Methanethiol (MT) is a volatile compound responsible for the unpleasant odor 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 reduced 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 N2. After 24 h in the dark at 20 °C, headspace samples from the 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., Capitata group), broccoflower (Brassica oleracea L., Botrytis group), and green and red cabbage (Brassica oleracea L., Capitata group). Broccoli stems, kale (Brassica oleracea L., Acephala group), Brussels sprouts (Brassica oleracea L., Gemmifera group), pak choi petioles, rutabaga (Brassica napus L., Napobrassica 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 produced by broccoli florets. Green tissues appeared to have a greater capacity to produce MT than nongreen tissues. Anaerobic production of CO2 and ethanol did not relate to the vegetable's ability to produce MT. The production of dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) were also induced by the anaerobic conditions. Green cabbage produced the greatest concentration of DMDS, followed by savoy cabbage and broccoli florets. Production of DMTS was similar to the pattern observed for MT, but DMDS production was not highly correlated with MT production.
Charles F. Forney and Michael A. Jordan
Green cauliflower (Broccoflower) (Brassica oleracea L. Botrytis Group cv. Alverda) is a relatively new vegetable crop in the United States. Experiments were initiated to investigate the yield potential of `Alverda' green cauliflower in three consecutive plantings (10 Oct. and 24 Nov. 1992 and 12 Jan. 1993) at two in-row spacings (31- and 38-cm) with the factorial combinations of N and K at 98, 196, and 294 kg·ha–1 under subtropical conditions. Crops were grown in an Eau Gallie fine sand with the full-bed polyethylene mulch-seepage (modified furrow) irrigation system. Marketable yields were highest in the January planting with N at 294 kg·ha–1 when 71% of the plants had marketable size (≥0.34 kg) and desirable quality curds. Yields were higher at 38- than at 31-cm spacing. Yields and curd size increased with increasing N rates at all three planting dates (P ≤ 0.01). Potassium rates had no significant effect on yields.
Charles F. Forney and Michael A. Jordan
Methanethiol (MT) is a volatile compound responsible for the strong off-odor that is evolved when fresh broccoli is held under anaerobic atmospheres. Inductive atmospheres can develop in modified-atmosphere packages, resulting in reduced 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 of these cut vegetables were sealed in 500-ml glass jars and flushed with N2. After flushing, jars were held for 24 h at 20C in the dark. Headspace samples from the jars then were analyzed for MT and other volatiles using a GC-MS> The concentration of MT was greatest in jars containing broccoli florets. Broccoli flower buds removed from florets produced 40 times more MT than peduncle and stem tissues (38.3 vs. 0.87 mmol·m–3). Headspace concentration of MT (mmol·m–3) in jars containing these different vegetables was: broccoli florets, 22.7; pak choi leaf blades, 17.8; savoy cabbage, 12.4; broccoflower, 7.5; green storage cabbage, 5.2; red cabbage, 2.7; kale, 0.81; Brussels sprouts, 0.36; pak choi petioles, 0.28; rutabaga root, 0.26; cauliflower florets, 0.18; Chinese cabbage, 0.03; and kohlrabi tubers, 0.02. In addition to MT, ethanol, dimethyl disulfide, and dimethyl trisulfide were detected in the headspace over each of the 12 vegetables. The contribution of these induced compounds to off-odor development in packaged, precut vegetables will be discussed.