Comparison of fatty acid profiles of dried and raw by‐products from cultured and wild fishes

Abstract

Fish by‐products may become alternative sources of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, due to the high enzymatic activity in these biological tissues, special care must be taken to prevent lipid oxidation and hydrolysis. In this work, several by‐products from Chilean fishes (farmed salmon and wild red cusk‐eel and yellowtail kingfish) were dried at 105°C for 3 h to remove water and inactivate enzymes. The effect of temperature on EPA and DHA levels was assessed by comparing fatty acid profiles of raw and dried by‐products. Drying at 105°C for 3 h was considered an adequate process to obtain dried powders from fish by‐products with appreciable amounts of EPA and DHA, even though EPA and DHA values showed a certain decrease after drying. Several methodologies involving food‐grade solvents were checked to evaluate their suitability for lipid extraction from dried by‐products, being Soxhlet extraction with n‐hexane identified as the most suitable process in terms of extraction yield and EPA/DHA values. Cholesterol amount was also studied, being the highest and lowest amounts found in liver and viscera from farmed salmon, respectively. Practical applications: In fish processing plants, raw by‐products are collected after fish evisceration, and they can be transported to oil extraction facilities, although their lipids may be easily degraded unless special precautions are taken to preserve such biomass. Raw fish by‐products must be subjected to water removal and enzyme inactivation to prevent lipid degradation and hydrolysis, and it is desirable that such actions are carried out in the processing plants themselves to ensure the maximum oil quality. Drying at 105°C for a short time (3 h) was assayed in this work because of its simplicity, low cost, scalability, and feasibility to be installed in fish processing plants. Soxhlet procedure with n‐hexane is effective to extract lipids containing EPA and DHA from dried by‐products for nutritional or nutraceutical purposes. Because of water removal, lipid extraction efficiency from dried by‐products is enhanced and less solvent is needed, which is economically and environmentally desirable. Raw by‐products from cultured and wild fishes are dried at 105°C for 3 h and fatty acid profiles are compared between raw and dried by‐products to assess the potential decreasing effect of temperature on the levels of polyunsaturated fatty acids, especially EPA and DHA. Different lipid extractions using solvents are also compared to check their influence on fatty acid profiles. Additionally, cholesterol amount is quantified in the lipid fraction extracted from dried fish by‐products.

Nutritional and bioactive oils from salmon (Salmo salar) side streams obtained by Soxhlet and optimized microwave-assisted extraction

“…More quantity of oil was also determined in salmon viscera than in a mixture of salmon heads and frames by Liu et al (2020). In addition, SE with nhexane as a solvent was applied to dried salmon viscera (excluding liver), obtaining an oil percentage of 65% (Rincón-Cervera, Villarreal-Rubio, Valenzuela, & Valenzuela, 2017).…”

“…Despite the use of different extraction techniques, the composition of the most representative fatty acids seems to remain stable in heads, viscera and backbones of Atlantic salmon. According to Rincón-Cervera et al (2017), application of temperatures above 100 • C (not used in these studies) could affect the fatty acids that are more susceptible to thermal degradation and, therefore, modify the lipid profile. In addition, microwave energy did not alter the fatty acid composition of fish muscle (dos Costa & Bragagnolo, 2017).…”

Quality of red tilapia viscera oil (Oreochromis sp.) as a function of extraction methods

“…This method is widely used for oil extraction for analytical purposes [ 11 ], and was therefore used as a reference method in this study. To obtain the oil, 600 g of viscera were triturated and homogenized for 1 min in a food processor model FP1336 (Black & Decker, United States), then divided into three containers in equal amounts (200 g) and immersed for 2 h at 20 °C in a dichloromethane-methanol mixture (2:1), in a 2:1 solvent-viscera ratio, in order to prevent oxidation of the tissues by the action of endogenous enzymes [ 20 ]. Subsequently, they were subjected to ultrasound in a Branson 5510R-DTH (Bransonic, United States) for 20 min and suction filtration was performed with gauze and Whatman No.…”

Métodos de extracción, refinación y concentración de aceite de pescado como fuente de ácidos grasos omega-3

“…Existen varios métodos que varían de acuerdo con el tipo de solvente o tratamiento de la muestra. Los más comunes son los de Soxhlet y Bligh-Dyer, pero también se han evaluado otros, como el de McGill-Moffatt, así como los de Randall y de Folch (Fiori et al, 2012;Immanuel et al, 2009;Rincón-Cervera, Villarreal-Rubio, Valenzuela, & Valenzuela, 2017).…”

“…Se han aplicado para la extracción de aceite de pescado como única tecnología (Adeniyi & Bawa, 2006;Boran, Karaçam, & Boran, 2006;Kołakowska, Domiszewski, Kozłowski, & Gajowniczek, 2006;Shamsudin & Salimon, 2006), así como en estudios comparativos con otros métodos (Chakraborty & Joseph, 2015a;Fiori et al, 2012;Immanuel et al, 2009;Létisse, Rozières, Hiol, Sergent, & Comeau, 2006;Rincón-Cervera et al, 2017;Sahena et al, 2010; Silva-Aguiar & Soares-Goulart, 2013) (tabla 2). La EFSC es una tecnología emergente de extracción por solventes, que ha ganado gran interés en años recientes, debido a ventajas como el uso de temperatura moderada, ambiente libre de oxígeno y extracción de lípidos de baja polaridad, lo cual evita la extracción de impurezas (Rubio et al, 2012).…”