2009_Book_FoodChemistry

16.2 Individual Constituents 761
Fig. 16.3. Biosynthesis of cyanogenic glucosides
Fig. 16.4. Lima beans: linamarin degradation, resulting in a release of hydrocyanic acid
Table 16.23. Amount of glycoside-bound hydrocyanic
acid in food
Food
HCN
(mg/100 g)
Lima bean a 210–310
Bitter almond 280–310
Sorghum sp. 250
Cassava 110
Pea 2.3
Bean 2.0
Chick pea 0.8
a In the United States new cultivars have been developed
that contain only 10 mg HCN/100 g seed.
As shown in Fig. 16.4, β-glucosidase hydrolysis
produces an unstable hydroxynitrile which slowly
degrades into the corresponding carbonyl compound
and HCN. However, most legume seeds
contain a hydroxynitrile lyase which accelerates
this reaction.
16.2.7 Lipids ∗
With the exception of soybeans and peanuts,
the lipid content of most legumes is so low
(cf. Table 16.2) that they can not be considered
rived from phenylalanine or tyrosine, but not linamarin.
∗ The composition of soy and peanut lipids is covered
in Chapters 3 and 14.