The Microorganisms Used In Production Of Dairy Products And Cheeses

The Microorganisms Used In Production Of Dairy Products And Cheeses

Spherical lactic-acid bacteria

Lactococcus lactis subspecies lactis

Lactic-acid streptococcus, in abbreviated form Lac. lactis. Optimum temperature of development makes 28-32 C. The fissile strains of this species curtail milk in 4–6 h, forming a smooth dense clot. The extreme acidity (in 5–7 days of development in milk) reaches 125 T. Strains of this species are a part of starters for dairy drinks, cottage cheese, sour cream, sour cream butter, cheeses with a low temperature of the second heating.

 

Lactococcus lactis ssp. cremoris

Creamy streptococcus – Lac. cremoris. Milk curtails in 6–8 h, forming the dense clot of slightly viscid or cream like consistency that is caused by ability of a creamy streptococcus to synthesize polysaccharides. The extreme acidity in milk does not exceed 110–115 T. The creamy streptococcus is used in starters for sour cream, sour cream butter and other fermented milk products.

 

Lactococcus lactis ssp. lactis biovar diacetylactis

Flavoring streptococcus – Lac. diacetylactis. Optimum temperature of growth is 25-30 C. It has quite weak acid-forming activity – milk curtails in 16–18 h, the extreme acidity does not exceed 70–100 T. Milk clot is dense, often with existence of vials of gas (CO2), It has the pleasant specific smell caused by diacetyl accumulation. Strains of this species split lactose and Citras with formation of carbon dioxide, diacetyl and acetoin. The flavoring streptococcus is widely used in starters for the majority of the fermented dairy products.

 

Streptococcus salivarius ssp. thermophilus

Thermophilic streptococcus – S. thermophilus. The fissile strains curtail milk in 3,5–4 h at an optimum temperature 40-42 C. Temperature range of growth makes 20-50 C. The extreme acidity in milk does not exceed 100–115 T. The thermophilic streptococcus is added into composition of starters for production of fermented baked milk, varenets, yogurt, cheeses with high temperature of the second heating

 

Leuconostoc mesenteroides ssp. cremoris

Leuc. cremoris. Optimum temperature of growth makes 22-25 C, minimum – about 5 C. Milk does not curtail as it has low proteinase activity. Leuc. cremoris are capable to grow in milk at adding growth factors in it (yeast or corn extract). The extreme acidity does not exceed 40–50 T. After decrease of рН environment to 5,0–4,5 it forms diacetyl therefore this species is used in multispecific starters for production of cheeses and sour-butter in combination with Lac. lactis and Lac. cremoris.

 

Leuconostoc mesenteroides ssp. dextranicum

This species is morphologically similar to Leuc. cremoris. It curtails milk at an optimum temperature 22-25 C within three-four days. The extreme acidity makes 70–80 T. Reproduction of leuconostocs stimulates addition into environment of manganese that leads also to the increased synthesis of metabolites: diacetyl, acetic acid, carbon dioxide. Leuconostocs are part of a natural microflora of a kefiric fungus and play a large role in formation of its taste and a smell.

 

Pediococcus cerevisiae

Optimum temperature of growth makes 22-25 C, at a temperature of 35C the growth stops. They can be often found in the spoiled beer, but seldom in dairy products. Pediococcus is included in composition of starters for production of raw smoked sausages.

Rhabdoid lactic bacteria

 

Lactobacillus delbrueckii ssp. bulgaricus

Bulgarian bacterium, or L. bulgaricus. Optimum temperature of growth makes 40-45C. Milk curtails for 4–6 h. The extreme acidity of milk reaches 200–350 T. Strains of the Bulgarian bacterium form the acetaldehyde providing a clot with the reference fruit smell. Strains of the Bulgarian bacterium are a part of starters for production of yogurt, curdled milk "Southern", "Bulgarian", Mechnikovskaya.

 

Lactobacillus acidophilus

Acidophilic bacterium. Optimum temperature of growth makes 37-38C. Milk curtails in 5–8 h, the extreme acidity of milk of 260-280 T. Some strains form a mucous clot. The acidophilic bacterium is the normal representative of an intestinal microflora of the person and warm-blooded animals. Therefore it is steady against alkaline reaction of the environment (рН 8,3); to existence in the phenol environment (0,3–0,4%) and biles (20%). 10

The acidophilic bacterium has high antagonistic activity in relation to a sour, opportunistic and pathogenic microflora. It produces two bacteriocines – acidophilus milk and lactocidin. In this regard L. acidophilus are referred to valuable pro-biotic cultures.

Lactic-acid bacteria of this species apply to preparation of acidophilus milk, acidophilic milk, children's fermented milk products.

 

Lactobacillus delbrueckii ssp. lactis

Lactic-acis bacteria – L. lactis. Optimum temperature of growth makes 40-42C; extreme acidity of milk, 11

Fermented L. lactis, – 160–200 T. It is used in production of cheeses with high temperature of the second heating

 

Lactobacillus helveticus

Swiss bacterium. Optimum temperature of their growth is equal to 42-45 C. Milk curtails in 5–6 h, the extreme acidity makes 300–350 T. Strains of L. helveticus can be selected from a rennet bag of calves. This species is used in starters for cheeses with high temperature of the second heating.

