Upcycling of Mud Crab Shell Waste as a Natural Source of Carotenoids: A Comparative Study of Scylla olivacea and Scylla paramamosain

Abstract

Mud crab shell waste is a food waste generated from crab processing and represents an underutilized by-product with the potential to serve as a natural source of carotenoids, particularly astaxanthin. This study aimed to compare the carotenoid extraction yield and astaxanthin content of shell extracts from Scylla olivacea and Scylla paramamosain. Carotenoids were extracted using 95% ethanol through three successive extraction cycles. The extraction yield was determined for each extraction cycle, while the presence and concentration of astaxanthin were analyzed using high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD). The results showed that the highest extraction yield was obtained during the first extraction cycle for both species and decreased in the subsequent cycles. Scylla olivacea showed a higher extraction yield than S. paramamosain. HPLC-DAD analysis confirmed the presence of astaxanthin in both species, with S. olivacea showing a significantly higher astaxanthin concentration (20.12 ± 0.36 µg/mL) than S. paramamosain (11.31 ± 0.08 µg/mL) (p < 0.05). The astaxanthin peak was detected at a retention time of approximately 8.5 min, consistent with the astaxanthin standard. In conclusion, mud crab shell waste, particularly S. olivacea, has potential for valorization as a natural source of carotenoids and astaxanthin. Further studies are recommended to optimize the extraction process and evaluate the stability and potential applications of the recovered astaxanthin. This approach may contribute to reducing food waste while promoting the utilization of crab processing by-products as value-added resources.