Quantitative Methods to Measure Pigmentation Variation in Farmed Giant 1 Methods on Cooked Colour. 3 4

18 Cooked prawn colour is known to be a driver of market price and a visual 19 indicator of product quality for the consumer. Although there is a general 20 understanding that colour variation exists in farmed prawns, there has been no 21 attempt to quantify this variation or identify where this variation is most 22 prevalent. The objectives of this study were threefold: firstly to compare three 23 different quantitative methods to measure prawn colour or pigmentation, two 24 different colorimeters and colour quantification from digital images. Secondly, to 25 quantify the amount of pigmentation variation that exists in farmed prawns 26 within ponds, across ponds and across farms. Lastly, to assess the effects of ice 27 storage or freeze-thawing of raw product prior to cooking. Each method was able 28 to detect quantitative differences in prawn colour, although conversion of image 29 based quantification of prawn colour from RGB to Lab was unreliable. 30 Considerable colour variation was observed between prawns from different 31 ponds and different farms, and this variation potentially affects product value. 32 Different post-harvest methods prior to cooking were also shown to have a 33 profound detrimental effect on prawn colour. Both long periods of ice storage 34 and freeze thawing of raw product was detrimental to prawn colour. However, 35 ice storage immediately after cooking was shown to be beneficial to prawn 36 colour. Results demonstrated that darker prawn colour was preserved by 37 holding harvested prawns live in chilled seawater, limiting the time between 38 harvesting and cooking, and avoiding long periods of ice storage or freeze 39 thawing of uncooked product. 40 41 42