 

Lactobacillus сasei ssp. casei

(L. casei). Optimum temperature of growth makes 28-32 C, at a temperature of 45 C growth stops.

 

Lactobacillus сasei ssp. rhamnosus

(L. rhamnosus). Optimum temperature of growth makes about 30 C. In comparison with mesophilic lactococcuses proteolytic activity of L. rhamnosus is twice higher. The extreme acidity in milk is equal to 80-180 T. It is used in starters for production of the following types of cheeses: emmentalsky, Edem, Chester, etc. It can be found in different types of cheeses as the accompanying microflora.

 

Lactobacillus plantarum

Optimum temperature makes about 30 C, the extreme acidity at development in milk reaches 180 T. It plays a positive role when maturing of cheeses as it can breed after a lactose fermentation by a starter microflora and at concentration of NaCl to 6%. This species forms hydrogen peroxide and synthesizes a bacteriocine plantarum – the substance suppressing growth of butyrate bacteria and an intestinal microflora.

 

L. brevis,
L. fermentum,
L. buchneri

Bacteria of types of L. brevis, L. fermentum, L. buchneri refer to Betabakterium subgenus. Beta bacteria do not curtail milk, however at addition to it of a barmy autolysate form a clot which extreme acidity can reach 150–160 T. It ferments glucose with a lactification, CO2, ethanol and slight amount of volatile acids. It forms DL-isomeres of lactic acid. Beta bacteria participate in maturing of cheeses with a low temperature of the second heating, promoting formation of the drawing and a smell of cheese. They can also be found in a stroma of a kefiric fungus.

Bifidobacteria

 

Bifidobacterium, Bifidobacterium animalis ssp.lactis 

Optimum temperature of their growth 36-40 C, temperature limits of growth is 20-50 C. Best value of рН environments is 6-7; at рН lower than 4,5 growth of bifidobacteria stops. Bifidobacteria ferment carbohydrates with formation of lactic and acetic acids. Strains of bifidobacteria use for production of children's, medical, and dietary fermented milk products (bioyoghurt, a bifidokefir, a bifilakt, etc.).

Propionate bacteria

 

Propionibacterium freudenreichii

The maximal growth is observed at a temperature of 30-37 C and value рН is about 7,0. Propionate bacteria in milk develop sluggishly and curtail it in 5–7 days. The extreme acidity of milk can reach 160–170 T. 14

Propionate bacteria are used in cheese making by production of cheeses with high temperature of the second heating. After the end of lactic fermentation in cheeses the stage of development of propionate bacteria begins. During propionate fermentation the latter accumulate propionic and acetic acids and carbon dioxide. Volatile acids provide cheeses with specific relish and a smell, and carbon dioxide forms the drawing of cheese

Acetic bacteria

 

Acetobacter aceti.

Acetobacter aceti Optimum temperature of development 30 C, optimum рН 5,4–6,3. Colonies of bacteria grow only on the surfaces of nutrient environment, on fluid environments they form a film. develop badly in milk and they don't form acids. in contact with air acetic bacteria oxidize alcohol into an acetic acid. Acetic bacteria are a part of kefiric fungi. AT moderate grpwth they play a positive role on production of kefir; their growth in sour cream, cottage cheese, curdled milk can cause emergence of an undesirable smell and smack of an acetic acid, and also sliming of a product.

 Yeast

 

Yeast plays a dual role in the dairy industry: some types of yiest are used in production of the fermented dairy products as the biological agents causing spirit fermentation; other types promote decay of dairy products.

The yeast which present at dairy products conditionally are subdivided into three groups: – the yeast fermenting lactose. Spore-forming (spore forming) yeast of types Saccharomyces lactis, Zygosac-charomyces lactis, Kluyveromyces fragilis, Debaryomyces and asporogenic (nesporoobrazuyushchy) yeast of types Torulopsis kefir, Torulopsis sphaerica, Candida pseudotropicalis var. lactosa, etc.; – the yeast which do not ferment lactose, but ferment monosugar. Such yeast can breed in milk and dairy products together with the lactic bacteria splitting lactose on glucose and a galactose; – the yeast which do not ferment lactose and other sugars, but causing their oxidation. They do not form spores and are not capable to spirit fermentation. First of all, Candida yeast belongs to them. Lactose forming yeast are used in production of such products of the mixed fermentation as kumis, tan, ayran, a yogurt, matzoon, a kurunga, etc. In these products they form specific taste, synthesize vitamins, stimulate growth of lactic bacteria. Some strains of the yeast reproduced in dairy products have antagonistic activity in relation to the causative agent of tuberculosis, and also to some opportunistic microorganisms. Separate types of yeast participate in maturing of cheeses, being in structure of a microflora of cheese mucilage. The yeast penetrating into dairy products.