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 (N DE) from pickling cucumbers were examined. Production capability was rapidl y destroyed in tissues exposed to freezing, fermentation or processing cond itions. Lower concentrations were produced by exocarp tissues than mesocarp or endocarp tissues, which probably accounted for an almost linear relatio nship between fruit size and NDE production. NDE production was reduced by acidification, enhanced by linolenic acid, and unaffected by other unsatura ted fatty acids NaCl or CaCl2. E-2-nonenal production was suppressed when N DE production was increased by linolenic acid. NDE was unstable in filtrate s of homogenized tissues. Its stability was substantially improved by acidi fying to pH 2 and unaffected by CaNa(2)EDTA. Extraction and concentration b y vacuum distillation further enhanced stability. Loss of NDE in distillate s averaged 0.3%/d during storage at 5 degreesC.