Understanding and reducing oxidative flavour deterioration in foods - Oxidation in Foods and Beverages and Antioxidant Applications - page 134

Table 6.3 Volatile compounds (carbonyls) from beef-fat

Carbonyls Flavour Flavour

(in order of concentration) threshold (ppm) significance

2-decenal 5.5 12

2-undecenal 4.2 11

2-nonenal 0.1 5

2-octenal 1.0 10

Hexanal 0.15 6

2-heptenal 0.63 9

Heptanal 0.042 3

Nonanal 0.32 8

Octanal 0.068 4

2,4-decadienal 0.28 7

Cis-4-heptenal 0.001 1

Trans-4-heptenal 0.32 8

Trans,trans-2,6-nonadienal 0.001 1

Trans,cis-2,6-nonadienal 0.002 2

Source: Frankel, E.N. 1984. Recent advances in the chemistry of rancidity of fats. In: A.J. Bailey
(ed.) Recent advances in the chemistry of meat. The Royal Society of Chemistry, London, pp. 87±118
with permission.

Summo et al. (2010) investigated oxidative and hydrolytic changes in
vacuum-packed ripened sausages during long term storage (5 months) using
both sensory analysis and HPSEC analysis of TAG oligopolymers, oxidized
TAG, DAG as well as analysis of free fatty acids and TBARS. They used the
following descriptors to describe defects occurring during storage due to lipid
oxidation and hydrolysis: rancid smell/flavour, pungent smell/flavour and acid
taste, whereas spiciness was used as a `positive' descriptor. Moreover, the panel
also evaluated the overall acceptability of the product. Despite the fact that the
sausages were vacuum packed the sensory panel was clearly able to pick up
undesirable changes in the flavour profile due to lipid oxidation and hydrolysis.
Thus, acid flavour increased significantly throughout the storage, whereas
pungent smell/flavour and rancid smell/flavour increased significantly up to 3
months whereafter they decreased. Rancid smell/flavour and acid taste
correlated well with HPSEC determination of oxidized TAG and determination
of free fatty acid, respectively. In contrast, TBARS neither increased signifi-
cantly during storage nor did it correlate to sensory data. The authors therefore
concluded that TBARS was not a reliable method for description of oxidation
and hydrolysis products during storage (Summo et al. 2010). This is most likely
due to the fact that the method underestimates malonaldehyde, which is the main
compound determined by the TBARS test, due to its reactions with amino acids,
sugars and nitrites.
In a recent study by Clausen et al. (2009) the eating quality of beef was
investigated in response to different types of modified atmosphere packaging
(MAP). MAP is increasingly being used by the food industry as it offers the
opportunity to extend the shelf life of the product. An important parameter is the