Preliminary Study for Tracing the Geographical Origin of Wheat Flour in Breads Using Stable Isotope Analysis of Wheat Proteins

To trace the geographical origin of wheat flour used in breads, we examined the stable carbon, nitrogen, and oxygen isotope ratios (delta C-13, delta N-15, and delta O-18) of wheat flour proteins. The presence or absence of auxiliary materials, such as yeast, butter, and non-fat dry milk powder, had little influence on the protein composition of wheat glutenin fractions extracted from breads. We determined the delta C-13, delta N-15, and delta O-18 values of the wheat glutenin fractions from bread samples made from wheat flour obtained from Canada, USA, and Japan. The delta C-13, delta N-15, and delta O-18 values of the glutenin fractions were positively correlated with those of wheat flour (R = 0.985,p < 0.001 in delta C-13;R = 0.989,p < 0.001 in delta N-15;R = 0.884,p < 0.001 in delta O-18), and the delta C-13 and delta N-15 values of the wheat glutenin fractions in bread made from Japanese wheat flour were lower than those of the other samples. This shows that stable isotope analysis of wheat glutenin fractions is a potentially useful tool for tracing the geographical origin of wheat flour in breads.