Tuning the Bioactive Properties of Dunaliella salina Water Extracts by Ultrasound-Assisted Extraction

Abstract

(1) Background: Microalgae are promising feedstock for obtaining valuable bioactive compounds. To facilitate the release of these important biomolecules from microalgae, effective cell disruption is usually necessary, where the use of ultrasound has achieved considerable popularity as an alternative to conventional methods. (2) Methods: This paper aims to evaluate the use of ultrasound technology in water medium as a green technology to recover high added-value compounds from Dunaliella salina and improve its sensory profile towards a high level of incorporation into novel food products. (3) Results: Among the variables, the solid concentration and extraction time have the most significant impact on the process. For the extraction of protein, or fat, the most influential factor is the extraction time. Total polyphenols are only significantly affected by the extraction time. The antioxidant capacity is strongly affected by the solid to liquid ratio and, to a small extent, by the extraction time. Ultrasound-assisted extraction improves the overall odor/aroma of D. salina with good acceptability by the panelists. (4) Conclusions: The application of ultrasonic-assisted extraction demonstrates a positive overall effect on enhancing the sensory profile, particularly the odor of microalgal biomass, while the bioactive properties are preserved. Notably, the intense sea/fish odors are reduced, while earthy and citrus notes become more prominent, resulting in an improved overall sensory profile score. This is the first time, to our knowledge, that this innovative, green, and efficient technology has been used to upgrade the aroma profile of microalgae.

Keywords: Dunaliella salina; bioactivities; extraction; sensory analysis; ultrasound.

Figure 1

Protein content (%, dw) of Dunaliella salina raw, biomass, and extract fractions obtained under different ultrasound-assisted extraction conditions, using water as the medium. C: continuous sonication mode; D: pulsed sonication mode. Raw (gray solid fill), biomass (pattern fill), extracts (solid fill). The data shown are mean values (n = 3) followed by a letter. Different letters mean significantly different results (Tukey’s HSD; p ≤ 0.05).

Figure 2

Fat content (%, dw) of Dunaliella salina biomass and extract fractions obtained under different ultrasound-assisted extraction conditions, using water as the medium. C: continuous sonication mode; D: pulsed sonication mode. Raw (gray solid fill), biomass (pattern fill), extracts (solid fill). The data shown are mean values (n = 3) followed by a letter. Different letters mean significantly different results (Tukey’s HSD; p ≤ 0.05).

Figure 3

Ash content (%, dw) of Dunaliella salina biomass and extract fractions obtained under different ultrasound-assisted extraction conditions, using water as the medium. C: continuous sonication mode; D: pulsed sonication mode. Raw (gray solid fill), biomass (pattern fill), extracts (solid fill). The data shown are mean values (n = 3) followed by a letter. Different letters mean significantly different results (Tukey’s HSD; p ≤ 0.05).

Figure 4

Carbohydrate content (%, dw) of Dunaliella salina biomass and extract fractions obtained under different ultrasound-assisted extraction conditions, using water as the medium. C: continuous sonication mode; D: pulsed sonication mode. Raw (gray solid fill), biomass (pattern fill), extracts (solid fill). The data shown are mean values (n = 3) followed by a letter. Different letters mean significantly different results (Tukey’s HSD; p ≤ 0.05).

Figure 5

Antioxidant capacity of Dunaliella salina biomass and extract fractions obtained under different ultrasound-assisted extraction conditions, using water as the medium, measured by DPPH (a) and FRAP (b) assays. C: continuous sonication mode; D: pulsed sonication mode. Raw (gray solid fill), biomass (pattern fill), extracts (solid fill). The data shown are mean values (n = 3) followed by a letter. Different letters mean significantly different results (Tukey’s HSD; p ≤ 0.05).

Figure 6

Total phenolic content (TPC), in mg GA/100 g dw, of Dunaliella salina biomass and extract fractions obtained under different ultrasound-assisted extraction conditions, using water as the medium. C: continuous sonication mode; D: pulsed sonication mode. Raw (gray solid fill), biomass (pattern fill), extracts (solid fill). The data shown are mean values (n = 3) followed by a letter. Different letters mean significantly different results (Tukey’s HSD; p ≤ 0.05).

Figure 7

Detected odors by sensory evaluation (n = 30) in Dunaliella salina biomass (B: darker color) and extract (E: lighter color) fractions obtained under different UAE conditions, using water as the medium. C: continuous sonication mode; D: pulsed sonication mode.

Figure 8

Sensory evaluation results (n = 30) of raw Dunaliella salina and correspondent biomass and extract fractions obtained after UAE using water as the medium.