Chemical Properties
Bitter almond has an intense, almond-like, cherry aroma with a slightly astringent, moldy taste. The term bitter almond
refers to the essential oil obtained by steam distillation of the partially de-oleated press-cake of kernels from any of the following:
bitter almond (P. amygdalus), apricot (P. armeniaca) and peach (P. persica). The kernels from these and other such fruits contain the
glucoside amygdalin, which on enzymatic hydrolysis yields benzaldehyde and HCN. The distilled oil must be rendered free of HCN
(prussic acid) prior to its marketing as a flavor ingredient. Very little essential oil is currently made exclusively from bitter almonds
or other fruit kernels; specially purified benzaldehyde is often used in its place
Chemical Properties
Bitter almond oil (free from hydrogen cyanide) contains benzaldehyde as its
main component. Benzaldehyde does not occur as such in the plant, but is formed,
together with hydrogen cyanide, by the hydrolytic cleavage of the glycoside amygdalin.
Amygdalin is present in bitter almonds, the seeds of Prunus dulcis var. amara
(DC.) Buchheim, and ripe apricot kernels, Prunus armeniaca L. (Rosaceae).The
press cake, which remains after removal of the fatty oils, is macerated with water
and left to stand for several hours, after which the “essential oil” is separated
by steam distillation. The crude oil contains 2–4% hydrogen cyanide, which
is removed by washing with alkaline solutions of iron(II) salts. Subsequent
redistillation yields an oil free from hydrogen cyanide. It is a colorless to slightly
yellow liquid with an intense, almond-like, cherry aroma and a slightly astringent, mild taste.
d
2525 1.025–1.065; n
20D 1.5350–1.5550; acid value: max. 8; solubility: 1 vol inmax.
6 vol 50% ethanol. HCN content: <0.01%; benzaldehyde content by GC: min. 98%.
Bitter almond oil is used almost exclusively in natural aroma compositions.
Essential oil composition
Bitter almond oil is obtained by first cold-expressing the fixed oils from the comminuted kernels, after
which the press-cake is macerated in about 10 parts of water for 12 to 20 hours to effect the enzymatic hydrolysis of amygdalin. The
mixture is then steam distilled to yield about 0.5 to 0.7% of the essential oil. Bitter almonds are rarely used because the yield of oil
is only 0.6%. Apricot kernels yield 1.2% of oil and are the preferred starting material. The major components of the oil are typically
97.5% benzaldehyde (bitter almond) and 2% hydrogen cyanide (bitter almond).
