Effect of High Electric Field on Secondary Structure of Wheat Gluten

Figures & data

TABLE 1 Infrared absorption bands of peptide linkages (adapted from [Kong & Yu, 2007; Georget & Belton, 2006])

Band	Frequency (cm^–1)	Description
Amide A	3300	NH stretching
Amide B	3100	NH stretching
Amide I	1690–1600	C=O stretching
Amide II	1575–1480	CN stretching, NH bending
Amide III	1301–1229	CN stretching, NH bending
Amide IV	767–625	OCN bending
Amide V	800–640	Out-of-plane NH bending
Amide VI	606–537	Out-of-plane C=O bending
Amide VII	200	Skeletal torsion

FIGURE 1 Schematic of the static high electric field treatment system.

TABLE 2 Amide I band frequencies and assignment to protein secondary structure in H₂O media (adapted from [Georget & Belton, 2006; Goormaghtigh et al., 1994; Kong & Yu, 2007; Pelton & McLean, 2000])

Secondary structure	Frequencies (cm^–1)	Average
α helix	1660–1648	1654
α helix turns	1630	1630
310 helix	1665–1663	1664
β sheets	1641–1612	1625
	1640–1626	1633
	1697–1670	1682
Turns	1684–1662	1673
Random coils	1650–1640	1645

FIGURE 2 (a) Typical FTIR spectra of hydrated wheat gluten protein; (b) FTIR spectra of hydrated (H) gluten proteins treated with high electric field intensities (0, 3.5, and 7 kV/cm) for time (30, 60, and 90 min).

FIGURE 3 (a) Normalized spectra of the amide I region of hydrated gluten protein; (b) Normalized amide I band of hydrated gluten protein subjected to control conditions of 0 kV electric field intensity for 30 min fitted with sums of Gaussian bands; (c) Second derivative of normalized spectra showing the valleys and peaks associated with specific secondary structures for all experimental conditions.

FIGURE 4 Variations in relative areas of the bands fitted to the normalized FTIR spectra of amide I region (1720–1580 cm-1) of gluten protein. Error bars represent standard errors.

FIGURE 5 PCA loadings plots of the FTIR spectra in the 1720–1580 cm-1 amide I region.