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Effects of Secondary Structures of Heated Egg White Protein on the Binding Between Prime Starch and Tailings Fractions in Fresh Wheat Flour

¹Faculty of Home Economics, Laboratory of Food Technology, Kobe Women's University, Suma-Ku, Kobe City, 654-8585 Japan. ²Corresponding author. Phone: 81787372431. Fax: 81787325161. E-mail: seguchi@suma.kobe-wu.ac.jp ³Laboratory of Quality Analysis and Assessment, Division of Agronomy and Horticultural Science, Graduate School of Agriculture, Kyoto University (Uji Campus), Gokasho, Uji, Kyoto 611-0011, Japan. ⁴Kobe Women's Junior College, Kobe City, 650-0046, Japan.

Dried egg white protein was heated at 120°C for 1 hr, added to a fresh wheat flour (protein 8.6%), and the protein and wheat flour were subjected to acetic acid (pH 3.5) fractionation. The results showed that egg white protein increased the binding between prime starch (PS) and tailings (T) fractions in wheat flour. Several conditions for heating of egg white protein were examined to determine 1) the effect of the amount of water added to the protein before heating; 2) the effect of heating time (hr) on protein at 120°C; and 3) the effect of heating temperature on the binding between PS and T fractions. The amount of protein per 50.0 g of wheat flour was further examined for the maximum binding between PS and T fractions. The heated egg white protein was analyzed by Fourier transform infrared (FT-IR) spectroscopy, and the changes in the secondary structures (α-helix, β-sheets, and others) of the protein caused by heating were studied. When egg white protein was heated at 120°C for 8 hr, 9.0% of the α-helix structures of egg white protein decreased to 3.0%, and 37.0% of the β-sheet structures increased to 41.0%. The decrease of α-helix and increase of β-sheet structures of heated egg white protein were related to the increase in the binding between PS and T fractions in the same heated egg white protein and wheat flour sample. A relationship between the structural changes in heated egg white protein (180°C, 1 hr) and the binding between PS and T fractions in the heated egg white protein and wheat flour was also observed.