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also classified as potentially bitter in the Q value model proposed by
Ney (1981). Amino acids are also known to elicit different taste
(see Table 14.10).
Several small peptides were identified in Comt´ cheese. Cyclic dipep-
tides were described as bitter (Roudot-Algaron et al., 1993) and
dipeptides with a gamma-glutamyl residue were found to be sour
(e.g.,
-Glu-Tyr), apart from
-Glu-Phe described to have a complex
taste, which was brothy and slightly sour, salty and metallic (Roudot-
Algaron et al., 1994). However, because of their low concentration
compared to their taste threshold value, they could not be directly
responsible of cheese taste.
A number of workers have studied taste-active compounds in Camembert
(Engel et al., 2001a,b,c), Cheddar (Yang and Vickers, 2004), Comt´ (Salles
et al., 1995), Goat (Engel et al., 2000a,b; Engel et al., 2002; Salles et al., 2002)
and Emmentaler cheeses (Warmke et al., 1996). Drake et al. (2007c) studied
compounds responsible for the umami taste in Cheddar and Swiss cheeses. Low
and high intensity umami-tasting cheeses were selected using a trained sensory
panel. Some compounds, namely monosodium glutamate (MSG), disodium-5'-
inosine monophosphate (IMP), disodium-5'-guanosine monophosphate
(GMP), sodium chloride, lactic acid, propionic acid and succinic acid, were
quantified in both types of cheese with and without umami taste. Comparison
of analytical data and sensory thresholds indicated that IMP and GMP thresh-
olds were 100-fold higher than their concentrations in cheese. All other com-
pounds contributed some umami taste within their concentration range in
umami cheeses. Sensory analysis of model cheeses clearly demonstrated that
Glu played a major role in the umami taste of both Cheddar and Swiss cheese,
while succinic and propionic acids contributed in Swiss cheese. The knowledge
of umami-tasting components of cheeses will be useful in developing technolo-
gies to control and regulate the level of this specific taste attribute in cheeses.
14.6.
Conclusions
A concerted series of chemical and biochemical reactions are involved in the
formation of dairy flavour and off-flavour compounds. The general chemical/
biochemical pathways, i.e., (1) heat-induced changes, (2) lipid oxidation,
(3) glycolysis, (4) lipolysis and (5) proteolysis, involved in the degradation
of milk constituents are now fairly well characterized. Recent works on the
enzymology and genetic manipulation of the starter and non-starter lactic
acid bacteria have helped in the better understanding of further catabolic
modification of the products of primary degradation pathways. This has lead
