Effect of natural antimicrobial extracts on shelf-life extension and quality improvement of the flounder sikhe

Abstract

Flounder sikhe is one of the traditional Korean fermented foods. Because honey, fucoidan, propolis, aronia berry, and horseradish are well known to have natural antimicrobial properties, we investigated their antimicrobial effects on improving the quality of flounder sikhe. Ethanol extracts of propolis inhibited the growth of Bacillus cereus, Staphylococcus aureus, and Listeria monocytogenes. The extracts of aronia berry showed similar effects against Salmonella Typhimurium. We also assessed the total polyphenol and total flavonoid content and 2,2-diphenyl-2-picrythydrazyl (DPPH) radical scavenging activity in the extracts obtained from these natural materials. The contents of polyphenols and flavonoids were the highest in propolis, which also showed a high DPPH radical scavenging activity. Therefore, addition of propolis 0.5% to flounder sikhe showed optimal improvement, with a storage stability of 15 days at pH 5.39, volatile basic nitrogen (VBN) content at 24.73 mg/100 g, and total bacterial count at 1.81×10 colony forming unit (CFU)/g.