Saskia Marieke van Ruth

Stable isotopes are commonly utilized for the geographical origin verification of foods, including wheat. However, assessing processed products poses a greater challenge due to the alterations that take place during processing and which have not been fully elucidated yet. In the current study, the effects of the formulation (the mass ratios of gluten to starch), boiling process and their interaction on the stable hydrogen (δ2H) and oxygen (δ18O) isotopic ratios of wheat noodles were evaluated. The δ2H and δ18O of noodles with different formulations (the mass ratios of gluten to starch) as raw materials, in uncooked and cooked (boiled in water) noodles, were examined. The results indicated that the δ2H of the boiled noodles ranged from −80.1‰ to −46.8‰ and were significantly lower than those of the raw materials, which ranged from −73.0‰ to −39.2‰, and the uncooked noodles, which ranged from −73.3‰ to −39.6‰. Oppositely, 18O was enriched in the boiled noodles, ranging from 27.7‰ to 31.3‰, compared with the uncooked noodles, ranging from 28.4‰ to 29.6‰. In addition, a significant interaction effect between the formulation and the boiling process was recorded for δ18O. This study shows that the hydrogen and oxygen stable isotopic compositions of noodles were significantly changed during the boiling process, and the isotopic fractionation varies with the different formulations.