Assessing the impact of limited and extended oven heating exposure on the stable hydrogen and oxygen isotopic composition of wheat-processed products with varying formulations

This study aims to assess the effects of oven heating on the isotopic ratios of eight formulated wheat-processed products with different gluten-to-starch ratios. Two heating treatments were applied: limited heating in an oven with exposure to 100 °C for a specific time (cooking time-dependent) and extended heating in an oven with exposure to 100 °C, 180 °C and 260 °C for 6 min. Results showed limited heating exposure did not alter the δ²H and δ¹⁸O in the wheat-processed products. However, compared with unheated noodles, extended heating exposure caused a significant decrease (p<0.05) in the δ²H. A - 3.8 ‰ offset should be applied to δ²H of wheat-processed products heated between 100 and 260 °C (with 80 °C intervals). On the contrary, the offset of 1.3 ‰ for δ¹⁸O is only needed for temperatures between 180 and 260 °C. The results also indicate noodle formulation and heat treatment interact to influence the isotopic difference between heat-treated and untreated noodles.