Emulsifying properties of β-lactoglobulin and Quillaja bark saponin mixtures: Effects of number of homogenization passes, pH, and NaCl concentration

Figures & data

Table 1. Average droplet size (z-average), polydispersity index (PDI), and droplet surface charge (ζ-potential) for emulsions homogenized at different numbers of passes and stabilized by Quillaja bark saponin and β-lactoglobulin.

Parameters	Number of homogenization passes at 10,000 psi	After homogenization	After storage (7 days at 25°C)
PDI	4	0.507 ± 0.141^aA	0.470 ± 0.040^A
	6	0.471 ± 0.033^aA	0.448 ± 0.068^A
	8	0.378 ± 0.040^aA	0.251 ± 0.006^A
z-average (nm)	4	323 ± 80^aA	358 ± 9^A
	6	322 ± 41^aA	318 ± 35^A
	8	298 ± 46^aA	227 ± 5^A
ζ-potential (mV)	4	–76.4 ± 0.5^aA	–71.0 ± 0.1^A
	6	–70.6 ± 1.8^bA	–63.7 ± 1.8^A
	8	–74.0 ± 0.1^abA	–71.5 ± 0.5^A

Different superscript letters indicate significant difference (p < 0.05).

Lowercase letters compare differences for the same parameter after homogenization process, whereas uppercase letters compare differences between the same parameter after storage.

Table 2. Rheological parameters obtained from the Herschel-Bulkley model and apparent viscosity at 100 s⁻¹ () for emulsions homogenized at different numbers of passes and stabilized by Quillaja bark saponin and β-lactoglobulin.

Rheological parameters	Number of homogenization passes at 10,000 psi
	4	6	8
(mPa)	214.8 ± 3.0^a	30.1 ± 4.1^b	17.5 ± 4.6^c
(mPa.s^n)	5.45 ± 0.38ª	2.38 ± 0.29^b	1.76 ± 0.28^b
	0.77 ± 0.01ª	0.91 ± 0.02^b	0.95 ± 0.03^b
(mPa.s)	2.03 ± 0.36ª	1.85 ± 0.04ª	1.56 ± 0.07ª

Different superscript letters indicate significant difference (p < 0.05) for the same parameter.

Figure 1. Influence of the number of homogenization passes—4 (●), 6 (▼), or 8 (■) passes—on the elastic modulus (G’, closed symbol) and the viscous modulus (G”, open symbol) of the emulsions stabilized by QBS and β-lg at pH 7.

Figure 2. Visual appearance of 10 wt% sunflower oil-in-water emulsions stabilized by Quillaja bark saponin (QBS) and β-lactoglobulin (β-lg) after 7 days of storage at 25°C. F1: pH 7 and A: 4; B: 6; and C: 8 homogenization passes; F2: 4 homogenization passes at 10,000 psi and pH A: 7; B: 8; and C: 9; F3: pH 7 and NaCl concentrations of A: 0, B: 100, and C: 200 mmol L-1. Black arrow denotes foam formation, observed during emulsion preparation.

Table 3. Average droplet size (z-average), polydispersity index (PDI), and ζ-potential for emulsions stabilized by Quillaja bark saponin and β-lactoglobulin at different pH values.

Parameters	pH	After homogenization	After storage (7 days at 25°C)
PDI	7	0.507 ± 0.141ª^A	0.470 ± 0.040^A
	8	0.368 ± 0.016ª^A	0.437 ± 0.008^A
	9	0.326 ± 0.002ª^A	0.431 ± 0.018^A
z-average (nm)	7	323 ± 80ª^A	358 ± 9^A
	8	283 ± 8ª^A	336 ± 22^A
	9	246 ± 4ª^A	334 ± 40^A
ζ-potential (mV)	7	–76.4 ± 0.5^aA	–71.0 ± 0.1^B
	8	–79.4 ± 0.0^bA	–72.8 ± 0.2^B
	9	–79.6 ± 0.1^bA	–76.3 ± 0.8^A

Different superscript letters indicate significant difference (p < 0.05).

Lowercase letters compare differences for the same parameter after homogenization process whereas uppercase letters compare differences between the same parameter after storage.

Table 4. Average droplet size (z-average), polydispersity index (PDI), and ζ-potential for emulsions stabilized by Quillaja bark saponin and β-lactoglobulin at different NaCl concentrations.

Parameters	NaCl concentration (mmol L^−1)	After homogenization	After storage (7 days at 25°C)
PDI	0	0.507 ± 0.141ª^A	0.470 ± 0.040^A
	100	0.386 ± 0.023ª^A	0.465 ± 0.065^A
	200	0.323 ± 0.057ª^A	0.307 ± 0.069^A
z-average (nm)	0	323 ± 80ª^A	358 ± 9^A
	100	277 ± 37ª^A	421 ± 119^A
	200	265 ± 19ª^A	251 ± 22^A
ζ-potential (mV)	0	–76.4 ± 0.5^aA	–71.0 ± 0.1^B
	100	–27.6 ± 0.3^bA	–28.8 ± 0.1^A
	200	–20.0 ± 1.1^cA	–20.1 ± 0.3^A

Different superscript letters indicate significant difference (p < 0.05).

Lowercase letters compare differences for the same parameter after homogenization process whereas uppercase letters compare differences between the same parameter after storage.