Abstract: The volatile composition of whole wheat flour and quick-frozen pre-fried whole wheat Youtiao before and after different reheating methods was analyzed comparatively using electronic nose and headspace solid phase microextraction combined with gas chromatography and mass spectrometry (HS-SPME-GC-MS). Meanwhile, the effect of different reheating methods on polyphenolic contents and antioxidant properties of quick-frozen pre-fried Youtiao was explored. It was found that different characteristic flavor substances were produced after different reheating methods. During the pre-frying and reheating processes, some flavor substances in whole wheat flour disappeared. The relative peak area of aldehydes in quick-frozen pre-fried Youtiao was 50%, which indicates that aldehydes may be the major flavor component of Youtiao. Among the three reheating methods evaluated, refrying produced the largest number of aldehydes and heterocyclic compounds. The contents of acids and hydrocarbons increased in the microwaved sample, and the highest content of aldehydes mostly non-flavor-active saturated aldehydes was observed in the steamed sample. Moreover, all three reheating processes reduced the content of polyphenols in Youtiao, and the loss of polyphenols in pre-fried and reheated Youtiao was ranked in decreasing order of steaming > microwave > pre-frying > refrying, while the opposite was observed for the antioxidant properties.

Key words: whole wheat flour; Youtiao; reheating; flavor substances; antioxidant properties