Antioxidant and antimicrobial activities of hydrophilic extracts from shallot and garlic bulbs, and their effects on round scad during iced storage

The present study aimed to investigate the in vitro antioxidant and antimicrobial activities of hydrophilic extracts prepared from shallot and garlic bulbs, and their effects on round scad during iced storage. Both the shallot and garlic extracts exhibited antioxidant activity concerning DPPH radical scavenging, total reducing power, and lipid peroxidation inhibition. The extracts also had antimicrobial activity against both Gram-positive (Bacillus cereus, Staphylococcus aureus) and Gramnegative (Escherichia coli, Salmonella typhimurium) pathogenic strains. Effects of treatment with the extracts on quality of round scad were evaluated by monitoring the total lipid hydroperoxides (HPO), thiobarbituric acid reactive substances (TBARS), total volatile basic nitrogen (TVB-N), total viable counts (TVC), and sensory characteristics. The spoilage indicators (HPO, TBARS, TVB-N, TVC) of the round scad treated with either shallot or garlic extracts were significantly suppressed during the ice storage period (P < 0.05). Round scad treated with either shallot or garlic extracts kept their natural sensory characteristics accepted for food-grade longer than 4 days of ice storage, compared with the control (without treatment). These results clearly show that the shallot and garlic extracts are potential natural preservatives, which can extend shelf-life of iced round scad.