2009_Book_FoodChemistry

10.3 Aroma of Milk and Dairy Products 541
Table 10.41. Aroma profile of samples of butter
No. Sample Odor quality Intensity a
1 Sour cream Buttery, 3
creamy, sweet
2 Sour cream Buttery, creamy 2–3
3 Sour cream Slightly buttery, 1–2
mild, sour
4 Sour cream Rancid, 3
like butyric acid
5 Sweet cream Mild, 1
somewhat sour
a Evaluation: 1, weak; 2, medium; 3, strong.
Fig. 10.33. Formation of diacetyl and butanediol
from citrate by Streptococci. 1 citratase, 2 oxaloacetate
decarboxylase, 3 pyruvate decarboxylase, 4 α-
acetolactate synthase, 5 diacetyl reductase, 6 α-
acetolactate decarboxylase, 7 2,3-butanediol dehydrogenase
Table 10.40. Concentrations of the key aroma substances
in five samples of butter a
Aroma substance
Concentration (mg/kg)
in sample number
1 2 3 4 5
Diacetyl 0.62 0.34 0.11 0.32 <0.01
(R)-δ-Decalactone 5.0 4.91 3.06 2.15 3.8
Butyric acid 4.48 3.63 2.66 94.5 2.48
a The aroma profiles of the samples are presented in
Table 10.41.
the concentrations of these three odorants, which
are present in Samples 1 and 2, produce an intensive
butter aroma. In Samples 3 and 4, especially
the diacetyl content is too low and in Sample
4, the excessively high butyric acid concentration
stimulates a rancid aroma defect. Lactic acid
is primarily involved in the taste of sour cream
butter.
If butter contains lipases, fatty acids are released
on storage. Above certain limiting concentrations
(cf. 3.2.1.1), these fatty acids cause a rancid offflavor.
Rancid, soapy aroma defects, which occur in butter
samples with very low concentrations of free
fatty acids, can be due to contamination with anionic
detergents (sodium dodecyl sulfate, sodium
dodecyl benzosulfonate). Detergents of this type
are used to disinfect the udder and the milking
machine.
10.3.5 Cheese
The aroma profile of unripened cheese,
e. g., Mozzarella, consists of butter-like, sweetish,
salty and sour notes produced by l, δ-decalactone,
NaCl and lactic acid. The characteristic odor and
taste of the type of cheese are formed during
ripening, whereby the composition of the microflora
and the storage conditions (temperature,
air humidity, time) have the greatest influence.
For a soft cheese (Camembert) and a hard
cheese (Emmentaler), the compounds mainly
responsible for the odor and taste in the ripened
product will be discussed here.
The butter-like note of unripened cheese can
still be detected in Camembert and Emmentaler,
but the intensity is lower, because other aroma
substances formed during ripening become evident.
Thus, Camembert also has mushroom-like,
sulfurous and flowery notes and Emmentaler,
nutty, sweet and fruity notes. In comparison with
unripened cheese, the taste profile is extended
to include a glutamate note and in the case of
Emmentaler, an additional and characteristic
sour/pungent impression.