Superficial Charge Density of Fining Agents: Influence of pH, Dose, and Temperature

Figures & data

Table 1 Characteristics of fining agents

Protein	% Protein	MW (kDa)	Hydrolysis treatment	Amino acids
Gel 1	>99	<32	Physic	Gly (28.5); Pro (17.1); Glu (11.5); Ala (9.7)
Gel 2	>99	60–140	Physic	—
Gel 3	>99	50–75	Enzymatic	—
Albumin	>99	45	Untreated	—
Gluten 1	75	6.5 to 200	Untreated	Glu (29.5); Pro (9.3); Leu (5.6); Ser (4.0)
Gluten 2	78	6.5 to 200	Heat	Glt (31.2); Pro (9.3); Leu (5.6); Ser (4.0)
Gluten 3	80	<20	Enzymatic	Glt (34.0); Pro (12.7); Leu (7.0); Ser (5.1)

Table 2 Isoelectric points of the proteins analyzed

Protein	Isoelectric point *
Gel 1	4.43 ± 0.05 ^a
Gel 2	6.60 ± 0.22 ^c
Gel 3	6.20 ± 0.07 ^b,c
Albumin	4.66 ± 0.12 ^a
Gluten 1	6.34 ± 0.09 ^b,c
Gluten 2	6.28 ± 0.09 ^b,c
Gluten 3	5.98 ± 0.05 ^b
*Mean ± standard deviation.
Significance level of 99%. ^a,b,cDifferent superscript letters in each file indicate significant differences.

Table 3 Fitted equation for the different proteins obtained by stepwise multiple regression

Fitted equation	R ^2	Adjusted R ^2
SCDGEL 1 = 1.1943 − 0.4065 pH − 0.0024 T + 0.0332 pH^2	0.938	0.938
SCDGEL 2 = −1.1027 + 1.4449 pH − 0.2385 pH^2	0.562	0.543
SCDGEL 3 = −0.0941 + 0.7274 pH − 0.1460 pH^2 + 0.0059 d	0.913	0.907
SCDALB = 0.1304 + 0.1390 pH − 0.0099 d − 0.0291 pH^2 + 0.0002 d ^2	0.929	0.923
SCDGLUTEN 1 = 0.0189 + 0.0419 pH + 0.0062 T + 0.0300 d − 0.0016 d ^2	0.565	0.556
SCDGLUTEN 2 = 0.614 − 0.213 pH − 0.003 d + 0.028 pH^2	0.635	0.614
SCDGLUTEN 3 = 0.4864 − 0.0725 pH − 0.0035 d	0.929	0.926

Figure 1 Response surface plot for superficial charge density (meq g⁻¹) of Gel 1 as function of pH, temperature (°C), and dose (g hl⁻¹): (a) 20°C; (b) dose 12 g hl⁻¹; (c) pH 3.4.

Figure 2 Response surface plot for superficial charge density (meq g⁻¹) of (a) Gel 2 and (b) Gel 3 as function of pH and dose (g hl⁻¹).

Figure 3 Response surface plot for superficial charge density (meq g⁻¹) of albumin as function of pH and dose (g hl⁻¹).

Figure 4 Response surface plot for superficial charge density (meq g⁻¹) of Gluten 1 as function of pH, temperature (°C), and dose (g hl⁻¹): (a) 20°C; (b) dose 12 g hl⁻¹; (c) pH 3.4.

Figure 5 Response surface plot for superficial charge density (meq g⁻¹) of (a) Gluten 2 and (b) Gluten 3 as function of pH and dose (g hl⁻¹).

Table 4 Minimum and maximum values of SCD (meq g⁻¹) of the fining agents in the range studied

Fining agent	Maximum SCD (temperature; dose; pH)	Minimum SCD (temperature; dose; pH)
Gel 1	0.402 (5°C; 20 g hl^−1; pH 2.5)	0.025 (25°C; 20 g hl^−1; pH 4.0)
Gel 2	1.272 (20°C; 8 g hl^−1; pH 3.1)	0.831 (20°C; 20 g hl^−1; pH 4.0)
Gel 3	0.879 (20°C; 12 g hl^−1; pH 3.1)	0.322 (20°C; 20 g hl^−1; pH 4.0)
Albumin	0.268 (20°C; 8 g hl^−1; pH 3.1)	0.118 (20°C; 20 g hl^−1; pH 4.0)
Gluten 1	0.548 (20°C; 12 g hl^−1; pH 4.0)	0.171 (20°C; 20 g hl^−1; pH 2.5)
Gluten 2	0.267 (20°C; 8 g hl^−1; pH 2.5)	0.152 (20°C; 20 g hl^−1; pH 4.0)
Gluten 3	0.305 (20°C; 8 g hl^−1; pH 2.8)	0.137 (20°C; 20 g hl^−1; pH 4.0)