Antioxidant and taste properties of fresh onion ( Allium cepa L.) leaves

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ORIGINAL PAPER

Antioxidant and taste properties of fresh onion (Allium cepa L.) leaves Masahiro Yuasa1   · Koji Kawabeta2 · Maho Morikawa2 · Momoe Iwami1 · Mihoko Tominaga3 Received: 15 July 2020 / Accepted: 12 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract We characterized the antioxidant properties and taste quality of fresh onion leaves compared with those of welsh onion (Allium fistulosum L.) (green-leafed small variety), which taste similar. In fresh onion leaves, the total oxygen radical absorbance capacity value and 1, 1-diphenyl-2-picrylhydrazyl free radical-scavenging activity were the same as in welsh onion. However, the total quercetin concentrations in fresh onion leaves were markedly higher than in welsh onion. The concentrations of total vitamin C, β-carotene, and chlorophylls were almost the same in the fresh onion leaves and welsh onion. In addition, the sourness and bitterness of taste responses and Brix for fresh onion leaves were higher and lower, respectively, than for welsh onion. The 5′-guanylate concentration was higher in fresh onion leaves than in welsh onion, and some free amino acids, citric acid and total organic acid concentrations were lower in fresh onion leaves than in welsh onion. These results indicate that fresh onion leaves are good dietary sources of some antioxidants, such as quercetin, vitamin C, β-carotene, and chlorophylls. In addition, the taste of fresh onion leaves is sour and lower bitterness and sweetness than welsh onion, which is due to differences in some taste profile components. Keywords  Fresh onion leaves · Welsh onion · Antioxidant activity · Antioxidant · Taste response · Taste component

Introduction Onion (Allium cepa L.) is a popular food in Western, Chinese, and Japanese dishes around the world. In Japan, onion is harvested from spring or summer to autumn. In the former case, onion is harvested from February to May and is called fresh onion [1], which is less pungent and tastes juicer than general onions; thus, it is often eaten raw. Before shipment to markets, leaves of fresh onion (fresh onion leaves) are discarded; because they have a very short shelf life [2], therefore, they are commonly considered non-edible in Japan. The 1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging activity, total vitamin C [3], total polyphenol, * Masahiro Yuasa [email protected] 1



Department of Nutrition, Faculty of Nursing and Nutrition, University of Nagasaki, 1‑1‑1 Manabino, Nagayo‑cho, Nishisonogi‑gun, Nagasaki 851‑2195, Japan

2



Graduate School of Human Health Science, University of Nagasaki, 1‑1‑1 Manabino, Nagayo‑cho, Nishisonogi‑gun, Nagasaki 851‑2195, Japan

3

Graduate School of Humanities and Social Sciences, Hiroshima University, 1‑1‑1 Kagamiyama, Higashi‑Hiroshima City, Hiroshima 739‑8524, Japan



total flavonoid, carotenoids, and chlorophylls [2] concentrations in fresh onion leaves are higher than they are in the bulbs, which is the edible part of fresh onions. In fresh onion leaves, the DPPH free ra