2009_Book_FoodChemistry

160 3 Lipids
Table 3.3. Aroma threshold values (odor and/or taste)
of free fatty acids in different food items
Fatty acid Aroma threshold (mg/kg) in
Cream Sweet cream Coconut fat
butter a
Odor Taste Odor Taste b
4:0 50 60 40 35 160
6:0 85 105 15 25 50
8:0 200 120 455 > 1000 25
10:0 > 400 90 250 > 1000 15
12:0 > 400 130 200 > 1000 35
14:0 > 400 > 400 5000 > 1000 75
16:0 n.d. n.d. 10,000 n.d. n.d.
18:0 n.d. n.d. 15,000 n.d. n.d.
a Odor/taste not separated.
b Quality of taste: 4:0 rancid, 6:0 rancid, like goat,
8:0 musty, rancid, soapy, 10:0, 12:0 and 14:0 soapy
n.d.: not determined.
Table 3.4. Threshold values a of fatty acids depending
on the pH-value of an aqueous solution
Fatty acids
Threshold (mg/kg) at pH
3.2 4.5 6.0
4:0 0.4 1.9 6.1
6:0 6.7 8.6 27.1
8:0 2.2 8.7 11.3
10:0 1.4 2.2 14.8
a Odor and taste.
Additive effects can be observed in mixtures:
examples No. 1 and 2 in Table 3.5 demonstrate
that the addition of a mixture of C 4 −C 12 fatty
acids to cream will produce a rancid soapy taste
if the capryl, capric and lauryl acid contents rise
from 30 to 40% of their threshold value concentration.
A further increase of these fatty acids to
about 50% of the threshold concentration, as in
mixture No. 3, results in a musty rancid odor.
Some high molecular weight fatty acids (>18:0)
are found in legumes (peanut butter). They
can be used, like lower molecular weight homologues,
for identification of the source of
triglycerides (cf. 14.5.2.3). Fatty acids with odd
numbers of carbon atoms, such as valeric (5:0)
or enanthic (7:0) acids (Table 3.6) are present
in food only in traces. Some of these shortchain
homologues are important as food aroma
constituents. Pentadecanoic and heptadecanoic
acids are odd-numbered fatty acids present in
milk and a number of plant oils. The common
name “margaric acid” for 17:0 is an erroneous
designation. Chevreul (1786–1889), who first
discovered that fats are glycerol esters of fatty
acids, coined the word “margarine” to denote
a product from oleomargarine (a fraction of
edible beef tallow), believing that the product
contained a new fatty acid, 17:0. Only
later was it clarified that such margarine or
“17:0 acid” was a mixture of palmitic and
stearic acids.
Branched-chain acids, such as iso- (with an isopropyl
terminal group) or anteiso- (a secondary
butyl terminal group) are rarely found in food.
Pristanic and phytanic acids have been detected
in milk fat (Table 3.6). They are isoprenoid acids
obtained from the degradation of the phytol side
chain of chlorophyll.
Table 3.5. Odor and taste of fatty acid mixtures in cream
No. Fatty acid mixtures of Odor Taste
4:0 6:0 8:0 10:0 12:0
Concentration in % of aroma threshold a
1 28 17 29 31 30 n.O. n.T.
2 28 17 40 42 37 n.O. rancid, soapy
3 28 17 52 53 45 musty, rancid rancid, soapy
4 48 29 29 31 30 musty, rancid n.T.
5 48 29 40 42 37 musty, rancid rancid, soapy
a The concentration of each fatty acid is based on the threshold values indicated
in Table 3.3 for odor for 4:0 and 6:0 and for taste for 8:0–12:0.
n.O. = no difference in odor from that of cream.
n.T. = no difference in taste from that of cream.