Mulberry leaves were fermented with mixed lactic acid bacteria, sensory evaluation and headspace-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) were used to analyze the changes of sensory attributes and flavor substances during fermentation. Gas chromatography olfactometry (GC-O) and odor activity value (OAV) combined with odor intensity value were used to identify the grassy smell of unfermented mulberry leaves. A total of 116 volatile substances were identified from mulberry leaves at different fermentation stages, and 49, 42, 53, and 61 volatile compounds were detected at 0, 24, 36, and 48 hours respectively. A total of 11 substances with obvious odor were identified by GC-O in unfermented mulberry leaves, and these substances could match with GC-MS results. Among these 11 substances, cis-3-hexenol, 1-octene-3-alcohol, trans-2-octenal, nonanal, decylaldehyde, and myristic aldehyde had obvious grassy and fishy odors. Apart from these 11 substances, one unknown substance was also identified by GC-O. After fermentation, the content of these odorous substances was significantly reduced (P<0.05), whereas some esters and alcohols with flower and fruit fragrance were produced, which was consistent with the results of sensory evaluation. It was proved that lactic acid bacteria fermentation can remove the grassy smell of mulberry leaves and improve the sensory quality of mulberry leaves.
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