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• δ 13C and δ 18O were used for geographical origin discrimination of kabocha pumpkin. • Kabocha of Hokkaido, Japan was discriminated from those of Mexico and New Zealand. • δ 13C and the δ 18O of flesh were affected by seasonings after cooking or processing. • Effects of seasonings on δ 13C and δ 18O were eliminated by extracting crude fiber. • δ 13C and δ 18O of crude fiber can be used for verification even after cooking. In this study, we investigated the possibility of the geographical origin discrimination between Japanese and Mexican kabocha pumpkin using δ13C and δ18O in lyophilized raw flesh. Kabocha harvested in Hokkaido, the major kabocha production area in Japan, could be discriminated against not only that grown in Mexico but also that in New Zealand. However, seasoning after cooking or processing affected the δ 13C and the δ 18O values. Crude fiber extraction eliminated the effect of seasonings and enabled the adoption of the δ 13C and δ 18O values in crude fiber for the geographical origin verification of kabocha even after cooking and processing. The usage of δ 13C and the δ 18O in crude fiber would extend the application possibilities of stable isotope analysis in the geographical origin determination of various cooked and processed vegetables and fruits as well as raw materials. [ABSTRACT FROM AUTHOR]