Table 2.

Secondary structures of whey protein isolate (WPI) in the absence and presence of lutein/zeaxanthin (Lut/Zx) under different pH conditions.

Sample	pH	α-helix (%)	β-sheet (%)	Turn (%)	Random coil (%)
WPI	2.5	18.5 ± 0.6	31.1 ± 0.1	31.7 ± 0.2	18.7 ± 0.7
	5.5	18.6 ± 0.3	28.9 ± 0.4	34.7 ± 0.8	17.8 ± 1.1
	7.5	19.4 ± 0.4	24.9 ± 0.2	35.2 ± 0.5	20.5 ± 0.5
	9.5	22.3 ± 0.4	19.7 ± 0.3	37.5 ± 0.8	20.4 ± 0.9
WPI-Lut	2.5	18.6 ± 0.3	31.2 ± 0.6	32.1 ± 0.2	18.1 ± 0.9
	5.5	18.2 ± 0.4	28.7 ± 0.6	34.7 ± 0.2	18.4 ± 0.7
	7.5	20.2 ± 0.3	24.7 ± 0.8	35.1 ± 0.4	20.0 ± 0.3
	9.5	22.4 ± 0.9	19.1 ± 0.7	38.4 ± 0.6	20.1 ± 0.7
WPI-Zx	2.5	18.7 ± 0.5	31.3 ± 0.4	31.9 ± 0.1	18.1 ± 0.3
	5.5	19.5 ± 0.3	28.3 ± 0.4	33.6 ± 0.6	18.6 ± 0.1
	7.5	19.8 ± 0.3	22.5 ± 0.7	38.6 ± 0.1	19.1 ± 0.6
	9.5	23.1 ± 0.9	18.6 ± 0.2	38.0 ± 0.4	20.3 ± 0.5