Food Chemistry

390 5 Aroma Compounds

Fig. 5.32.Influence of the fat content on the aroma profile of emulsions; a) 20% fat, b) 5% fat, c) 1% fat. The in-
tensities of the aroma qualities buttery(I), pungent, sharp (II), fatty (III), sweet (IV) and green (V) were evaluated
as 1 (weak) to 4 (strong) (according toWidderandFischer, 1996)

Fig. 5.33.Influence of the fat content of an emulsion on the concentration of aroma substances in the gas phase
(according toWidderandFischer, 1996).
diacetyl,(Z)-3-hexenol, allyl isothiocyanate,allyl thiocyanate

Table 5.36.Mayonnaise model: gas chromatography/olfactometry of headspace samples

Aroma substancea Odor quality Odor intensityb

1% fat 5% fat 20% fat

Diacetyl Buttery 3 4 > 4
(Z)-3-Hexenol Green 2 1 0
(E,Z)-2-6-Nonadienol Green, fatty 4 < 10
Allyl isothiocyanate Pungent, mustard-like 4 3 < 1
Allyl thiocyanate Pungent, mustard-like 4 3 < 1
aComponents of an aroma cocktail to which an oil emulsion was added.
bIntensity on sniffing the carrier gas stream 1 (weak)–4 (strong).

5.4.1 Lipids.................................................

In an o/w emulsion (cf. 8.15.1), the distribution
coefficient, K, for aroma compounds is related to
aroma activity:

K=

Co

Cw

(5.37)

where Cois the concentration of the aroma com-

pound in the oil phase, and Cwthe concentration

of the aroma compound in the aqueous phase.

In a homologous series, e. g., n-alkane alcohols

(cf. Fig. 5.34), the value of K increases with in-

creasing chain length. The solubility in the fat or

oil phase rises proportionally as the hydrophobic-