Glycosylation, denaturation, and aggregation of soy proteins in defatted soy flakes flour: Influence of thermal and homogenization treatments

Figures & data

Table 1. Sample nomenclature for heated samples prepared from defatted soy flakes flour (DSFF).

Sample	Dispersing treatment	RH control	Heating time (h)	Sample nomenclature
DSFF aqueous dispersion	MS	No	12	M-12
		Yes	24	Mc-24
			48	Mc-48
	MS + HSH	No	12	U-12
			24	U-24
			48	U-48
		Yes	12	Uc-12
			24	Uc-24
			48	Uc-48
	MS + HSH + HPH	No	12	V-12
		Yes	24	Vc-24
			48	Vc-48
DSFF solid sample	NA*	No	12	F-12
			24	F-24
			48	F-48
		Yes	12	Fc-12
			24	Fc-24
			48	Fc-48

Heating (62 ± 2°C without or with relative humidity control, RH = 79%) was performed on DSFF aqueous dispersions (10.0 g total solids/100 g) or solid samples.

Dispersing treatments: MS: magnetic stirring; HSH, high-speed homogenization; HPH: high-pressure homogenization.

NA*: not applicable.

Figure 1. a) Dispersible material (DM, expressed as g of dispersible solids per 100 g total solids), De Brouckere mean diameter (D_4,3) values and b) FTIR spectra for or unheated DSFF aqueous dispersions prepared using various dispersing treatments. MS: magnetic stirring, HSH: high-speed homogenization and HPH: high-pressure homogenization. Mean values with different lowercase letters indicate significant differences between aqueous dispersions treated with different dispersing treatments (p<0.05).

Figure 2. a) DSC thermograms (30.0 g sample/100 g in 1.0 mol/L NaCl) for defatted soy flakes flour (DSFF control sample, without any previous heating) and heated Uc-12, Uc-24 and Uc-48 samples (62 ± 2 °C, HR = 79% for 12, 24 and 48 h, respectively); b) FTIR spectra for DSFF, Uc-12, Uc-24 and Uc-48 samples. Sample nomenclature was defined in Table 1. Figure 2: a) DSC thermograms (30.0 g sample/100 g in 1.0 mol/L NaCl) for defatted soy flakes flour (DSFF control sample, without any previous heating) and heated Uc-12, Uc-24 and Uc-48 samples (62 ± 2 °C, HR = 79% for 12, 24 and 48 h, respectively); b) FTIR spectra for DSFF, Uc-12, Uc-24 and Uc-48 samples. Sample nomenclature was defined in Table 1.

Table 2. DSC and FTIR parameters for heated DSFF aqueous dispersions (62 ± 2°C, without and with relative humidity control, RH = 79%).

Samples	Relative denaturation enthalpy (rΔHd%, respect to DSFF control)			FTIR parameters
				Maximum wavenumber (νmax, cm^−1)			Absorbance at νmax
	Peak I	Peak II	Peak III	AI	AII	AIII	AI	AII	AIII
DSFF	100	100	100	1635.6	1537.3	1396.5	1.40	1.32	1.08
Uc-12	37.3	86.1	100	1635.6	1541.1	1398.4	1.26	1.11	0.94
Uc-24	21.8	67.0	68.6	1633.7	1543.0	1398.4	1.10	0.98	0.91
Uc-48	<1.0	60.2	67.5	1620.2		1394.5	0.69		0.67
Mc-24	26.6	80.7	75.7	1633.7	1543.8	1398.6	1.16	1.03	1.03
Mc-48	5.1	78.9	86.1	1627.9	1545.5	1394.5	0.82	0.60	0.82
Vc-24	6.9	68.5	62.7	1633.7	1543.9	1397.2	1.09	0.97	0.97
Vc-48	3.9	47.6	38.4	1606.7		1394.5	0.70		0.71
U-12	100	83.1	77.6	1633.7	1539.2	1398.4	1.41	1.30	1.07
U-24	100	81.6	81.1	1635.6	1541.1	1398.4	1.37	1.23	1.03
U-48	94	63.7	71.9	1635.6	1537.3	1396.5	1.49	1.36	1.14

Maximum standard deviation: 5%. For comparative purposes, the corresponding parameters for control DSFF sample were also included. Sample nomenclature was provided in Table 1.

Figure 3. a) Effect of heating time on residual parameters (%) for heated DSFF aqueous dispersions treated by MS/HSH dispersing treatments (10.0 g total solids/100 g, 62 ± 2 °C, RH = 79%) (Uc samples). Residual parameters were: trypsin inhibitor activity (r-TIA), urease activity (r-UA), reactive lysine (r-RL), protein solubility in water (r-S_W) and 0.2 g/100 g potassium hydroxide solution (r-S_KOH); b) Relative residual parameters (%) for DSFF aqueous dispersions treated by MS and MS/HSH/HPH, heated for 24 h (10.0 g total solids/100 g, 62 ± 2 °C, RH = 79%), corresponding to Mc-24 and Vc-24 samples, respectively; c) Idem b) for 48 h, corresponding to Mc-48 and Vc-48 samples, respectively.

Figure 4. a) Effect of heating time on residual parameters (%) for heated DSFF aqueous dispersions treated by MS/HSH dispersing treatments (10.0 g total solids/100 g, 62 ± 2 °C without RH control) (U samples). Residual parameters were: trypsin inhibitor activity (r-TIA), urease activity (r-UA), reactive lysine (r-RL), protein solubility in water (r-S_W) and 0.2 g/100 g potassium hydroxide solution (r-S_KOH); b) Relative residual parameters (%) for DSFF aqueous dispersions treated by MS and MS/HSH/HPH, heated for 12 h (10.0 g total solids/100 g, 62 ± 2 °C without RH control) corresponding to M-12 and V-12 samples, respectively.

Figure 5. a) Effect of heating time on residual parameters (%) for heated DSFF solids samples: a) 62 ± 2 °C, RH= 79% and b) 62 ± 2 °C, without RH control. Residual parameters were: trypsin inhibitor activity (r-TIA), urease activity (r-UA), reactive lysine (r-RL), protein solubility in water (r-S_W) and 0.2 g/100 g potassium hydroxide solution (r-S_KOH).

Table 3. DSC and FTIR parameters for DSFF solid samples (62 ± 2°C, without and with relative humidity control, RH = 79%).

Samples	Relative denaturation enthalpy (rΔHd%, respect to DSFF control)			FTIR parameters
				Maximum wavenumber (νmax, cm^−1)			Absorbance at νmax
	Peak I	Peak II	Peak III	AI	AII	AIII	AI	AII	AIII
DSFF	100	100	100	1635.6	1537.3	1396.5	1.40	1.32	1.08
Fc-12	100	72.0	79.1	1635.6	1541.1	1398.4	1.48	1.32	1.14
Fc-24	53.0	72.1	83.5	1633.7	1541.1	1398.4	1.28	1.10	0.93
Fc-48	44.3	76.2	92.0	1631.8	1541.1	1398.4	0.98	0.87	0.81
F-12	87.7	64.2	82.1	1635.6	1541.1	1398.4	1.41	1.28	1.05
F-24	85.8	52.9	72.2	1635.6	1541.1	1398.4	1.43	1.33	1.10
F-48	81.3	70.4	88.0	1635.6	1541.1	1398.4	1.44	1.34	1.13

Maximum standard deviation: 5%. For comparative purposes, the corresponding parameters for control DSFF sample were also included. Sample nomenclature was provided in Table 1.