Abstract:With recent advances in detection technology the volatile substances in green algae, brown algae, red algae, and other algae have been identified. However, few studies have investigated the volatile substances of laver (genus Porphyra), especially, the analysis of the flavor change in Porphyra yezoensis after roasting. To address this issue, the electronic nose, FlavourSpec® flavor analyzer and SPME-GC-MS were used to compare the volatile components of P. yezoensis before and after roasting. The results of the electronic nose analysis showed that there were some differences in the volatile components derived from P. yezoensis before and after roasting. The two main components were the same, but the contribution of hydrocarbon compounds to the main components were different. Thus, the electronic nose was capable of discriminating the flavor differences in P. yezoensis before and after roasting. Flavor analysis showed that the volatile components of P. yezoensis before and after roasting were significantly different. The contents of nonanal, octanal, hexanal, valeraldehyde, benzaldehyde, and 2-ethyl-furan, were relatively higher in P. yezoensis. After roasting, the contents of methyl-pyrazine, 1-pentanol, furfural, 3-methyl-butanol, and 3-methyl-butanal were higher. The characteristic flavor and relative content of pyrazines also increased after roasting. The SPME-GC-MS analysis showed that the total volatile flavor compounds of laver samples before and after roasting were 83 and 86, respectively. The major volatile compounds of P. yezoensis were aldehydes, alcohols, ketones, and alkanes. The pyrazines consisted of methyl pyrazine, 2,5-dimethyl-pyrazine, 2-ethyl-5-methyl-pyrazine, 3-ethyl-2,5-dimethyl-pyrazine and 2-ethyl-6-methyl- pyrazine. These compounds increased significantly after roasting. In summary, the main flavor substances of P. yezoensis varied significantly after roasting, especially the content of pyrazines (increased significantly). This research clarifies how the roast flavor is generated, allowing us to optimize our processing technology. Future research is required to understand the mechanisms underlying the formation of flavor.
