Effects of green tea- and amla extracts on quality and melanosis of Indian white prawn (Fenneropenaeus indicus, Milne Edwards, 1837) during chilled storage

Effect of ethanol extracts of green tea (Camellia sinensis L.) and amla (Phyllanthus emblica Linn) were investigated on quality and melanosis of chilled stored Indian white prawn (Fenneropenaeus indicus) during 28 days. Extracts were subjected to antioxidant assays viz.1,1-diphenyl-2-picryl hydrazyl radical reducing power methods (DPPH), total antioxidant capacity (TAC), total phenolic content (TPC) and ferric reducing antioxidant power(FRAP) to evaluate antioxidant potentiality and fourier-transform infrared spectroscopy (FT-IR) to identify organic constituents. Polyphenol oxidase (PPO) inhibition was assessed to check the efficacy of the extracts as anti-melanogenic agents. Biochemical (total volatile nitrogen, free fatty acid and peroxide values), bacteriological (aerobic counts), melanosis inhibition and sensory quality of chilled stored shrimp were addressed to investigate the efficacy of extracts as preservative and anti-melanogenic remedy. Free reducing power of green tea - and amla extracts were in a range of 28.72–65.67%and 17.38–66.95%, respectively. Phenolic content level was almost same for green tea and amla extract (2.46 ± 0.002 and 2.51 ± 0.036 mg GAE/gram). Total antioxidant capacity of green tea (210.33 ± 4.63 mg EqAsc/g) was slightly higher than that of amla extracts (145.56 ± 1.98 mg EqAsc/g). FRAP value revealed that green tea(477.49 ± 3.25 mgE Fe (II)/g) had more ferric reducing power than amla (324.39 ± 5.85 mgE Fe (II)/g).FT-IR analysis revealed the presence of essential organic bioactive compounds, which play an important role in reducing lipid oxidation and quality loss, and both extracts possess an encouraging PPO inhibition ability. Treatment by green tea - and amla extracts on chilled stored shrimp showed promising effects on biochemical and microbiological parameters followed by melanosis inhibition and enhanced sensory attributes. Treated Indian white prawn with green tea – and amla extract revealed significantly (P < 0.05) lower value of biochemical indices and microbial load during chilled storage compared to untreated sample.