Production and stability of (E,Z)-2,6-nonadienal, the major flavor volatile of cucumbers

Factors affecting the production and stability of (E, Z)-2, 6-nonadienal (NDE) from pickling cucumbers were examined. Production capability was rapidly destroyed in tissues exposed to freezing, fermentation or processing conditions. Lower concentrations were produced by exocarp tissues than mesocarp or endocarp tissues, which probably accounted for an almost linear relationship between fruit size and NDE production. NDE production was reduced by acidification, enhanced by linolenic acid, and unaffected by other unsaturated fatty acids NaCl or CaCl2. E-2-nonenal production was suppressed when NDE production was increased by linolenic acid. NDE was unstable in filtrates of homogenized tissues. Its stability was substantially improved by acidifying to pH 2 and unaffected by CaNa(2)EDTA. Extraction and concentration by vacuum distillation further enhanced stability. Loss of NDE in distillates averaged 0.3%/d during storage at 5 degreesC.