Corylus avellana
hazelnut
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Corylus avellana L. (Betulaceae); haselneut (Afrikaans); ou zhe (Chinese); hazelnoot (Dutch); noisette (French); Haselnuss (German); nocciola (Italian); avely (Portugueae); avellana (Spanish)
DESCRIPTION Hazelnut (cobnuts) are spherical to oval (ca. 15 mm or just over ½ in. in diameter) with a smooth shell enclosed in a fibrous husk (involucre). The closely related filbert (C. maxima) has larger, more oblong nuts and longer involucres that cover most of the nut. It is sometimes regarded as a mere cultivar of C. avellana. American hazelnut (C. americana) and Turkish hazelnut (C. colurna) are other sources of hazelnuts.1
THE PLANT A deciduous shrub or small tree with rounded, markedly toothed leaves. Male flowers (slender, hanging catkins) and female flowers (in small erect groups) are borne on separate trees and appear before the leaves.
ORIGIN The common hazel (one of about 18 species)1 is indigenous to Europe and western Asia, from the British Isles (where it is an important component of hedgerows) northwards and eastwards to the Caucasus and northwestern Iran. Hazelnuts have been used as human food all over Europe since prehistoric times2 and the plant features prominently in folklore.1
CULTIVATION The nuts were apparently first cultivated by the Romans.1 Plants can be propagated from seeds or vegetatively by layering, and are grown in temperate countries. Commercial production is now centred in Turkey (ca. 70% of global trade),3 with smaller quantities originating from Spain, Italy and France. Modern cultivars, mostly based on the filbert (C. maxima) and hybrids with C. avellana, are grown in plantations. A small percentage of nuts are wild-harvested.
HARVESTING Nuts are picked by hand in autumn, often while still enclosed in the husks. The nuts are sold with shell and all or more often after being mechanically dehulled.
CULINARY USES Roasted hazelnuts are an important flavour ingredient in chocolates, nut truffles, sweetmeats and confectionery (biscuits, cakes, pastries), to which they also add a delicate crisp texture. Hazelnut flavour is commonly used in alcoholic beverages. Whole or grated hazelnuts are used to some extent in cooking, especially in chicken and fish dishes, as well as in stuffings and stews. Ground hazelnuts are added to butter and various types of spreads for flavour. Extracted oil may be used as salad dressing. Roasted and salted hazelnuts are popular dessert nuts in many parts of the world.
FLAVOUR COMPOUNDS The main chemical compounds responsible for the distinctive aroma of hazelnuts are filbertone (5-methyl-2-hepten-4-one) and 1,3-dimethoxybenzene (resorcinol dimethyl ether).3 Roasting results in numerous additional flavour compounds such as pyrazines, ketones, aldehydes, furans and pyrones, all contributing to some extent to the complex aroma of roasted hazelnuts4.
NOTES 1,3-dimethoxybenzene has also been found in port wine.5
1. Mabberley, D.J. 2008. Mabberley’s plant-book (3rd ed.). Cambridge University Press, Cambridge.
2. Zohary, D., Hopf, M. 2000. Domestication of plants in the Old World (3rd ed.). Clarendon Press, Oxford.
3. Alasalvar C., Shahidi, F., Cadwallader, K.R. 2003. Comparison of natural and roasted Turkish Tombul hazelnut (Corylus avellana L.) volatiles and flavor by DHA/GC/MS and descriptive sensory analysis. Journal of Agricultural and Food Chemistry 51: 5067–5072.
4. Alasalvar C., Pelvan, E., Bahar, B., Korel, F., Ölmez, H. 2012. Flavour of natural and roasted Turkish hazelnut varieties (Corylus avellana L.) by descriptive sensory analysis, electronic nose and chemometrics. International Journal of Food Science & Technology 47: 122–131.
5. Rogerson, F.S.S., Azevedo, Z., Fortunato, N., de Freitas, V.A.P. 2002. 1,3-Dimethoxybenzene, a newly identified component of port wine. Journal of the Science of Food and Agriculture 82: 1287–1292.