This work examines the potential valorization of mullet roe by-products for the production of mullet roe oil using mild processes. Three different extraction methods with potential of scale-up for the food industry, namely pressure (PE), supercritical fluid extraction (SFE), and solvent extraction (SE) are examined. Mild temperature conditions to prevent oil oxidation and (wherever applicable) food-grade solvents are used. The oil yield, the composition of oils in fatty acids by GC-FID, the level of oil oxidation (peroxide value (PV), p-anisidine value (AV), K 232 K 268 , TOTOX)) and the antioxidant activity (DPPH, ABTS) are determined. SE provided the highest oil recovery, followed by SFE and PE (68%, 28% and 10% respectively). The extracted oils had a high concentration of EPA and DHA and a total of 20.7%-24.3% of identified PUFAs among the fatty acids. Oxidation was the lowest in the SFE extracted oil followed by PE, PV was <2.5 meq O2 , AV≤10 and TOTOX <15 in all examined oil samples. Further research is needed to optimize processing conditions for the increase in oil recovery.

Striped mullet (Mugil cephalus) roe is used for the production of high nutritional and added‐value delicacies. Its lipid fraction is rich in polyunsaturated fatty acids (PUFA) and bioactive compounds. This study examines scalable oil extraction methods for mullet roe oil extraction. Namely, solvent extraction (SE) using ethanol in two different temperatures, supercritical fluid extraction (SFE) using CO2‐ethanol mixture (SFE‐E) in two different temperatures, expeller oil press (EP) extraction, expeller oil press combined with ethanol extraction (EP‐SE) and wet reduction (WR) are examined. The methods are evaluated with regard to the oil yield and recovery, the oil oxidation and the composition in fatty acids, and polar compounds and unsaponifiable matter. EP‐SE and SE provide the highest oil recovery for tested extraction temperatures (76% and 65% respectively), followed by SFE‐E (46%) and EP (36%). Extracted oils present high PUFA content (28.5–33.9%). The type of extraction process and the process variables affect oil oxidation as well as the concentration of polar compounds and unsaponifiable matter. In terms of oxidation levels, 85% of the extracted oil samples were within the limits set by the Codex Alimentarius Commission. The potential of the examined methods for industrial mullet roe oil production is discussed. Practical applications: Oil rich in polyunsaturated fatty acids was extracted from stripped mullet roe. The work proposes several scalable extraction methods using mild conditions which could be applied to obtain edible and high nutritional value mullet roe oil with high recovery reaching up to 76%. The same methods could be employed also for mullet roe by‐products. The obtained results improve the knowledge regarding the potential of roe valorization for oil extraction as well as the effect of the extraction method on the oil yield, main composition features and the quality characteristics of oil extracted by mullet roe. This research could offer new opportunities for the food industry for fish roe valorization for high nutritional quality oil production.

In this work, alginate-chitosan microgel particles were formed at different pH levels with the aim of using them as viscoelastic interfacial layers, which confer emulsion stability to food systems. The particles’ size and structural characteristics were determined using laser diffraction, confocal laser microscopy (CLSM), and time-domain nuclear magnetic resonance (TD-NMR). The pH affected the microgel characteristics, with larger particles formed at lower pH levels. T2 relaxation measurements with TD-NMR did not reveal differences in the mobility within the particles for the different pH levels, which could have been related to the more or less swollen structure. The rate of adsorption of the particles at the sunflower oil–water interface differed between particles formed at different pH levels, but the equilibrium interfacial tension of all systems was similar. Higher interfacial dilatational viscoelasticity was obtained for the systems at lower pH (3, 4, 5), with G’ reaching 13.6 mN/m (0.1 Hz) at pH 3. The interfacial rheological regime transitioned from a linear elastic regime at lower pH to a linear but more viscoelastic one at higher pH. The thicker, highly elastic interfacial layer at low pH, in combination with the higher charges expected at lower pH, was related to its performance during emulsification and the performance of the emulsion during storage. As revealed by laser diffraction and CLSM, the droplet sizes of emulsions formed at pH 6 and 7 were significantly larger and increased in size during 1 week of storage. CLSM examination of the emulsions revealed bridging flocculation with the higher pH. Nevertheless, all emulsions formed with microgel systems presented macroscopic volumetric stability for periods exceeding 1 week at 25 °C. A potential application of the present systems could be in the formation of stable, low-fat dressings without the addition of any emulsifier, allowing, at the same time, the release of the bioactive compounds for which such particles are known.

Striped mullet (Mugil cephalus) roe is used for the production of traditional delicacies in Greece (avgotaracho), Japan (karasumi) and Italy (botargo). In Greece avgotaracho is a Protected Designation of Origin product and its special taste combined with its high nutritional value of this rich in polyunsaturated fatty acids (PUFA) and bioactive compounds delicacy attracts many consumers. During the production of avgotaracho and the similar products some of the egg sacs (skeins) either break or have an inappropriate size (too small) and they can not be used for avgotaracho production. On the other hand the nutritional quality of the eggs in the broken or smaller skein is by no means inferior comparing to the rest. Proper valorization of the mullet roe by-products could lead to high nutrition value products. This work focuses on examining the potential valorization of these high nutritional value by-products for producing mullet roe oil. Three different extraction methods with potential of scale-up are examined. Namely pressure, supercritical extraction, solvent extraction are examined where mild temperature conditions and (wherever applicable) food-grade solvents are used. The oil yield, the composition of oils in fatty acids by GC-FID, the level of oil oxidation (peroxide value, p-anisidine value, K232 K268, TOTOX) and antioxidant activity (DPPH, ABTS) are determined. The potential of the above extraction methods for the production of mullet roe oil in terms of yield and oil quality is discussed.