Coupled multidimensional GC and odor activity value calculation to identify off-odors in thermally processed muskmelon juice.

Predominant contributors to thermally-induced off-notes in muskmelon juice were investigated by combination of sensory evaluation, GC-olfactometry (GC-O), multidimensional GC, odor activity value (OAV) calculation and addition experiments. "Fermented" and "sulfurous" were revealed as the dominant heat-induced offensive off-notes, and fundamental heat-led changes in odorant compositions were observed. Comparative aroma extract dilution analysis revealed that the off-flavors were mainly caused by newly heat-formed compounds with extremely low odor threshold and unpleasant smells. These included volatile sulfur compounds with "rotten" odors, Strecker aldehydes having "fermented" notes, and heterocyclics exhibiting "roasted" smells. Specifically, dimethyl sulfide, methional, methanethiol, dimethyl trisulfide, dimethyl disulfide, and acetaldehyde were identified as the predominant off-note contributors, among which DMS was the most important one, showing the highest OAV. Multiple extraction techniques, GC-O coupling to GC × GC-QTOF-MS and OAV calculation are powerful tools for accurate location and reliable identification of trace and key off-odorants in natural complex matrices.