Color of rainbow trout (Oncorhynchus mykiss) fillets by image and sensory analysis, and correlation with SalmoFan numbers.

72 male and 50 female trout (Oncorhynchus mykiss) fillets were weighed (range 328-794 g, mean 546.2±101.8 g; and range 426-994 g, mean 672.2±106.1 g, respectively), their pictures were taken in a light box, and image analysis was done to measure pixel colors, length and view area of the fillets. Weight (W) was predicted using view area (V) obtained by image analysis using linear (W = A + BV), and power (W = A VB ) equations. R2 values were between 0.823 and 0.937. While there was no difference between mean L* and a* values of male and female fillets, significant differences were found between mean b* values (p< .05). The colors of SalmoFanTM (SF) mini were also measured by image analysis and their mean L*, a*, b* values, their Entire Color Index (ECI) and reduced RGB values from 122 images were calculated. 96 untrained panelists were asked to select the SF color of 5 representative fillets, and to designate which point on the fillet image best described the SF color chosen. To predict SF numbers of the fillets by image analysis 4 cases were considered: a) whole fillet, b) whole fillet with pixels a*>25, c) a rectangle along the length of the fillet to approximate panelists' selection, d) pixels in this rectangle with a*>25. Mean L*a*b* values, mean reduced RGB values, mean ECI of the 4 cases were used to predict fillet SF numbers. Different results obtained imply that image analysis can do repeatable and objective SF color classification of fillets, depending on the pixel selection method, and the color representation. PRACTICAL APPLICATION: Rainbow trout fillets can be assigned SalmoFan numbers using image analysis of the fillets. However, the selection of pixels, and the color representation method affect the results. If these are standardized, SalmoFan numbers can be assigned objectively and automatically.