Image analysis-based quantification of the visual attributes of fish, with emphasis on color and visual texture

Images of Red Sea goatfish Parupeneus forsskali were taken in a light box to perform color and visual texture analyses. The average L* and b* values did not change significantly during storage of 7 days, but the a* values decreased (P < 0.05). The change of visual texture parameters energy and entropy (calculated based on histograms, and based on co-occurrence matrices [COM]), box counting-based fractal results, and texture change index (TCI) values are presented. The appearance of fish became smoother over time. The entropy values calculated by histograms decreased with storage (P 0.05), and the maximum range was 0.395. That for COM-based entropies was 71.96. TCI also decreased with storage (P 0.05) with a maximum range of 10.67. However, energy values increased during storage. The maximum range of the energy values calculated by histograms over time for any color channel was 0.0036. That for COM-based energies was 5.7. There was no observable change in fractal dimension. These image analysis-based parameters were compared with sensory analysis. A trained sensory panel evaluated the visual texture of a sub-set of images. The R-2 values for equation fit between sensory score and texture features were, in increasing order: COM based energy (0.185), COM-based entropy (0.313), histogram-based energy (0.375), histogram-based entropy (0.386), TCI values (0.575). Since TCI correlated better with sensory values, it is recommended to be used in this type of visual texture evaluation.

Automated summary

Images of Red Sea goatfish were analyzed to evaluate changes in color and visual texture during a 7-day storage period. The results showed that while L* and b* values remained relatively stable, a* values decreased significantly. The visual texture of the fish became smoother over time. Sensory analysis results were compared with image analysis parameters, and it was found that TCI values had the best correlation with sensory scores.