Cheese lactic acid bacteria associated with

Lactic acid-producing bacteria associated with fermented dairy products have been found to produce antibiotic-like compounds caUed bacteriocins. Concentrations of these natural antibiotics can be added to refrigerated foods in the form of an extract of the fermentation process to help prevent microbial spoilage. Other natural antibiotics are produced by Penicillium wqueforti the mold associated with Roquefort and blue cheese, and by Propionibacterium sp., which produce propionic acid and are associated with Swiss-type cheeses (3). 

Fruity flavor in Cheddar cheese is also associated with high levels of ethyl butyrate and ethyl hexanoate (Bills et al. 1965). However, this defect is usually caused by esterase activity from lactic acid bacteria, especially S. lactis and S. lactis subsp. diacetylactis (Vedamuthu et al. 1966). Fruity-flavored cheeses tend to have abnormally high levels of ethanol, which is available for esterification (Bills et al. 1965). Streptococcal esterase activity in cheese is affected by the level of glutathione, which suggests a dependence on free sulfhydral groups for activity (Harper et al. 1980). 

The transformation of curd into cheese is accomplished by the influence of various enzymes (i) galactase, a special trypsin, secreted by the mammary glamd simultaneously with the milk, an active substance of which we have previously had occasion to speak (2) pepsin, which is always found associated with rermet and which some writers even confound with it (3) various tryptases, or caseases, secreted by molds, bacteria, yeasts, etc., which develop on the surface or in the interior of the mass. To these enzymes, which dissolve casein and bring it to the simpler state of peptones, amino-acids, and ammonia, it is proper to add (4) amidases, that produce the formation of volatile acids (5) lactase and lactacidase, enzymes secreted by lactic bacilli, and which transform lactose into glucose and then into lactic add (6) lipases, which apparently decompose a part of the fatty material (7) finally oxidases, which bum the organic wastes, especially the adds. 

---