Historic of Cheese
The production of cheese began about 4000 years ago and nowadays, there are more than 1000 cheese varieties, with unique flavors and form.
The first cheese, according to a legend, was accidentally made by an Arabian merchant who put his supply of milk into a pouch made from a sheep's stomach, as he set out on a day's journey across the desert. The rennet in the lining of the pouch, combined with the heat of the sun, caused the milk to separate into curd and whey. That night he found that the whey satisfied his thirst, and the cheese (curd) had a delightful flavor which satisfied his hunger.
General Process
The combination of four ingredients: milk, rennet, microorganisms and salt manufacture most of cheese varieties. They are processes through some common steps such as: whey expulsion, acid production and salt addition and period of ripening. Application of lactic acid bacteria is the main point of cheese making, because it causes an acidification of milk because the production of lactic acid and consequently, occurs a decrease in pH. All this modification affects a number of aspects of the cheese and determine type of cheese and quality.
Starter Bacteria
The first function of starter bacteria is:
-> production of acid during the fermentation process;
But, they also have importance to the process of cheese ripening where their enzymes are involved in proteolysis and conversion of amino acids into flavor compounds.
Starter bacteria could be defined as isolates that produce sufficient acid to reduce the pH of milk to <5.3 in 6 h at 30–37 °C.
Examples of the roles of the acid production:
-
Control and prevent the growth of spoilage and pathogenic bacteria
-
affects retention and coagulant activity during clotting
-
solubilizes calcium phosphate affecting therefore the texture of the cheese
-
promotes syneresis and therefore influences the cheese composition and also the activity of enzymes during maturation.
-
Lower the redox potential of +250 mV passing in milk, to -150 mV in cheese, essentian modification for the biochemical development of maturing cheese.
Selection of Bacteria
There is a lot of bacteria which can be used as yeast in cheese making.
-
The mesophilic Lactococcus lactis subsp homofermentativos . Lactis and Lactococcus lactis subsp. cremoris which are acidifying bacteria suitable for cheese with low baking temperature and mass and closed little flavor ( Mines Cured Plate slicing , Mozzarella etc.);
-
The mesophilic Lactococcus lactis subsp heterofermentativos . lactis biovar . Diacetylactis and Leuconostoc mesenteroides subsp. cremoris which are flavoring mesophilic bacteria with CO2 production function and diacetyl (main compound aroma of cheese and butter ) suitable for open cheeses and more pronounced aroma (Prato , Gouda , Cottage etc.);
-
Yeasts thermophilic Streptococcus salivarius subsp. thermophilus , Lactobacillus helveticus and Lactobacillus delbrueckii subsp. bulgaricus lactic acid bacteria that are suitable for cooked cheeses , or half-baked ( Mozzarella , Provolone , Parmesan etc.) .
So, the choice to produce cheese was Streptococcus salivarus because they are frequently used as starter in production of Mozzarela and is able to survive at the high temperatures. Furthermore, for cheese-making, S. thermophiles are traditional used in combination with Lactobacillus bulgaricus to produce varieties of cheese, including Mozzarella.
In addition, S. termophilus has demonstrated that can produce several bacteriocins against Clostridium sporogenes, Clostridium botulinum, Bacillus cereus and Listeria monocytogenes.
Another studies has shown that S. termophilus can survive in gastro intestinal transit and can provide probiotic characteristics for example, have positive effects on diarrhea in children and inflammatory gut disease.
Want to see our presentation for the teaching class?!
Bioreactor
The bioreactor works in FedBatch.
Beside this, the ancilliaries that we need to take care are: pH, temperature and time.
References
Delorme, C. (2008). Safety assessment of dairy microorganisms: Streptococcus thermophilus. International Journal of Food Microbiology, 126, 274–277.
Briggiler-Marcó, M., Capra, ML., Quiberoni, A., Vinderola, G., Reinheimer, J.A., & Hynes, E. (2007) Nonstarter Lactobacillus strains as adjunct cultures for cheese making: in vitro characterization and performance in two model cheeses. J Dairy Sci 90, 4532-4542.
Sandine, W. E., & Elliker, P. R. (1970). Microbially induced flavours and fermented foods flavour in fermented dairy products. Journal of Agriculture and Food Chemistry, 18, 557–562.