Ethanolic guava leaf extracts with different chlorophyll removal processes: Anti-melanosis, antibacterial properties and the impact on qualities of Pacific white shrimp during refrigerated storage

Ethanolic guava leaf extract (EGLE) without chlorophyll removal (GLE-C) and those with chlorophyll removal using sedimentation process (GLE-S) or dechlorophyllization using chloroform (GLE-Ch) were prepared. Antibacterial and anti-melanosis properties of all extracts were examined. All extracts showed promising antibacterial properties, polyphenoloxidase inhibitory activity and copper chelating activity. These activities were highest in GLE-S (P < 0.05). Piceatannol 4′-galloylglucoside, epicatechin, 8-hydroxyluteolin 8-sulfate, quercetin 3-(2′'-galloyl-alpha-L-arabinopyranoside), and aclurin 3-C-(6′'-p-hydroxybenzoyl-glucoside) were dominant in GLE-S. When Pacific white shrimp were treated with GLE-S at different concentrations (0.5 and 1), the quality changes were monitored compared to those treated with 1.25 sodium metabisulphite (SMS-1.25) and the control (without any treatment) during 12 days of storage at 4 °C. Changes in microbial and chemical qualities were lower in shrimps treated with GLE-S solution as compared to others. Therefore, melanosis and quality deterioration were effectively reduced by pretreating shrimps in GLE-S before refrigerated storage.