A paper-based Colorimetric Indicator Label using Natural Dye for Monitoring Shrimp Spoilage

Shrimp is a type of perishable food. This study developed a simple indicator label using colorimetric method for monitoring shrimp freshness. This indicator label was made from natural dye extract of Ruellia simplex flowers which immobilized on cellulose paper by dip coating method. The indicator labels were used for examining freshness of shrimp. In this experiment, shrimp were stored in sealed bottles that have been labeled using the indicator and stored at 13 degrees C, 25 degrees C, and 40 degrees C for a certain range of time. Color changes of the indicator labels were observed using digital photography after shrimp storage for 0 h, 2 h, 17 h and 24 h. The color changes that occur were quantified and analyzed using the ImageJ program. The color of the indicator label when detecting the fresh shrimp was pink and after the shrimp spoilage began, the color of the label changed to purple and then became yellow when the shrimp is badly spoilage. The color change rates of label indicator increases as the shrimp storage temperature increased. These results indicate that this label indicator can be used as an indicator of the freshness of shrimps and it is not toxic and safe for food.