Onion (Allium cepa L.) is potentially a good source of important antioxidants
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Six different cultivars of onions available in the Kuwaiti market were analyzed for various physic-chemical properties, such as, moisture content, sugar composition, TBARS as malondialdehyde, total phenolic content, as well as trolox equivalent antioxidant capacity, these cultivars comprised of US onions white, US onions yellow, Indian onions red, Egyptian onions red, New Zealand onions golden and Saudi onions white. Layers from each onion bulb were manually cut and separated into three nearly equal portions, i.e., outer layers, middle layers and the inner layers. The outermost layers of the bulb showed the highest concentration of antioxidant compounds and a distinct decreasing trend was observed towards the innermost layers in all types of onion samples. The onion samples studied showed variations in carbohydrate contents (glucose, fructose and sucrose), which would have important implications in affecting the flavor (sweetness and pungency) and the suitability of these onions for processing. An important observation is about the distribution of antioxidant compounds with the highest contents in the outmost layers of the onions than in their middle and inner layers. Unfortunately, these outer layers are generally discarded by the consumers thus depriving them of the important health-promoting phytochemicals.
KeywordsAllium cepa Antioxidant capacity Total phenolics Sugars Free radical scavenging activity
The authors thank the Kuwait University for financial support, Mr. Suleiman form Kuwait Institute for Scientific Research for carrying out the sugar analysis, Ms. JS Divya from the Biochemistry section, Biological Sciences Dept, Kuwait University, for carrying out the required chemical analyses of onion samples and for the statistical analyses of research data. Funding was provided by Kuwait University (Grant No. WF01/05).
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