Quality and shelf-life extension of refrigerated (4°C) Spotted snakehead (Channa punctata) using γ-radiation and food-grade preservative

Investigations were carried out to evaluate the effect of gamma radiation (1.0 and 1.5 kGy) and food-grade preservative (2% potassium sorbate) on the shelf-life of refrigerated (4°C) Spotted snakehead, Channa punctata (Bloch, 1793). Quality assessments were evaluated by sensory (OS), chemical (TV), microbial (TBC and TCC) analyses. Based on control panel, OS was shown to be gradually decreased with the storage time. Irradiated and potassium sorbate treated samples were found acceptable (edible) up to 28 and 21 days, respectively of storage period. TV were lower in irradiated samples with dose of 1.5 kGy compared to other samples. Though microbial load of each of the irradiated samples were within the acceptable limits up to 28 days but 1.5 kGy dose was found more effective. Gamma radiation in combination with good refrigeration could be most effective treatment for the shelf-life extension and microbiological quality improvement for snakehead preservation. Moreover, this preservation technique may be applicable for other fish species to enhance food safety for public health issues. Jahangirnagar University J. Biol. Sci. 9(1 & 2): 1-12, 2020 (June & December)

Water hyacinth (Eichhornia crassipes) leaves enhances disease resistance in Channa punctata from Vibrio harveyi infection

Background Channa punctata, Indian spotted snakehead, has a great economic value in south and south-east Asia being an important protein source for humans. Fish cultures are affected due to various bacterial and viral infections. Vibrio harveyi is a fish pathogenic bacteria which causes several outbreaks throughout the world and leads to huge mortalities. In this study, leaves of Eichhornia crassipes (water hyacinth) were used to investigate its immunostimulatory potential in Channa punctata. Results The immunostimulatory effects of water hyacinth leaves were studied in fish fed with 2.5% and 5% supplementary feed (experimental groups) in comparison to normal feed (control groups). Gas chromatography mass spectrometry (GC-MS) analysis of E. crassipes methanol extract showed presence of various components which have immunostimulatory, antioxidant, antibacterial, and anti-inflammatory activities. The antibacterial activity, antioxidant potential, and presence of phenol and flavonoids in methanol and ethanol extracts supported its use in fish feed. The healthy acclimatized fish were challenged with V. harveyi weekly. Liver function tests, alkaline phosphatase levels, and immunoglobulin content in the experimental groups were improved with respect to those in the positive control group. The spleen and head kidney were obtained at the final day of experiment, and macrophages were isolated; higher percentage of phagocytosis and phagocytic index indicated enhanced cell-mediated immune response in fish due to supplemented feed. Conclusion Plant-infused feed with leaves of E. crassipes can be recommended as a regular feed supplement to enhance fish immunity and disease resistance against the V. harveyi infection.