also belongs to lactic acid streptococci, covering a couple of species known to do so, that in addition to lactic acid, they also produce some amounts of volatile - aromatic compounds (inter alia diacetyl). For example, the species Betacoccus cremoris (other name: Streptococcus citrovorus) it grows together with the common streptococci in dairy leaven, giving them, and consequently butter, better flavor.