Flavor formation in different production steps during the processing of cold-smoked Spanish mackerel

•Odor formation was monitored during cold smoking of Spanish mackerel.•Volatile compounds formed in different processes were monitored using purge-and-trap extraction with GC–MS.•Heat map and PLS-DA were suitable ways to describe differences of odors.•A conversion of sulfur compounds during cold smoking of mackerel is described. This study aimed to determine the changes in the flavor profile during different operating units when making cold-smoked Spanish mackerel. Sensory evaluation and instrumental analysis of tenderness were applied to optimize the processing parameters. For the overall odor perception, distinct odor among fresh and processed samples could be distinguished using electronic nose (e-Nose). Purge-and-trap (P&T) extraction combined with gas chromatography–mass spectrometry (GC–MS) was used to identify volatile compounds. Alcohols were the major volatiles in Spanish mackerel over the whole processing, while 2-butanol was found in the highest concentration. Curing was an effective way to remove fishy odor. Drying decreased the concentration of volatiles, especially sulfur compounds. Odor formation in cold-smoked mackerel could be divided into four steps (curing, drying, cold smoking and heating) as a result of partial least squares discriminant analysis (PLS–DA).