Amount of characteristic compounds in 15 cultivars of onion (Allium cepa L.) in controlled field trials

BACKGROUND: In order to develop the production of sweet onions (Allium cepa L.) and onions with a high content of flavonols and fibre in Norway, it was necessary to evaluate available cultivars with respect to their content of selected chemical compounds. A field trial with 15 different cultivars was conducted at Landvik in southern Norway. Compounds that reflect onion pungency and sweetness (pyruvate, sugars) and parameters known to have a beneficial impact on health (fructo-oligosaccharides (FOS), flavonols, antioxidant capacity) were analysed. RESULTS: The sweetest onions with respect to low content of pyruvate and high amount of fructose and glucose ranged in pyruvate content from 2.7 to 3.6 mu mol. mL(-1). These cultivars were juicy and contained low amounts of FOS and total flavonols. The most pungent onions contained the highest amounts of FOS among the cultivars: 4.53, 3.80 and 5.81 g per 100 g fresh weight (FW) respectively. They also had a high content of flavonols (86.6, 159.2 and 97.6 mg per 100 g FW) and high dry weight content (14.6, 13.5 and 15.6 g per 100 g). CONCLUSION: The sweetest onion cultivars were found to be 'NUN 9746', 'Musica', 'Domenica Supersweet', 'Colossus' and 'Cronus'. The most pungent cultivars were 'Powell Brown' and 'Tilbury', which also contained the highest amounts of flavonols and gave the highest Trolox equivalent antioxidant capacity (TEAC) values among the IS cultivars. (c) 2007 Society of Chemical Industry.