Anaerobic production of methanethiol and other compounds by Brassica vegetables

Methanethiol (MT) is a volatile compound responsible for the unpleasant odo r evolved when fresh broccoli (Brassica oleracea L., Italica group) is held under anaerobic conditions. Inductive atmospheres can develop in storage, transportation containers, or modified atmosphere packages, resulting in re duced quality. To determine if related vegetables are capable of producing MT, 12 different vegetables from the genus Brassica were cut into ready-to- eat forms. Fifty-gram samples were sealed in 500-mL glass jars and flushed with N-2. After 24 h in the dark at 20 degrees C, headspace samples from th e jars were analyzed for MT and other volatiles. Headspace concentration of MT was greatest in broccoli florets, followed by pak choi (Brassica rapa L ., Chinensis group) leaf blades, savoy cabbage (Brassica oleracea L., Capit ata group), broccoflower (Brassica oleracea L., Botrytis group), and green and red cabbage (Brassica oleracea L., Capitata group). Broccoli stems, hal e (Brassica oleracea L., Acephala group), Brussels sprouts (Brassica olerac ea L., Gemmifera group), pak choi petioles, rutabaga (Brassica napus L., Na pobrassica group) root, cauliflower (Brassica oleracea L., Botrytis group) florets, Chinese cabbage (Brassica rapa L., Pekinensis group), and kohlrabi (Brassica oleracea L., Gongylodes group) tubers produced <3% of the MT pro duced by broccoli florets. Green tissues appeared to have a greater capacit y to produce MT than nongreen tissues. Anaerobic production of CO2 and etha nol did not relate to the vegetable's ability to produce MT. The production of dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) were also indu ced by the anaerobic conditions. Green cabbage produced the greatest concen tration of DMDS, followed by savoy cabbage and broccoli florets. Production of DMTS was similar to the pattern observed for MT, but DMDS production wa s not highly correlated with MT production.