A circular economy approach for the processing of fisheries waste: Pressure-intensified extraction of valuable products from fish roes

Abstract

The urgent need for environmental protection and human health preservation is forcing industrial processes to adopt a circular economy scheme. This transformative approach aims to minimize waste generation, maximize resource efficiency, and foster sustainability. While advancements in technology have revolutionized many industries, the fishing industry has historically lagged behind in adopting these innovations, particularly in the treatment of byproducts and waste recovery. Currently, fish by-products are utilized in the production of fish oil, fishmeal, fertilizers, and feed for pets and livestock [1]. These products often have a limited economic value, which poses challenges in implementing advanced technologies that could improve their utilization. Fish viscera contain added-value components that are not fully exploited. In particular, fish roes stand out for their high content of polyunsaturated fatty acids (PUFAs), especially omega-3 fatty acids, which are highly valuable in the food, cosmetic, and pharmaceutical industries [2]. Furthermore, the roes contain secondary metabolites that protect themselves from the substantial exposure to UV rays they suffer in their natural environment. These remarkable photoprotective attributes are derived mainly from gadusol and gadusol derivatives, which are highly polar compounds with great potential in the cosmetic industry for use in sunscreen formulations [2,3]. The conventional methods used to extract these highadded-value components from fish roes often rely on the use of toxic organic solvents, which pose risks to both the environment and human health. In addition, these procedures involve lengthy and energy-intensive separation steps, further adding to their inefficiency. Therefore, it is crucial to explore efficient and environmentally friendly alternatives. In this context, extraction and fractionation techniques based on pressure-intensified technologies, particularly those involving the use of supercritical fluids, emerge as an appealing solution [4]. In this work, omega-3-rich oil was extracted from dried roes of aquacultured Wreckfish (Polyprion americanus) using supercritical CO2 (scCO2) with and without ethanol as a cosolvent. At a temperature and pressure of 313 K and 35 MPa, respectively, an extraction yield of fatty acids of approximately 7.0 % relative to the dry weight of the roes was achieved. According to the chemical profile, the extracted fatty acids consist of 30.0 wt. % saturated fatty acids (SFAs), with palmitic acid (C16:0) as the predominant component (61.0wt. % of total SFAs), 36.9 wt. % monounsaturated fatty acids (MUFAs), with oleic acid (C18:1n9) as the main constituent (55.5 wt. % of total MUFAs), and 32.9 wt. % PUFAs, from which omega-3 fatty acids account for 92.1 wt. % and omega-6 fatty acids account for 7.9 wt. %. While DHA (C22:6n3) and EPA (C20:5n3) were identified as the primary omega-3 fatty acids (85.5wt. %and 9.9 wt. % of total omega-3 fatty acids, respectively), linoleic acid (C18:2n6) was determined to be the predominant omega-6 fatty acid (65.4 wt. % of total omega-6 fatty acids). Both the yield and chemical profile of the extracted fatty acids remained similar regardless of the addition of ethanol as a cosolvent. However, when pure scCO2 was used for the extraction, the highly polar compound gadusol was not extracted, and hence, its concentration in the roesremained unaltered. In contrast, the addition of ethanol at a cosolvent-to-feed mass ratio of 5 g/g resulted in a 30 wt. % reduction in the gadusol content of the roes after the extraction. The proposed approaches allow for the efficient extraction of valuable compounds from fish by-products while minimizing waste generation and environmental impact. Thus, the adoption of supercritical fluid technologies presents a promising alternative for the fishing industry's transition toward sustainability.