Abstract
Determination of antioxidant activity is one of the key elements for understanding the biological properties of a widely used spice onion (A. cepa). In contrast, physical properties help understand the textural quality of onion necessary for postharvest operations of sorting and grading in particular. Considering the physicochemical importance of onion, the present study focused on the determination of physical attributes and antioxidant content of the onion germplasm in Bangladesh using visual methods and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, respectively. The five-onion germplasms (BARI Piaz-2, BARI Piaz-3, BARI Piaz-4, BARI Piaz-5, Faridpuri Vati) collected from selected onion growers of the Department of Agricultural Extension (DAE) of the southwestern part of Bangladesh were used as treatments for physicochemical analysis at the Horticulture laboratory of the Agrotechnology Discipline, Khulna University, Khulna, Bangladesh during the period from February to August 2019. The laboratory study was laid out in Completely Randomized Design (CRD) with three replications. Most of the physical characteristics of onion were highest in germplasm-1 than those of the other germplasm tested. The results showed that the DPPH free radicals were scavenged by all onion germplasm extracts in a concentration-dependent pattern. The highest IC50 value (238.10 ppm) was noticed in germplasm-3 and the lowest in germplasm-5 (161.29 ppm) with no statistical difference from germplasm-4 (172.41 ppm). The lower IC50 value indicating that onion germplasms-5 and -4 extracts were more potent in scavenging free radicals than the other onion germplasms. Thus, the low IC50 value facilitated the germplasm-5 and -4 to be enriched with antioxidant compounds significantly in higher amounts than the others. SAARC J. Agric., 19(1): 113-123 (2021)
Highlights
Onion (Allium cepa L.) belongs to the family Alliaceae is one of the most widely used spices all over the world (Kuete, 2017)
The percentage of edible portion was the highest in germplasm-1 (98.80%), which was statistically similar to the germplasm-2 (Figure 1), while the lowest edible portion was measured in germplasm-5 (88.56%), which did not statistically differ from germplasm -3 and germplasm-4
The IC50 value of DPPH radical scavenging activity The results showed that germplasm-5 and germplasm-4 extract exhibited the highest antioxidant activity (161.29 ppm and 172.41 ppm) than the other germplasms extract (Figure 3)
Summary
Onion (Allium cepa L.) belongs to the family Alliaceae is one of the most widely used spices all over the world (Kuete, 2017). Its edible part is bulb which varies in size, shape, color, and pungency It can be grown in any type of soil, but welldrained, fertile silty to sandy loam soils rich in humus are best for onion cultivation (Azad et al, 2018; Rashid, 2010). Agronomic practices and environmental factors have great effects on yield and quality of onion crops (Khan et al, 2002). Bahnasawy et al (2004), and Vijaya and Srivastava (2006) researched on physical and mechanical properties of onion constituting weight and size of bulb, weight of dried scale, linear dimensions, shape index, surface area, friction angle, coefficient of static friction, etc. Pusa Red variety was found to be denser (270 kg/m) than the other two varieties
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