Effect of Maillard reaction conditions on antigenicity of β-lactoglobulin and the properties of glycated whey protein during simulated gastric digestion

Figures & data

Table 1. Coded and uncoded settings of independent variables for Maillard reaction conditions according to central composite rotatable design.

	Independent variables
Coded level	Weight ratio	Temperature (°C)	Time (h)
1.682	7.36	76.8	44.2
1	6	70	36
0	4	60	24
−1	2	50	12
−1.682	0.64	43.2	3.8

Table 2. Full factorial central composite design matrix and the antigenicity of β-LG in WPI-oligoisomaltose conjugates.

	Independent variables^a			Dependent variable
Assay	Weight ratio	Temperature (°C)	Time (h)	β-LG antigenicity (µg/mL)
1	2 (−1)	50 (−1)	12 (−1)	141.1
2	2 (−1)	50 (−1)	36 (1)	105.7
3	2 (−1)	70 (1)	12 (−1)	64.1
4	2 (−1)	70 (1)	36 (1)	36.4
5	6 (1)	50 (−1)	12 (−1)	172.6
6	6 (1)	50 (−1)	36 (1)	88.6
7	6 (1)	70 (1)	12 (−1)	51.0
8	6 (1)	70 (1)	36 (1)	33.2
9	0.64 (−1.682)	60 (0)	24 (0)	143.6
10	7.36 (1.682)	60 (0)	24 (0)	70.1
11	4 (0)	43.2 (−1.682)	24 (0)	192.3
12	4 (0)	76.8 (1.682)	24 (0)	39.7
13	4 (0)	60 (0)	3.8 (−1.682)	141.9
14	4 (0)	60 (0)	44.2 (1.682)	62.5
15	4 (0)	60 (0)	24 (0)	68.0
16	4 (0)	60 (0)	24 (0)	63.2
17	4 (0)	60 (0)	24 (0)	66.2
18	4 (0)	60 (0)	24 (0)	65.1
19	4 (0)	60 (0)	24 (0)	66.9
20	4 (0)	60 (0)	24 (0)	64.0
21	4 (0)	60 (0)	24 (0)	65.1
22	4 (0)	60 (0)	24 (0)	65.0
23	4 (0)	60 (0)	24 (0)	65.4

^a Values in parentheses are the coded levels of independent variables.

Table 3. Regression coefficients for the regression prediction model of the antigenicity of β-LG.

	Full model		Fitted model
	b-coefficient	p	b-coefficient	p
Intercept	65.96		70.73
Linear
Weight ratio	−9.20	0.075	−9.20	0.088
Temperture	−42.51	0.000	−42.51	0.000
Time	−21.84	0.001	−21.84	0.000
Quadratic
Weight ratio^2	9.58	0.049	9.53	0.059
Temperture^2	12.89	0.012	12.83	0.015
Time^2	7.93	0.095
Interactions
Weight ratio×temperature	−3.83	0.548
Weight ratio×time	−4.83	0.451
Temperature×time	9.24	0.161
Other statistics
R^2	83.95%		81.66%
F	13.79	0.0001	20.59	0.0001

Figure 1. Response surfaces of the antigenicity of β-LG (Y): (a) effect of oligoisomaltose/whey protein isolate (O/WPI) weight ratio (X₁) and temperature (X₂) on antigenicity at fixed time of 24 h; (b) effect of O/WPI weight ratio (X₁) and time (X₃) on antigenicity at fixed temperature of 60 °C; (c) effect of temperature (X₂) and time (X₃) on antigenicity at fixedO/WPI weight ratio of 4:1.

Table 4. The free amino acid and the antigenicity of β-LG and α-LA in WPI and WPI-oligoisomaltose during simulated gastric digestion.

	Free amino acid (mmol L^−1)		Antigenicity of β-LG (µg mL^−1)		Antigenicity of α-LA (µg mL^−1)
Time/min	WPI	WPI-oligoisomaltose	WPI	WPI-oligoisomaltose	WPI	WPI-oligoisomaltose
0	1.568±0.136^c	0.573±0.032^f	241.68±6.83^a	36.55±0.04^a	26.73±1.54^a	4.71±0.9^a
2.5	1.569±0.016^c	0.707±0.010^e	106.88±1.85^b	33.84±0.20^b	25.37±0.07^b	2.22±0.25^b
5	1.618±0.017^bc	0.780±0.029^d	82.28±3.95^c	25.49±1.85^c	23.83±0.31^c	1.92±0.14^b
10	1.667±0.014^b	0.857±0.039^c	61.77±1.15^d	20.84±1.42^d	14.29±0.91^d	0.72±0.09^c
20	1.859±0.027^a	0.933±0.024^b	52.61±2.82^e	19.68±0.05^d	2.87±0.04^e	0.16±0.04^cd
30	1.874±0.008^a	0.943±0.022^b	51.00±0.08^e	19.73±0.95^d	2.63±0.05^e	0.14±0.04^cd
60	1.904±0.002^a	0.970±0.005^ab	49.85±1.70^e	17.08±1.17^e	2.30±0.09^e	0.14±0.03^cd
120	1.943±0.038^a	0.996±0.014^a	42.83±4.40^f	15.66±1.68^e	0.78±0.07^f	0.03±0.02^d

Values with common letters are not significantly different (P>0.05).