Effect of ultrasonic power on the stability of low-molecular-weight oyster peptides functional-nutrition W1/O/W2 double emulsion

Abstract

Ultrasonic-assisted treatment is an eco-friendly and cost-effective emulsification method, and the acoustic cavitation effect produced by ultrasonic equipment is conducive to the formation of stable emulsion. However, its effect on the underlying stability of low-molecular-weight oyster peptides (LOPs) functional-nutrition W₁/O/W₂ double emulsion has not been reported. The effects of different ultrasonic power (50, 75, 100, 125, and 150 W) on the stability of double emulsions and the ability to mask the fishy odor of LOPs were investigated. Low ultrasonic power (50 W and 75 W) treatment failed to form a well-stabilized double emulsion, and excessive ultrasound treatment (150 W) destroyed its structure. At an ultrasonic power of 125 W, smaller particle-sized double emulsion was formed with more uniform distribution, more whiteness, and a lower viscosity coefficient. Meanwhile, the cavitation effect generated by 125 W ultrasonic power improved storage, and oxidative stabilities, emulsifying properties of double emulsion by reducing the droplet size and improved sensorial acceptability by masking the undesirable flavor of LOPs. The structure of the double emulsion was further confirmed by optical microscopy and confocal laser scanning microscopy. The ultrasonic-assisted treatment is of potential value for the industrial application of double emulsion in functional-nutrition foods.

Keywords: Double emulsion; Electronic nose; Low-molecular-weight oyster peptides; Stability; Ultrasonic power.

Graphical abstract

Fig. 1

Turbidity and whiteness of LOPs double emulsion at different ultrasonic power. Different letters represent significant differences (P < 0.05).

Fig. 2

Emulsifying activity index (EAI) and emulsifying stability index (ESI) of LOPs double emulsion at different ultrasonic power. Different letters for the same index represent significant differences (P < 0.05).

Fig. 3

Effect of different ultrasonic power on the droplet size of LOPs double emulsion. (A) Particle distribution. (B) Average particle size and polydispersity index (PDI). Different letters for the same index represent significant differences (P < 0.05).

Fig. 4

The Optical microscopy images (100 × magnification) of LOPs double emulsion at different ultrasonic power.

Fig. 5

The confocal laser scanning microscopy (CLSM) images (100 × magnification) of LOPs double emulsion at different ultrasonic power. Arrows represent W₁/O/W₂ double emulsion.

Fig. 6

(A) Apparent viscosity of LOPs double emulsion at different ultrasonic power. (B) The viscosity coefficient (k) and the flow behavior index (n) from the Herschel-Bulkley model.

Fig. 7

The e-nose results of double emulsion on the fishy odor of LOPs at different ultrasonic power. (A) Principal component analysis (PCA). (B) Pearson correlations heatmap. Different colors of squares represent different R values of Pearson correlations. *P < 0.05, ^**P < 0.01.

Fig. 8

Storage stability of LOPs double emulsion at different ultrasonic power. (A) Visual appearance. (B) Creaming index. (C) Conjugated dienes (CD) value. Different letters for the same ultrasonic power group represent significant differences.

Fig. 9

Physical stability of LOPs double emulsion at 125 W ultrasonic power to environment stresses. (A) Average particle size and (B) zeta potential at temperatures of 30, 50, 70, and 90 ℃ (left to right). (C) Average particle size and (D) zeta potential under different ionic strengths, using NaCl at different concentrations of 0, 50, 100, 200, and 300 mM (left to right). (E) Average particle size and (F) zeta potential under different pH conditions from 4.0 to 9.0 (left to right). Different letters for the same index represent significant differences (P < 0.05).