Compositional and nutritional evaluation of viscera from commercially harvested wild-caught Australian abalones (Haliotis spp.)

Discarded abalone viscera accounts for 25-42 % weight of total abalone waste and represents a cost-burden to producers. Previous research has identified these discarded abalone viscera as having the potential for pharmaceutical, nutraceutical and therapeutical outcomes, which have not been investigated in Australian varieties. Thus, comprehensive nutritional evaluation was conducted on the viscera of four commercially harvested wild-caught abalone in Australia; roe's abalone (Haliotis roei), greenlip abalone (Haliotis laevigata), brownlip abalone (Haliotis rubra conicopora), and blacklip abalone (Haliotis rubra rubra) collected from various locations and processors. Proximate composition, amino acid, fatty acid and protein and fat algorithmic quality evaluation were investigated. Protein and fat quality evaluation demonstrated the opportunity for utilizing abalone viscera to potentially improve the health status of aging populations, as well as exercise performance. Such evaluations included high essential amino acid index (EAAI) (81-85), predicted biological value (p-BV) (77-81) and predicted protein efficiency ratio (p-PER) (2.44-2.48). Samples were shown to have a unique docosapentaenoic acid (DPA) and arachidonic acid (ARA)-dominated polyunsaturated fatty acid (PUFA) profile leading to a favorable index of atherogenicity (IA), index of thrombogenicity (IT), health-promoting index (HPI), and hypocholester-olemic/hypercholesterolemic (HH) values (0.95-1.36, 0.42-0.76, 0.74-1.05, 1.02-1.56). Challenges to valorisation in maintaining product consistency were identified with the noted variation in proximate composition (moisture: 72.96-79.97 %, protein: 55.82-68.04 % carbohydrates: 9.96-28.82 %, ash: 10.02-16.75 %, fat: 3.12-13.37 %). Multi-categorical regression identified external factors predominantly determine compositional results. The exception was amino acids characterization which remained consistent within and between species. This study provided an arching overview of the opportunities and challenges in utilizing abalone processing waste, as well as identifying future research directions in commercialization of viscera products. Such directions may include simultaneous hydrolytic recovery of macronutrients.