Green extraction methods using a combination of mechanical, enzymatic, and green chemical treatments were evaluated for the sequential extraction of carotenoid pigments, protein, and chitin from crab processing discards. Key objectives included avoiding the use of hazardous chemical solvents, conducting as close to a 100% green extraction as possible, and developing simple processes to facilitate implementation into processing plants without the need for complicated and expensive equipment. Three crab bio-products were obtained: pigmented vegetable oil, pigmented protein powder, and chitin. Carotenoid extractions were performed using vegetable oils (corn, canola, and sunflower oils), giving between 24.85% and 37.93% astaxanthin recovery. Citric acid was used to demineralize the remaining material and afforded a pigmented protein powder. Three different proteases were used to deproteinate and isolate chitin in yields between 17.06% and 19.15%. The chitin was still highly colored and therefore decolorization was attempted using hydrogen peroxide. Characterization studies were conducted on each of the crab bio-products isolated including powder X-ray diffraction analysis on the chitin (80.18% crystallinity index, CI, achieved using green methods). Overall, three valuable bio-products could be obtained but further research is needed to obtain pigment-free chitin in an environmentally friendly manner.
Keywords: astaxanthin; carotenoprotein; chitin; citric acid; eco-friendly; green extraction; marine bio-products; processing discards; snow crab; vegetable oil.