2009_Book_FoodChemistry

522 10 Milk and Dairy Products
Table 10.25. Lactic acid bacteria
Microorganisms
L-Lactic Remarks
acid a
(%)
Lactobacillus
bulgaricus 0.6–4 thermophilic,
L. lactis 0 homofermentative,
L. leichmanii D-, L-or
L. delbrueckii D,L-Lactic acid
L. helveticus 70
L. jugurti
L. acidophilus 60
L. casei subsp. casei mesophilic,
L. casei subsp. homofermentative,
alactosus
L. casei subsp. pseudo D-, L-or
plantarum
D,L-Lactic acid
L. casei subsp.
rhamnosus
L. casei subsp.
fusiformis
L. casei subsp.
tolerans
L. plantarum
L. curvatus
L. fermentum heterofermentative,
L. cellobiosus D,L-Lactic acid
L. brevii
L. hilgardii
L. vermiformis
L. reuteri
Streptococcus
thermophilic,
thermophilus 99 homofermentative
S. faecium homofermentative
Lactococcus lactis
mesophilic,
subsp. lactis 92–99 homofermentativ
Lactococcus lactis
subsp. cremoris 99
Leuconostoc cremoris
heterofermentative,
L. mesenteroides D-Lactic acid
L. dextranicum
L. lactis
Pediococcus acidilactici thermophilic,
homofermentative,
D,L-Lactic acid
a Orientation values; the proportion of L-lactic acid
depends on the bacterial strain and on the culture conditions.
the microorganisms involved. As shown in Table
10.25, both enantiomers are formed in varying
amounts. Table 10.26 lists the content of total
lactic acid and L-lactic acid in various dairy products.
In human metabolism, L-lactic acid is formed
exclusively and only one L-lactate dehydrogenase
is available. Therefore, the intake of
larger amounts of D-lactic acid can result in
enrichment in the blood and hyperacidity of the
urine. For this reason, the WHO recommends
a limitation of the intake of D-lactic acid to
100 mg per day and kg of body weight. Apart
from the main products mentioned, various
aroma substances are formed in the course of
fermentation (cf. 10.3.3). In addition, proteolytic
and lipolytic processes occur to a certain extent.
During proteolysis, peptides can be formed
which have opiate activity and hypotensive,
immune-stimulating or antimicrobial effects
(cf. Literature).
According to the consistency, a distinction is
made between stiff, gel-like products, stirred,
creamy products, and drinkable, flowable
products. The thermal pretreatment of milk
influences the rheological properties of the
products as described in section 10.1.2.1.3.
The keeping time of sour milk products can
be increased if they are produced and filled
under aseptic conditions or produced under
normal conditions but subsequently heat
treated.
Table 10.26. Total lactic acid and L-lactic acid in some
dairy products
Product Total lactic acid L-Lactic acid
(%) (%) b
Sour milk 0.97 88
Buttermilk 0.86 87
Sour cream 0.86 96
Joghurt 1.08 54
Curd 0.59 94
Cottage cheese 0.34 92
Emmental 0.27 76
Sbrinz 1.53 58
Tilset cheese 1.27 52
a Average values. b Based on total lactic acid.