Supercritical CO2 Fluid Extraction and Microencapsulation of Oil from Anchovy (Engraulis mordax) By-Products

Abstract

Research background: Fish by-products are discarded as waste, which has a significant impact on the environment. They have no economic value, but there are many opportunities to turn them into high value products. Due to significant quantities generated internationally and the continuous expansion of the market for ω-3 and ω-6 fatty acids as nutraceuticals, innovative technological approaches are needed to transform this waste into marketable products with added value, while limiting the risk of environmental pollution.

Experimental approach: In this study, two temperatures (40 and 60 °C) at a constant pressure during the extraction of anchovy by-products with supercritical CO₂ fluid were used to determine extraction yield, fatty acid, tocopherol and phytosterol composition, followed by microencapsulation with two matrices based on the transglutaminase-mediated crosslinking reaction between whey protein isolates and casein. Before microencapsulation, the binding parameters were estimated using quenching studies.

Results and conclusions: The results showed a higher content of total fatty acids when extracted at 40 °C, resulting in two fractions on a dry mass basis of (712±12) mg/g in the fraction obtained in the separator with code S40 and (732±10) mg/g in the fraction obtained in the separator with code S45, respectively. The monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs) accounted for 40-44 %. The extracts showed a higher mass fraction of eicosapentaenoic acid ((28.7±1.0) mg/g) in fraction S45 when extracted at 60 °C. A minimum inhibitory and bactericidal concentration of 0.66 μg/mL against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 was found for all fractions. Higher binding constants were found for palmitoleic and oleic acids than for palmitic acid. The control variant, without crosslinking, enabled the microencapsulation of a higher amount of fatty acids, while in both powders the sum of MUFAs and PUFAs was 40 %.

Novelty and scientific contribution: The approaches used in our study open up new opportunities for adding value to the fish by-products through extraction and microencapsulation, extending their potential use to food, cosmetics and nutraceuticals.

Keywords: anchovy by-products; binding constants; polyunsaturated fatty acids; supercritical extraction; transglutaminase-mediated crosslinking.

Fig. 1

Fluorecence emission spectra of the isolated whey protein and casein matrices without (C₀) (grey dotted line) and with (T₀) transglutaminase-mediated crosslinking (black dotted line)

Fig. 2

Dark-field hyperspectral images (DF-HSI) of the isolated whey protein and casein matrices: a) without (C₀) and b) with transglutaminase-mediated crosslinking (T₀), and microencapsulated extract of anchovy by-products: c) without (C_m) and d) with transglutaminase-mediated crosslinking (T_m)

Fig. 3

Mapping of the spectral profiles of control sample (T₀; white) vs microencapsulated fish oil sample (T_m; red) using CytoViva HSI optical microscopy