Characterization of different ‘tropea red onion’ (Allium cepa L.) ecotypes by aroma precursors, aroma profiles and polyphenolic composition
2012
E09606
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Title
Characterization of different ‘tropea red onion’ (Allium cepa L.) ecotypes by aroma precursors, aroma profiles and polyphenolic composition
Publication Date
2012
Call Number
E09606
Summary
Many epidemiological studies have shown that the consumption of fruits and vegetables is associated with a reduced risk for the development of chronic diseases, such as cardiovascular disease and cancer. Phytochemicals, including polyphenols and flavonoids, are suggested to be the major bioactive compounds of fruits and vegetables contributing to the health benefits. Onion bulbs (Allium cepa L.) are among the richest sources of dietary flavonoids and contribute to a large extent to the overall daily intake of flavonoids. A particular sweet red onion, ‘Tropea Red Onion’, characterized by a large red envelope and internal white tunics, grown in Calabria region (south of Italy), for the excellent organoleptic characteristics (tenderness, crispness, sweetness), is considered the pride of Calabrian’s horticultural products. Because of the few available scientific studies on this particular red onion, a large-scale study to characterize different ‘Tropea red onion’ ecotypes was started. Onions contain bioactive components belonging to two main chemical groups: the flavonoids and the alk(en)yl cysteine sulphoxides (ACSOs). Flavonoid and in particular the anthocyanins and flavanols such as quercetin were found in onion while the ACSOs are the flavour precursors, which, when cleaved by the enzyme alliinase, generate the characteristic odour and taste of onion (thiosulphinates, thiosulphonates, mono-, di- and tri-sulphides). Because of the few available scientific studies on this particular red onion, a large-scale study was started to characterize different ‘Tropea red onion’ ecotypes and to identify markers of authentication to protect it on the national and international market. Moreover, ‘Tropea red onion’ ecotypes are evaluated for their characteristic tastes, aroma profile and for their flavonoids composition in comparison with other red onions. The alk(en)yl-L-cysteine sulphoxides ACSOs are the main precursors of onion flavour due to the presence of thiosulphinates, thiosulphonates, mono-, di- and tri-sulphides that arise in the ground tissues after reaction with the enzyme alliinase. The components of aroma profile are correlated with the pattern of aroma precursors (cysteine sulfoxides). Altogether at least 25 different flavonols have been characterized; quercetin derivatives are the most important flavonoids in Calabrian onion ecotypes. Analogous derivatives of kaempferol and isorhamnetin have been identified\n as minor pigments. HPLC, GC/MS, SPME/GC/MS, and e-nose had been used to classify different ‘Tropea red onion’ ecotypes.
Journal Citation
939:197-204, ACTA HORTICULTURAE
Contact Information
harvest@worldveg.org
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Research > Published Articles