Changes of volatile sulfur compounds of "Nori" products, Porphyra spp. during storage.

Abstract

The changes in the flavor of dried and toasted laver Porphyra spp. stored over three months were examined by focusing on the changes in three volatile sulfur compounds, hydrogen sulfide (H2S), methyl mercaptan (MM) and dimethyl sulfide (DMS) monitored by gas chromatography. In dried laver with 8% moisture content, the decline of H2S and DMS and the icnrease of MM were negligible only when stored at -30°C with air or at 5°C with nitrogen gas or an oxygen ab-sorber. When the moisture content declined to 4.5%, changes in the H2S and MM levels were minimized by the nitrogen gas and by the oxygen absorber at both 5° and 25°C. DMS, however, increased with nitrogen gas at both 5° and 25°C. In toasted laver, the levels of the three compounds were well preserved when stored at 5°C with nitrogen gas or an oxygen absorber. At 25°C with nitrogen gas or an oxygen absorber, how-ever, H2S and MM declined moderately. Meanwhile DMS was well preserved, resulting in the maintenance of good flavor. Therefore, the storage of all nori products at 5°C with nitrogen gas or an oxygen absorber is recommended.