10.2 Dairy Products 521Fig. 10.19.Schematic presentation of milk processing
10.2 Dairy Products
Milk processing is illustrated schematically in
Fig. 10.19.
10.2.1 Fermented Milk Products
All sour milk products have undergone fermenta-
tion, which can involve not only lacticacid bac-
teria, but also other microorganisms, e. g., yeasts.
To the lactic acid bacteria count the generaLac-
tobacillus, Lactococcus, Leuconostoc,andPedio-
coccus.The most important species are presented
in Table 10.25.
Depending on the microorganisms involved,
fermentation proceeds via the glycolysis path-
Fig. 10.20.Glucose metabolism in lactic acid bacteria. A: homofermentation, B: Bifidus pathway, and C: hetero-
fermentation (6-phosphogluconate pathway)
way with the almost exclusive formation of
lactic acid (homofermentation), via the pentose
phosphate pathway with formation of lactic
acid, acetic acid (ethanol), and possibly CO 2
(heterofermentation) or via both pathways. These
metabolic pathways are shown in Fig. 10.20.
Organisms that are obligatorily homofermen-
tative have fructose-bisphosphate aldolase, but
not glucose 6-phosphate dehydrogenase and
6-phosphogluconate dehydrogenase. However,
organisms that are obligatorily heterofermenta-
tive have both dehydrogenases, but no aldolase.
Facultatively homofermentative organisms have
all three enzymes and can use both metabolic
pathways.
Apart from the type of fermentation, the configu-
ration of the lactic acid formed also depends on