Developing a chromatic value for determining melanosis of high pressure processed snow crab (Chionoecetes opilio) clusters by digital imaging

Melanosis is an important shelf-life limiting factor of both fresh and processed (i.e., cooking and high pressure processing) snow crab (Chionoecetes opilio) clusters, as it gives an unpleasant discolouration. A cluster includes four walking legs, and one claw attached to a shoulder joint. To be able to give a fast and objective measurement of melanosis, a chromatic value using analysis of digital images of high pressure processed clusters (0.1-600 MPa) has been developed and tested against sensory melanosis judgment by three trained assessors. Using L* and b* values from 35% of the pixels in the picture of the clusters gave a chromatic melanosis value with a significant (p < 0.001, r(2) = 0.7984) linear regression against sensory melanosis score. The prediction error was 0.47 points. This shows that melanosis can be assessed by determining the defined chromatic value on a pixel level using digital imaging.