Volatile compounds and aroma descriptions in overfermented tempe (tempe bosok) with different packaging and blanching treatment

The unique and specific aroma of overfermented tempe has been used as a seasoning in traditional Javanese cooking. Different fermentation times and packaging methods are used, but there is currently no information regarding the length of tempe fermentation time that can still provide a pleasant aroma, which is important for consumers. To address this, a study was conducted in which fermentation was carried out until larvae appeared, followed by blanching to stop the fermentation process before drying the tempe. This study aimed to characterize and compare the key volatile compounds and aroma attributes in blanched and nonblanched tempe samples fermented for 1, 4, 7, and 10 days. The key volatile compounds in the overfermented tempe included acetaldehyde (odor activity value [OAV] = 13,311), nonanal (OAV = 134,826), 1-octen-3-ol (OAV = 45,482), butyric acid (OAV = 45,135), 2-nonanone (OAV = 17,058), phenol (OAV = 20,149), 3-ethyl-2,5-dimethylpyrazine (OAV = 15,433), 2,3-dimethylpyridine (OAV = 19,879), and indole (OAV = 22,164). Samples fermented for more than 4 days had more diverse aroma attributes, including toasted, woody, umami, sour, beefy, seafood, musty, spicy, salty, rancid, pungent, caramelic, and floral. Blanching was found to reduce the concentration of volatile compounds responsible for the off flavors, such as acids and indole. In addition, the panelists perceived that the blanched tempe with plastic wrapping exhibited an aroma consistent with the public's perception (distinctive and unique), enhancing the overall flavor of the dish. The findings of this study will help control aroma quality from overfermented tempe when used as a food seasoning.