Effect of Green Tea Extract in Combination with Ascorbic Acid on the Retardation of Melanosis and Quality Changes of Pacific White Shrimp During Iced Storage

Abstract

Melanosis and quality changes of Pacific white shrimp (Litopenaeus vannamei) treated with 0.1% green tea extract (GTE) in combination with ascorbic acid (AA) at different levels (0%, 0.005%, and 0.01%) were monitored during iced storage of 12 days. Based on in vitro study, 0.1% GTE inhibited polyphenoloxidase (PPO) from cephalothorax of Pacific white shrimp by 60.2%. Nevertheless, 0.1% GTE in combination with 0.01% AA exhibited the greater PPO inhibitory activity (93.0%) (P < 0.05). When shrimp treated with 0.1% GTE in combination with AA (0.005 or 0.01%; GTE + AA), the increase in psychrophilic bacteria and spoilage microorganisms including H2S- producing bacteria and enterobacteriaceae were retarded to a higher extent, in comparison with the control and those treated with 1.25% sodium metabisulfite (SMS; P < 0.05). The coincidental lowered rates of increase in pH, total volatile base content and thiobarbituric acid reactive substances were obtained in the shrimp treated with GTE + AA (P < 0.05). Additionally, shrimp treated with GTE + AA had the lower melanosis score but higher score for color, odor, taste, flavor, and overall likeness, compared with the control and those treated with SMS (P < 0.05). Generally, AA at levels of 0.005% and 0.01% showed a similar synergist effect with GTE on both melanosis inhibition as well as retardation of quality loss of shrimp.