Food Chemistry

10.3 Aroma of Milk and Dairy Products 541

Fig. 10.33. Formation of diacetyl and butanediol
from citrate by Streptococci. 1 citratase, 2 oxaloac-
etate decarboxylase, 3 pyruvate decarboxylase, 4 α-
acetolactate synthase, 5 diacetyl reductase, 6 α-
acetolactate decarboxylase, 7 2,3-butanediol dehydro-
genase

Table 10.40.Concentrations of the key aroma sub-
stances in five samples of buttera

Aroma substance Concentration (mg/kg)
in sample number
12345

Diacetyl 0 .62 0.34 0.11 0. 32 < 0. 01
(R)-δ-Decalactone 5. 04 .91 3.06 2.15 3. 8
Butyric acid 4 .48 3.63 2.66 94. 52. 48
aThe 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 in-
tensive butter aroma. In Samples 3 and 4, espe-
cially the diacetyl content is too low and in Sam-
ple 4, the excessively high butyric acid concentra-
tion 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

Table 10.41.Aroma profile of samples of butter

No. Sample Odor quality Intensitya

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

aEvaluation: 1, weak; 2, medium; 3, strong.

(cf. 3.2.1.1), these fatty acids cause a rancid off-

flavor.

Rancid, soapy aroma defects, which occur in but-

ter samples with very low concentrations of free

fatty acids, can be due to contamination with an-

ionic 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 mi-

croflora 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 evi-

dent. 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.