Melanosis Of Pacific White Shrimp Research Articles

Effective Treatment of Curry (Murraya koenigii) and Moringa (Moringa oleifera) Leaves Extracts on Melanosis of Pacific White Shrimp (Litopenaeus vannamei) during Chilled Storage

ABSTRACT This study investigated the treatment effect of curry leaves extract (CLE) and moringa leaves extract (MLE) on the melanosis of Pacific white shrimp during 15 days of chilled storage. These extracts have a high number of phytochemicals that have various therapeutic potentials. In this study, shrimp samples were divided into 4 groups; 1% CLE treated, 1% MLE treated, 1:1 (CLE+MLE) treated and control, and stored for 15 days. Biochemical indices and microbiological analysis wereperformedat 3 days interval. In this study, both extracts showed significant results on chemical indices, but highest qualitative results were obtained by the 1:1 (CLE+MLE) treated group. Among the treated groups, 1:1 (CLE+MLE) had a greater effect on microbial spoilage in comparison with the control group. This study revealed that CLE and MLE contain a variety of phytochemicals withdifferent properties that could be utilized as a natural substitute for synthetic antimelanosic agents used to control melanosis in shrimp.

Prevention of quality loss and melanosis of Pacific white shrimp by cashew leaf extracts

Inhibition of Pacific white shrimp polyphenoloxidase (PPO) by the selected Thai indigenous leaf extracts (Liang, Mun-poo, cashew and lead) was comparatively studied. Cashew leaf extract (CE) showed the highest PPO inhibitory activity and copper chelating activity at all concentrations (0.025–0.5%) tested (P < 0.05). Inhibitory activity was in a dose dependent manner. Epifisetinidol-4alpha-ol and hinokiflavone were identified as the most dominant polyphenols in CE using LC-DAD-ESI-MS/MS. Quality changes and melanosis of raw Pacific white shrimps treated with CE solution at various concentrations (0.1–1%) were monitored during refrigerated storage at 4 °C for 12 days. Microbiological analyses showed that shrimps treated with CE solution exhibited the lower total viable count, psychrophilic bacteria, Pseudomonas spp., H2S-producing bacteria and Enterobacteriaceae counts than the control throughout 12 days of storage (P < 0.05). Lower total volatile base content and thiobarbituric acid reactive substances were observed in shrimps treated with CE solution, compared to the control. Efficacy in quality maintenance of CE generally increased with increasing concentrations used. Shrimps treated with 1% CE solution and those treated with 1.25% sodium metabisulfite had the lowest melanosis scores throughout the storage (P < 0.05). Moreover, shrimps treated with 1% CE had the higher color and overall likeness scores, compared to the others, after the storage of 12 days at 4 °C. Therefore, soaking of raw shrimps in 1% CE solution for 30 min could be a promising method to prevent deterioration and melanosis during the extended refrigerated storage.

Effect of catechin and its derivatives on inhibition of polyphenoloxidase and melanosis of Pacific white shrimp

This study aimed to investigate the effect of tea catechin (C) and 4 of its derivatives on the Pacific white shrimp PPO inhibition and melanosis during refrigerated storage. Epigallocatechin gallate (EGCG) exhibited the highest inhibition towards PPO, followed by C. Inhibitory activity of all compounds tested was in a dose dependent manner (0.1-2.0mM). Based on activity staining, EGCG most effectively inhibited PPO. For inhibition kinetic studies, C and epicatechin (EC) showed uncompetitive type, whereas epicatechin gallate (ECG), epigallocatechin (EGC) and EGCG exhibited mixed type inhibition. When whole shrimps were treated with EGCG solution at various concentrations (0.25-0.75%), those treated with 0.5 or 0.75% EGCG had lower melanosis scores throughout storage for 10days at 4°C, compared with the control and the 1.25% sodium metabisulfite treated samples (P<0.05). Therefore, EGCG could be used as a potential inhibitor for melanosis in raw Pacific white shrimp during refrigerated storage.

Effect of pre-cooking times on enzymes, properties, and melanosis of Pacific white shrimp during refrigerated storage

Abstract Pre-cooked shrimp have gained interest due to their attractive color and flavor. However, shrimp without sufficient pre-cooking have faced melanosis, particularly during the extended storage. This leads to the rejection by consumers and the market. Therefore, pre-cooking with appropriate time would be a means to tackle such a problem. The objective of this study was to investigate the effect of pre-cooking times on enzyme activities, properties, microstructure, and melanosis of Pacific white shrimp (Litopenaeus vannamei). Pacific white shrimp were subjected to pre-cooking at 80°C for various times (0 to 120 s). The residual activities of polyphenoloxidase (PPO) and protease decreased with increasing pre-cooking times (p &lt; 0.05). Nevertheless, the increasing pre-cooking time resulted in more cooking loss. With cooking time above 60 s, a cooking loss of 9.85% was obtained (p &lt; 0.05). Marked decreases in the relative PPO and protease activities were observed within the first 30 s of pre-cooking, and negligible activities were detected after 120 s. The microstructure study revealed that the muscle fibers of pre-cooked shrimps were less attached with concomitantly higher shrinkage of the sarcomere, compared with those of the raw counterpart. Shrimps pre-cooked with longer time showed a lower development of black spots as evidenced by a lower melanosis score throughout storage of 7 days at 4°C. Therefore, a pre-cooking time of 30 s at 80°C was sufficient to lower PPO and protease activities with the minimized cooking loss and melanosis during refrigerated storage.

Effect of catechin and ferulic acid on melanosis and quality of Pacific white shrimp subjected to prior freeze–thawing during refrigerated storage

Melanosis of Pacific white shrimp ( Litopenaeus vannamei) subjected to freeze–thawing with different thawing methods and various cycles were monitored during subsequent refrigerated storage (4 °C) up to 4 days. Melanosis score was lower in Pacific white shrimp thawed at 4 °C, compared with that found in samples thawed at room temperature or using tap water. Polyphenol oxidase (PPO) activity increased as freeze–thaw cycles increased ( P < 0.05). Enhanced PPO activity was most likely associated with increased melanosis. Pacific white shrimp treated with catechin (0.05%, 0.1% and 0.2% (w/v)) or ferulic acid (1%, 2% and 3% (w/v)) and subjected to freeze–thawing with various cycles showed the retarded melanosis during the subsequent refrigerated storage of 4 days, compared with the control ( P < 0.05). Treatment of shrimp with both phenolic compounds could impede the growth of psychrophilic bacteria and the spoilage as evidenced by the lowered psychrophilic bacteria count and total volatile base content (TVB). Sample treated with 0.2% catechin or 3% ferulic acid also exhibited the retarded lipid oxidation during the subsequent refrigerated storage, compared with the control ( P < 0.05). Thus, either catechin or ferulic acid could be used as the potential additive to lower melanosis of shrimp with prior freeze–thawing.