Active exopolysaccharides based edible coatings enriched with red seaweed (Gracilaria gracilis) extract to improve shrimp preservation during refrigerated storage

Active edible coatings from microalgal exopolysaccharides (EPS) enriched with different concentrations of red seaweed extract (RSE) (0.5, 1 and 1.5% (w/v)) were developed and their effects on shrimp quality with refrigerated storage (4 +/- 1 degrees C) were studied over a period of 8 days. Untreated and treated shrimp were regularly evaluated bacteriologically (total viable bacteria, psychrotrophic bacteria and Enterobacteriaceae counts), chemically (pH, TVB-N, TMA-N, PV, TBARS), texturally and sensorially. The coating of a mixture of EPS and RSE, significantly reduced (p < 0.05) TVB-N, TMA and TBARS values. With storage, EPS coatings containing RSE at 1 and 1.5% were most effective in the inhibition of the enumerated bacterial species, especially psychrotrophic bacteria. Also, EPS + RSE coated samples had lower polyphenol oxidase activity and better oxidative stability (p < 0.05) until the end of shelf life. Generally, EPS coatings significantly improved hardness and color of shrimp. Moreover, sensory evaluation showed that the initial sensory attributes of shrimp were not significantly affected with any treatment. Overall, the results showed that the application of EPS-based coating treatments led to a quality improvement and extended shelf life of refrigerated shrimp.