## 3 Results and Discussion
### Rheology and \(\zeta\)-Potential Emulsions Measurements  
The emulsions prepared using only vegetable proteins as stabilizing agents were all unstable, indicating that the interfacial properties controlled by vegetable proteins are not sufficient to stabilize the whole system. The instability phenomena are not only due to the interface but also to the difference in density between the mixed phases (oily and aqueous), which leads to obvious phenomena of phase separation, such as the cream of large drops, or sedimentation. On the contrary, the emulsion with gellan gum was also visually monitored to verify the formation of any layers, and it was observed that no stratification had occurred within one week. Therefore, the visual observation evidence that the polysaccharide, in the quantity of 0.05% \(w/w\), can avoid destabilization phenomena. In light of these results, the viscosity of the sample H_2_G was measured because this is an important measure for understanding the structural organization and the network formation. The viscosity is also an important commercial parameter that influences the texture and the sensory properties [17]. A previous work of literature shows that emulsions prepared with only help protein isolate have a Newtonian behaviour [17] while, as Figure 4 shows, the emulsion prepared with gellan shows a non-Newtonian behaviour. The shear thinning behaviour can be due to the stabilizing agent added to control the instability phenomena. In fact, as reported by [PERSON] [22], emulsions obtained with gellan gum show high viscosity, probably caused by the presence of Ca\({}^{2+}\) that causes carboxylate-cation2+-carboxylate interactions increasing the gel structure [22]. The same result was found by [PERSON] and coworkers [24] using pectin as a stabilizing agent. Pectin as gellan gum probably forms a three-dimensional network, and this network gives a high-viscosity and shear-thinning behaviour to the emulsion [24]. The result found is also confirmed by the charge analysis of the emulsions carried out at the different protein quantities as shown in Figure 5. Before measuring the zeta-potential, pH was measured, obtaining a pH of 6.8 \(\pm\) 0.1 for all the emulsions. As is possible to observe, all the samples have a negative charge in accordance with the H isoelectric point [15]. For the studied emulsions, it is worth noting that the \(\zeta\)-potential seems to slightly decrease with increasing protein quantity, but only after the addition of gellan gum, the \(\zeta\)-potential absolute value at 2% \(w/w\) of H increase from \(-\)33 \(\pm\) 2 to \(-\)26.5 \(\pm\) 2.6 mV. As is well known, absolute zeta potential greater than 30 mV indicates a  
Figure 3: Average droplet diameter, \(d_{s}\) and standard deviation, \(\sigma_{s}\), for the different O/W emulsions. The square symbol indicates samples without stabilizing while the circle symbol is for the emulsion with gellan gum (H_2_G). stable system. The electrostatic repulsion between the polysaccharide and protein particles, coupled with the tridimensional network formation, enhances the stability and the result obtained thanks to the polysaccharide addition, which was also obtained for oil-in-water hemp emulsions with another polysaccharide, pectin, as a stabilizing agent by [PERSON] et al. [24]. This formulation can give the possibility of creating food-grade emulsions, capable of valorising both the oil and the hemp protein isolate. Interesting applications could be in creating high nutritional food thanks to the good amino acid profile of the isolate  
Figure 4: Flow curve of the sample with 2% \(w/w\) of hemp protein and 0.05% of gellan gum (H_2_G) at 25 \({}^{\circ}\)C.  
Figure 5: \(\zeta\)-potential values for investigated samples. The square symbol indicates samples without stabilizing while the circle symbol is for the emulsion with gellan gum (H_2_G).