2009_Book_FoodChemistry

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 intensities
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 to Widder and Fischer, 1996)
Fig. 5.33. Influence of the fat content of an emulsion on the concentration of aroma substances in the gas phase
(according to Widder and Fischer, 1996).
□ diacetyl, (Z)-3-hexenol, ⊠ allyl isothiocyanate, allyl thiocyanate
Table 5.36. Mayonnaise model: gas chromatography/olfactometry of headspace samples
Aroma substance a Odor quality Odor intensity b
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 <1 0
Allyl isothiocyanate Pungent, mustard-like 4 3 <1
Allyl thiocyanate Pungent, mustard-like 4 3 <1
a Components of an aroma cocktail to which an oil emulsion was added.
b Intensity 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 = C o
C w
(5.37)
where C o is the concentration of the aroma compound
in the oil phase, and C w the 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 increasing
chain length. The solubility in the fat or
oil phase rises proportionally as the hydrophobic-