Structure and Property Changes of Transglutaminase-Induced Modification of Sodium Caseinate in the Presence of Oligochitosan of 5 kDa

Figures & data

FIGURE 1 SDS-PAGE profiles of three protein samples stained for (a) protein and (b) saccharide fractions. Lane M, standard protein markers; lane 1, horseradish peroxidase; lane 2, sodium caseinate; lane 3, GC-caseinate I; lane 4, GC-caseinate II. The arrows indicate protein polymers.

FIGURE 2 FT-IR spectra of sodium caseinate, GC-caseinate I and II.

FIGURE 3 CD spectra of sodium caseinate, GC-caseinate I and II dispersed in a phosphate buffer (10 mmol/L, pH 7.0) at 0.1 g/L.

FIGURE 4 (a) Original thermogravimetric (TG) curves for sodium caseinate, GC-caseinate I and II, and (b) the respective derivative function (DTG) versus temperatures ranging from ambient temperature to 450°C.

TABLE 1 Some thermogravimetric parameters of sodium caseinate, GC-caseinate I and II

Regions	Parameters	Sodium caseinate	GC-caseinate I	GC-caseinate II
Region I	Tmax1 (ºC)	47.5 ± 0.2^b	38.7 ± 0.2^a	38.2 ± 0.3^a
	Mass loss (%)	8.3 ± 0.3^a	12.7 ± 0.2^b	12.6 ± 0.3^b
Region II	Tmax2 (ºC)	291.5 ± 0.7^b	286.2 ± 0.6^a	286.3 ± 0.4^a
	Mass loss (%)	52.1 ± 0.2^a	54.2 ± 0.1^b	58.3 ± 0.4^c
	Total mass loss (%)	60.4 ± 0.2^a	66.9 ± 0.3^b	70.9 ± 0.6^c

Regions I has a temperature range of ambient temperature to 105ºC, while regions II has a temperature range of 105 to 450ºC. T_max1 and T_max2 are the respective temperatures of the first and second DTG peaks (that is, the largest DTG values in regions I and II) shown in Fig. 4b. Different lowercase letters after the mean values in the same row as superscripts indicate significant differences (p < 0.05).

FIGURE 5 Distribution profiles of the hydrodynamic radius of sodium caseinate, GC-caseinate I and II dispersed in a phosphate buffer (10 mmol/L, pH 7.0) at 1.0 g/L. PSD, particle size distribution.

TABLE 2 Some properties of sodium caseinate, GC-caseinate I and II

Indexes	Sodium caseinate	GC-caseinate I	GC-caseinate II
Hydrodynamic radius (nm)	145.3 ± 6.2^a	173.9 ± 12.6^b	168.2 ± 8.6^ab
Zeta-potential (mV)	−27.6 ± 0.9^a	−32.9 ± 1.1^b	−30.9 ± 1.2^b
WBC (g/g protein)	5.62 ± 0.06^a	14.32 ± 0.10^c	10.14 ± 0.20^b
In vitro digestibility by pepsin	0.406 ± 0.002^b	0.385 ± 0.001^a	0.438 ± 0.002^c
In vitro digestibility by pepsin and trypsin	1.013 ± 0.008^b	0.956 ± 0.008^a	1.042 ± 0.002^c

WBC represents water-binding capacity. Different lowercase letters after the mean values in the same row as superscripts indicate significant differences (p < 0.05).