Chemistry Reference
In-Depth Information
volatile compounds in a model cheese matrix had Cheddar aroma, attribute
profiling described it as lacking in sour, mouldy and sulfurous notes relative
to the real cheese. Also, the overall odour was described as weak. This
discrepancy in sensory character between the aromatized model and the
real cheese was caused partially by aroma-matrix interactions, which resulted
in quantitative errors (Wang and Reineccius, 1998).
A comparison of the volatile components of full- and reduced-fat
Cheddar showed that the level of methanethiol in the cheese is highly
correlated with the flavour grade. This observation may indicate that the
lack of aroma in reduced-fat Cheddar is due to the lack of methanethiol.
However, a combination of methanethiol and decanoic acid or butanoic
acid in all cheeses gave a better correlation with Cheddar flavour than
methanethiol alone (Dimos et al., 1996). Addition of methanethiol to a
bland slurry of reduced-fat Cheddar produced a strong Cheddar aroma
(Urbach, 1997b).
The use of dynamic headspace dilution analysis (DHDA) methodology
has suggested additional volatiles as being important to Cheddar cheese
aroma as compared to the aforementioned results from GCO-H and solvent
extraction/AEDA (Zehentbauer and Reineccius, 2002) (Table 14.8). Results
of DHDA showed that in addition to the odorants previously identified by
AEDA and GCO-H, (Z)-4-heptenal, 2-acetyl-1-pyrroline, dimethyl trisul-
phide, 1-octen-3-one, (Z)-1,5-octadiene-3-one and (E)/(Z)-2-nonenal, which
have been underestimated or not even perceived during AEDA, may also
contribute to the overall aroma of Cheddar cheese.
The volatile aroma components of two sharp Cheddar cheeses of British
Farmhouse origin, made using raw milk and ripened for at least l year, were
analyzed by AEDA (Suriyaphan et al., 2001b, Table 14.8). Descriptive sen-
sory analysis of these cheeses was also conducted. Key flavours in sharp
Cheddar cheeses were barnyard and earthy. Following instrumental analysis,
model system addition was used to confirm compounds responsible for
specific flavour notes. p-Cresol was mainly responsible for a 'cowy-barny'
note, whereas an intense 'soil-like' note was due to 2-isopropyl-3-methoxy-
pyrazine. At much lower odour intensity, 2-isobutyl-3-methoxypyrazine con-
tributed a 'bell pepper-like' note. Direct addition of p-cresol (
>
100 mg/kg) or
2-isopropyl-3-methoxypyrazine (
>
3 mg/kg) to a mild domestic Cheddar
cheese resulted in increased intensities of cowy/phenolic and earthy/bell pep-
per aroma notes. Additionally, within the same wedge of cheese, the concen-
trations of p-cresol and 2-isopropyl-3-methoxypyrazine were lower at the
center than at the rind.
Avsar et al. (2004) determined that the aldehydes, 2- and 3-methyl
butanal and methyl propanal, which are derived from leucine, isoleucine
and valine, respectively, have central roles in the nutty flavour of Cheddar
