TIMING AND CONTROL OF METHANETHIOL EMISSION FROM BROCCOLI FLORETS INDUCED BY ATMOSPHERIC MODIFICATION

Storage of broccoli (Brassica oleracea L., Italica Group) under condit ions of low O-2 concentration extends its shelf life. Excessively low O-2, however, leads to the formation of an offensive odour which is pr imarily due to the emission of methanethiol. In this study, we investi gated the initial induction and control of methanethiol production of broccoli florets exposed to various levels of O-2 and CO2 over short-t erm periods of 10 h or less. Lowering the O-2 concentration surroundin g the broccoli florets by continuously flowing N-2 through the sample containers acted to initiate the production of methanethiol within 1 h after the 0(2) concentration had reached 0.5 %. After initiation the rate of production showed a slow but steady increase during the 10 h o f experimentation. In contrast, introduction of O-2 into the sample co ntainers while the broccoli florets were actively producing methanethi ol led to a rapid 79% drop in the amount of methanethiol detected with in 15 min, followed by a complete absence of methanethiol within anoth er 15 min. Resumption of N-2 flow acted to reinitiate methanethiol pro duction, with the initiation requiring a lesser amount of time than th at required for the initial induction of methanethiol production. Expe riments with elevated CO2 concentrations of up to 26.5% determined tha t CO2 is an inhibitor of methanethiol production.