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Abstract
Antioxidants of onion, garlic, and chives were extracted with 99% ethanol in ratios of 1:2; 1:3, and 1:4 (w/v). The ratio of 1:4 obtained the highest extraction yield for all three materials, in which, garlic had the highest extraction yield, reaching 19.81% compared to 18.23% and 16.90% for chives and onion, respectively. DPPH assay was used to determine the antioxidant activity of extracts from garlic, onion and chives based on the free radical scavenging activities (%). Free radical scavenging activities (%) of garlic extract were higher than both onion and chives extracts at all tested concentrations, 300, 600, and 900 µg/L. The higher the extract concentrations, the greater the free radical scavenging activities. At 900 µg/L of garlic, chives and onion extracts, free radical scavenging activities reached 51,13%, 48,97% và 20,78%, respectively. Adding garlic extract into crude peanut oil at a concentration of 900 µg/L helped to maintain the quality of the oil for 8 months of storage at room temperature when the peroxide (9.94 meqO2/kg), acidity (4.19 mgKOH/g), saponification (198.21 mgKOH/g) and iodine value (80.04 Wijs) were still within allowable limits. The control sample (without garlic extract) had the values of acidity (4.12 mgKOH/g), saponification (197.05 mgKOH/g), and iodine (79.25 Wijs) which exceeded their allowable limits according to TCVN 7597:2018 on edible peanut oil after 6 months. Thus, the addition of garlic extract with a concentration of 900 µg/L into traditional groundnut oil helps to extend the shelf life of the oil for 2 months.