Chemistry Reference
In-Depth Information
Triglyceride
Intramolecular trans-esterification
involving 4-/5-hydroxy acids
Lipase
δ
- or
γ
- Lactones
Fatty acids
β
-ketoacids
Unsaturated
fatty acids
4- or 5-
hydroxy acids
Hydroperoxides
Hydroperoxide lyase
Aldehydes
Methyl ketones
δ
γ
Free
fatty acids
-
Lactones
- or
Alcohols
Secondary alcohols
Acids
FLAVOR COMPOUNDS
Figure 14.6.
General pathways for the metabolism of milk triglycerides and fatty acids (repro-
duced with permission from Singh et al., 2003; # Blackwell Publishing, Inc.).
acids between C
4:0
and C
12:0
, have specific flavours (rancid, sharp, goaty,
soapy, coconut-like). The flavour intensity of FFAs depends not only on the
concentration but also on the distribution between aqueous and fat phases,
the pH of the medium, the presence of certain cations (e.g., Na
+
,Ca
2+
)and
protein degradation products (Adda et al., 1982). The pH has a major
influence on the flavour impact of FFAs. At the pH of Cheddar cheese
(pH
5.2), a considerable portion of the FFAs are present as salts, which are
non-volatile, thus reducing their flavour impact. In most cheese varieties,
relatively little lipolysis occurs during ripening and too much is considered
undesirable. Most consumers would consider Cheddar, Dutch and Swiss-
type cheeses containing even moderate levels of free fatty acids to be rancid.
Even lesser amounts of FFAs would make fermented milk such as yogurt
rancid. However, extensive lipolysis is desirable as part of overall flavour
development in certain cheeses, such as hard Italian cheeses (Romano,
Provolone), Blue and Feta.
The fat fraction of dairy products is also important for the development
of typical flavour. Cheddar cheese made from non-fat milk does not develop
full aroma, even after 12 months (Ohern and Tuckey, 1969). Foda et al. (1974)
suggested that the fatty acid composition and natural emulsion of milk fat are
important for flavour development.
