A preliminary study on the impact of drying treatments on the H and O isotopic compositions of wheat noodles with different gluten-to-starch ratios

Stable hydrogen (δ²H) and oxygen (δ¹⁸O) isotopic ratios are key in wheat authentication, but the effects of formulation and drying processes on these ratios remain unclear. This study investigated how gluten-to-starch ratios, drying methods, and drying time influence δ²H and δ¹⁸O in noodles. Eight noodle formulations and five drying methods were used, and 960 noodle samples were measured. Results showed gluten-to-starch ratio significantly affected δ²H, with higher gluten contents (55 %–100 %) causing greater variation. Traditional drying methods (T40, T60, T80) yielded higher δ²H and δ¹⁸O values than industrial stepwise drying (I30, I40), indicating stronger isotope fractionation. High-temperature drying, especially T80, led to notable shifts in isotopic ratios, particularly in gluten-rich formulations. Although drying time had no statistically significant overall effect, δ²H and δ¹⁸O increased under certain conditions but stabilized after 240 min. In view of product authentication, for low-temperature dried noodles, the δ²H and δ¹⁸O isotopic ratios can be considered relatively stable, but at higher temperature drying, corrections to compensate for the drying effects are required.