Rheological behavior and stability of emulsions obtained from Pereskia aculeata Miller via different drying methods

Figures & data

Table 1. Rheological parameters of the emulsions that were obtained from the hydrocolloids that were vacuum oven-dried and freeze-dried at different concentrations.

	Power law
Drying method	Concentrations g/100 g of aqueous phase	R^2	MSE	K	n	Apparent viscosity at 100 s^−1 (Pa.s^−1)
Vacuum oven	0.5	0.941	0.123	0.036	0.691	0.008
	1.0	0.995	0.109	0.101	0.703	0.026
	1.5	0.990	0.222	0.172	0.681	0.039
	2.0	0.998	0.173	0.469	0.626	0.083
	2.5	0.969	0.915	0.522	0.639	0.098
	3.0	0.999	0.229	0.694	0.630	0.126
Freeze-dryer	0.5	0.965	0.128	0.054	0.679	0.011
	1.0	0.991	0.175	0.196	0.635	0.035
	1.5	0.988	0.450	0.367	0.657	0.073
	2.0	0.999	0.151	0.669	0.628	0.119
	2.5	0.999	0.248	0.970	0.598	0.152
	3.0	0.998	0.401	2.279	0.507	0.236

K = consistency index (Pa.sⁿ); n = flow behavior index (dimensionless); R² = coefficient of determination; MSE = residual of mean square.

Figure 1. Shear stress as a function of shear rate and curves adjusted by power law for emulsions prepared with OPN hydrocolloids (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 g OPN/100 g aqueous phase) that were (a) vacuum oven-dried and (b) freeze-dried.

Table 2. Thixotropy mean values for the emulsions that were obtained from the OPN hydrocolloids that were vacuum oven-dried and freeze-dried at different concentrations.

Concentration	Vacuum oven (Pa.s^−1)	Freeze-drier (Pa.s^−1)
0.5	−12 abA*	−15 aA
1.0	−34 aA	−33 aA
1.5	−18 abA	99 aB
2.0	119 cA	764 bB
2.5	42 bA	899 bB
3.0	356 dA	1289 cB

*Means followed by the same lower letter in the column do not differ by Tukey test (p < 0.05).

Means followed by the same capital letter in the row do not differ by Tukey test (p < 0.05).

Figure 2. Thixotropic behavior of emulsions prepared with different OPN hydrocolloid concentrations (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 g OPN/100 g aqueous phase) and drying methods (a) vacuum oven (VO)-dried and (b) freeze-dried (FD).

Figure 3. (1) Elastic modulus (G’),viscous modulus (G”), and (2) tan δ as function of frequency for emulsions prepared with different concentrations of OPN hydrocolloids (1.0, 2.0, and 3.0 g OPN/100 g aqueous phase) obtained from different drying methods: (a) Vacuum oven and (b) freeze-drying.

Table 3. Parameters of exponential model adjusts applied in the droplet size analyses.

	$y=y_0+A{e}^{Bx}$ (3)
y	y0	A	B	R^2
ND/area*	−334.5	304.4	0.598	0.993
Area (μm^2)	86.0	5597.7	−2.53	0.999
DAV (μm)	0.839	3.567	0.164	0.992
SD (μm)	3.637	58.475	−2.541	0.953

ND/area = number of droplets/area; D_AV = Feret diameter; SD = standard deviation.

Figure 4. Micrographs of the FD emulsions at concentrations of (a) 0.5 g OPN/100 g aqueous phase; (b) 2.5 g OPN/100 g aqueous phase.

Figure 5. (a) Results of droplet size analyses of freeze-dried OPN hydrocolloids; (b) Results for secondary parameters, compactness, and shape factor.

Figure 6. Droplet size distributions for emulsions prepared with freeze-dried OPN hydrocolloids at concentrations of (a) 0.5; (b) 1.0; (c) 1.5; (d) 2.0; (e) 2.5; and (f) 3.0 g OPN/100 g aqueous phase.

Figure 7. Fluorescence photomicrograph of emulsions constituted of 2.0 g of OPN gum/100 g of aqueous phase stained with (a) Red Nile (fluorescence of lipids) and (b) Rhodamine B (fluorescence of proteins) dyes.