Tracing isotopic fingerprints: Unveiling the impact of noodle formulation and cooking water on the isotopic signatures of wheat-derived noodles

This study examines how variations in δ²H and δ¹⁸O values of cooking water affect the isotopic fingerprint of noodles with different gluten-to-starch formulations, aiming to enhance the current understanding of isotopic changes during food processing and their implications for food authenticity. Eight differently formulated noodles were boiled using waters with six distinct isotopic compositions ranging from of −160‰ to +50‰ for δ²H and from −22.9‰ to +99.9‰ for δ¹⁸O, respectively. Linear regression analysis revealed that formulation and water isotopic composition significantly affected the δ²H in cooked noodles (p < 0.05), with model R² values ranging from 0.66 to 0.94. Additionally, the δ²H values of noodles changed with the isotopic signatures of the cooking water. On the contrary, δ¹⁸O in the noodles remained stable despite boiling processing and was also not changing due to the water's isotopic signature. Since consistent effects of formulation and cooking water isotopic signature was observed, an equation for determining the exchange factor (f(H)ex) between noodles and cooking water was developed. The fraction of hydrogen atoms in different noodles for exchange was highest at 19.3% in noodles with the formulation of 45:55(gluten-to-starch) and the lowest at 11.1% in noodles with 100% gluten. The findings prove that cooking water systematically alters the isotopic signatures of noodles, underscoring the necessity of considering this type of effect in food authentication and traceability practices.