Understanding and reducing oxidative flavour deterioration in foods - Oxidation in Foods and Beverages and Antioxidant Applications - page 126

Table 6.2 Odour threshold values of selected aldehydes produced by lipid oxidation

Aldehydes Odour threshold in oil (ppm) Description

Nasal Retronasal

Hexanal 320 75 Tallowy, green, leafy

Heptanal 3200 50 Oily, fatty

Octanal 320 50 Oily, fatty, soapy

Nonanal 13500 260 Tallowy, soapy-fruity

Decanal 6700 850 Orange peel-like

2-t-pentenal 2300 600 Pungent, apple

2-t-hexenal 10000 400 Apple

3-c-hexenal 14 3 Green, leafy

2-t-heptenal 14000 400 Fatty, bitter almond

2-t-nonenal 900 65 Tallowy, cucumber

3-c-nonenal 250 35 Cucumber

2-t-decenal 33800 150 Tallowy, orange

2,4-t,c-heptadienal 4000 50 Frying odour, tallowy

2,4-t,t-heptadienal 10000 30 Fatty, oily

2,6-t,t-nonadienal 2500 460 Fatty, oily

2,6-t,c-nonadienal 4 1.5 Cucumber-like

2,4-t,c-decadienal 10 ± Frying odour

2,4-t,t-decadienal 180 40 Frying odour

2,4,7-t,t,c-decatrienal ± 24 Cut beans

4,5,2-t-epoxy-t-decenal 1.3 3 Metallic

Source: Belitz H.D. and Grosch W. (1999). Food Chemistry. Springer-Verlag, Heidelberg, Berlin,
with permission.

the oil may develop a painty odour. A number of different volatile oxidation
compounds have been suggested to contribute to these off-flavours. Table 6.2
shows some of these volatiles and the odour that have been ascribed to them.
Oxidized oil will contain a mixture of different volatiles and the relationship
between the concentration of these volatiles and their sensory impact is poorly
understood. To the author's knowledge only one model describing the quantita-
tive relationship between volatiles and an important off-flavour in oxidized oils
has been reported. This model describes the intensity of the fishy taste in fish oil
as a function of the concentration of three volatiles, 2,6-nonadienal, 4-heptenal,
and 3,6-nonadienal oil (MacFarlane et al. 2001).

6.3.2 Mayonnaise
Hartvigsen et al. (2000) identified and quantified the levels of volatile oxidation
products in stored mayonnaise with or without fish oil by dynamic headspace
GC-MS. Subsequently, they used GC-olfactometry to identify the most potent
odorants, i.e. the compounds that most likely are responsible for the fishy off-
flavour observed in the oxidized product. More than 140 volatiles were found in
the fish oil enriched mayonnaise and slightly fewer volatiles were found in the