Impact of Noodle Formulation, Boiling Methodology and Their Interactions on Stable Hydrogen and Oxygen Isotope Ratios

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 (delta H-2) and oxygen (delta O-18) isotopic ratios of wheat noodles were evaluated. The delta H-2 and delta O-18 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 delta H-2 of the boiled noodles ranged from -80.1 parts per thousand to -46.8 parts per thousand and were significantly lower than those of the raw materials, which ranged from -73.0 parts per thousand to -39.2 parts per thousand, and the uncooked noodles, which ranged from -73.3 parts per thousand to -39.6 parts per thousand. Oppositely, O-18 was enriched in the boiled noodles, ranging from 27.7 parts per thousand to 31.3 parts per thousand, compared with the uncooked noodles, ranging from 28.4 parts per thousand to 29.6 parts per thousand. In addition, a significant interaction effect between the formulation and the boiling process was recorded for delta O-18. 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.