Ultrasonication-driven optimization of cricket protein nanoemulsions: influence of pH and rheological stabilizers

Abstract

This study investigates the formulation of sustainable nanoemulsions using cricket protein as a natural emulsifier and linseed oil as the dispersed phase, emphasizing the effects of pH, ultrasonication, and rheological modifiers on emulsion stability and structure. Surface and interfacial tension analyses revealed significant reductions with increasing protein concentration, stabilizing at ≥1 g/L. At alkaline pH (≥12), interfacial tension became unmeasurable due to complete phase merging, attributed to enhanced protein solubility and surface activity. Droplet size distribution exhibited bimodal patterns across all pH levels, with the smallest Sauter diameter (0.54 μm) and optimal span (1.91) achieved at pH 12.5. Ultrasonication parameters (amplitude and sonication time) were optimized using response surface methodology. The smallest droplet size (0.365 μm) was predicted at 63 % amplitude and 9.6 min of sonication. However, higher energy inputs also increased polydispersity, likely due to droplet recoalescence in the absence of sufficient emulsifier. To enhance stability, guar gum (GG) and advanced performance xanthan gum (APXG) were tested. APXG, particularly at ≥0.25 wt%, significantly improved viscoelasticity (G' > G″) and increased consistency (K = 9.87 Pa·sⁿ at 0.5 wt%), forming gel-like structures and reducing the Turbiscan Stability Index (TSI) over a 21-day period. These results underscore the critical roles of pH, ultrasonic processing, and rheological modification in designing robust nanoemulsions. The integration of cricket protein and APXG under optimized conditions offers a promising platform for stable, eco-friendly emulsions in functional food and nutraceutical applications.

Keywords: Cricket protein; Food processing; Nanoemulsion; Sustainable; Ultrasonic.

Graphical abstract

Fig. 1

ABTS scavenging activity of ethanolic extract of cricket flour.

Fig. 2

Surface tension of solutions of cricket protein as a function of emulsifier concentration; the standard deviation of the measured parameters was lower than 4 % (A), interfacial tension between linseed oil and solutions of cricket protein as a function of emulsifier concentration; the standard deviation of the measured parameters was lower than 6 % (B) and droplet size distribution as a function of different pH values of the continuous phase (C).

Fig. 3

Droplet size distribution as a function of (A) amplitude for samples 2, 5, and 8 (fixed time = 5 min) and (B) time for samples 4, 5, and 6 (fixed amplitude = 50 %).

Fig. 4

Three-dimensional representation (and projection on the plane) of the response surface for Eq. (4), in which the value of the Sauter diameter (d_3.2) is plotted as a function of amplitude (AMP) and time (t).

Fig. 5

Microstructure observed by FESEM of the optimum emulsion.

Fig. 6

Flow behaviour of emulsions as a function of guar gum concentration and advanced performance xanthan gum concentration. The standard deviation of the measured parameters was lower than 5 %.

Fig. 7

Frequency sweep of emulsions as a function of guar gum concentration (A), and advanced performance xanthan gum concentration (B). The standard deviation of the measured parameters was lower than 6 %.

Fig. 8

Variations in Turbiscan Stability Index (TSI) for optimal emulsion developed without rheological modifier, 0.5 wt% guar gum (GG) and 0.5 wt% advanced performance xanthan gum (APXG).