Lactic acid fermentation, milk protein

Modification of Milk Protein during Lactic Acid Fermentation..209... 

These results suggest that presence of lactic acid in milk at concentrations in the range of 0.5-1% can positively affect the ACE inhibitory activity. This positive effect could be due to protein denaturation and modification from lactic acid and not the direct effect of lactic acid alone. These findings fiirther support the observation that the increase in ACE inhibitory activity in milk fermentations is higher in the case of L. bulgaricus fermentation, where 1.3% lactic acid was produced, compared to L. acidophilus fermentation, where 2.7% lactic acid was produced (Apostolidis etal. 2007). 

The main role of propionic acid bacteria in cheese ripening consists in the utilization of lactate produced by lactic acid bacteria as an end product of lactose fermentation. Lactate is then transformed into propionic and acetic acids and CO2. The volatile acids provide a specific sharp taste and help preserve a milk protein, casein. Hydrolysis of lipids with the formation of fatty acids is essential for the taste qualities of cheese. The release of proline and other amino acids and such volatile compounds as acetoin, diacetyl, dimethylsulfide, acetaldehyde is important for the formation of cheese aroma. Carbon dioxide released in the processes of propionic acid fermentation and decarboxylation of amino acids (mainly) forms eyes, or holes. Propionic acid bacteria also produce vitamins, first of all, vitamin At the same time, an important condition is to keep propionibacteria from growing and producing CO2 at low temperatures, since this would cause cracks and fissures in cheese. 

The succession of bacterial species during alcoholic fermentation can be explained by a difference in the sensitivity of bacteria to interactions with yeasts. Interactions between lactic acid bacteria must also exist, simultaneously. Like other microorganisms, they can synthesize and liberate substances with antimicrobial activities. This problem has been examined closely in the milk industry, where the consequences are more serious. These substances are simple (hydrogen peroxide, organic acids, etc.) or more complex. Bacteriocins are a class of proteins whose bactericidal activity generally has a narrow range of action. It is sometimes even limited to the same species as the producing strain. Fundamental and applied research on... 

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