ABSTRACT
World shrimp production (capture and aquaculture) touched 7.0 million tonnes in 2015. Process wastes represent up to 70% of original weight. In order to minimize the problem of disposal and also to generate additional income, several attempts have been made to separate high-value functional and bioactive components, such as protein, carotenoprotein, lipids, chitin, minerals, sterol, flavorant protein and enzymes, from waste. The natural carotenoids in process wastes vary from 26 to 50 ppm. Carotenoproteins (CP) are stable complexes in which carotenoids are bound to a high density lipoprotein. Astaxanthin in complex gives a blue to green color in shrimps and is the major pigment (67.4–70%) among carotenoids. Minor pigments are β-carotene, canthaxanthin, lutein and zeaxanthin. Unfavorable temperature/pH/salt concentration/solvent produces a red-orange colour in shrimp and its process waste due to free astaxanthin released from CP. Different methods of extraction of CP from process wastes are described using different commercially available proteases in controlled/optimum process conditions followed by precipitation of CP at iso-electric pH, with the objective to get stable product. The recovery of carotenoids is 80–90% by trypsin ( 45°C), 60–84% by pepsin (45°C) and 70–75% by papain (55°C) depending on the type tropical shrimp waste. CP (150–270 ppm carotene) frozen and stored at –20°C lost less than 20% carotene in 12 months. Freeze-dried CP with concentrated carotene (800–900 ppm), protein (40%) and lipid (40%) needs the addition of antioxidant and storage in amber glass bottles at 5–10°C to prevent lipid oxidation. Other valuable products, protein isolate (30–40% protein) and chitin, are separated during the process. Carotenoprotein isolate, with increased antioxidant activity, can be prepared by hydrolyzing white shrimp waste at a higher temperature of 50°C with higher alcalase concentration of 0.5% for a shorter duration (< 4hr); the resultant carotenoprotein isolate with high antioxidant activity finds its use in food and feed applications. Astaxanthin in CP has approximately 500 times higher antioxidant capacity than that in alpha-tocopherol. The demand of CP, a natural flesh colorant, in shrimp/fish/poultry feed has been growing due to health considerations over the use of synthetic astaxanthin. Astaxanthin and β-carotene play the role of a precursor of vitamin A. 100–200 ppm dietary astaxanthin improves resistance to bacterial and viral infection in tiger shrimp. The non-allergic natural form of CP is considered for cosmetic applications.
