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Homo = homofermentative; hetero = heterofermentative. a Several are pathogenic. b Many are pathogenic.

c Ferment glucose by the homofermentative pathway and pentoses and 6-P-glyconate by the heterofermentative pathway.

Homo = homofermentative; hetero = heterofermentative. a Several are pathogenic. b Many are pathogenic.

c Ferment glucose by the homofermentative pathway and pentoses and 6-P-glyconate by the heterofermentative pathway.

thermophilic LAB; however, mixtures can also occur. Mesophilic starter cultures originate from north and east Europe. They consist primarily of Lactococcus lactis subsp. cremoris (L. cremoris), Lactococcus lactis subsp. lactis (L. lactis), Lactococcus lactis subsp. lactis biovar. diacetylactis (L. diacetylactis), Leuconostoc mesenteroides subsp. cremoris, and Leuconostoc lactis. Especially, L. cremoris and L. cremoris are capable of rapid acidification of milk. L. diacetylactis, Leuconostoc mesenteroides subsp. cremoris, and Leuconostoc lactis can catabolize citrate into CO2 and diacetyl. CO2 is responsible for the production of holes in the cheeses, and diacetyl, the characteristic flavor of butter, is important for the flavor of many cheeses and fermented milk products. The diacetyl-producing organisms are often called the aroma producers or L. lactis subsp. lactis (citrate + ). Lactobacillus paracasei and Lactobacillus casei are the most common mesophilic lactobacilli found in many cheeses and are in some cases used as adjunct cultures (16-19). Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus curvatus are also found in many cheeses (17,18,20). The dairy propionibacteria Propionibacterium shermanii and Propionibacterium freudenreichii are used in some Swiss-type cheeses such as Emmental, Gruyère, and Comté;, in which they slowly catabolize lactate to propionate, acetate, and CO2. This is important for the production of holes and taste of the cheeses (20,21). Micrococcacaceae and Brevibacterium are used as surface flora in various cheeses (22); they are important for cheese ripening.

Different types of mixed starter cultures have been developed. The composition of the different mesophilic starter cultures, and examples of products for which they are used, is shown in Table 5. The most abundant cheese produced is Cheddar cheese. It is commonly produced by the use of a multiple strain starter culture of Lactococcus lactis subsp. cremoris and Lactococcus lactis subsp. lactis, with or without Streptococcus ther-mophilus. However, a mixed O-culture, TK5, has also been developed (23,24).

Table 5 Composition of Different Types of Mesophilic Starter Cultures and Some Examples of Their Products

Type

Organisms

Composition

Products

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