2011/731 Optimising external colour in farmed crustaceans, using Penaeus monodon as a model species.

By Nick Wade

Consistent, deep red coloured cooked prawns are highly sought after in the Australian market and accordingly fetch premium market prices. Farmed crustacean species commonly have suboptimal colour consistency and/or colour intensity. There is an industry driven need to therefore optimise colour consistency and intensity of farmed crustacean product. This project sought to define the amount of colour variation that exists in farmed prawns, as well as test a recently established method for manipulating prawn colour.

It developed and validated three novel methods to quantify the colour of uncooked or cooked prawns. These methods were used to define the colour variation that existed in farmed prawns, and determined it was largely due to variation between ponds. This effect is likely to produce significant variability in product colour and therefore quality across a single farm, as well as between different farms. A number of interacting factors may have a role in causing this variation, including diet, harvest methods, pond substrate, the pond algal community and possibly harvest stress.

This work also quantified the effects of different harvest practices on prawn colour, and demonstrated that extended periods of ice storage, freeze thawing of uncooked product or harvesting into white holding bins was detrimental to cooked prawn colour. They were able to demonstrate that changes in pigment prior to processing are retained through cooking and storage. Based on these research findings, a series of pre-harvest recommendations have been developed to optimise colour in farmed prawns.