Methanethiol Formation in Disrupted Tissue Solution of Fresh Broccoli.

Abstract

Factors for the formation of methanethiol using a disrupted broccoli tissue solution were investigated. A trace amount of methanethiol was detected in the headspace of a capped test tube containing the disrupted fresh tissue solution after incubation at 20 °C for 1 hr. When L-cysteine or reduced glutathione was added to the sample solution, a considerable amount of methanethiol was formed. In a molecular weight of below 10, 000 fraction of the fresh sample solution, a significant amount of methanethiol was formed by adding L-cysteine. However, in a disrupted tissue solution prepared from a heat-treated tissue, no detectable methanethiol was formed by adding L-cysteine.We propose that methanethiol is a degradation product of methyl methanethiosulfinate (MMTSO) which is present in the disrupted fresh tissue solution. The concentration of the MMTSO is pH-dependent, being higher in basic than in acidic solutions. No MMTSO was detected in the disrupted tissue solution prepared from a heat-treated tissue. When L-cysteine was mixed with the fresh sample solution, MMTSO disappeared.It was confirmed that MMTSO was formed by an enzymatic reaction in the disrupted fresh broccoli solution which reacts nonenzymatically with L-cysteine or reduced glutathione to produce methanethiol.